Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

212 files changed, 27047 insertions, 0 deletions

diff --git a/toolkit/components/glean/Cargo.toml b/toolkit/components/glean/Cargo.toml
new file mode 100644
index 0000000000..2bf4a745e0
--- /dev/null
+++ b/toolkit/components/glean/Cargo.toml
@@ -0,0 +1,28 @@
+[package]
+name = "fog_control"
+version = "0.1.0"
+authors = ["Glean SDK team <glean-team@mozilla.com>"]
+edition = "2018"
+license = "MPL-2.0"
+
+[dependencies]
+glean = "51.8.2"
+log = "0.4"
+nserror = { path = "../../../xpcom/rust/nserror" }
+nsstring = { path = "../../../xpcom/rust/nsstring" }
+static_prefs = { path = "../../../modules/libpref/init/static_prefs" }
+xpcom = { path = "../../../xpcom/rust/xpcom" }
+once_cell = "1.2.0"
+fog = { path = "./api" }
+cstr = "0.2"
+viaduct = "0.1"
+url = "2.1"
+thin-vec = { version = "0.2.1", features = ["gecko-ffi"] }
+
+[features]
+# Leave data collection enabled, but disable upload.
+disable_upload = []
+# Letting us know we're compiling with Gecko symbols.
+with_gecko = ["fog/with_gecko"]
+# Opt into a larger preinit queue
+million_queue = ["glean/preinit_million_queue"]
diff --git a/toolkit/components/glean/api/Cargo.toml b/toolkit/components/glean/api/Cargo.toml
new file mode 100644
index 0000000000..9879bc800a
--- /dev/null
+++ b/toolkit/components/glean/api/Cargo.toml
@@ -0,0 +1,27 @@
+[package]
+name = "fog"
+version = "0.1.0"
+authors = ["Glean SDK team <glean-team@mozilla.com>"]
+edition = "2018"
+publish = false
+license = "MPL-2.0"
+
+[dependencies]
+bincode = "1.0"
+chrono = "0.4.10"
+glean = "51.8.2"
+inherent = "1.0.0"
+log = "0.4"
+nsstring = { path = "../../../../xpcom/rust/nsstring", optional = true }
+once_cell = "1.2.0"
+serde = { version = "1.0", features = ["derive"] }
+uuid = { version = "1.0", features = ["v4"] }
+xpcom = { path = "../../../../xpcom/rust/xpcom", optional = true }
+thin-vec = { version = "0.2.1", features = ["gecko-ffi"] }
+mozbuild = "0.1"
+
+[dev-dependencies]
+tempfile = "3.1.0"
+
+[features]
+with_gecko = ["xpcom", "nsstring"]
diff --git a/toolkit/components/glean/api/src/common_test.rs b/toolkit/components/glean/api/src/common_test.rs
new file mode 100644
index 0000000000..49b7416d72
--- /dev/null
+++ b/toolkit/components/glean/api/src/common_test.rs
@@ -0,0 +1,52 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use std::sync::{Mutex, MutexGuard};
+
+use once_cell::sync::Lazy;
+
+const GLOBAL_APPLICATION_ID: &str = "org.mozilla.firefox.test";
+
+/// UGLY HACK.
+/// We use a global lock to force synchronization of all tests, even if run multi-threaded.
+/// This allows us to run without `--test-threads 1`.`
+pub fn lock_test() -> (MutexGuard<'static, ()>, tempfile::TempDir) {
+    static GLOBAL_LOCK: Lazy<Mutex<()>> = Lazy::new(|| Mutex::new(()));
+
+    let lock = GLOBAL_LOCK.lock().unwrap();
+
+    let dir = setup_glean(None);
+    (lock, dir)
+}
+
+// Create a new instance of Glean with a temporary directory.
+// We need to keep the `TempDir` alive, so that it's not deleted before we stop using it.
+fn setup_glean(tempdir: Option<tempfile::TempDir>) -> tempfile::TempDir {
+    let dir = match tempdir {
+        Some(tempdir) => tempdir,
+        None => tempfile::tempdir().unwrap(),
+    };
+    let tmpname = dir.path().to_path_buf();
+
+    let cfg = glean::Configuration {
+        upload_enabled: true,
+        data_path: tmpname,
+        application_id: GLOBAL_APPLICATION_ID.into(),
+        max_events: None,
+        delay_ping_lifetime_io: false,
+        server_endpoint: None,
+        uploader: None,
+        use_core_mps: false,
+    };
+
+    let client_info = glean::ClientInfoMetrics {
+        app_build: "test-build".into(),
+        app_display_version: "1.2.3".into(),
+        channel: None,
+    };
+
+    glean::test_reset_glean(cfg, client_info, true);
+
+    dir
+}
diff --git a/toolkit/components/glean/api/src/factory.rs b/toolkit/components/glean/api/src/factory.rs
new file mode 100644
index 0000000000..f7984f4c46
--- /dev/null
+++ b/toolkit/components/glean/api/src/factory.rs
@@ -0,0 +1,16 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! This file contains the Generated JOG Factory for the runtime-registration
+//! of Glean metrics in Firefox on Glean.
+//! You probably should just ignore stuff in here and ask on the
+//! [#glean Matrix channel](https://chat.mozilla.org/#/room/#glean:mozilla.org)
+//! if you have questions.
+//!
+//! Most of the contents of this module are generated by
+//! `toolkit/components/glean/build_scripts/glean_parser_ext/run_glean_parser.py`
+
+include!(mozbuild::objdir_path!(
+    "toolkit/components/glean/api/src/factory.rs"
+));
diff --git a/toolkit/components/glean/api/src/ffi/boolean.rs b/toolkit/components/glean/api/src/ffi/boolean.rs
new file mode 100644
index 0000000000..9184b23c00
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/boolean.rs
@@ -0,0 +1,28 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+
+#[no_mangle]
+pub extern "C" fn fog_boolean_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(BOOLEAN_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_boolean_test_get_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(BOOLEAN_MAP, id, metric, test_get!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_boolean_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(BOOLEAN_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
+
+#[no_mangle]
+pub extern "C" fn fog_boolean_set(id: u32, value: bool) {
+    with_metric!(BOOLEAN_MAP, id, metric, metric.set(value));
+}
diff --git a/toolkit/components/glean/api/src/ffi/counter.rs b/toolkit/components/glean/api/src/ffi/counter.rs
new file mode 100644
index 0000000000..5fba7c0dea
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/counter.rs
@@ -0,0 +1,28 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_counter_add(id: u32, amount: i32) {
+    with_metric!(COUNTER_MAP, id, metric, metric.add(amount));
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_counter_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(COUNTER_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_counter_test_get_value(id: u32, ping_name: &nsACString) -> i32 {
+    with_metric!(COUNTER_MAP, id, metric, test_get!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_counter_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(COUNTER_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/custom_distribution.rs b/toolkit/components/glean/api/src/ffi/custom_distribution.rs
new file mode 100644
index 0000000000..853a6e9845
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/custom_distribution.rs
@@ -0,0 +1,82 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+use thin_vec::ThinVec;
+
+#[no_mangle]
+pub extern "C" fn fog_custom_distribution_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(
+        CUSTOM_DISTRIBUTION_MAP,
+        id,
+        metric,
+        test_has!(metric, ping_name)
+    )
+}
+
+#[no_mangle]
+pub extern "C" fn fog_custom_distribution_test_get_value(
+    id: u32,
+    ping_name: &nsACString,
+    sum: &mut u64,
+    buckets: &mut ThinVec<u64>,
+    counts: &mut ThinVec<u64>,
+) {
+    let val = with_metric!(
+        CUSTOM_DISTRIBUTION_MAP,
+        id,
+        metric,
+        test_get!(metric, ping_name)
+    );
+    // FIXME(bug 1771885): Glean should use `u64` where it can.
+    *sum = val.sum as _;
+    for (&bucket, &count) in val.values.iter() {
+        buckets.push(bucket as _);
+        counts.push(count as _);
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn fog_custom_distribution_accumulate_samples(id: u32, samples: &ThinVec<u64>) {
+    // N.B.: Avoid reallocation here by making the underlying type take a slice.
+    let samples = samples.into_iter().map(|&i| i as i64).collect();
+    with_metric!(
+        CUSTOM_DISTRIBUTION_MAP,
+        id,
+        metric,
+        metric.accumulate_samples_signed(samples)
+    );
+}
+
+#[no_mangle]
+pub extern "C" fn fog_custom_distribution_accumulate_samples_signed(
+    id: u32,
+    samples: &ThinVec<i64>,
+) {
+    // N.B.: Avoid reallocation here by making the underlying type take a slice.
+    let samples = samples.to_vec();
+    with_metric!(
+        CUSTOM_DISTRIBUTION_MAP,
+        id,
+        metric,
+        metric.accumulate_samples_signed(samples)
+    );
+}
+
+#[no_mangle]
+pub extern "C" fn fog_custom_distribution_test_get_error(
+    id: u32,
+
+    error_str: &mut nsACString,
+) -> bool {
+    let err = with_metric!(
+        CUSTOM_DISTRIBUTION_MAP,
+        id,
+        metric,
+        test_get_errors!(metric)
+    );
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/datetime.rs b/toolkit/components/glean/api/src/ffi/datetime.rs
new file mode 100644
index 0000000000..7529a524e6
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/datetime.rs
@@ -0,0 +1,66 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+
+#[repr(C)]
+pub struct FogDatetime {
+    year: i32,
+    month: u32,
+    day: u32,
+    hour: u32,
+    minute: u32,
+    second: u32,
+    nano: u32,
+    offset_seconds: i32,
+}
+
+#[no_mangle]
+pub extern "C" fn fog_datetime_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(DATETIME_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_datetime_test_get_value(
+    id: u32,
+    ping_name: &nsACString,
+    value: &mut FogDatetime,
+) {
+    let val = with_metric!(DATETIME_MAP, id, metric, test_get!(metric, ping_name));
+    value.year = val.year;
+    value.month = val.month;
+    value.day = val.day;
+    value.hour = val.hour;
+    value.minute = val.minute;
+    value.second = val.second;
+    value.nano = val.nanosecond;
+    value.offset_seconds = val.offset_seconds;
+}
+
+#[no_mangle]
+pub extern "C" fn fog_datetime_set(id: u32, dt: &FogDatetime) {
+    with_metric!(
+        DATETIME_MAP,
+        id,
+        metric,
+        metric.set_with_details(
+            dt.year,
+            dt.month,
+            dt.day,
+            dt.hour,
+            dt.minute,
+            dt.second,
+            dt.nano,
+            dt.offset_seconds
+        )
+    );
+}
+
+#[no_mangle]
+pub extern "C" fn fog_datetime_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(DATETIME_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/denominator.rs b/toolkit/components/glean/api/src/ffi/denominator.rs
new file mode 100644
index 0000000000..ccb047f530
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/denominator.rs
@@ -0,0 +1,28 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_denominator_add(id: u32, amount: i32) {
+    with_metric!(DENOMINATOR_MAP, id, metric, metric.add(amount));
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_denominator_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(DENOMINATOR_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_denominator_test_get_value(id: u32, ping_name: &nsACString) -> i32 {
+    with_metric!(DENOMINATOR_MAP, id, metric, test_get!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_denominator_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(DENOMINATOR_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/event.rs b/toolkit/components/glean/api/src/ffi/event.rs
new file mode 100644
index 0000000000..bd167021d6
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/event.rs
@@ -0,0 +1,168 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use std::collections::HashMap;
+
+use nsstring::{nsACString, nsCString};
+use thin_vec::ThinVec;
+
+use crate::metrics::__glean_metric_maps as metric_maps;
+use crate::private::EventRecordingError;
+
+#[no_mangle]
+pub extern "C" fn fog_event_record(
+    id: u32,
+    extra_keys: &ThinVec<nsCString>,
+    extra_values: &ThinVec<nsCString>,
+) {
+    // If no extra keys are passed, we can shortcut here.
+    if extra_keys.is_empty() {
+        if id & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::EVENT_MAP
+                .read()
+                .expect("Read lock for dynamic metric map was poisoned");
+            match map.get(&id.into()) {
+                Some(m) => m.record_raw(Default::default()),
+                None => panic!("No (dynamic) metric for event with id {}", id),
+            }
+            return;
+        }
+
+        if metric_maps::record_event_by_id(id, Default::default()).is_err() {
+            panic!("No event for id {}", id);
+        }
+
+        return;
+    }
+
+    assert_eq!(
+        extra_keys.len(),
+        extra_values.len(),
+        "Extra keys and values differ in length. ID: {}",
+        id
+    );
+
+    // Otherwise we need to decode them and pass them along.
+    let extra = extra_keys
+        .iter()
+        .zip(extra_values.iter())
+        .map(|(k, v)| (k.to_string(), v.to_string()))
+        .collect();
+    if id & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+        let map = crate::factory::__jog_metric_maps::EVENT_MAP
+            .read()
+            .expect("Read lock for dynamic metric map was poisoned");
+        match map.get(&id.into()) {
+            Some(m) => m.record_raw(extra),
+            None => panic!("No (dynamic) metric for event with id {}", id),
+        }
+        return;
+    } else {
+        match metric_maps::record_event_by_id(id, extra) {
+            Ok(()) => {}
+            Err(EventRecordingError::InvalidId) => panic!("No event for id {}", id),
+            Err(_) => panic!("Unpossible!"),
+        }
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_event_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    let storage = if ping_name.is_empty() {
+        None
+    } else {
+        Some(ping_name.to_utf8().into_owned())
+    };
+    if id & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+        let map = crate::factory::__jog_metric_maps::EVENT_MAP
+            .read()
+            .expect("Read lock for dynamic metric map was poisoned");
+        match map.get(&id.into()) {
+            Some(m) => m.test_get_value(storage.as_deref()).is_some(),
+            None => panic!("No (dynamic) metric for event with id {}", id),
+        }
+    } else {
+        metric_maps::event_test_get_value_wrapper(id, storage).is_some()
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn fog_event_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = if id & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+        let map = crate::factory::__jog_metric_maps::EVENT_MAP
+            .read()
+            .expect("Read lock for dynamic metric map was poisoned");
+        match map.get(&id.into()) {
+            Some(m) => test_get_errors!(m),
+            None => panic!("No (dynamic) metric for event with id {}", id),
+        }
+    } else {
+        metric_maps::event_test_get_error(id)
+    };
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
+
+/// FFI-compatible representation of recorded event data.
+#[repr(C)]
+pub struct FfiRecordedEvent {
+    timestamp: u64,
+    category: nsCString,
+    name: nsCString,
+
+    /// Array of extra data, keys and values are interleaved.
+    extras: ThinVec<nsCString>,
+}
+
+#[no_mangle]
+pub extern "C" fn fog_event_test_get_value(
+    id: u32,
+    ping_name: &nsACString,
+    out_events: &mut ThinVec<FfiRecordedEvent>,
+) {
+    let storage = if ping_name.is_empty() {
+        None
+    } else {
+        Some(ping_name.to_utf8().into_owned())
+    };
+
+    let events = if id & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+        let map = crate::factory::__jog_metric_maps::EVENT_MAP
+            .read()
+            .expect("Read lock for dynamic metric map was poisoned");
+        let events = match map.get(&id.into()) {
+            Some(m) => m.test_get_value(storage.as_deref()),
+            None => return,
+        };
+        match events {
+            Some(events) => events,
+            None => return,
+        }
+    } else {
+        match metric_maps::event_test_get_value_wrapper(id, storage) {
+            Some(events) => events,
+            None => return,
+        }
+    };
+
+    for event in events {
+        let extra = event.extra.unwrap_or_else(HashMap::new);
+        let extra_len = extra.len();
+        let mut extras = ThinVec::with_capacity(extra_len * 2);
+        for (k, v) in extra.into_iter() {
+            extras.push(nsCString::from(k));
+            extras.push(nsCString::from(v));
+        }
+
+        let event = FfiRecordedEvent {
+            timestamp: event.timestamp,
+            category: nsCString::from(event.category),
+            name: nsCString::from(event.name),
+            extras,
+        };
+
+        out_events.push(event);
+    }
+}
diff --git a/toolkit/components/glean/api/src/ffi/labeled.rs b/toolkit/components/glean/api/src/ffi/labeled.rs
new file mode 100644
index 0000000000..8aeb095d54
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/labeled.rs
@@ -0,0 +1,41 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+use std::sync::atomic::Ordering;
+
+#[no_mangle]
+pub extern "C" fn fog_labeled_boolean_get(id: u32, label: &nsACString) -> u32 {
+    labeled_submetric_get!(
+        id,
+        label,
+        LABELED_BOOLEAN_MAP,
+        BOOLEAN_MAP,
+        LabeledBooleanMetric
+    )
+}
+
+#[no_mangle]
+pub extern "C" fn fog_labeled_counter_get(id: u32, label: &nsACString) -> u32 {
+    labeled_submetric_get!(
+        id,
+        label,
+        LABELED_COUNTER_MAP,
+        COUNTER_MAP,
+        LabeledCounterMetric
+    )
+}
+
+#[no_mangle]
+pub extern "C" fn fog_labeled_string_get(id: u32, label: &nsACString) -> u32 {
+    labeled_submetric_get!(
+        id,
+        label,
+        LABELED_STRING_MAP,
+        STRING_MAP,
+        LabeledStringMetric
+    )
+}
diff --git a/toolkit/components/glean/api/src/ffi/macros.rs b/toolkit/components/glean/api/src/ffi/macros.rs
new file mode 100644
index 0000000000..17b2faa6eb
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/macros.rs
@@ -0,0 +1,204 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! Helper macros for implementing the FFI API for metric types.
+
+/// Get a metric object by ID from the corresponding map, then
+/// execute the provided closure with it.
+///
+/// # Arguments
+///
+/// * `$map` - The name of the hash map within `metrics::__glean_metric_maps`
+///            (or `factory::__jog_metric_maps`)
+///            as generated by glean_parser.
+/// * `$id`  - The ID of the metric to get.
+/// * `$m`   - The identifier to use for the retrieved metric.
+///            The expression `$f` can use this identifier.
+/// * `$f`   - The expression to execute with the retrieved metric `$m`.
+macro_rules! with_metric {
+    (BOOLEAN_MAP, $id:ident, $m:ident, $f:expr) => {
+        maybe_labeled_with_metric!(BOOLEAN_MAP, $id, $m, $f)
+    };
+    (COUNTER_MAP, $id:ident, $m:ident, $f:expr) => {
+        maybe_labeled_with_metric!(COUNTER_MAP, $id, $m, $f)
+    };
+    (STRING_MAP, $id:ident, $m:ident, $f:expr) => {
+        maybe_labeled_with_metric!(STRING_MAP, $id, $m, $f)
+    };
+    ($map:ident, $id:ident, $m:ident, $f:expr) => {
+        just_with_metric!($map, $id, $m, $f)
+    };
+}
+
+/// Get a metric object by id from the corresponding map, then
+/// execute the provided closure with it.
+///
+/// Ignores the possibility that the $id might be for a labeled submetric.
+///
+/// # Arguments
+///
+/// * `$map` - The name of the hash map within `metrics::__glean_metric_maps`
+///            (or `factory::__jog_metric_maps`)
+///            as generated by glean_parser.
+/// * `$id`  - The ID of the metric to get.
+/// * `$m`   - The identifier to use for the retrieved metric.
+///            The expression `$f` can use this identifier.
+/// * `$f`   - The expression to execute with the retrieved metric `$m`.
+macro_rules! just_with_metric {
+    ($map:ident, $id:ident, $m:ident, $f:expr) => {
+        if $id & (1 << $crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = $crate::factory::__jog_metric_maps::$map
+                .read()
+                .expect("Read lock for dynamic metric map was poisoned");
+            match map.get(&$id.into()) {
+                Some($m) => $f,
+                None => panic!("No (dynamic) metric for id {}", $id),
+            }
+        } else {
+            match $crate::metrics::__glean_metric_maps::$map.get(&$id.into()) {
+                Some($m) => $f,
+                None => panic!("No metric for id {}", $id),
+            }
+        }
+    };
+}
+
+/// Get a metric object by id from the corresponding map, then
+/// execute the provided closure with it.
+///
+/// Requires that the provided $map be of a type that can be labeled, since it
+/// assumes the presence of a same-named map in
+/// `metrics::_glean_metrics_map::submetric_maps`.
+///
+/// # Arguments
+///
+/// * `$map` - The name of the hash map within `metrics::__glean_metric_maps`
+///            and `metrics::__glean_metric_maps::submetric_maps` as generated
+///            by glean_parser.
+/// * `$id`  - The ID of the metric to get.
+/// * `$m`   - The identifier to use for the retrieved metric.
+///            The expression `$f` can use this identifier.
+/// * `$f`   - The expression to execute with the retrieved metric `$m`.
+macro_rules! maybe_labeled_with_metric {
+    ($map:ident, $id:ident, $m:ident, $f:expr) => {
+        if $id & (1 << $crate::metrics::__glean_metric_maps::submetric_maps::SUBMETRIC_BIT) > 0 {
+            let map = $crate::metrics::__glean_metric_maps::submetric_maps::$map
+                .read()
+                .expect("Read lock for labeled metric map was poisoned");
+            match map.get(&$id.into()) {
+                Some($m) => $f,
+                None => panic!("No submetric for id {}", $id),
+            }
+        } else {
+            just_with_metric!($map, $id, $m, $f)
+        }
+    };
+}
+
+/// Test whether a value is stored for the given metric.
+///
+/// # Arguments
+///
+/// * `$metric`  - The metric to test.
+/// * `$storage` - the storage name to look into.
+macro_rules! test_has {
+    ($metric:ident, $storage:ident) => {{
+        let storage = if $storage.is_empty() {
+            None
+        } else {
+            Some($storage.to_utf8())
+        };
+        $metric.test_get_value(storage.as_deref()).is_some()
+    }};
+}
+
+/// Get the currently stored value for the given metric.
+///
+/// # Arguments
+///
+/// * `$metric`  - The metric to test.
+/// * `$storage` - the storage name to look into.
+macro_rules! test_get {
+    ($metric:ident, $storage:ident) => {{
+        let storage = if $storage.is_empty() {
+            None
+        } else {
+            Some($storage.to_utf8())
+        };
+        $metric.test_get_value(storage.as_deref()).unwrap()
+    }};
+}
+
+/// Check the provided metric in the provided storage for errors.
+/// On finding one, return an error string.
+///
+/// # Arguments
+///
+/// * `$metric`  - The metric to test.
+macro_rules! test_get_errors {
+    ($metric:path) => {{
+        let error_types = [
+            glean::ErrorType::InvalidValue,
+            glean::ErrorType::InvalidLabel,
+            glean::ErrorType::InvalidState,
+            glean::ErrorType::InvalidOverflow,
+        ];
+        let mut error_str = None;
+        for &error_type in error_types.iter() {
+            let num_errors = $metric.test_get_num_recorded_errors(error_type);
+            if num_errors > 0 {
+                error_str = Some(format!(
+                    "Metric had {} error(s) of type {}!",
+                    num_errors,
+                    error_type.as_str()
+                ));
+                break;
+            }
+        }
+        error_str
+    }};
+}
+
+/// Get the submetric id for a given labeled metric and label.
+///
+/// # Arguments
+///
+/// * `$id`						- The id of the labeled metric.
+/// * `$label`				- The label of the submetric.
+/// * `$labeled_map`	- The name of the labeled metric's map for retrieval.
+/// * `$submetric_map`- The name of the submetrics' map for storage.
+/// * `$metric_type`  - The submetric's type (needed for an internal closure).
+macro_rules! labeled_submetric_get {
+    ($id:ident, $label:ident, $labeled_map:ident, $submetric_map:ident, $metric_type:ty) => {{
+        let tuple = ($id, $label.to_utf8().into());
+        {
+            let map = $crate::metrics::__glean_metric_maps::submetric_maps::LABELED_METRICS_TO_IDS
+                .read()
+                .expect("read lock of submetric ids was poisoned");
+            if let Some(submetric_id) = map.get(&tuple) {
+                return *submetric_id;
+            }
+        }
+
+        // Gotta actually create a new submetric with a new id.
+        let submetric_id =
+            $crate::metrics::__glean_metric_maps::submetric_maps::NEXT_LABELED_SUBMETRIC_ID
+                .fetch_add(1, Ordering::SeqCst);
+        {
+            with_metric!($labeled_map, $id, metric, {
+                let submetric = metric.get(&tuple.1);
+                let mut map = $crate::metrics::__glean_metric_maps::submetric_maps::$submetric_map
+                    .write()
+                    .expect("write lock of submetric map was poisoned");
+                map.insert(submetric_id.into(), submetric);
+            });
+        }
+
+        let mut map = $crate::metrics::__glean_metric_maps::submetric_maps::LABELED_METRICS_TO_IDS
+            .write()
+            .expect("write lock of submetric ids was poisoned");
+        map.insert(tuple, submetric_id);
+        submetric_id
+    }};
+}
diff --git a/toolkit/components/glean/api/src/ffi/memory_distribution.rs b/toolkit/components/glean/api/src/ffi/memory_distribution.rs
new file mode 100644
index 0000000000..cf09d3f8de
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/memory_distribution.rs
@@ -0,0 +1,64 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+use thin_vec::ThinVec;
+
+#[no_mangle]
+pub extern "C" fn fog_memory_distribution_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(
+        MEMORY_DISTRIBUTION_MAP,
+        id,
+        metric,
+        test_has!(metric, ping_name)
+    )
+}
+
+#[no_mangle]
+pub extern "C" fn fog_memory_distribution_test_get_value(
+    id: u32,
+    ping_name: &nsACString,
+    sum: &mut u64,
+    buckets: &mut ThinVec<u64>,
+    counts: &mut ThinVec<u64>,
+) {
+    let val = with_metric!(
+        MEMORY_DISTRIBUTION_MAP,
+        id,
+        metric,
+        test_get!(metric, ping_name)
+    );
+    *sum = val.sum as _;
+    for (&bucket, &count) in val.values.iter() {
+        buckets.push(bucket as _);
+        counts.push(count as _);
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn fog_memory_distribution_accumulate(id: u32, sample: u64) {
+    with_metric!(
+        MEMORY_DISTRIBUTION_MAP,
+        id,
+        metric,
+        metric.accumulate(sample)
+    );
+}
+
+#[no_mangle]
+pub extern "C" fn fog_memory_distribution_test_get_error(
+    id: u32,
+
+    error_str: &mut nsACString,
+) -> bool {
+    let err = with_metric!(
+        MEMORY_DISTRIBUTION_MAP,
+        id,
+        metric,
+        test_get_errors!(metric)
+    );
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/mod.rs b/toolkit/components/glean/api/src/ffi/mod.rs
new file mode 100644
index 0000000000..8f31d769c2
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/mod.rs
@@ -0,0 +1,27 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+#[macro_use]
+mod macros;
+
+mod boolean;
+mod counter;
+mod custom_distribution;
+mod datetime;
+mod denominator;
+mod event;
+mod labeled;
+mod memory_distribution;
+mod numerator;
+mod ping;
+mod quantity;
+mod rate;
+mod string;
+mod string_list;
+mod timespan;
+mod timing_distribution;
+mod url;
+mod uuid;
diff --git a/toolkit/components/glean/api/src/ffi/numerator.rs b/toolkit/components/glean/api/src/ffi/numerator.rs
new file mode 100644
index 0000000000..e679e426c4
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/numerator.rs
@@ -0,0 +1,35 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_numerator_add_to_numerator(id: u32, amount: i32) {
+    with_metric!(NUMERATOR_MAP, id, metric, metric.add_to_numerator(amount));
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_numerator_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(NUMERATOR_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_numerator_test_get_value(
+    id: u32,
+    ping_name: &nsACString,
+    num: &mut i32,
+    den: &mut i32,
+) {
+    let rate = with_metric!(NUMERATOR_MAP, id, metric, test_get!(metric, ping_name));
+    *num = rate.numerator;
+    *den = rate.denominator;
+}
+
+#[no_mangle]
+pub extern "C" fn fog_numerator_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(NUMERATOR_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/ping.rs b/toolkit/components/glean/api/src/ffi/ping.rs
new file mode 100644
index 0000000000..2834655a03
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/ping.rs
@@ -0,0 +1,18 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use crate::pings;
+use nsstring::nsACString;
+
+#[no_mangle]
+pub extern "C" fn fog_submit_ping_by_id(id: u32, reason: &nsACString) {
+    let reason = if reason.is_empty() {
+        None
+    } else {
+        Some(reason.to_utf8())
+    };
+    pings::submit_ping_by_id(id, reason.as_deref());
+}
diff --git a/toolkit/components/glean/api/src/ffi/quantity.rs b/toolkit/components/glean/api/src/ffi/quantity.rs
new file mode 100644
index 0000000000..7f94bcff27
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/quantity.rs
@@ -0,0 +1,28 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+
+#[no_mangle]
+pub extern "C" fn fog_quantity_set(id: u32, value: i64) {
+    with_metric!(QUANTITY_MAP, id, metric, metric.set(value));
+}
+
+#[no_mangle]
+pub extern "C" fn fog_quantity_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(QUANTITY_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_quantity_test_get_value(id: u32, ping_name: &nsACString) -> i64 {
+    with_metric!(QUANTITY_MAP, id, metric, test_get!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_quantity_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(QUANTITY_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/rate.rs b/toolkit/components/glean/api/src/ffi/rate.rs
new file mode 100644
index 0000000000..c14b33f3ea
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/rate.rs
@@ -0,0 +1,40 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_rate_add_to_numerator(id: u32, amount: i32) {
+    with_metric!(RATE_MAP, id, metric, metric.add_to_numerator(amount));
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_rate_add_to_denominator(id: u32, amount: i32) {
+    with_metric!(RATE_MAP, id, metric, metric.add_to_denominator(amount));
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_rate_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(RATE_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fog_rate_test_get_value(
+    id: u32,
+    ping_name: &nsACString,
+    num: &mut i32,
+    den: &mut i32,
+) {
+    let rate = with_metric!(RATE_MAP, id, metric, test_get!(metric, ping_name));
+    *num = rate.numerator;
+    *den = rate.denominator;
+}
+
+#[no_mangle]
+pub extern "C" fn fog_rate_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(RATE_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/string.rs b/toolkit/components/glean/api/src/ffi/string.rs
new file mode 100644
index 0000000000..fc28e03a38
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/string.rs
@@ -0,0 +1,33 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+
+#[no_mangle]
+pub extern "C" fn fog_string_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(STRING_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_string_test_get_value(
+    id: u32,
+    ping_name: &nsACString,
+    value: &mut nsACString,
+) {
+    let val = with_metric!(STRING_MAP, id, metric, test_get!(metric, ping_name));
+    value.assign(&val);
+}
+
+#[no_mangle]
+pub extern "C" fn fog_string_set(id: u32, value: &nsACString) {
+    with_metric!(STRING_MAP, id, metric, metric.set(value.to_utf8()));
+}
+
+#[no_mangle]
+pub extern "C" fn fog_string_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(STRING_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/string_list.rs b/toolkit/components/glean/api/src/ffi/string_list.rs
new file mode 100644
index 0000000000..42ebd9e445
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/string_list.rs
@@ -0,0 +1,42 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::{nsACString, nsCString};
+use thin_vec::ThinVec;
+
+#[no_mangle]
+pub extern "C" fn fog_string_list_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(STRING_LIST_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_string_list_test_get_value(
+    id: u32,
+    ping_name: &nsACString,
+    value: &mut ThinVec<nsCString>,
+) {
+    let val = with_metric!(STRING_LIST_MAP, id, metric, test_get!(metric, ping_name));
+    for v in val {
+        value.push(v.into());
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn fog_string_list_add(id: u32, value: &nsACString) {
+    with_metric!(STRING_LIST_MAP, id, metric, metric.add(value.to_utf8()));
+}
+
+#[no_mangle]
+pub extern "C" fn fog_string_list_set(id: u32, value: &ThinVec<nsCString>) {
+    let value = value.iter().map(|s| s.to_utf8().into()).collect();
+    with_metric!(STRING_LIST_MAP, id, metric, metric.set(value));
+}
+
+#[no_mangle]
+pub extern "C" fn fog_string_list_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(STRING_LIST_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/timespan.rs b/toolkit/components/glean/api/src/ffi/timespan.rs
new file mode 100644
index 0000000000..5de411ffab
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/timespan.rs
@@ -0,0 +1,48 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+
+#[no_mangle]
+pub extern "C" fn fog_timespan_start(id: u32) {
+    with_metric!(TIMESPAN_MAP, id, metric, metric.start());
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timespan_stop(id: u32) {
+    with_metric!(TIMESPAN_MAP, id, metric, metric.stop());
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timespan_cancel(id: u32) {
+    with_metric!(TIMESPAN_MAP, id, metric, metric.cancel());
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timespan_set_raw(id: u32, duration: u32) {
+    with_metric!(
+        TIMESPAN_MAP,
+        id,
+        metric,
+        metric.set_raw_unitless(duration.into())
+    );
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timespan_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(TIMESPAN_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timespan_test_get_value(id: u32, ping_name: &nsACString) -> u64 {
+    with_metric!(TIMESPAN_MAP, id, metric, test_get!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timespan_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(TIMESPAN_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/timing_distribution.rs b/toolkit/components/glean/api/src/ffi/timing_distribution.rs
new file mode 100644
index 0000000000..4ac5d03986
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/timing_distribution.rs
@@ -0,0 +1,90 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+use std::time::Duration;
+use thin_vec::ThinVec;
+
+#[no_mangle]
+pub extern "C" fn fog_timing_distribution_start(id: u32) -> u64 {
+    with_metric!(TIMING_DISTRIBUTION_MAP, id, metric, metric.start().id)
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timing_distribution_stop_and_accumulate(id: u32, timing_id: u64) {
+    with_metric!(
+        TIMING_DISTRIBUTION_MAP,
+        id,
+        metric,
+        metric.stop_and_accumulate(timing_id.into())
+    );
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timing_distribution_accumulate_raw_nanos(id: u32, sample: u64) {
+    with_metric!(
+        TIMING_DISTRIBUTION_MAP,
+        id,
+        metric,
+        metric.accumulate_raw_duration(Duration::from_nanos(sample))
+    );
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timing_distribution_cancel(id: u32, timing_id: u64) {
+    with_metric!(
+        TIMING_DISTRIBUTION_MAP,
+        id,
+        metric,
+        metric.cancel(timing_id.into())
+    );
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timing_distribution_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(
+        TIMING_DISTRIBUTION_MAP,
+        id,
+        metric,
+        test_has!(metric, ping_name)
+    )
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timing_distribution_test_get_value(
+    id: u32,
+    ping_name: &nsACString,
+    sum: &mut u64,
+    buckets: &mut ThinVec<u64>,
+    counts: &mut ThinVec<u64>,
+) {
+    let val = with_metric!(
+        TIMING_DISTRIBUTION_MAP,
+        id,
+        metric,
+        test_get!(metric, ping_name)
+    );
+    *sum = val.sum as _;
+    for (&bucket, &count) in val.values.iter() {
+        buckets.push(bucket as _);
+        counts.push(count as _);
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn fog_timing_distribution_test_get_error(
+    id: u32,
+
+    error_str: &mut nsACString,
+) -> bool {
+    let err = with_metric!(
+        TIMING_DISTRIBUTION_MAP,
+        id,
+        metric,
+        test_get_errors!(metric)
+    );
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/url.rs b/toolkit/components/glean/api/src/ffi/url.rs
new file mode 100644
index 0000000000..b94915f7cf
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/url.rs
@@ -0,0 +1,29 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+
+#[no_mangle]
+pub extern "C" fn fog_url_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(URL_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_url_test_get_value(id: u32, ping_name: &nsACString, value: &mut nsACString) {
+    let val = with_metric!(URL_MAP, id, metric, test_get!(metric, ping_name));
+    value.assign(&val);
+}
+
+#[no_mangle]
+pub extern "C" fn fog_url_set(id: u32, value: &nsACString) {
+    with_metric!(URL_MAP, id, metric, metric.set(value.to_utf8()));
+}
+
+#[no_mangle]
+pub extern "C" fn fog_url_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(URL_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ffi/uuid.rs b/toolkit/components/glean/api/src/ffi/uuid.rs
new file mode 100644
index 0000000000..e3101863ea
--- /dev/null
+++ b/toolkit/components/glean/api/src/ffi/uuid.rs
@@ -0,0 +1,37 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#![cfg(feature = "with_gecko")]
+
+use nsstring::nsACString;
+use uuid::Uuid;
+
+#[no_mangle]
+pub extern "C" fn fog_uuid_test_has_value(id: u32, ping_name: &nsACString) -> bool {
+    with_metric!(UUID_MAP, id, metric, test_has!(metric, ping_name))
+}
+
+#[no_mangle]
+pub extern "C" fn fog_uuid_test_get_value(id: u32, ping_name: &nsACString, value: &mut nsACString) {
+    let uuid = with_metric!(UUID_MAP, id, metric, test_get!(metric, ping_name)).to_string();
+    value.assign(&uuid);
+}
+
+#[no_mangle]
+pub extern "C" fn fog_uuid_set(id: u32, value: &nsACString) {
+    if let Ok(uuid) = Uuid::parse_str(&value.to_utf8()) {
+        with_metric!(UUID_MAP, id, metric, metric.set(uuid));
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn fog_uuid_generate_and_set(id: u32) {
+    with_metric!(UUID_MAP, id, metric, metric.generate_and_set());
+}
+
+#[no_mangle]
+pub extern "C" fn fog_uuid_test_get_error(id: u32, error_str: &mut nsACString) -> bool {
+    let err = with_metric!(UUID_MAP, id, metric, test_get_errors!(metric));
+    err.map(|err_str| error_str.assign(&err_str)).is_some()
+}
diff --git a/toolkit/components/glean/api/src/ipc.rs b/toolkit/components/glean/api/src/ipc.rs
new file mode 100644
index 0000000000..ac5653d9e6
--- /dev/null
+++ b/toolkit/components/glean/api/src/ipc.rs
@@ -0,0 +1,349 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! IPC Implementation, Rust part
+
+use crate::private::MetricId;
+use once_cell::sync::Lazy;
+use serde::{Deserialize, Serialize};
+use std::collections::HashMap;
+#[cfg(not(feature = "with_gecko"))]
+use std::sync::atomic::AtomicBool;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Mutex;
+#[cfg(feature = "with_gecko")]
+use {std::convert::TryInto, std::sync::atomic::AtomicU32, xpcom::interfaces::nsIXULRuntime};
+
+use super::metrics::__glean_metric_maps;
+
+type EventRecord = (u64, HashMap<String, String>);
+
+/// Contains all the information necessary to update the metrics on the main
+/// process.
+#[derive(Debug, Default, Deserialize, Serialize)]
+pub struct IPCPayload {
+    pub counters: HashMap<MetricId, i32>,
+    pub custom_samples: HashMap<MetricId, Vec<i64>>,
+    pub denominators: HashMap<MetricId, i32>,
+    pub events: HashMap<MetricId, Vec<EventRecord>>,
+    pub labeled_counters: HashMap<MetricId, HashMap<String, i32>>,
+    pub memory_samples: HashMap<MetricId, Vec<u64>>,
+    pub numerators: HashMap<MetricId, i32>,
+    pub rates: HashMap<MetricId, (i32, i32)>,
+    pub string_lists: HashMap<MetricId, Vec<String>>,
+    pub timing_samples: HashMap<MetricId, Vec<u64>>,
+}
+
+/// Global singleton: pending IPC payload.
+static PAYLOAD: Lazy<Mutex<IPCPayload>> = Lazy::new(|| Mutex::new(IPCPayload::default()));
+/// Global singleton: number of times the IPC payload was accessed.
+static PAYLOAD_ACCESS_COUNT: AtomicUsize = AtomicUsize::new(0);
+
+// The maximum size of an IPC message in Firefox Desktop is 256MB.
+// (See IPC::Channel::kMaximumMessageSize)
+// In `IPCPayload` the largest size can be attained in the fewest accesses via events.
+// Each event could be its own u64 id, u64 timestamp, and HashMap of ten i32 to ten 100-byte strings.
+// That's 1056B = 8 + 8 + 10(4 + 100)
+// In 256MB we can fit 254200 or so of these, not counting overhead.
+// Let's take a conservative estimate of 100000 to
+// 0) Account for overhead
+// 1) Not be greedy
+// 2) Allow time for the dispatch to main thread which will actually perform the flush
+// "Why the -1?" Because fetch_add returns the value before the addition.
+const PAYLOAD_ACCESS_WATERMARK: usize = 100000 - 1;
+
+pub fn with_ipc_payload<F, R>(f: F) -> R
+where
+    F: FnOnce(&mut IPCPayload) -> R,
+{
+    if PAYLOAD_ACCESS_COUNT.fetch_add(1, Ordering::SeqCst) > PAYLOAD_ACCESS_WATERMARK {
+        // We reset this before the actual flush to keep all the logic together.
+        // Otherwise the count reset would need to happen down in take_buf().
+        // This may overcount (resulting in undersized payloads) which is okay.
+        PAYLOAD_ACCESS_COUNT.store(0, Ordering::SeqCst);
+        handle_payload_filling();
+    }
+    let mut payload = PAYLOAD.lock().unwrap();
+    f(&mut payload)
+}
+
+/// Do we need IPC?
+///
+/// Thread-safe.
+#[cfg(feature = "with_gecko")]
+static PROCESS_TYPE: Lazy<AtomicU32> = Lazy::new(|| {
+    extern "C" {
+        fn FOG_GetProcessType() -> i32;
+    }
+    // SAFETY NOTE: Safe because it returns a primitive by value.
+    let process_type = unsafe { FOG_GetProcessType() };
+    // It's impossible for i32 to overflow u32, but maybe someone got clever
+    // and introduced a negative process type constant. Default to parent.
+    let process_type = process_type
+        .try_into()
+        .unwrap_or(nsIXULRuntime::PROCESS_TYPE_DEFAULT);
+    // We don't have process-specific init locations outside of the main
+    // process, so we introduce this side-effect to a global static init.
+    // This is the absolute first time we decide which process type we're
+    // treating this process as, so this is the earliest we can do this.
+    register_process_shutdown(process_type);
+    AtomicU32::new(process_type)
+});
+
+#[cfg(feature = "with_gecko")]
+pub fn need_ipc() -> bool {
+    PROCESS_TYPE.load(Ordering::Relaxed) != nsIXULRuntime::PROCESS_TYPE_DEFAULT
+}
+
+/// The first time we're used in a process,
+/// we'll need to start thinking about cleanup.
+///
+/// Please only call once per process.
+/// Multiple calls may register multiple handlers.
+#[cfg(feature = "with_gecko")]
+fn register_process_shutdown(process_type: u32) {
+    match process_type {
+        nsIXULRuntime::PROCESS_TYPE_DEFAULT => {
+            // Parent process shutdown is handled by the FOG XPCOM Singleton.
+        }
+        nsIXULRuntime::PROCESS_TYPE_CONTENT => {
+            // Content child shutdown is in C++ for access to RunOnShutdown().
+            extern "C" {
+                fn FOG_RegisterContentChildShutdown();
+            }
+            unsafe {
+                FOG_RegisterContentChildShutdown();
+            };
+        }
+        nsIXULRuntime::PROCESS_TYPE_GMPLUGIN => {
+            // GMP process shutdown is handled in GMPChild::ActorDestroy.
+        }
+        nsIXULRuntime::PROCESS_TYPE_GPU => {
+            // GPU process shutdown is handled in GPUParent::ActorDestroy.
+        }
+        nsIXULRuntime::PROCESS_TYPE_RDD => {
+            // RDD process shutdown is handled in RDDParent::ActorDestroy.
+        }
+        nsIXULRuntime::PROCESS_TYPE_SOCKET => {
+            // Socket process shutdown is handled in SocketProcessChild::ActorDestroy.
+        }
+        nsIXULRuntime::PROCESS_TYPE_UTILITY => {
+            // Utility process shutdown is handled in UtilityProcessChild::ActorDestroy.
+        }
+        _ => {
+            // We don't yet support other process types.
+            log::error!("Process type {} tried to use FOG, but isn't supported! (Process type constants are in nsIXULRuntime.rs)", process_type);
+        }
+    }
+}
+
+/// An RAII that, on drop, restores the value used to determine whether FOG
+/// needs IPC. Used in tests.
+/// ```rust,ignore
+/// #[test]
+/// fn test_need_ipc_raii() {
+///     assert!(false == ipc::need_ipc());
+///     {
+///         let _raii = ipc::test_set_need_ipc(true);
+///         assert!(ipc::need_ipc());
+///     }
+///     assert!(false == ipc::need_ipc());
+/// }
+/// ```
+#[cfg(not(feature = "with_gecko"))]
+pub struct TestNeedIpcRAII {
+    prev_value: bool,
+}
+
+#[cfg(not(feature = "with_gecko"))]
+impl Drop for TestNeedIpcRAII {
+    fn drop(&mut self) {
+        TEST_NEED_IPC.store(self.prev_value, Ordering::Relaxed);
+    }
+}
+
+#[cfg(not(feature = "with_gecko"))]
+static TEST_NEED_IPC: AtomicBool = AtomicBool::new(false);
+
+/// Test-only API for telling FOG to use IPC mechanisms even if the test has
+/// only the one process. See TestNeedIpcRAII for an example.
+#[cfg(not(feature = "with_gecko"))]
+pub fn test_set_need_ipc(need_ipc: bool) -> TestNeedIpcRAII {
+    TestNeedIpcRAII {
+        prev_value: TEST_NEED_IPC.swap(need_ipc, Ordering::Relaxed),
+    }
+}
+
+#[cfg(not(feature = "with_gecko"))]
+pub fn need_ipc() -> bool {
+    TEST_NEED_IPC.load(Ordering::Relaxed)
+}
+
+pub fn take_buf() -> Option<Vec<u8>> {
+    with_ipc_payload(move |payload| {
+        let buf = bincode::serialize(&payload).ok();
+        *payload = IPCPayload {
+            ..Default::default()
+        };
+        buf
+    })
+}
+
+#[cfg(not(feature = "with_gecko"))]
+fn handle_payload_filling() {
+    // Space intentionally left blank.
+    // Without Gecko IPC to drain the buffer, there's nothing we can do.
+}
+
+#[cfg(feature = "with_gecko")]
+fn handle_payload_filling() {
+    extern "C" {
+        fn FOG_IPCPayloadFull();
+    }
+    // SAFETY NOTE: Safe because it doesn't take or return values.
+    unsafe { FOG_IPCPayloadFull() };
+}
+
+// Reason: We instrument the error counts,
+// but don't need more detailed error information at the moment.
+#[allow(clippy::result_unit_err)]
+pub fn replay_from_buf(buf: &[u8]) -> Result<(), ()> {
+    // TODO: Instrument failures to find metrics by id.
+    let ipc_payload: IPCPayload = bincode::deserialize(buf).map_err(|_| ())?;
+    for (id, value) in ipc_payload.counters.into_iter() {
+        if id.0 & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::COUNTER_MAP
+                .read()
+                .expect("Read lock for dynamic counter map was poisoned");
+            if let Some(metric) = map.get(&id) {
+                metric.add(value);
+            }
+        } else if let Some(metric) = __glean_metric_maps::COUNTER_MAP.get(&id) {
+            metric.add(value);
+        }
+    }
+    for (id, samples) in ipc_payload.custom_samples.into_iter() {
+        if id.0 & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::CUSTOM_DISTRIBUTION_MAP
+                .read()
+                .expect("Read lock for dynamic custom distribution map was poisoned");
+            if let Some(metric) = map.get(&id) {
+                metric.accumulate_samples_signed(samples);
+            }
+        } else if let Some(metric) = __glean_metric_maps::CUSTOM_DISTRIBUTION_MAP.get(&id) {
+            metric.accumulate_samples_signed(samples);
+        }
+    }
+    for (id, value) in ipc_payload.denominators.into_iter() {
+        if id.0 & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::DENOMINATOR_MAP
+                .read()
+                .expect("Read lock for dynamic denominator map was poisoned");
+            if let Some(metric) = map.get(&id) {
+                metric.add(value);
+            }
+        } else if let Some(metric) = __glean_metric_maps::DENOMINATOR_MAP.get(&id) {
+            metric.add(value);
+        }
+    }
+    for (id, records) in ipc_payload.events.into_iter() {
+        if id.0 & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::EVENT_MAP
+                .read()
+                .expect("Read lock for dynamic event map was poisoned");
+            if let Some(metric) = map.get(&id) {
+                for (timestamp, extra) in records.into_iter() {
+                    metric.record_with_time(timestamp, extra);
+                }
+            }
+        } else {
+            for (timestamp, extra) in records.into_iter() {
+                let _ = __glean_metric_maps::record_event_by_id_with_time(id, timestamp, extra);
+            }
+        }
+    }
+    for (id, labeled_counts) in ipc_payload.labeled_counters.into_iter() {
+        if id.0 & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::LABELED_COUNTER_MAP
+                .read()
+                .expect("Read lock for dynamic labeled counter map was poisoned");
+            if let Some(metric) = map.get(&id) {
+                for (label, count) in labeled_counts.into_iter() {
+                    metric.get(&label).add(count);
+                }
+            }
+        } else if let Some(metric) = __glean_metric_maps::LABELED_COUNTER_MAP.get(&id) {
+            for (label, count) in labeled_counts.into_iter() {
+                metric.get(&label).add(count);
+            }
+        }
+    }
+    for (id, samples) in ipc_payload.memory_samples.into_iter() {
+        if id.0 & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::MEMORY_DISTRIBUTION_MAP
+                .read()
+                .expect("Read lock for dynamic memory dist map was poisoned");
+            if let Some(metric) = map.get(&id) {
+                samples
+                    .into_iter()
+                    .for_each(|sample| metric.accumulate(sample));
+            }
+        } else if let Some(metric) = __glean_metric_maps::MEMORY_DISTRIBUTION_MAP.get(&id) {
+            samples
+                .into_iter()
+                .for_each(|sample| metric.accumulate(sample));
+        }
+    }
+    for (id, value) in ipc_payload.numerators.into_iter() {
+        if id.0 & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::NUMERATOR_MAP
+                .read()
+                .expect("Read lock for dynamic numerator map was poisoned");
+            if let Some(metric) = map.get(&id) {
+                metric.add_to_numerator(value);
+            }
+        } else if let Some(metric) = __glean_metric_maps::NUMERATOR_MAP.get(&id) {
+            metric.add_to_numerator(value);
+        }
+    }
+    for (id, (n, d)) in ipc_payload.rates.into_iter() {
+        if id.0 & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::RATE_MAP
+                .read()
+                .expect("Read lock for dynamic rate map was poisoned");
+            if let Some(metric) = map.get(&id) {
+                metric.add_to_numerator(n);
+                metric.add_to_denominator(d);
+            }
+        } else if let Some(metric) = __glean_metric_maps::RATE_MAP.get(&id) {
+            metric.add_to_numerator(n);
+            metric.add_to_denominator(d);
+        }
+    }
+    for (id, strings) in ipc_payload.string_lists.into_iter() {
+        if id.0 & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::STRING_LIST_MAP
+                .read()
+                .expect("Read lock for dynamic string list map was poisoned");
+            if let Some(metric) = map.get(&id) {
+                strings.iter().for_each(|s| metric.add(s));
+            }
+        } else if let Some(metric) = __glean_metric_maps::STRING_LIST_MAP.get(&id) {
+            strings.iter().for_each(|s| metric.add(s));
+        }
+    }
+    for (id, samples) in ipc_payload.timing_samples.into_iter() {
+        if id.0 & (1 << crate::factory::DYNAMIC_METRIC_BIT) > 0 {
+            let map = crate::factory::__jog_metric_maps::TIMING_DISTRIBUTION_MAP
+                .read()
+                .expect("Read lock for dynamic timing distribution map was poisoned");
+            if let Some(metric) = map.get(&id) {
+                metric.accumulate_raw_samples_nanos(samples);
+            }
+        } else if let Some(metric) = __glean_metric_maps::TIMING_DISTRIBUTION_MAP.get(&id) {
+            metric.accumulate_raw_samples_nanos(samples);
+        }
+    }
+    Ok(())
+}
diff --git a/toolkit/components/glean/api/src/lib.rs b/toolkit/components/glean/api/src/lib.rs
new file mode 100644
index 0000000000..2f51b94917
--- /dev/null
+++ b/toolkit/components/glean/api/src/lib.rs
@@ -0,0 +1,27 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! The public FOG APIs, for Rust consumers.
+
+// Re-exporting for later use in generated code.
+pub extern crate chrono;
+pub extern crate once_cell;
+pub extern crate uuid;
+
+// Re-exporting for use in user tests.
+pub use private::{DistributionData, ErrorType, RecordedEvent};
+
+// Must appear before `metrics` or its use of `ffi`'s macros will fail.
+#[macro_use]
+mod ffi;
+
+pub mod factory;
+pub mod metrics;
+pub mod pings;
+pub mod private;
+
+pub mod ipc;
+
+#[cfg(test)]
+mod common_test;
diff --git a/toolkit/components/glean/api/src/metrics.rs b/toolkit/components/glean/api/src/metrics.rs
new file mode 100644
index 0000000000..196edee293
--- /dev/null
+++ b/toolkit/components/glean/api/src/metrics.rs
@@ -0,0 +1,24 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! This file contains the Generated Glean Metrics API
+//!
+//! The contents of this module are generated by
+//! `toolkit/components/glean/build_scripts/glean_parser_ext/run_glean_parser.py`, from
+//! metrics files identified in 'toolkit/components/glean/metrics_index.py`.
+//!
+//! When running clippy, the contents are not generated.
+//! There is a clippy-only section at the bottom that may need to be hand-edited
+//! to fix linter errors.
+
+include!(mozbuild::objdir_path!(
+    "toolkit/components/glean/api/src/metrics.rs"
+));
+
+use crate::private::{EventMetric, ExtraKeys};
+
+/// Helper to get the number of allowed extra keys for a given event metric.
+fn extra_keys_len<K: ExtraKeys>(_event: &EventMetric<K>) -> usize {
+    K::ALLOWED_KEYS.len()
+}
diff --git a/toolkit/components/glean/api/src/pings.rs b/toolkit/components/glean/api/src/pings.rs
new file mode 100644
index 0000000000..f1d0332695
--- /dev/null
+++ b/toolkit/components/glean/api/src/pings.rs
@@ -0,0 +1,13 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! This file contains the Generated Glean Metrics API (Ping portion)
+//!
+//! The contents of this module are generated by
+//! `toolkit/components/glean/build_scripts/glean_parser_ext/run_glean_parser.py`, from
+//! 'toolkit/components/glean/pings.yaml`.
+
+include!(mozbuild::objdir_path!(
+    "toolkit/components/glean/api/src/pings.rs"
+));
diff --git a/toolkit/components/glean/api/src/private/boolean.rs b/toolkit/components/glean/api/src/private/boolean.rs
new file mode 100644
index 0000000000..3869b31f3b
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/boolean.rs
@@ -0,0 +1,152 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+use std::sync::Arc;
+
+use glean::traits::Boolean;
+
+use super::CommonMetricData;
+
+use crate::ipc::need_ipc;
+use crate::private::MetricId;
+
+/// A boolean metric.
+///
+/// Records a simple true or false value.
+#[derive(Clone)]
+pub enum BooleanMetric {
+    Parent(Arc<glean::private::BooleanMetric>),
+    Child(BooleanMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct BooleanMetricIpc;
+
+impl BooleanMetric {
+    /// Create a new boolean metric.
+    pub fn new(_id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            BooleanMetric::Child(BooleanMetricIpc)
+        } else {
+            BooleanMetric::Parent(Arc::new(glean::private::BooleanMetric::new(meta)))
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            BooleanMetric::Parent(_) => BooleanMetric::Child(BooleanMetricIpc),
+            BooleanMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl Boolean for BooleanMetric {
+    /// Set to the specified boolean value.
+    ///
+    /// ## Arguments
+    ///
+    /// * `value` - the value to set.
+    pub fn set(&self, value: bool) {
+        match self {
+            BooleanMetric::Parent(p) => {
+                p.set(value);
+            }
+            BooleanMetric::Child(_) => {
+                log::error!("Unable to set boolean metric in non-parent process. Ignoring.");
+                // TODO: Record an error.
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Get the currently stored value as a boolean.
+    /// This doesn't clear the stored value.
+    ///
+    /// ## Arguments
+    ///
+    /// * `ping_name` - the storage name to look into.
+    ///
+    /// ## Return value
+    ///
+    /// Returns the stored value or `None` if nothing stored.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(&self, ping_name: S) -> Option<bool> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            BooleanMetric::Parent(p) => p.test_get_value(ping_name),
+            BooleanMetric::Child(_) => {
+                panic!("Cannot get test value for boolean metric in non-parent process!",)
+            }
+        }
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the number of recorded errors for the given metric and error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors reported.
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            BooleanMetric::Parent(p) => p.test_get_num_recorded_errors(error),
+            BooleanMetric::Child(_) => panic!(
+                "Cannot get the number of recorded errors for boolean metric in non-parent process!"
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_boolean_value() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_bool;
+        metric.set(true);
+
+        assert!(metric.test_get_value("store1").unwrap());
+    }
+
+    #[test]
+    fn boolean_ipc() {
+        // BooleanMetric doesn't support IPC.
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_bool;
+
+        parent_metric.set(false);
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            // scope for need_ipc RAII
+            let _raii = ipc::test_set_need_ipc(true);
+
+            // Instrumentation calls do not panic.
+            child_metric.set(true);
+
+            // (They also shouldn't do anything,
+            // but that's not something we can inspect in this test)
+        }
+
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert!(
+            false == parent_metric.test_get_value("store1").unwrap(),
+            "Boolean metrics should only work in the parent process"
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/counter.rs b/toolkit/components/glean/api/src/private/counter.rs
new file mode 100644
index 0000000000..7e1498f70f
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/counter.rs
@@ -0,0 +1,182 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+use std::sync::Arc;
+
+use glean::traits::Counter;
+
+use super::{CommonMetricData, MetricId};
+use crate::ipc::{need_ipc, with_ipc_payload};
+
+/// A counter metric.
+///
+/// Used to count things.
+/// The value can only be incremented, not decremented.
+#[derive(Clone)]
+pub enum CounterMetric {
+    Parent {
+        /// The metric's ID.
+        ///
+        /// **TEST-ONLY** - Do not use unless gated with `#[cfg(test)]`.
+        id: MetricId,
+        inner: Arc<glean::private::CounterMetric>,
+    },
+    Child(CounterMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct CounterMetricIpc(MetricId);
+
+impl CounterMetric {
+    /// Create a new counter metric.
+    pub fn new(id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            CounterMetric::Child(CounterMetricIpc(id))
+        } else {
+            let inner = Arc::new(glean::private::CounterMetric::new(meta));
+            CounterMetric::Parent { id, inner }
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn metric_id(&self) -> MetricId {
+        match self {
+            CounterMetric::Parent { id, .. } => *id,
+            CounterMetric::Child(c) => c.0,
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            CounterMetric::Parent { id, .. } => CounterMetric::Child(CounterMetricIpc(*id)),
+            CounterMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl Counter for CounterMetric {
+    /// Increase the counter by `amount`.
+    ///
+    /// ## Arguments
+    ///
+    /// * `amount` - The amount to increase by. Should be positive.
+    ///
+    /// ## Notes
+    ///
+    /// Logs an error if the `amount` is 0 or negative.
+    pub fn add(&self, amount: i32) {
+        match self {
+            CounterMetric::Parent { inner, .. } => {
+                inner.add(amount);
+            }
+            CounterMetric::Child(c) => {
+                with_ipc_payload(move |payload| {
+                    if let Some(v) = payload.counters.get_mut(&c.0) {
+                        *v += amount;
+                    } else {
+                        payload.counters.insert(c.0, amount);
+                    }
+                });
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Get the currently stored value as an integer.
+    /// This doesn't clear the stored value.
+    ///
+    /// ## Arguments
+    ///
+    /// * `ping_name` - the storage name to look into.
+    ///
+    /// ## Return value
+    ///
+    /// Returns the stored value or `None` if nothing stored.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(&self, ping_name: S) -> Option<i32> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            CounterMetric::Parent { inner, .. } => inner.test_get_value(ping_name),
+            CounterMetric::Child(c) => {
+                panic!("Cannot get test value for {:?} in non-parent process!", c.0)
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Gets the number of recorded errors for the given metric and error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors reported.
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            CounterMetric::Parent { inner, .. } => inner.test_get_num_recorded_errors(error),
+            CounterMetric::Child(c) => panic!(
+                "Cannot get the number of recorded errors for {:?} in non-parent process!",
+                c.0
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_counter_value_parent() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_counter;
+        metric.add(1);
+
+        assert_eq!(1, metric.test_get_value("store1").unwrap());
+    }
+
+    #[test]
+    fn sets_counter_value_child() {
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_counter;
+        parent_metric.add(3);
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            // scope for need_ipc RAII
+            let _raii = ipc::test_set_need_ipc(true);
+            let metric_id = child_metric.metric_id();
+
+            child_metric.add(42);
+
+            ipc::with_ipc_payload(move |payload| {
+                assert!(
+                    42 == *payload.counters.get(&metric_id).unwrap(),
+                    "Stored the correct value in the ipc payload"
+                );
+            });
+        }
+
+        assert!(
+            false == ipc::need_ipc(),
+            "RAII dropped, should not need ipc any more"
+        );
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert!(
+            45 == parent_metric.test_get_value("store1").unwrap(),
+            "Values from the 'processes' should be summed"
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/custom_distribution.rs b/toolkit/components/glean/api/src/private/custom_distribution.rs
new file mode 100644
index 0000000000..2114430898
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/custom_distribution.rs
@@ -0,0 +1,171 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use super::{CommonMetricData, MetricId};
+use glean::{DistributionData, ErrorType, HistogramType};
+
+use crate::ipc::{need_ipc, with_ipc_payload};
+use glean::traits::CustomDistribution;
+
+/// A custom distribution metric.
+///
+/// Custom distributions are used to record the distribution of arbitrary values.
+pub enum CustomDistributionMetric {
+    Parent {
+        /// The metric's ID.
+        ///
+        /// **TEST-ONLY** - Do not use unless gated with `#[cfg(test)]`.
+        id: MetricId,
+        inner: glean::private::CustomDistributionMetric,
+    },
+    Child(CustomDistributionMetricIpc),
+}
+#[derive(Debug)]
+pub struct CustomDistributionMetricIpc(MetricId);
+
+impl CustomDistributionMetric {
+    /// Create a new timing distribution metric.
+    pub fn new(
+        id: MetricId,
+        meta: CommonMetricData,
+        range_min: u64,
+        range_max: u64,
+        bucket_count: u64,
+        histogram_type: HistogramType,
+    ) -> Self {
+        if need_ipc() {
+            CustomDistributionMetric::Child(CustomDistributionMetricIpc(id))
+        } else {
+            debug_assert!(
+                range_min <= i64::MAX as u64,
+                "sensible limits enforced by glean_parser"
+            );
+            debug_assert!(
+                range_max <= i64::MAX as u64,
+                "sensible limits enforced by glean_parser"
+            );
+            debug_assert!(
+                bucket_count <= i64::MAX as u64,
+                "sensible limits enforced by glean_parser"
+            );
+            let inner = glean::private::CustomDistributionMetric::new(
+                meta,
+                range_min as i64,
+                range_max as i64,
+                bucket_count as i64,
+                histogram_type,
+            );
+            CustomDistributionMetric::Parent { id, inner }
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            CustomDistributionMetric::Parent { id, .. } => {
+                CustomDistributionMetric::Child(CustomDistributionMetricIpc(*id))
+            }
+            CustomDistributionMetric::Child(_) => {
+                panic!("Can't get a child metric from a child metric")
+            }
+        }
+    }
+}
+
+#[inherent]
+impl CustomDistribution for CustomDistributionMetric {
+    pub fn accumulate_samples_signed(&self, samples: Vec<i64>) {
+        match self {
+            CustomDistributionMetric::Parent { inner, .. } => inner.accumulate_samples(samples),
+            CustomDistributionMetric::Child(c) => {
+                with_ipc_payload(move |payload| {
+                    if let Some(v) = payload.custom_samples.get_mut(&c.0) {
+                        v.extend(samples);
+                    } else {
+                        payload.custom_samples.insert(c.0, samples);
+                    }
+                });
+            }
+        }
+    }
+
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(
+        &self,
+        ping_name: S,
+    ) -> Option<DistributionData> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            CustomDistributionMetric::Parent { inner, .. } => inner.test_get_value(ping_name),
+            CustomDistributionMetric::Child(c) => {
+                panic!("Cannot get test value for {:?} in non-parent process!", c)
+            }
+        }
+    }
+
+    pub fn test_get_num_recorded_errors(&self, error: ErrorType) -> i32 {
+        match self {
+            CustomDistributionMetric::Parent { inner, .. } => {
+                inner.test_get_num_recorded_errors(error)
+            }
+            CustomDistributionMetric::Child(c) => panic!(
+                "Cannot get number of recorded errors for {:?} in non-parent process!",
+                c
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn smoke_test_custom_distribution() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_custom_dist;
+
+        metric.accumulate_samples_signed(vec![1, 2, 3]);
+
+        assert!(metric.test_get_value("store1").is_some());
+    }
+
+    #[test]
+    fn custom_distribution_child() {
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_custom_dist;
+        parent_metric.accumulate_samples_signed(vec![1, 268435458]);
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            // scope for need_ipc RAII
+            let _raii = ipc::test_set_need_ipc(true);
+
+            child_metric.accumulate_samples_signed(vec![4, 268435460]);
+        }
+
+        let buf = ipc::take_buf().unwrap();
+        assert!(buf.len() > 0);
+        assert!(ipc::replay_from_buf(&buf).is_ok());
+
+        let data = parent_metric
+            .test_get_value("store1")
+            .expect("should have some data");
+
+        assert_eq!(2, data.values[&1], "Low bucket has 2 values");
+        assert_eq!(
+            2, data.values[&268435456],
+            "Next higher bucket has 2 values"
+        );
+        assert_eq!(
+            1 + 4 + 268435458 + 268435460,
+            data.sum,
+            "Sum of all recorded values"
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/datetime.rs b/toolkit/components/glean/api/src/private/datetime.rs
new file mode 100644
index 0000000000..9892ccf90c
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/datetime.rs
@@ -0,0 +1,238 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use super::{CommonMetricData, MetricId};
+
+use super::TimeUnit;
+use crate::ipc::need_ipc;
+use chrono::{FixedOffset, TimeZone};
+use glean::traits::Datetime;
+
+/// A datetime metric of a certain resolution.
+///
+/// Datetimes are used to make record when something happened according to the
+/// client's clock.
+#[derive(Clone)]
+pub enum DatetimeMetric {
+    Parent(glean::private::DatetimeMetric),
+    Child(DatetimeMetricIpc),
+}
+#[derive(Debug, Clone)]
+pub struct DatetimeMetricIpc;
+
+impl DatetimeMetric {
+    /// Create a new datetime metric.
+    pub fn new(_id: MetricId, meta: CommonMetricData, time_unit: TimeUnit) -> Self {
+        if need_ipc() {
+            DatetimeMetric::Child(DatetimeMetricIpc)
+        } else {
+            DatetimeMetric::Parent(glean::private::DatetimeMetric::new(meta, time_unit))
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            DatetimeMetric::Parent { .. } => DatetimeMetric::Child(DatetimeMetricIpc),
+            DatetimeMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+
+    /// Sets the metric to a date/time including the timezone offset.
+    ///
+    /// # Arguments
+    ///
+    /// * `year` - the year to set the metric to.
+    /// * `month` - the month to set the metric to (1-12).
+    /// * `day` - the day to set the metric to (1-based).
+    /// * `hour` - the hour to set the metric to (0-23).
+    /// * `minute` - the minute to set the metric to.
+    /// * `second` - the second to set the metric to.
+    /// * `nano` - the nanosecond fraction to the last whole second.
+    /// * `offset_seconds` - the timezone difference, in seconds, for the Eastern
+    ///   Hemisphere. Negative seconds mean Western Hemisphere.
+    #[cfg_attr(not(feature = "with-gecko"), allow(dead_code))]
+    #[allow(clippy::too_many_arguments)]
+    pub(crate) fn set_with_details(
+        &self,
+        year: i32,
+        month: u32,
+        day: u32,
+        hour: u32,
+        minute: u32,
+        second: u32,
+        nano: u32,
+        offset_seconds: i32,
+    ) {
+        match self {
+            DatetimeMetric::Parent(p) => {
+                let tz = FixedOffset::east_opt(offset_seconds);
+                if tz.is_none() {
+                    log::error!(
+                        "Unable to set datetime metric with invalid offset seconds {}",
+                        offset_seconds
+                    );
+                    // TODO: Record an error
+                    return;
+                }
+
+                let value = FixedOffset::east(offset_seconds)
+                    .ymd_opt(year, month, day)
+                    .and_hms_nano_opt(hour, minute, second, nano);
+                match value.single() {
+                    Some(d) => p.set(Some(d.into())),
+                    _ => {
+                        log::error!("Unable to construct datetime")
+                        // TODO: Record an error
+                    }
+                }
+            }
+            DatetimeMetric::Child(_) => {
+                log::error!("Unable to set datetime metric in non-parent process. Ignoring.");
+                // TODO: Record an error.
+            }
+        }
+    }
+}
+
+#[inherent]
+impl Datetime for DatetimeMetric {
+    /// Sets the metric to a date/time which including the timezone offset.
+    ///
+    /// ## Arguments
+    ///
+    /// - `value` - The date and time and timezone value to set.
+    ///             If None we use the current local time.
+    pub fn set(&self, value: Option<glean::Datetime>) {
+        match self {
+            DatetimeMetric::Parent(p) => {
+                p.set(value);
+            }
+            DatetimeMetric::Child(_) => {
+                log::error!(
+                    "Unable to set datetime metric DatetimeMetric in non-parent process. Ignoring."
+                );
+                // TODO: Record an error.
+            }
+        }
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the currently stored value as a Datetime.
+    ///
+    /// The precision of this value is truncated to the `time_unit` precision.
+    ///
+    /// This doesn't clear the stored value.
+    ///
+    /// # Arguments
+    ///
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(
+        &self,
+        ping_name: S,
+    ) -> Option<glean::Datetime> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            DatetimeMetric::Parent(p) => p.test_get_value(ping_name),
+            DatetimeMetric::Child(_) => {
+                panic!("Cannot get test value for DatetimeMetric in non-parent process!")
+            }
+        }
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the number of recorded errors for the given metric and error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors reported.
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            DatetimeMetric::Parent(p) => p.test_get_num_recorded_errors(error),
+            DatetimeMetric::Child(_) => panic!("Cannot get the number of recorded errors for DatetimeMetric in non-parent process!"),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use chrono::{DateTime, FixedOffset, TimeZone};
+
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_datetime_value() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_date;
+
+        let a_datetime = FixedOffset::east(5 * 3600)
+            .ymd(2020, 05, 07)
+            .and_hms(11, 58, 00);
+        metric.set(Some(a_datetime.into()));
+
+        let expected: glean::Datetime = DateTime::parse_from_rfc3339("2020-05-07T11:58:00+05:00")
+            .unwrap()
+            .into();
+        assert_eq!(expected, metric.test_get_value("store1").unwrap());
+    }
+
+    #[test]
+    fn sets_datetime_value_with_details() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_date;
+
+        metric.set_with_details(2020, 05, 07, 11, 58, 0, 0, 5 * 3600);
+
+        let expected: glean::Datetime = DateTime::parse_from_rfc3339("2020-05-07T11:58:00+05:00")
+            .unwrap()
+            .into();
+        assert_eq!(expected, metric.test_get_value("store1").unwrap());
+    }
+
+    #[test]
+    fn datetime_ipc() {
+        // DatetimeMetric doesn't support IPC.
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_date;
+
+        // Instrumentation calls do not panic.
+        let a_datetime = FixedOffset::east(5 * 3600)
+            .ymd(2020, 10, 13)
+            .and_hms(16, 41, 00);
+        parent_metric.set(Some(a_datetime.into()));
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            let _raii = ipc::test_set_need_ipc(true);
+
+            let a_datetime = FixedOffset::east(0).ymd(2018, 4, 7).and_hms(12, 01, 00);
+            child_metric.set(Some(a_datetime.into()));
+
+            // (They also shouldn't do anything,
+            // but that's not something we can inspect in this test)
+        }
+
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        let expected: glean::Datetime = DateTime::parse_from_rfc3339("2020-10-13T16:41:00+05:00")
+            .unwrap()
+            .into();
+        assert_eq!(expected, parent_metric.test_get_value("store1").unwrap());
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/denominator.rs b/toolkit/components/glean/api/src/private/denominator.rs
new file mode 100644
index 0000000000..64982b5050
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/denominator.rs
@@ -0,0 +1,157 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use super::CommonMetricData;
+
+use glean::traits::Counter;
+
+use crate::ipc::{need_ipc, with_ipc_payload};
+use crate::private::MetricId;
+
+/// Developer-facing API for recording counter metrics that are acting as
+/// external denominators for rate metrics.
+///
+/// Instances of this class type are automatically generated by the parsers
+/// at build time, allowing developers to record values that were previously
+/// registered in the metrics.yaml file.
+#[derive(Clone)]
+pub enum DenominatorMetric {
+    Parent {
+        /// The metric's ID.
+        ///
+        /// **TEST-ONLY** - Do not use unless gated with `#[cfg(test)]`.
+        id: MetricId,
+        inner: glean::private::DenominatorMetric,
+    },
+    Child(DenominatorMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct DenominatorMetricIpc(MetricId);
+
+impl DenominatorMetric {
+    /// The constructor used by automatically generated metrics.
+    pub fn new(id: MetricId, meta: CommonMetricData, numerators: Vec<CommonMetricData>) -> Self {
+        if need_ipc() {
+            DenominatorMetric::Child(DenominatorMetricIpc(id))
+        } else {
+            let inner = glean::private::DenominatorMetric::new(meta, numerators);
+            DenominatorMetric::Parent { id, inner }
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn metric_id(&self) -> MetricId {
+        match self {
+            DenominatorMetric::Parent { id, .. } => *id,
+            DenominatorMetric::Child(c) => c.0,
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            DenominatorMetric::Parent { id, .. } => {
+                DenominatorMetric::Child(DenominatorMetricIpc(*id))
+            }
+            DenominatorMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl Counter for DenominatorMetric {
+    pub fn add(&self, amount: i32) {
+        match self {
+            DenominatorMetric::Parent { inner, .. } => {
+                inner.add(amount);
+            }
+            DenominatorMetric::Child(c) => {
+                with_ipc_payload(move |payload| {
+                    if let Some(v) = payload.denominators.get_mut(&c.0) {
+                        *v += amount;
+                    } else {
+                        payload.denominators.insert(c.0, amount);
+                    }
+                });
+            }
+        }
+    }
+
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(&self, ping_name: S) -> Option<i32> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            DenominatorMetric::Parent { inner, .. } => inner.test_get_value(ping_name),
+            DenominatorMetric::Child(c) => {
+                panic!("Cannot get test value for {:?} in non-parent process!", c.0);
+            }
+        }
+    }
+
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            DenominatorMetric::Parent { inner, .. } => inner.test_get_num_recorded_errors(error),
+            DenominatorMetric::Child(c) => {
+                panic!(
+                    "Cannot get the number of recorded errors for {:?} in non-parent process!",
+                    c.0
+                );
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_denominator_value_parent() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::an_external_denominator;
+        metric.add(1);
+
+        assert_eq!(1, metric.test_get_value("store1").unwrap());
+    }
+
+    #[test]
+    fn sets_denominator_value_child() {
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::an_external_denominator;
+        parent_metric.add(3);
+
+        {
+            // scope for need_ipc RAII
+            let child_metric = parent_metric.child_metric();
+            let _raii = ipc::test_set_need_ipc(true);
+            let metric_id = child_metric.metric_id();
+
+            child_metric.add(42);
+
+            ipc::with_ipc_payload(move |payload| {
+                assert_eq!(
+                    42,
+                    *payload.denominators.get(&metric_id).unwrap(),
+                    "Stored the correct value in the ipc payload"
+                );
+            });
+        }
+
+        assert_eq!(
+            false,
+            ipc::need_ipc(),
+            "RAII dropped, should not need ipc any more"
+        );
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert_eq!(
+            45,
+            parent_metric.test_get_value("store1").unwrap(),
+            "Values from the 'processes' should be summed"
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/event.rs b/toolkit/components/glean/api/src/private/event.rs
new file mode 100644
index 0000000000..0f45eb9b93
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/event.rs
@@ -0,0 +1,241 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use std::collections::HashMap;
+
+use inherent::inherent;
+
+use super::{CommonMetricData, MetricId, RecordedEvent};
+
+use crate::ipc::{need_ipc, with_ipc_payload};
+
+use glean::traits::Event;
+pub use glean::traits::{EventRecordingError, ExtraKeys, NoExtraKeys};
+
+/// An event metric.
+///
+/// Events allow recording of e.g. individual occurences of user actions, say
+/// every time a view was open and from where. Each time you record an event, it
+/// records a timestamp, the event's name and a set of custom values.
+pub enum EventMetric<K> {
+    Parent {
+        /// The metric's ID.
+        ///
+        /// **TEST-ONLY** - Do not use unless gated with `#[cfg(test)]`.
+        id: MetricId,
+        inner: glean::private::EventMetric<K>,
+    },
+    Child(EventMetricIpc),
+}
+
+#[derive(Debug)]
+pub struct EventMetricIpc(MetricId);
+
+impl<K: 'static + ExtraKeys + Send + Sync> EventMetric<K> {
+    /// Create a new event metric.
+    pub fn new(id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            EventMetric::Child(EventMetricIpc(id))
+        } else {
+            let inner = glean::private::EventMetric::new(meta);
+            EventMetric::Parent { id, inner }
+        }
+    }
+
+    pub fn with_runtime_extra_keys(
+        id: MetricId,
+        meta: CommonMetricData,
+        allowed_extra_keys: Vec<String>,
+    ) -> Self {
+        if need_ipc() {
+            EventMetric::Child(EventMetricIpc(id))
+        } else {
+            let inner =
+                glean::private::EventMetric::with_runtime_extra_keys(meta, allowed_extra_keys);
+            EventMetric::Parent { id, inner }
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            EventMetric::Parent { id, .. } => EventMetric::Child(EventMetricIpc(*id)),
+            EventMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+
+    /// Record a new event with the raw `extra key ID -> String` map.
+    ///
+    /// Should only be used when taking in data over FFI, where extra keys only exists as IDs.
+    pub(crate) fn record_raw(&self, extra: HashMap<String, String>) {
+        let now = glean::get_timestamp_ms();
+        self.record_with_time(now, extra);
+    }
+
+    /// Record a new event with the given timestamp and the raw `extra key ID -> String` map.
+    ///
+    /// Should only be used when applying previously recorded events, e.g. from IPC.
+    pub(crate) fn record_with_time(&self, timestamp: u64, extra: HashMap<String, String>) {
+        match self {
+            EventMetric::Parent { inner, .. } => {
+                inner.record_with_time(timestamp, extra);
+            }
+            EventMetric::Child(c) => {
+                with_ipc_payload(move |payload| {
+                    if let Some(v) = payload.events.get_mut(&c.0) {
+                        v.push((timestamp, extra));
+                    } else {
+                        let v = vec![(timestamp, extra)];
+                        payload.events.insert(c.0, v);
+                    }
+                });
+            }
+        }
+    }
+}
+
+#[inherent]
+impl<K: 'static + ExtraKeys + Send + Sync> Event for EventMetric<K> {
+    type Extra = K;
+
+    pub fn record<M: Into<Option<K>>>(&self, extra: M) {
+        match self {
+            EventMetric::Parent { inner, .. } => {
+                inner.record(extra);
+            }
+            EventMetric::Child(_) => {
+                let now = glean::get_timestamp_ms();
+                let extra = extra.into().map(|extra| extra.into_ffi_extra());
+                let extra = extra.unwrap_or_else(HashMap::new);
+                self.record_with_time(now, extra);
+            }
+        }
+    }
+
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(
+        &self,
+        ping_name: S,
+    ) -> Option<Vec<RecordedEvent>> {
+        match self {
+            EventMetric::Parent { inner, .. } => inner.test_get_value(ping_name),
+            EventMetric::Child(_) => {
+                panic!("Cannot get test value for event metric in non-parent process!",)
+            }
+        }
+    }
+
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            EventMetric::Parent { inner, .. } => inner.test_get_num_recorded_errors(error),
+            EventMetric::Child(c) => panic!(
+                "Cannot get the number of recorded errors for {:?} in non-parent process!",
+                c.0
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn smoke_test_event() {
+        let _lock = lock_test();
+
+        let metric = EventMetric::<NoExtraKeys>::new(
+            0.into(),
+            CommonMetricData {
+                name: "event_metric".into(),
+                category: "telemetry".into(),
+                send_in_pings: vec!["store1".into()],
+                disabled: false,
+                ..Default::default()
+            },
+        );
+
+        // No extra keys
+        metric.record(None);
+
+        let recorded = metric.test_get_value("store1").unwrap();
+
+        assert!(recorded.iter().any(|e| e.name == "event_metric"));
+    }
+
+    #[test]
+    fn event_ipc() {
+        use metrics::test_only_ipc::AnEventExtra;
+
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::an_event;
+
+        // No extra keys
+        parent_metric.record(None);
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            // scope for need_ipc RAII.
+            let _raii = ipc::test_set_need_ipc(true);
+
+            child_metric.record(None);
+
+            let extra = AnEventExtra {
+                extra1: Some("a-child-value".into()),
+                ..Default::default()
+            };
+            child_metric.record(extra);
+        }
+
+        // Record in the parent after the child.
+        let extra = AnEventExtra {
+            extra1: Some("a-valid-value".into()),
+            ..Default::default()
+        };
+        parent_metric.record(extra);
+
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        let events = parent_metric.test_get_value("store1").unwrap();
+        assert_eq!(events.len(), 4);
+
+        // Events from the child process are last, they might get sorted later by Glean.
+        assert_eq!(events[0].extra, None);
+        assert!(events[1].extra.as_ref().unwrap().get("extra1").unwrap() == "a-valid-value");
+        assert_eq!(events[2].extra, None);
+        assert!(events[3].extra.as_ref().unwrap().get("extra1").unwrap() == "a-child-value");
+    }
+
+    #[test]
+    fn events_with_typed_extras() {
+        use metrics::test_only_ipc::EventWithExtraExtra;
+        let _lock = lock_test();
+
+        let event = &metrics::test_only_ipc::event_with_extra;
+        // Record in the parent after the child.
+        let extra = EventWithExtraExtra {
+            extra1: Some("a-valid-value".into()),
+            extra2: Some(37),
+            extra3_longer_name: Some(false),
+        };
+        event.record(extra);
+
+        let recorded = event.test_get_value("store1").unwrap();
+
+        assert_eq!(recorded.len(), 1);
+        assert!(recorded[0].extra.as_ref().unwrap().get("extra1").unwrap() == "a-valid-value");
+        assert!(recorded[0].extra.as_ref().unwrap().get("extra2").unwrap() == "37");
+        assert!(
+            recorded[0]
+                .extra
+                .as_ref()
+                .unwrap()
+                .get("extra3_longer_name")
+                .unwrap()
+                == "false"
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/labeled.rs b/toolkit/components/glean/api/src/private/labeled.rs
new file mode 100644
index 0000000000..b0bedafa15
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/labeled.rs
@@ -0,0 +1,356 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use super::{
+    CommonMetricData, ErrorType, LabeledBooleanMetric, LabeledCounterMetric, LabeledStringMetric,
+    MetricId,
+};
+use crate::ipc::need_ipc;
+
+/// Sealed traits protect against downstream implementations.
+///
+/// We wrap it in a private module that is inaccessible outside of this module.
+mod private {
+    use super::{
+        need_ipc, LabeledBooleanMetric, LabeledCounterMetric, LabeledStringMetric, MetricId,
+    };
+    use crate::private::CounterMetric;
+    use std::sync::Arc;
+
+    /// The sealed trait.
+    ///
+    /// This allows us to define which FOG metrics can be used
+    /// as labeled types.
+    pub trait Sealed {
+        type GleanMetric: glean::private::AllowLabeled + Clone;
+        fn from_glean_metric(id: MetricId, metric: Arc<Self::GleanMetric>, label: &str) -> Self;
+    }
+
+    // `LabeledMetric<LabeledBooleanMetric>` is possible.
+    //
+    // See [Labeled Booleans](https://mozilla.github.io/glean/book/user/metrics/labeled_booleans.html).
+    impl Sealed for LabeledBooleanMetric {
+        type GleanMetric = glean::private::BooleanMetric;
+        fn from_glean_metric(_id: MetricId, metric: Arc<Self::GleanMetric>, _label: &str) -> Self {
+            if need_ipc() {
+                // TODO: Instrument this error.
+                LabeledBooleanMetric::Child(crate::private::boolean::BooleanMetricIpc)
+            } else {
+                LabeledBooleanMetric::Parent(metric)
+            }
+        }
+    }
+
+    // `LabeledMetric<LabeledStringMetric>` is possible.
+    //
+    // See [Labeled Strings](https://mozilla.github.io/glean/book/user/metrics/labeled_strings.html).
+    impl Sealed for LabeledStringMetric {
+        type GleanMetric = glean::private::StringMetric;
+        fn from_glean_metric(_id: MetricId, metric: Arc<Self::GleanMetric>, _label: &str) -> Self {
+            if need_ipc() {
+                // TODO: Instrument this error.
+                LabeledStringMetric::Child(crate::private::string::StringMetricIpc)
+            } else {
+                LabeledStringMetric::Parent(metric)
+            }
+        }
+    }
+
+    // `LabeledMetric<LabeledCounterMetric>` is possible.
+    //
+    // See [Labeled Counters](https://mozilla.github.io/glean/book/user/metrics/labeled_counters.html).
+    impl Sealed for LabeledCounterMetric {
+        type GleanMetric = glean::private::CounterMetric;
+        fn from_glean_metric(id: MetricId, metric: Arc<Self::GleanMetric>, label: &str) -> Self {
+            if need_ipc() {
+                LabeledCounterMetric::Child {
+                    id,
+                    label: label.to_string(),
+                }
+            } else {
+                LabeledCounterMetric::Parent(CounterMetric::Parent { id, inner: metric })
+            }
+        }
+    }
+}
+
+/// Marker trait for metrics that can be nested inside a labeled metric.
+///
+/// This trait is sealed and cannot be implemented for types outside this crate.
+pub trait AllowLabeled: private::Sealed {}
+
+// Implement the trait for everything we marked as allowed.
+impl<T> AllowLabeled for T where T: private::Sealed {}
+
+/// A labeled metric.
+///
+/// Labeled metrics allow to record multiple sub-metrics of the same type under different string labels.
+///
+/// ## Example
+///
+/// The following piece of code will be generated by `glean_parser`:
+///
+/// ```rust,ignore
+/// use glean::metrics::{LabeledMetric, BooleanMetric, CommonMetricData, Lifetime};
+/// use once_cell::sync::Lazy;
+///
+/// mod error {
+///     pub static seen_one: Lazy<LabeledMetric<BooleanMetric>> = Lazy::new(|| LabeledMetric::new(CommonMetricData {
+///         name: "seen_one".into(),
+///         category: "error".into(),
+///         send_in_pings: vec!["ping".into()],
+///         disabled: false,
+///         lifetime: Lifetime::Ping,
+///         ..Default::default()
+///     }, None));
+/// }
+/// ```
+///
+/// It can then be used with:
+///
+/// ```rust,ignore
+/// errro::seen_one.get("upload").set(true);
+/// ```
+pub struct LabeledMetric<T: AllowLabeled> {
+    /// The metric ID of the underlying metric.
+    id: MetricId,
+
+    /// Wrapping the underlying core metric.
+    ///
+    /// We delegate all functionality to this and wrap it up again in our own metric type.
+    core: glean::private::LabeledMetric<T::GleanMetric>,
+}
+
+impl<T> LabeledMetric<T>
+where
+    T: AllowLabeled,
+{
+    /// Create a new labeled metric from the given metric instance and optional list of labels.
+    ///
+    /// See [`get`](#method.get) for information on how static or dynamic labels are handled.
+    pub fn new(
+        id: MetricId,
+        meta: CommonMetricData,
+        labels: Option<Vec<String>>,
+    ) -> LabeledMetric<T> {
+        let core = glean::private::LabeledMetric::new(meta, labels);
+        LabeledMetric { id, core }
+    }
+}
+
+#[inherent]
+impl<U> glean::traits::Labeled<U> for LabeledMetric<U>
+where
+    U: AllowLabeled + Clone,
+{
+    /// Gets a specific metric for a given label.
+    ///
+    /// If a set of acceptable labels were specified in the `metrics.yaml` file,
+    /// and the given label is not in the set, it will be recorded under the special `OTHER_LABEL` label.
+    ///
+    /// If a set of acceptable labels was not specified in the `metrics.yaml` file,
+    /// only the first 16 unique labels will be used.
+    /// After that, any additional labels will be recorded under the special `OTHER_LABEL` label.
+    ///
+    /// Labels must be `snake_case` and less than 30 characters.
+    /// If an invalid label is used, the metric will be recorded in the special `OTHER_LABEL` label.
+    pub fn get(&self, label: &str) -> U {
+        let metric = self.core.get(label);
+        U::from_glean_metric(self.id, metric, label)
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the number of recorded errors for the given metric and error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors reported.
+    pub fn test_get_num_recorded_errors(&self, error: ErrorType) -> i32 {
+        if need_ipc() {
+            panic!("Use of labeled metrics in IPC land not yet implemented!");
+        } else {
+            self.core.test_get_num_recorded_errors(error)
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use once_cell::sync::Lazy;
+
+    use super::*;
+    use crate::common_test::*;
+
+    // Smoke test for what should be the generated code.
+    static GLOBAL_METRIC: Lazy<LabeledMetric<LabeledBooleanMetric>> = Lazy::new(|| {
+        LabeledMetric::new(
+            0.into(),
+            CommonMetricData {
+                name: "global".into(),
+                category: "metric".into(),
+                send_in_pings: vec!["ping".into()],
+                disabled: false,
+                ..Default::default()
+            },
+            None,
+        )
+    });
+
+    #[test]
+    fn smoke_test_global_metric() {
+        let _lock = lock_test();
+
+        GLOBAL_METRIC.get("a_value").set(true);
+        assert_eq!(
+            true,
+            GLOBAL_METRIC.get("a_value").test_get_value("ping").unwrap()
+        );
+    }
+
+    #[test]
+    fn sets_labeled_bool_metrics() {
+        let _lock = lock_test();
+        let store_names: Vec<String> = vec!["store1".into()];
+
+        let metric: LabeledMetric<LabeledBooleanMetric> = LabeledMetric::new(
+            0.into(),
+            CommonMetricData {
+                name: "bool".into(),
+                category: "labeled".into(),
+                send_in_pings: store_names,
+                disabled: false,
+                ..Default::default()
+            },
+            None,
+        );
+
+        metric.get("upload").set(true);
+
+        assert!(metric.get("upload").test_get_value("store1").unwrap());
+        assert_eq!(None, metric.get("download").test_get_value("store1"));
+    }
+
+    #[test]
+    fn sets_labeled_string_metrics() {
+        let _lock = lock_test();
+        let store_names: Vec<String> = vec!["store1".into()];
+
+        let metric: LabeledMetric<LabeledStringMetric> = LabeledMetric::new(
+            0.into(),
+            CommonMetricData {
+                name: "string".into(),
+                category: "labeled".into(),
+                send_in_pings: store_names,
+                disabled: false,
+                ..Default::default()
+            },
+            None,
+        );
+
+        metric.get("upload").set("Glean");
+
+        assert_eq!(
+            "Glean",
+            metric.get("upload").test_get_value("store1").unwrap()
+        );
+        assert_eq!(None, metric.get("download").test_get_value("store1"));
+    }
+
+    #[test]
+    fn sets_labeled_counter_metrics() {
+        let _lock = lock_test();
+        let store_names: Vec<String> = vec!["store1".into()];
+
+        let metric: LabeledMetric<LabeledCounterMetric> = LabeledMetric::new(
+            0.into(),
+            CommonMetricData {
+                name: "counter".into(),
+                category: "labeled".into(),
+                send_in_pings: store_names,
+                disabled: false,
+                ..Default::default()
+            },
+            None,
+        );
+
+        metric.get("upload").add(10);
+
+        assert_eq!(10, metric.get("upload").test_get_value("store1").unwrap());
+        assert_eq!(None, metric.get("download").test_get_value("store1"));
+    }
+
+    #[test]
+    fn records_errors() {
+        let _lock = lock_test();
+        let store_names: Vec<String> = vec!["store1".into()];
+
+        let metric: LabeledMetric<LabeledBooleanMetric> = LabeledMetric::new(
+            0.into(),
+            CommonMetricData {
+                name: "bool".into(),
+                category: "labeled".into(),
+                send_in_pings: store_names,
+                disabled: false,
+                ..Default::default()
+            },
+            None,
+        );
+
+        metric
+            .get("this_string_has_more_than_thirty_characters")
+            .set(true);
+
+        assert_eq!(
+            1,
+            metric.test_get_num_recorded_errors(ErrorType::InvalidLabel)
+        );
+    }
+
+    #[test]
+    fn predefined_labels() {
+        let _lock = lock_test();
+        let store_names: Vec<String> = vec!["store1".into()];
+
+        let metric: LabeledMetric<LabeledBooleanMetric> = LabeledMetric::new(
+            0.into(),
+            CommonMetricData {
+                name: "bool".into(),
+                category: "labeled".into(),
+                send_in_pings: store_names,
+                disabled: false,
+                ..Default::default()
+            },
+            Some(vec!["label1".into(), "label2".into()]),
+        );
+
+        metric.get("label1").set(true);
+        metric.get("label2").set(false);
+        metric.get("not_a_label").set(true);
+
+        assert_eq!(true, metric.get("label1").test_get_value("store1").unwrap());
+        assert_eq!(
+            false,
+            metric.get("label2").test_get_value("store1").unwrap()
+        );
+        // The label not in the predefined set is recorded to the `other` bucket.
+        assert_eq!(
+            true,
+            metric.get("__other__").test_get_value("store1").unwrap()
+        );
+
+        assert_eq!(
+            0,
+            metric.test_get_num_recorded_errors(ErrorType::InvalidLabel)
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/labeled_counter.rs b/toolkit/components/glean/api/src/private/labeled_counter.rs
new file mode 100644
index 0000000000..73a6697601
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/labeled_counter.rs
@@ -0,0 +1,179 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use glean::traits::Counter;
+
+use super::CommonMetricData;
+
+use crate::ipc::{need_ipc, with_ipc_payload};
+use crate::private::{CounterMetric, MetricId};
+use std::collections::HashMap;
+
+/// A counter metric that knows it's a labeled counter's submetric.
+///
+/// It has special work to do when in a non-parent process.
+/// When on the parent process, it dispatches calls to the normal CounterMetric.
+#[derive(Clone)]
+pub enum LabeledCounterMetric {
+    Parent(CounterMetric),
+    Child { id: MetricId, label: String },
+}
+
+impl LabeledCounterMetric {
+    /// Create a new labeled counter submetric.
+    pub fn new(id: MetricId, meta: CommonMetricData, label: String) -> Self {
+        if need_ipc() {
+            LabeledCounterMetric::Child { id, label }
+        } else {
+            LabeledCounterMetric::Parent(CounterMetric::new(id, meta))
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn metric_id(&self) -> MetricId {
+        match self {
+            LabeledCounterMetric::Parent(p) => p.metric_id(),
+            LabeledCounterMetric::Child { id, .. } => *id,
+        }
+    }
+}
+
+#[inherent]
+impl Counter for LabeledCounterMetric {
+    /// Increase the counter by `amount`.
+    ///
+    /// ## Arguments
+    ///
+    /// * `amount` - The amount to increase by. Should be positive.
+    ///
+    /// ## Notes
+    ///
+    /// Logs an error if the `amount` is 0 or negative.
+    pub fn add(&self, amount: i32) {
+        match self {
+            LabeledCounterMetric::Parent(p) => p.add(amount),
+            LabeledCounterMetric::Child { id, label } => {
+                with_ipc_payload(move |payload| {
+                    if let Some(map) = payload.labeled_counters.get_mut(id) {
+                        if let Some(v) = map.get_mut(label) {
+                            *v += amount;
+                        } else {
+                            map.insert(label.to_string(), amount);
+                        }
+                    } else {
+                        let mut map = HashMap::new();
+                        map.insert(label.to_string(), amount);
+                        payload.labeled_counters.insert(*id, map);
+                    }
+                });
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Get the currently stored value as an integer.
+    /// This doesn't clear the stored value.
+    ///
+    /// ## Arguments
+    ///
+    /// * `ping_name` - the storage name to look into.
+    ///
+    /// ## Return value
+    ///
+    /// Returns the stored value or `None` if nothing stored.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(&self, ping_name: S) -> Option<i32> {
+        match self {
+            LabeledCounterMetric::Parent(p) => p.test_get_value(ping_name),
+            LabeledCounterMetric::Child { id, .. } => {
+                panic!("Cannot get test value for {:?} in non-parent process!", id)
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Gets the number of recorded errors for the given metric and error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors reported.
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            LabeledCounterMetric::Parent(p) => p.test_get_num_recorded_errors(error),
+            LabeledCounterMetric::Child { id, .. } => panic!(
+                "Cannot get the number of recorded errors for {:?} in non-parent process!",
+                id
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_labeled_counter_value_parent() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_labeled_counter;
+        metric.get("a_label").add(1);
+
+        assert_eq!(1, metric.get("a_label").test_get_value("store1").unwrap());
+    }
+
+    #[test]
+    fn sets_labeled_counter_value_child() {
+        let _lock = lock_test();
+
+        let label = "some_label";
+
+        let parent_metric = &metrics::test_only_ipc::a_labeled_counter;
+        parent_metric.get(label).add(3);
+
+        {
+            // scope for need_ipc RAII
+            let _raii = ipc::test_set_need_ipc(true);
+            let child_metric = parent_metric.get(label);
+
+            let metric_id = child_metric.metric_id();
+
+            child_metric.add(42);
+
+            ipc::with_ipc_payload(move |payload| {
+                assert_eq!(
+                    42,
+                    *payload
+                        .labeled_counters
+                        .get(&metric_id)
+                        .unwrap()
+                        .get(label)
+                        .unwrap(),
+                    "Stored the correct value in the ipc payload"
+                );
+            });
+        }
+
+        assert!(
+            false == ipc::need_ipc(),
+            "RAII dropped, should not need ipc any more"
+        );
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert_eq!(
+            45,
+            parent_metric.get(label).test_get_value("store1").unwrap(),
+            "Values from the 'processes' should be summed"
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/memory_distribution.rs b/toolkit/components/glean/api/src/private/memory_distribution.rs
new file mode 100644
index 0000000000..b529819562
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/memory_distribution.rs
@@ -0,0 +1,206 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+use std::convert::TryInto;
+
+use super::{CommonMetricData, DistributionData, MemoryUnit, MetricId};
+
+use glean::traits::MemoryDistribution;
+
+use crate::ipc::{need_ipc, with_ipc_payload};
+
+/// A memory distribution metric.
+///
+/// Memory distributions are used to accumulate and store memory measurements for analyzing distributions of the memory data.
+#[derive(Clone)]
+pub enum MemoryDistributionMetric {
+    Parent {
+        /// The metric's ID.
+        ///
+        /// **TEST-ONLY** - Do not use unless gated with `#[cfg(test)]`.
+        id: MetricId,
+        inner: glean::private::MemoryDistributionMetric,
+    },
+    Child(MemoryDistributionMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct MemoryDistributionMetricIpc(MetricId);
+
+impl MemoryDistributionMetric {
+    /// Create a new memory distribution metric.
+    pub fn new(id: MetricId, meta: CommonMetricData, memory_unit: MemoryUnit) -> Self {
+        if need_ipc() {
+            MemoryDistributionMetric::Child(MemoryDistributionMetricIpc(id))
+        } else {
+            let inner = glean::private::MemoryDistributionMetric::new(meta, memory_unit);
+            MemoryDistributionMetric::Parent { id, inner }
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            MemoryDistributionMetric::Parent { id, .. } => {
+                MemoryDistributionMetric::Child(MemoryDistributionMetricIpc(*id))
+            }
+            MemoryDistributionMetric::Child(_) => {
+                panic!("Can't get a child metric from a child metric")
+            }
+        }
+    }
+}
+
+#[inherent]
+impl MemoryDistribution for MemoryDistributionMetric {
+    /// Accumulates the provided sample in the metric.
+    ///
+    /// ## Arguments
+    ///
+    /// * `sample` - The sample to be recorded by the metric. The sample is assumed to be in the
+    ///   configured memory unit of the metric.
+    ///
+    /// ## Notes
+    ///
+    /// Values bigger than 1 Terabyte (2<sup>40</sup> bytes) are truncated
+    /// and an `ErrorType::InvalidValue` error is recorded.
+    pub fn accumulate(&self, sample: u64) {
+        match self {
+            MemoryDistributionMetric::Parent { inner, .. } => {
+                // values are capped at 2**40.
+                // If the value doesn't fit into `i64` it's definitely to large
+                // and cause an error.
+                // glean-core handles that.
+                let sample = sample.try_into().unwrap_or_else(|_| {
+                    log::warn!(
+                        "Memory size too large to fit into into 64-bytes. Saturating at i64::MAX."
+                    );
+                    i64::MAX
+                });
+                inner.accumulate(sample);
+            }
+            MemoryDistributionMetric::Child(c) => {
+                with_ipc_payload(move |payload| {
+                    if let Some(v) = payload.memory_samples.get_mut(&c.0) {
+                        v.push(sample);
+                    } else {
+                        payload.memory_samples.insert(c.0, vec![sample]);
+                    }
+                });
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Get the currently-stored histogram as a DistributionData of the serialized value.
+    /// This doesn't clear the stored value.
+    ///
+    /// ## Arguments
+    ///
+    /// * `ping_name` - the storage name to look into.
+    ///
+    /// ## Return value
+    ///
+    /// Returns the stored value or `None` if nothing stored.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(
+        &self,
+        ping_name: S,
+    ) -> Option<DistributionData> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            MemoryDistributionMetric::Parent { inner, .. } => inner.test_get_value(ping_name),
+            MemoryDistributionMetric::Child(c) => {
+                panic!("Cannot get test value for {:?} in non-parent process!", c.0)
+            }
+        }
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the number of recorded errors for the given error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors recorded.
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            MemoryDistributionMetric::Parent { inner, .. } => {
+                inner.test_get_num_recorded_errors(error)
+            }
+            MemoryDistributionMetric::Child(c) => panic!(
+                "Cannot get the number of recorded errors for {:?} in non-parent process!",
+                c.0
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn smoke_test_memory_distribution() {
+        let _lock = lock_test();
+
+        let metric = MemoryDistributionMetric::new(
+            0.into(),
+            CommonMetricData {
+                name: "memory_distribution_metric".into(),
+                category: "telemetry".into(),
+                send_in_pings: vec!["store1".into()],
+                disabled: false,
+                ..Default::default()
+            },
+            MemoryUnit::Kilobyte,
+        );
+
+        metric.accumulate(42);
+
+        let metric_data = metric.test_get_value("store1").unwrap();
+        assert_eq!(1, metric_data.values[&42494]);
+        assert_eq!(0, metric_data.values[&44376]);
+        assert_eq!(43008, metric_data.sum);
+    }
+
+    #[test]
+    fn memory_distribution_child() {
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_memory_dist;
+        parent_metric.accumulate(42);
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            // scope for need_ipc RAII
+            let _raii = ipc::test_set_need_ipc(true);
+            child_metric.accumulate(13 * 9);
+        }
+
+        let metric_data = parent_metric.test_get_value("store1").unwrap();
+        assert_eq!(1, metric_data.values[&42494]);
+        assert_eq!(0, metric_data.values[&44376]);
+        assert_eq!(43008, metric_data.sum);
+
+        // Single-process IPC machine goes brrrrr...
+        let buf = ipc::take_buf().unwrap();
+        assert!(buf.len() > 0);
+        assert!(ipc::replay_from_buf(&buf).is_ok());
+
+        let data = parent_metric.test_get_value(None).expect("must have data");
+        assert_eq!(2, data.values.values().fold(0, |acc, count| acc + count));
+        assert_eq!(1, data.values[&42494]);
+        assert_eq!(1, data.values[&115097]);
+        assert_eq!(162816, data.sum);
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/mod.rs b/toolkit/components/glean/api/src/private/mod.rs
new file mode 100644
index 0000000000..9b8b57818c
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/mod.rs
@@ -0,0 +1,74 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! The different metric types supported by the Glean SDK to handle data.
+
+use serde::{Deserialize, Serialize};
+
+// Re-export of `glean` types we can re-use.
+// That way a user only needs to depend on this crate, not on glean (and there can't be a
+// version mismatch).
+pub use glean::{
+    traits, CommonMetricData, DistributionData, ErrorType, Lifetime, MemoryUnit, RecordedEvent,
+    TimeUnit, TimerId,
+};
+
+mod boolean;
+mod counter;
+mod custom_distribution;
+mod datetime;
+mod denominator;
+mod event;
+mod labeled;
+mod labeled_counter;
+mod memory_distribution;
+mod numerator;
+mod ping;
+mod quantity;
+mod rate;
+pub(crate) mod string;
+mod string_list;
+mod timespan;
+mod timing_distribution;
+mod url;
+mod uuid;
+
+pub use self::boolean::BooleanMetric;
+pub use self::boolean::BooleanMetric as LabeledBooleanMetric;
+pub use self::counter::CounterMetric;
+pub use self::custom_distribution::CustomDistributionMetric;
+pub use self::datetime::DatetimeMetric;
+pub use self::denominator::DenominatorMetric;
+pub use self::event::{EventMetric, EventRecordingError, ExtraKeys, NoExtraKeys};
+pub use self::labeled::LabeledMetric;
+pub use self::labeled_counter::LabeledCounterMetric;
+pub use self::memory_distribution::MemoryDistributionMetric;
+pub use self::numerator::NumeratorMetric;
+pub use self::ping::Ping;
+pub use self::quantity::QuantityMetric;
+pub use self::rate::RateMetric;
+pub use self::string::StringMetric;
+pub use self::string::StringMetric as LabeledStringMetric;
+pub use self::string_list::StringListMetric;
+pub use self::timespan::TimespanMetric;
+pub use self::timing_distribution::TimingDistributionMetric;
+pub use self::url::UrlMetric;
+pub use self::uuid::UuidMetric;
+
+/// Uniquely identifies a single metric within its metric type.
+#[derive(Debug, PartialEq, Eq, Hash, Copy, Clone, Deserialize, Serialize)]
+#[repr(transparent)]
+pub struct MetricId(pub(crate) u32);
+
+impl MetricId {
+    pub fn new(id: u32) -> Self {
+        Self(id)
+    }
+}
+
+impl From<u32> for MetricId {
+    fn from(id: u32) -> Self {
+        Self(id)
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/numerator.rs b/toolkit/components/glean/api/src/private/numerator.rs
new file mode 100644
index 0000000000..0a22bf5bfc
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/numerator.rs
@@ -0,0 +1,152 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use super::CommonMetricData;
+
+use glean::traits::Numerator;
+use glean::Rate;
+
+use crate::ipc::{need_ipc, with_ipc_payload};
+use crate::private::MetricId;
+
+/// Developer-facing API for recording rate metrics with external denominators.
+///
+/// Instances of this class type are automatically generated by the parsers
+/// at build time, allowing developers to record values that were previously
+/// registered in the metrics.yaml file.
+#[derive(Clone)]
+pub enum NumeratorMetric {
+    Parent {
+        /// The metric's ID.
+        ///
+        /// **TEST-ONLY** - Do not use unless gated with `#[cfg(test)]`.
+        id: MetricId,
+        inner: glean::private::NumeratorMetric,
+    },
+    Child(NumeratorMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct NumeratorMetricIpc(MetricId);
+
+impl NumeratorMetric {
+    /// The public constructor used by automatically generated metrics.
+    pub fn new(id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            NumeratorMetric::Child(NumeratorMetricIpc(id))
+        } else {
+            let inner = glean::private::NumeratorMetric::new(meta);
+            NumeratorMetric::Parent { id, inner }
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn metric_id(&self) -> MetricId {
+        match self {
+            NumeratorMetric::Parent { id, .. } => *id,
+            NumeratorMetric::Child(c) => c.0,
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            NumeratorMetric::Parent { id, .. } => NumeratorMetric::Child(NumeratorMetricIpc(*id)),
+            NumeratorMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl Numerator for NumeratorMetric {
+    pub fn add_to_numerator(&self, amount: i32) {
+        match self {
+            NumeratorMetric::Parent { inner, .. } => {
+                inner.add_to_numerator(amount);
+            }
+            NumeratorMetric::Child(c) => {
+                with_ipc_payload(move |payload| {
+                    if let Some(v) = payload.numerators.get_mut(&c.0) {
+                        *v += amount;
+                    } else {
+                        payload.numerators.insert(c.0, amount);
+                    }
+                });
+            }
+        }
+    }
+
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(&self, ping_name: S) -> Option<Rate> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            NumeratorMetric::Parent { inner, .. } => inner.test_get_value(ping_name),
+            NumeratorMetric::Child(c) => {
+                panic!("Cannot get test value for {:?} in non-parent process!", c.0);
+            }
+        }
+    }
+
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            NumeratorMetric::Parent { inner, .. } => inner.test_get_num_recorded_errors(error),
+            NumeratorMetric::Child(c) => {
+                panic!(
+                    "Cannot get the number of recorded errors for {:?} in non-parent process!",
+                    c.0
+                );
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_numerator_value_parent() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::rate_with_external_denominator;
+        metric.add_to_numerator(1);
+
+        assert_eq!(1, metric.test_get_value("store1").unwrap().numerator);
+    }
+
+    #[test]
+    fn sets_numerator_value_child() {
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::rate_with_external_denominator;
+        parent_metric.add_to_numerator(3);
+
+        {
+            // scope for need_ipc RAII
+            let child_metric = parent_metric.child_metric();
+            let _raii = ipc::test_set_need_ipc(true);
+            let metric_id = child_metric.metric_id();
+
+            child_metric.add_to_numerator(42);
+
+            ipc::with_ipc_payload(move |payload| {
+                assert!(
+                    42 == *payload.numerators.get(&metric_id).unwrap(),
+                    "Stored the correct value in the ipc payload"
+                );
+            });
+        }
+
+        assert!(
+            false == ipc::need_ipc(),
+            "RAII dropped, should not need ipc any more"
+        );
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert!(
+            45 == parent_metric.test_get_value("store1").unwrap().numerator,
+            "Values from the 'processes' should be summed"
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/ping.rs b/toolkit/components/glean/api/src/private/ping.rs
new file mode 100644
index 0000000000..0934752657
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/ping.rs
@@ -0,0 +1,113 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use crate::ipc::need_ipc;
+
+/// A Glean ping.
+///
+/// See [Glean Pings](https://mozilla.github.io/glean/book/user/pings/index.html).
+#[derive(Clone)]
+pub enum Ping {
+    Parent(glean::private::PingType),
+    Child,
+}
+
+impl Ping {
+    /// Create a new ping type for the given name, whether to include the client ID and whether to
+    /// send this ping empty.
+    ///
+    /// ## Arguments
+    ///
+    /// * `name` - The name of the ping.
+    /// * `include_client_id` - Whether to include the client ID in the assembled ping when submitting.
+    /// * `send_if_empty` - Whether the ping should be sent empty or not.
+    /// * `reason_codes` - The valid reason codes for this ping.
+    pub fn new<S: Into<String>>(
+        name: S,
+        include_client_id: bool,
+        send_if_empty: bool,
+        reason_codes: Vec<String>,
+    ) -> Self {
+        if need_ipc() {
+            Ping::Child
+        } else {
+            Ping::Parent(glean::private::PingType::new(
+                name,
+                include_client_id,
+                send_if_empty,
+                reason_codes,
+            ))
+        }
+    }
+
+    /// **Test-only API**
+    ///
+    /// Attach a callback to be called right before a new ping is submitted.
+    /// The provided function is called exactly once before submitting a ping.
+    ///
+    /// Note: The callback will be called on any call to submit.
+    /// A ping might not be sent afterwards, e.g. if the ping is otherwise empty (and
+    /// `send_if_empty` is `false`).
+    pub fn test_before_next_submit(&self, cb: impl FnOnce(Option<&str>) + Send + 'static) {
+        match self {
+            Ping::Parent(p) => p.test_before_next_submit(cb),
+            Ping::Child => {
+                panic!("Cannot use ping test API from non-parent process!");
+            }
+        };
+    }
+}
+
+#[inherent]
+impl glean::traits::Ping for Ping {
+    /// Submits the ping for eventual uploading
+    ///
+    /// # Arguments
+    ///
+    /// * `reason` - the reason the ping was triggered. Included in the
+    ///   `ping_info.reason` part of the payload.
+    pub fn submit(&self, reason: Option<&str>) {
+        match self {
+            Ping::Parent(p) => {
+                p.submit(reason);
+            }
+            Ping::Child => {
+                log::error!("Unable to submit ping in non-main process. Ignoring.");
+                // TODO: Record an error.
+            }
+        };
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use once_cell::sync::Lazy;
+
+    use super::*;
+    use crate::common_test::*;
+
+    use std::sync::{
+        atomic::{AtomicBool, Ordering},
+        Arc,
+    };
+
+    // Smoke test for what should be the generated code.
+    static PROTOTYPE_PING: Lazy<Ping> = Lazy::new(|| Ping::new("prototype", false, true, vec![]));
+
+    #[test]
+    fn smoke_test_custom_ping() {
+        let _lock = lock_test();
+
+        let called = Arc::new(AtomicBool::new(false));
+        let rcalled = Arc::clone(&called);
+        PROTOTYPE_PING.test_before_next_submit(move |reason| {
+            (*rcalled).store(true, Ordering::Relaxed);
+            assert_eq!(None, reason);
+        });
+        PROTOTYPE_PING.submit(None);
+        assert!((*called).load(Ordering::Relaxed));
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/quantity.rs b/toolkit/components/glean/api/src/private/quantity.rs
new file mode 100644
index 0000000000..cce42c4aea
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/quantity.rs
@@ -0,0 +1,154 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use glean::traits::Quantity;
+
+use super::CommonMetricData;
+
+use crate::ipc::need_ipc;
+use crate::private::MetricId;
+
+/// A quantity metric.
+///
+/// Records a single numeric value of a specific unit.
+#[derive(Clone)]
+pub enum QuantityMetric {
+    Parent(glean::private::QuantityMetric),
+    Child(QuantityMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct QuantityMetricIpc;
+
+impl QuantityMetric {
+    /// Create a new quantity metric.
+    pub fn new(_id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            QuantityMetric::Child(QuantityMetricIpc)
+        } else {
+            QuantityMetric::Parent(glean::private::QuantityMetric::new(meta))
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            QuantityMetric::Parent(_) => QuantityMetric::Child(QuantityMetricIpc),
+            QuantityMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl Quantity for QuantityMetric {
+    /// Set the value. Must be non-negative.
+    ///
+    /// # Arguments
+    ///
+    /// * `value` - The value. Must be non-negative.
+    ///
+    /// ## Notes
+    ///
+    /// Logs an error if the `value` is negative.
+    pub fn set(&self, value: i64) {
+        match self {
+            QuantityMetric::Parent(p) => {
+                p.set(value);
+            }
+            QuantityMetric::Child(_) => {
+                log::error!("Unable to set quantity metric in non-parent process. Ignoring.");
+                // TODO: Record an error.
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Get the currently stored value.
+    /// This doesn't clear the stored value.
+    ///
+    /// ## Arguments
+    ///
+    /// * `ping_name` - the storage name to look into.
+    ///
+    /// ## Return value
+    ///
+    /// Returns the stored value or `None` if nothing stored.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(&self, ping_name: S) -> Option<i64> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            QuantityMetric::Parent(p) => p.test_get_value(ping_name),
+            QuantityMetric::Child(_) => {
+                panic!("Cannot get test value for quantity metric in non-parent process!",)
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Gets the number of recorded errors for the given metric and error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors reported.
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            QuantityMetric::Parent(p) => {
+                p.test_get_num_recorded_errors(error)
+            }
+            QuantityMetric::Child(_) => panic!(
+                "Cannot get the number of recorded errors for quantity metric in non-parent process!"
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_quantity_metric() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_quantity;
+        metric.set(14);
+
+        assert_eq!(14, metric.test_get_value("store1").unwrap());
+    }
+
+    #[test]
+    fn quantity_ipc() {
+        // QuantityMetric doesn't support IPC.
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_quantity;
+
+        parent_metric.set(15);
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            // scope for need_ipc RAII
+            let _raii = ipc::test_set_need_ipc(true);
+
+            // Instrumentation calls do not panic.
+            child_metric.set(30);
+
+            // (They also shouldn't do anything,
+            // but that's not something we can inspect in this test)
+        }
+
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert_eq!(15, parent_metric.test_get_value(None).unwrap());
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/rate.rs b/toolkit/components/glean/api/src/private/rate.rs
new file mode 100644
index 0000000000..39f04db767
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/rate.rs
@@ -0,0 +1,186 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use super::CommonMetricData;
+
+use glean::traits::Rate;
+
+use crate::ipc::{need_ipc, with_ipc_payload};
+use crate::private::MetricId;
+
+/// Developer-facing API for recording rate metrics.
+///
+/// Instances of this class type are automatically generated by the parsers
+/// at build time, allowing developers to record values that were previously
+/// registered in the metrics.yaml file.
+#[derive(Clone)]
+pub enum RateMetric {
+    Parent {
+        /// The metric's ID.
+        ///
+        /// **TEST-ONLY** - Do not use unless gated with `#[cfg(test)]`.
+        id: MetricId,
+        inner: glean::private::RateMetric,
+    },
+    Child(RateMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct RateMetricIpc(MetricId);
+
+impl RateMetric {
+    /// The public constructor used by automatically generated metrics.
+    pub fn new(id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            RateMetric::Child(RateMetricIpc(id))
+        } else {
+            let inner = glean::private::RateMetric::new(meta);
+            RateMetric::Parent { id, inner }
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn metric_id(&self) -> MetricId {
+        match self {
+            RateMetric::Parent { id, .. } => *id,
+            RateMetric::Child(c) => c.0,
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            RateMetric::Parent { id, .. } => RateMetric::Child(RateMetricIpc(*id)),
+            RateMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl Rate for RateMetric {
+    pub fn add_to_numerator(&self, amount: i32) {
+        match self {
+            RateMetric::Parent { inner, .. } => {
+                inner.add_to_numerator(amount);
+            }
+            RateMetric::Child(c) => {
+                with_ipc_payload(move |payload| {
+                    if let Some(r) = payload.rates.get_mut(&c.0) {
+                        r.0 += amount;
+                    } else {
+                        payload.rates.insert(c.0, (amount, 0));
+                    }
+                });
+            }
+        }
+    }
+
+    pub fn add_to_denominator(&self, amount: i32) {
+        match self {
+            RateMetric::Parent { inner, .. } => {
+                inner.add_to_denominator(amount);
+            }
+            RateMetric::Child(c) => {
+                with_ipc_payload(move |payload| {
+                    if let Some(r) = payload.rates.get_mut(&c.0) {
+                        r.1 += amount;
+                    } else {
+                        payload.rates.insert(c.0, (0, amount));
+                    }
+                });
+            }
+        }
+    }
+
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(
+        &self,
+        ping_name: S,
+    ) -> Option<glean::Rate> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            RateMetric::Parent { inner, .. } => inner.test_get_value(ping_name),
+            RateMetric::Child(c) => {
+                panic!("Cannot get test value for {:?} in non-parent process!", c.0);
+            }
+        }
+    }
+
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            RateMetric::Parent { inner, .. } => inner.test_get_num_recorded_errors(error),
+            RateMetric::Child(c) => {
+                panic!(
+                    "Cannot get the number of recorded errors for {:?} in non-parent process!",
+                    c.0
+                );
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+    use glean::Rate;
+
+    #[test]
+    fn sets_rate_value_parent() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::irate;
+        metric.add_to_numerator(1);
+        metric.add_to_denominator(100);
+
+        assert_eq!(
+            Rate {
+                numerator: 1,
+                denominator: 100
+            },
+            metric.test_get_value("store1").unwrap()
+        );
+    }
+
+    #[test]
+    fn sets_rate_value_child() {
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::irate;
+        parent_metric.add_to_numerator(3);
+        parent_metric.add_to_denominator(9);
+
+        {
+            // scope for need_ipc RAII
+            let child_metric = parent_metric.child_metric();
+            let _raii = ipc::test_set_need_ipc(true);
+            let metric_id = child_metric.metric_id();
+
+            child_metric.add_to_numerator(42);
+            child_metric.add_to_denominator(24);
+
+            ipc::with_ipc_payload(move |payload| {
+                assert_eq!(
+                    (42, 24),
+                    *payload.rates.get(&metric_id).unwrap(),
+                    "Stored the correct value in the ipc payload"
+                );
+            });
+        }
+
+        assert!(
+            false == ipc::need_ipc(),
+            "RAII dropped, should not need ipc any more"
+        );
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert_eq!(
+            Rate {
+                numerator: 45,
+                denominator: 33
+            },
+            parent_metric.test_get_value("store1").unwrap(),
+            "Values from the 'processes' should be summed"
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/string.rs b/toolkit/components/glean/api/src/private/string.rs
new file mode 100644
index 0000000000..06e5cd3db1
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/string.rs
@@ -0,0 +1,182 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+use std::sync::Arc;
+
+use super::{CommonMetricData, MetricId};
+use crate::ipc::need_ipc;
+
+/// A string metric.
+///
+/// Record an Unicode string value with arbitrary content.
+/// Strings are length-limited to `MAX_LENGTH_VALUE` bytes.
+///
+/// # Example
+///
+/// The following piece of code will be generated by `glean_parser`:
+///
+/// ```rust,ignore
+/// use glean::metrics::{StringMetric, CommonMetricData, Lifetime};
+/// use once_cell::sync::Lazy;
+///
+/// mod browser {
+///     pub static search_engine: Lazy<StringMetric> = Lazy::new(|| StringMetric::new(CommonMetricData {
+///         name: "search_engine".into(),
+///         category: "browser".into(),
+///         lifetime: Lifetime::Ping,
+///         disabled: false,
+///         dynamic_label: None
+///     }));
+/// }
+/// ```
+///
+/// It can then be used with:
+///
+/// ```rust,ignore
+/// browser::search_engine.set("websearch");
+/// ```
+#[derive(Clone)]
+pub enum StringMetric {
+    Parent(Arc<glean::private::StringMetric>),
+    Child(StringMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct StringMetricIpc;
+
+impl StringMetric {
+    /// Create a new string metric.
+    pub fn new(_id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            StringMetric::Child(StringMetricIpc)
+        } else {
+            StringMetric::Parent(Arc::new(glean::private::StringMetric::new(meta)))
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            StringMetric::Parent(_) => StringMetric::Child(StringMetricIpc),
+            StringMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl glean::traits::String for StringMetric {
+    /// Sets to the specified value.
+    ///
+    /// # Arguments
+    ///
+    /// * `value` - The string to set the metric to.
+    ///
+    /// ## Notes
+    ///
+    /// Truncates the value if it is longer than `MAX_STRING_LENGTH` bytes and logs an error.
+    pub fn set<S: Into<std::string::String>>(&self, value: S) {
+        match self {
+            StringMetric::Parent(p) => {
+                p.set(value.into());
+            }
+            StringMetric::Child(_) => {
+                log::error!("Unable to set string metric in non-main process. Ignoring.");
+                // TODO: Record an error.
+            }
+        };
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the currently stored value as a string.
+    ///
+    /// This doesn't clear the stored value.
+    ///
+    /// # Arguments
+    ///
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(
+        &self,
+        ping_name: S,
+    ) -> Option<std::string::String> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            StringMetric::Parent(p) => p.test_get_value(ping_name),
+            StringMetric::Child(_) => {
+                panic!("Cannot get test value for string metric in non-parent process!")
+            }
+        }
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the number of recorded errors for the given metric and error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors reported.
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            StringMetric::Parent(p) => p.test_get_num_recorded_errors(error),
+            StringMetric::Child(_) => panic!(
+                "Cannot get the number of recorded errors for string metric in non-parent process!"
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_string_value() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_string;
+
+        metric.set("test_string_value");
+
+        assert_eq!(
+            "test_string_value",
+            metric.test_get_value("store1").unwrap()
+        );
+    }
+
+    #[test]
+    fn string_ipc() {
+        // StringMetric doesn't support IPC.
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_string;
+
+        parent_metric.set("test_parent_value");
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            let _raii = ipc::test_set_need_ipc(true);
+
+            // Instrumentation calls do not panic.
+            child_metric.set("test_string_value");
+
+            // (They also shouldn't do anything,
+            // but that's not something we can inspect in this test)
+        }
+
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert!(
+            "test_parent_value" == parent_metric.test_get_value("store1").unwrap(),
+            "String metrics should only work in the parent process"
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/string_list.rs b/toolkit/components/glean/api/src/private/string_list.rs
new file mode 100644
index 0000000000..b3c7dd4d26
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/string_list.rs
@@ -0,0 +1,209 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use super::{CommonMetricData, MetricId};
+
+use glean::traits::StringList;
+
+use crate::ipc::{need_ipc, with_ipc_payload};
+
+/// A string list metric.
+///
+/// This allows appending a string value with arbitrary content to a list.
+#[derive(Clone)]
+pub enum StringListMetric {
+    Parent {
+        /// The metric's ID.
+        ///
+        /// **TEST-ONLY** - Do not use unless gated with `#[cfg(test)]`.
+        id: MetricId,
+        inner: glean::private::StringListMetric,
+    },
+    Child(StringListMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct StringListMetricIpc(MetricId);
+
+impl StringListMetric {
+    /// Create a new string list metric.
+    pub fn new(id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            StringListMetric::Child(StringListMetricIpc(id))
+        } else {
+            let inner = glean::private::StringListMetric::new(meta);
+            StringListMetric::Parent { id, inner }
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            StringListMetric::Parent { id, .. } => {
+                StringListMetric::Child(StringListMetricIpc(*id))
+            }
+            StringListMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl StringList for StringListMetric {
+    /// Add a new string to the list.
+    ///
+    /// ## Arguments
+    ///
+    /// * `value` - The string to add.
+    ///
+    /// ## Notes
+    ///
+    /// Truncates the value if it is longer than `MAX_STRING_LENGTH` bytes and logs an error.
+    /// See [String list metric limits](https://mozilla.github.io/glean/book/user/metrics/string_list.html#limits).
+    pub fn add<S: Into<String>>(&self, value: S) {
+        match self {
+            StringListMetric::Parent { inner, .. } => {
+                inner.add(value.into());
+            }
+            StringListMetric::Child(c) => {
+                with_ipc_payload(move |payload| {
+                    if let Some(v) = payload.string_lists.get_mut(&c.0) {
+                        v.push(value.into());
+                    } else {
+                        let v = vec![value.into()];
+                        payload.string_lists.insert(c.0, v);
+                    }
+                });
+            }
+        }
+    }
+
+    /// Set to a specific list of strings.
+    ///
+    /// ## Arguments
+    ///
+    /// * `value` - The list of string to set the metric to.
+    ///
+    /// ## Notes
+    ///
+    /// If passed an empty list, records an error and returns.
+    /// Truncates the list if it is longer than `MAX_LIST_LENGTH` and logs an error.
+    /// Truncates any value in the list if it is longer than `MAX_STRING_LENGTH` and logs an error.
+    pub fn set(&self, value: Vec<String>) {
+        match self {
+            StringListMetric::Parent { inner, .. } => {
+                inner.set(value);
+            }
+            StringListMetric::Child(c) => {
+                log::error!(
+                    "Unable to set string list metric {:?} in non-main process. Ignoring.",
+                    c.0
+                );
+                // TODO: Record an error.
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Get the currently stored values.
+    /// This doesn't clear the stored value.
+    ///
+    /// ## Arguments
+    ///
+    /// * `storage_name` - the storage name to look into.
+    ///
+    /// ## Return value
+    ///
+    /// Returns the stored value or `None` if nothing stored.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(
+        &self,
+        ping_name: S,
+    ) -> Option<Vec<String>> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            StringListMetric::Parent { inner, .. } => inner.test_get_value(ping_name),
+            StringListMetric::Child(c) => {
+                panic!("Cannot get test value for {:?} in non-parent process!", c.0)
+            }
+        }
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the number of recorded errors for the given error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors recorded.
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            StringListMetric::Parent { inner, .. } => inner.test_get_num_recorded_errors(error),
+            StringListMetric::Child(c) => panic!(
+                "Cannot get the number of recorded errors for {:?} in non-parent process!",
+                c.0
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    #[ignore] // TODO: Enable them back when bug 1677454 lands.
+    fn sets_string_list_value() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_string_list;
+
+        metric.set(vec!["test_string_value".to_string()]);
+        metric.add("another test value");
+
+        assert_eq!(
+            vec!["test_string_value", "another test value"],
+            metric.test_get_value("store1").unwrap()
+        );
+    }
+
+    #[test]
+    #[ignore] // TODO: Enable them back when bug 1677454 lands.
+    fn string_list_ipc() {
+        // StringListMetric supports IPC only for `add`, not `set`.
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_string_list;
+
+        parent_metric.set(vec!["test_string_value".to_string()]);
+        parent_metric.add("another test value");
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            // scope for need_ipc RAII
+            let _raii = ipc::test_set_need_ipc(true);
+
+            // Recording APIs do not panic, even when they don't work.
+            child_metric.set(vec!["not gonna be set".to_string()]);
+
+            child_metric.add("child_value");
+            assert!(ipc::take_buf().unwrap().len() > 0);
+        }
+
+        // TODO: implement replay. See bug 1646165.
+        // Then perform the replay and assert we have the values from both "processes".
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+        assert_eq!(
+            vec!["test_string_value", "another test value"],
+            parent_metric.test_get_value("store1").unwrap()
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/timespan.rs b/toolkit/components/glean/api/src/private/timespan.rs
new file mode 100644
index 0000000000..0d215cd7ff
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/timespan.rs
@@ -0,0 +1,165 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use super::{CommonMetricData, MetricId, TimeUnit};
+use std::convert::TryInto;
+use std::time::Duration;
+
+use glean::traits::Timespan;
+
+use crate::ipc::need_ipc;
+
+/// A timespan metric.
+///
+/// Timespans are used to make a measurement of how much time is spent in a particular task.
+pub enum TimespanMetric {
+    Parent(glean::private::TimespanMetric, TimeUnit),
+    Child,
+}
+
+impl TimespanMetric {
+    /// Create a new timespan metric.
+    pub fn new(_id: MetricId, meta: CommonMetricData, time_unit: TimeUnit) -> Self {
+        if need_ipc() {
+            TimespanMetric::Child
+        } else {
+            TimespanMetric::Parent(
+                glean::private::TimespanMetric::new(meta, time_unit),
+                time_unit,
+            )
+        }
+    }
+
+    /// Only to be called from the MLA FFI.
+    /// If you don't know what that is, don't call this.
+    pub fn set_raw_unitless(&self, duration: u64) {
+        match self {
+            TimespanMetric::Parent(p, time_unit) => {
+                p.set_raw(Duration::from_nanos(time_unit.as_nanos(duration)));
+            }
+            TimespanMetric::Child => {
+                log::error!(
+                    "Unable to set_raw_unitless on timespan in non-main process. Ignoring."
+                );
+                // TODO: Record an error. bug 1704504.
+            }
+        }
+    }
+}
+
+#[inherent]
+impl Timespan for TimespanMetric {
+    pub fn start(&self) {
+        match self {
+            TimespanMetric::Parent(p, _) => p.start(),
+            TimespanMetric::Child => {
+                log::error!("Unable to start timespan metric in non-main process. Ignoring.");
+                // TODO: Record an error. bug 1704504.
+            }
+        }
+    }
+
+    pub fn stop(&self) {
+        match self {
+            TimespanMetric::Parent(p, _) => p.stop(),
+            TimespanMetric::Child => {
+                log::error!("Unable to stop timespan metric in non-main process. Ignoring.");
+                // TODO: Record an error. bug 1704504.
+            }
+        }
+    }
+
+    pub fn cancel(&self) {
+        match self {
+            TimespanMetric::Parent(p, _) => p.cancel(),
+            TimespanMetric::Child => {
+                log::error!("Unable to cancel timespan metric in non-main process. Ignoring.");
+                // TODO: Record an error. bug 1704504.
+            }
+        }
+    }
+
+    pub fn set_raw(&self, elapsed: Duration) {
+        let elapsed = elapsed.as_nanos().try_into().unwrap_or(i64::MAX);
+        match self {
+            TimespanMetric::Parent(p, _) => p.set_raw_nanos(elapsed),
+            TimespanMetric::Child => {
+                log::error!("Unable to set_raw on timespan in non-main process. Ignoring.");
+                // TODO: Record an error. bug 1704504.
+            }
+        }
+    }
+
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(&self, ping_name: S) -> Option<u64> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            // Conversion is ok here:
+            // Timespans are really tricky to set to excessive values with the pleasant APIs.
+            TimespanMetric::Parent(p, _) => p.test_get_value(ping_name).map(|i| i as u64),
+            TimespanMetric::Child => {
+                panic!("Cannot get test value for in non-parent process!");
+            }
+        }
+    }
+
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            TimespanMetric::Parent(p, _) => p.test_get_num_recorded_errors(error),
+            TimespanMetric::Child => {
+                panic!("Cannot get the number of recorded errors for timespan metric in non-parent process!");
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn smoke_test_timespan() {
+        let _lock = lock_test();
+
+        let metric = TimespanMetric::new(
+            0.into(),
+            CommonMetricData {
+                name: "timespan_metric".into(),
+                category: "telemetry".into(),
+                send_in_pings: vec!["store1".into()],
+                disabled: false,
+                ..Default::default()
+            },
+            TimeUnit::Nanosecond,
+        );
+
+        metric.start();
+        // Stopping right away might not give us data, if the underlying clock source is not precise
+        // enough.
+        // So let's cancel and make sure nothing blows up.
+        metric.cancel();
+
+        assert_eq!(None, metric.test_get_value("store1"));
+    }
+
+    #[test]
+    fn timespan_ipc() {
+        let _lock = lock_test();
+        let _raii = ipc::test_set_need_ipc(true);
+
+        let child_metric = &metrics::test_only::can_we_time_it;
+
+        // Instrumentation calls do not panic.
+        child_metric.start();
+        // Stopping right away might not give us data,
+        // if the underlying clock source is not precise enough.
+        // So let's cancel and make sure nothing blows up.
+        child_metric.cancel();
+
+        // (They also shouldn't do anything,
+        // but that's not something we can inspect in this test)
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/timing_distribution.rs b/toolkit/components/glean/api/src/private/timing_distribution.rs
new file mode 100644
index 0000000000..44ebf0a884
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/timing_distribution.rs
@@ -0,0 +1,444 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+use std::collections::HashMap;
+use std::convert::TryInto;
+use std::sync::{
+    atomic::{AtomicUsize, Ordering},
+    RwLock,
+};
+use std::time::{Duration, Instant};
+
+use super::{CommonMetricData, MetricId, TimeUnit};
+use glean::{DistributionData, ErrorType, TimerId};
+
+use crate::ipc::{need_ipc, with_ipc_payload};
+use glean::traits::TimingDistribution;
+
+/// A timing distribution metric.
+///
+/// Timing distributions are used to accumulate and store time measurements for analyzing distributions of the timing data.
+pub enum TimingDistributionMetric {
+    Parent {
+        /// The metric's ID.
+        ///
+        /// No longer test-only, is also used for GIFFT.
+        id: MetricId,
+        inner: glean::private::TimingDistributionMetric,
+    },
+    Child(TimingDistributionMetricIpc),
+}
+#[derive(Debug)]
+pub struct TimingDistributionMetricIpc {
+    metric_id: MetricId,
+    next_timer_id: AtomicUsize,
+    instants: RwLock<HashMap<u64, Instant>>,
+}
+
+impl TimingDistributionMetric {
+    /// Create a new timing distribution metric.
+    pub fn new(id: MetricId, meta: CommonMetricData, time_unit: TimeUnit) -> Self {
+        if need_ipc() {
+            TimingDistributionMetric::Child(TimingDistributionMetricIpc {
+                metric_id: id,
+                next_timer_id: AtomicUsize::new(0),
+                instants: RwLock::new(HashMap::new()),
+            })
+        } else {
+            let inner = glean::private::TimingDistributionMetric::new(meta, time_unit);
+            TimingDistributionMetric::Parent { id, inner }
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            TimingDistributionMetric::Parent { id, .. } => {
+                TimingDistributionMetric::Child(TimingDistributionMetricIpc {
+                    metric_id: *id,
+                    next_timer_id: AtomicUsize::new(0),
+                    instants: RwLock::new(HashMap::new()),
+                })
+            }
+            TimingDistributionMetric::Child(_) => {
+                panic!("Can't get a child metric from a child metric")
+            }
+        }
+    }
+
+    pub(crate) fn accumulate_raw_samples_nanos(&self, samples: Vec<u64>) {
+        match self {
+            TimingDistributionMetric::Parent { inner, .. } => {
+                inner.accumulate_raw_samples_nanos(samples);
+            }
+            TimingDistributionMetric::Child(_) => {
+                // TODO: Instrument this error
+                log::error!("Can't record samples for a timing distribution from a child metric");
+            }
+        }
+    }
+
+    /// Accumulates a time duration sample for the provided metric.
+    ///
+    /// Adds a count to the corresponding bucket in the timing distribution.
+    /// Saturates at u64::MAX nanoseconds.
+    ///
+    /// Prefer start() and stop_and_accumulate() where possible.
+    ///
+    /// Users of this API are responsible for ensuring the timing source used
+    /// to calculate the duration is monotonic and consistent across platforms.
+    ///
+    /// # Arguments
+    ///
+    /// * `duration` - The [`Duration`] of the accumulated sample.
+    pub fn accumulate_raw_duration(&self, duration: Duration) {
+        let sample = duration.as_nanos().try_into().unwrap_or_else(|_| {
+            // TODO: Instrument this error
+            log::warn!(
+                "Elapsed nanoseconds larger than fits into 64-bytes. Saturating at u64::MAX."
+            );
+            u64::MAX
+        });
+        // May be unused in builds without gecko.
+        let _sample_ms = duration.as_millis().try_into().unwrap_or_else(|_| {
+            // TODO: Instrument this error
+            log::warn!(
+                "Elapsed milliseconds larger than fits into 32-bytes. Saturating at u32::MAX."
+            );
+            u32::MAX
+        });
+        match self {
+            TimingDistributionMetric::Parent {
+                id: _metric_id,
+                inner,
+            } => {
+                #[cfg(feature = "with_gecko")]
+                {
+                    extern "C" {
+                        fn GIFFT_TimingDistributionAccumulateRawMillis(metric_id: u32, sample: u32);
+                    }
+                    // SAFETY: using only primitives, no return value.
+                    unsafe {
+                        GIFFT_TimingDistributionAccumulateRawMillis(_metric_id.0, _sample_ms);
+                    }
+                }
+                inner.accumulate_raw_samples_nanos(vec![sample]);
+            }
+            TimingDistributionMetric::Child(c) => {
+                #[cfg(feature = "with_gecko")]
+                {
+                    extern "C" {
+                        fn GIFFT_TimingDistributionAccumulateRawMillis(metric_id: u32, sample: u32);
+                    }
+                    // SAFETY: using only primitives, no return value.
+                    unsafe {
+                        GIFFT_TimingDistributionAccumulateRawMillis(c.metric_id.0, _sample_ms);
+                    }
+                }
+                with_ipc_payload(move |payload| {
+                    if let Some(v) = payload.timing_samples.get_mut(&c.metric_id) {
+                        v.push(sample);
+                    } else {
+                        payload.timing_samples.insert(c.metric_id, vec![sample]);
+                    }
+                });
+            }
+        }
+    }
+}
+
+#[inherent]
+impl TimingDistribution for TimingDistributionMetric {
+    /// Starts tracking time for the provided metric.
+    ///
+    /// This records an error if it’s already tracking time (i.e.
+    /// [`start`](TimingDistribution::start) was already called with no corresponding
+    /// [`stop_and_accumulate`](TimingDistribution::stop_and_accumulate)): in that case the
+    /// original start time will be preserved.
+    ///
+    /// # Returns
+    ///
+    /// A unique [`TimerId`] for the new timer.
+    pub fn start(&self) -> TimerId {
+        match self {
+            TimingDistributionMetric::Parent { id: _id, inner } => {
+                let timer_id = inner.start();
+                #[cfg(feature = "with_gecko")]
+                {
+                    extern "C" {
+                        fn GIFFT_TimingDistributionStart(metric_id: u32, timer_id: u64);
+                    }
+                    // SAFETY: using only primitives, no return value.
+                    unsafe {
+                        GIFFT_TimingDistributionStart(_id.0, timer_id.id);
+                    }
+                }
+                timer_id.into()
+            }
+            TimingDistributionMetric::Child(c) => {
+                // There is no glean-core on this process to give us a TimerId,
+                // so we'll have to make our own and do our own bookkeeping.
+                let id = c
+                    .next_timer_id
+                    .fetch_add(1, Ordering::SeqCst)
+                    .try_into()
+                    .unwrap();
+                let mut map = c
+                    .instants
+                    .write()
+                    .expect("lock of instants map was poisoned");
+                if let Some(_v) = map.insert(id, Instant::now()) {
+                    // TODO: report an error and find a different TimerId.
+                }
+                #[cfg(feature = "with_gecko")]
+                {
+                    extern "C" {
+                        fn GIFFT_TimingDistributionStart(metric_id: u32, timer_id: u64);
+                    }
+                    // SAFETY: using only primitives, no return value.
+                    unsafe {
+                        GIFFT_TimingDistributionStart(c.metric_id.0, id);
+                    }
+                }
+                id.into()
+            }
+        }
+    }
+
+    /// Stops tracking time for the provided metric and associated timer id.
+    ///
+    /// Adds a count to the corresponding bucket in the timing distribution.
+    /// This will record an error if no [`start`](TimingDistribution::start) was
+    /// called.
+    ///
+    /// # Arguments
+    ///
+    /// * `id` - The [`TimerId`] to associate with this timing. This allows
+    ///   for concurrent timing of events associated with different ids to the
+    ///   same timespan metric.
+    pub fn stop_and_accumulate(&self, id: TimerId) {
+        match self {
+            TimingDistributionMetric::Parent {
+                id: _metric_id,
+                inner,
+            } => {
+                #[cfg(feature = "with_gecko")]
+                {
+                    extern "C" {
+                        fn GIFFT_TimingDistributionStopAndAccumulate(metric_id: u32, timer_id: u64);
+                    }
+                    // SAFETY: using only primitives, no return value.
+                    unsafe {
+                        GIFFT_TimingDistributionStopAndAccumulate(_metric_id.0, id.id);
+                    }
+                }
+                inner.stop_and_accumulate(id);
+            }
+            TimingDistributionMetric::Child(c) => {
+                #[cfg(feature = "with_gecko")]
+                {
+                    extern "C" {
+                        fn GIFFT_TimingDistributionStopAndAccumulate(metric_id: u32, timer_id: u64);
+                    }
+                    // SAFETY: using only primitives, no return value.
+                    unsafe {
+                        GIFFT_TimingDistributionStopAndAccumulate(c.metric_id.0, id.id);
+                    }
+                }
+                let mut map = c
+                    .instants
+                    .write()
+                    .expect("Write lock must've been poisoned.");
+                if let Some(start) = map.remove(&id.id) {
+                    let now = Instant::now();
+                    let sample = now
+                        .checked_duration_since(start)
+                        .map(|s| s.as_nanos().try_into());
+                    let sample = match sample {
+                        Some(Ok(sample)) => sample,
+                        Some(Err(_)) => {
+                            log::warn!("Elapsed time larger than fits into 64-bytes. Saturating at u64::MAX.");
+                            u64::MAX
+                        }
+                        None => {
+                            log::warn!("Time went backwards. Not recording.");
+                            // TODO: report an error (timer id for stop was started, but time went backwards).
+                            return;
+                        }
+                    };
+                    with_ipc_payload(move |payload| {
+                        if let Some(v) = payload.timing_samples.get_mut(&c.metric_id) {
+                            v.push(sample);
+                        } else {
+                            payload.timing_samples.insert(c.metric_id, vec![sample]);
+                        }
+                    });
+                } else {
+                    // TODO: report an error (timer id for stop wasn't started).
+                }
+            }
+        }
+    }
+
+    /// Aborts a previous [`start`](TimingDistribution::start) call. No
+    /// error is recorded if no [`start`](TimingDistribution::start) was
+    /// called.
+    ///
+    /// # Arguments
+    ///
+    /// * `id` - The [`TimerId`] to associate with this timing. This allows
+    ///   for concurrent timing of events associated with different ids to the
+    ///   same timing distribution metric.
+    pub fn cancel(&self, id: TimerId) {
+        match self {
+            TimingDistributionMetric::Parent {
+                id: _metric_id,
+                inner,
+            } => {
+                #[cfg(feature = "with_gecko")]
+                {
+                    extern "C" {
+                        fn GIFFT_TimingDistributionCancel(metric_id: u32, timer_id: u64);
+                    }
+                    // SAFETY: using only primitives, no return value.
+                    unsafe {
+                        GIFFT_TimingDistributionCancel(_metric_id.0, id.id);
+                    }
+                }
+                inner.cancel(id);
+            }
+            TimingDistributionMetric::Child(c) => {
+                let mut map = c
+                    .instants
+                    .write()
+                    .expect("Write lock must've been poisoned.");
+                if map.remove(&id.id).is_none() {
+                    // TODO: report an error (cancelled a non-started id).
+                }
+                #[cfg(feature = "with_gecko")]
+                {
+                    extern "C" {
+                        fn GIFFT_TimingDistributionCancel(metric_id: u32, timer_id: u64);
+                    }
+                    // SAFETY: using only primitives, no return value.
+                    unsafe {
+                        GIFFT_TimingDistributionCancel(c.metric_id.0, id.id);
+                    }
+                }
+            }
+        }
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the currently stored value of the metric.
+    ///
+    /// This doesn't clear the stored value.
+    ///
+    /// # Arguments
+    ///
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(
+        &self,
+        ping_name: S,
+    ) -> Option<DistributionData> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            TimingDistributionMetric::Parent { inner, .. } => inner.test_get_value(ping_name),
+            TimingDistributionMetric::Child(c) => {
+                panic!("Cannot get test value for {:?} in non-parent process!", c)
+            }
+        }
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the number of recorded errors for the given error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors recorded.
+    pub fn test_get_num_recorded_errors(&self, error: ErrorType) -> i32 {
+        match self {
+            TimingDistributionMetric::Parent { inner, .. } => {
+                inner.test_get_num_recorded_errors(error)
+            }
+            TimingDistributionMetric::Child(c) => panic!(
+                "Cannot get number of recorded errors for {:?} in non-parent process!",
+                c
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn smoke_test_timing_distribution() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_timing_dist;
+
+        let id = metric.start();
+        // Stopping right away might not give us data, if the underlying clock source is not precise
+        // enough.
+        // So let's cancel and make sure nothing blows up.
+        metric.cancel(id);
+
+        // We can't inspect the values yet.
+        assert!(metric.test_get_value("store1").is_none());
+    }
+
+    #[test]
+    fn timing_distribution_child() {
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_timing_dist;
+        let id = parent_metric.start();
+        std::thread::sleep(std::time::Duration::from_millis(10));
+        parent_metric.stop_and_accumulate(id);
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            // scope for need_ipc RAII
+            let _raii = ipc::test_set_need_ipc(true);
+
+            let id = child_metric.start();
+            let id2 = child_metric.start();
+            assert_ne!(id, id2);
+            std::thread::sleep(std::time::Duration::from_millis(10));
+            child_metric.stop_and_accumulate(id);
+
+            child_metric.cancel(id2);
+        }
+
+        let buf = ipc::take_buf().unwrap();
+        assert!(buf.len() > 0);
+        assert!(ipc::replay_from_buf(&buf).is_ok());
+
+        let data = parent_metric
+            .test_get_value("store1")
+            .expect("should have some data");
+
+        // No guarantees from timers means no guarantees on buckets.
+        // But we can guarantee it's only two samples.
+        assert_eq!(
+            2,
+            data.values.values().fold(0, |acc, count| acc + count),
+            "record 2 values, one parent, one child measurement"
+        );
+        assert!(0 < data.sum, "record some time");
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/url.rs b/toolkit/components/glean/api/src/private/url.rs
new file mode 100644
index 0000000000..1ad49c3a7d
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/url.rs
@@ -0,0 +1,124 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use super::{CommonMetricData, MetricId};
+
+use crate::ipc::need_ipc;
+
+/// Developer-facing API for recording URL metrics.
+///
+/// Instances of this class type are automatically generated by the parsers
+/// at build time, allowing developers to record values that were previously
+/// registered in the metrics.yaml file.
+#[derive(Clone)]
+pub enum UrlMetric {
+    Parent(glean::private::UrlMetric),
+    Child(UrlMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct UrlMetricIpc;
+
+impl UrlMetric {
+    /// Create a new Url metric.
+    pub fn new(_id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            UrlMetric::Child(UrlMetricIpc)
+        } else {
+            UrlMetric::Parent(glean::private::UrlMetric::new(meta))
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            UrlMetric::Parent(_) => UrlMetric::Child(UrlMetricIpc),
+            UrlMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl glean::traits::Url for UrlMetric {
+    pub fn set<S: Into<std::string::String>>(&self, value: S) {
+        match self {
+            UrlMetric::Parent(p) => p.set(value),
+            UrlMetric::Child(_) => {
+                log::error!("Unable to set Url metric in non-main process. Ignoring.");
+                // TODO: Record an error.
+            }
+        };
+    }
+
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(
+        &self,
+        ping_name: S,
+    ) -> Option<std::string::String> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            UrlMetric::Parent(p) => p.test_get_value(ping_name),
+            UrlMetric::Child(_) => {
+                panic!("Cannot get test value for Url metric in non-parent process!")
+            }
+        }
+    }
+
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            UrlMetric::Parent(p) => p.test_get_num_recorded_errors(error),
+            UrlMetric::Child(_) => panic!(
+                "Cannot get the number of recorded errors for Url metric in non-parent process!"
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_url_value() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_url;
+
+        metric.set("https://example.com");
+
+        assert_eq!(
+            "https://example.com",
+            metric.test_get_value("store1").unwrap()
+        );
+    }
+
+    #[test]
+    fn url_ipc() {
+        // UrlMetric doesn't support IPC.
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_url;
+
+        parent_metric.set("https://example.com/parent");
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            let _raii = ipc::test_set_need_ipc(true);
+
+            // Instrumentation calls do not panic.
+            child_metric.set("https://example.com/child");
+
+            // (They also shouldn't do anything,
+            // but that's not something we can inspect in this test)
+        }
+
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert!(
+            "https://example.com/parent" == parent_metric.test_get_value("store1").unwrap(),
+            "Url metrics should only work in the parent process"
+        );
+    }
+}
diff --git a/toolkit/components/glean/api/src/private/uuid.rs b/toolkit/components/glean/api/src/private/uuid.rs
new file mode 100644
index 0000000000..a34602ac48
--- /dev/null
+++ b/toolkit/components/glean/api/src/private/uuid.rs
@@ -0,0 +1,165 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use inherent::inherent;
+
+use uuid::Uuid;
+
+use super::{CommonMetricData, MetricId};
+
+use crate::ipc::need_ipc;
+
+/// A UUID metric.
+///
+/// Stores UUID values.
+pub enum UuidMetric {
+    Parent(glean::private::UuidMetric),
+    Child(UuidMetricIpc),
+}
+
+#[derive(Debug)]
+pub struct UuidMetricIpc;
+
+impl UuidMetric {
+    /// Create a new UUID metric.
+    pub fn new(_id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            UuidMetric::Child(UuidMetricIpc)
+        } else {
+            UuidMetric::Parent(glean::private::UuidMetric::new(meta))
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            UuidMetric::Parent(_) => UuidMetric::Child(UuidMetricIpc),
+            UuidMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl glean::traits::Uuid for UuidMetric {
+    /// Set to the specified value.
+    ///
+    /// ## Arguments
+    ///
+    /// * `value` - The UUID to set the metric to.
+    pub fn set(&self, value: Uuid) {
+        match self {
+            UuidMetric::Parent(p) => p.set(value.to_string()),
+            UuidMetric::Child(_c) => {
+                log::error!("Unable to set the uuid metric in non-main process. Ignoring.");
+                // TODO: Record an error.
+            }
+        };
+    }
+
+    /// Generate a new random UUID and set the metric to it.
+    ///
+    /// ## Return value
+    ///
+    /// Returns the stored UUID value or `Uuid::nil` if called from
+    /// a non-parent process.
+    pub fn generate_and_set(&self) -> Uuid {
+        match self {
+            UuidMetric::Parent(p) => Uuid::parse_str(&p.generate_and_set()).unwrap(),
+            UuidMetric::Child(_c) => {
+                log::error!("Unable to set the uuid metric in non-main process. Ignoring.");
+                // TODO: Record an error.
+                Uuid::nil()
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Get the stored UUID value.
+    /// This doesn't clear the stored value.
+    ///
+    /// ## Arguments
+    ///
+    /// * `storage_name` - the storage name to look into.
+    ///
+    /// ## Return value
+    ///
+    /// Returns the stored value or `None` if nothing stored.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(&self, storage_name: S) -> Option<Uuid> {
+        let storage_name = storage_name.into().map(|s| s.to_string());
+        match self {
+            UuidMetric::Parent(p) => p
+                .test_get_value(storage_name)
+                .and_then(|s| Uuid::parse_str(&s).ok()),
+            UuidMetric::Child(_c) => panic!("Cannot get test value for in non-parent process!"),
+        }
+    }
+
+    /// **Exported for test purposes.**
+    ///
+    /// Gets the number of recorded errors for the given metric and error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors reported.
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            UuidMetric::Parent(p) => p.test_get_num_recorded_errors(error),
+            UuidMetric::Child(_c) => {
+                panic!("Cannot get test value for UuidMetric in non-parent process!")
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_uuid_value() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_uuid;
+        let expected = Uuid::new_v4();
+        metric.set(expected.clone());
+
+        assert_eq!(expected, metric.test_get_value("store1").unwrap());
+    }
+
+    #[test]
+    fn uuid_ipc() {
+        // UuidMetric doesn't support IPC.
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_uuid;
+        let expected = Uuid::new_v4();
+        parent_metric.set(expected.clone());
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            // Instrumentation calls do not panic.
+            child_metric.set(Uuid::new_v4());
+
+            // (They also shouldn't do anything,
+            // but that's not something we can inspect in this test)
+        }
+
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert_eq!(
+            expected,
+            parent_metric.test_get_value("store1").unwrap(),
+            "UUID metrics should only work in the parent process"
+        );
+    }
+}
diff --git a/toolkit/components/glean/bindings/Category.cpp b/toolkit/components/glean/bindings/Category.cpp
new file mode 100644
index 0000000000..112fc365d4
--- /dev/null
+++ b/toolkit/components/glean/bindings/Category.cpp
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/GleanBinding.h"
+#include "mozilla/glean/bindings/Glean.h"
+#include "mozilla/glean/bindings/Category.h"
+#include "mozilla/glean/bindings/GleanJSMetricsLookup.h"
+#include "mozilla/glean/bindings/jog/JOG.h"
+
+namespace mozilla::glean {
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_0(Category)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(Category)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(Category)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Category)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+JSObject* Category::WrapObject(JSContext* aCx,
+                               JS::Handle<JSObject*> aGivenProto) {
+  return dom::GleanCategory_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+already_AddRefed<nsISupports> Category::NamedGetter(const nsAString& aName,
+                                                    bool& aFound) {
+  aFound = false;
+
+  nsCString metricName;
+  metricName.AppendASCII(mName);
+  metricName.AppendLiteral(".");
+  AppendUTF16toUTF8(aName, metricName);
+
+  Maybe<uint32_t> metricIdx = JOG::GetMetric(metricName);
+  if (metricIdx.isNothing() && !JOG::AreRuntimeMetricsComprehensive()) {
+    metricIdx = MetricByNameLookup(metricName);
+  }
+
+  if (metricIdx.isNothing()) {
+    aFound = false;
+    return nullptr;
+  }
+
+  aFound = true;
+  return NewMetricFromId(metricIdx.value());
+}
+
+bool Category::NameIsEnumerable(const nsAString& aName) { return false; }
+
+void Category::GetSupportedNames(nsTArray<nsString>& aNames) {
+  // We don't get dynamic metric names because we don't want to store them.
+  if (!JOG::AreRuntimeMetricsComprehensive()) {
+    for (metric_entry_t entry : sMetricByNameLookupEntries) {
+      const char* identifierBuf = GetMetricIdentifier(entry);
+      nsDependentCString identifier(identifierBuf);
+
+      // We're iterating all metrics,
+      // so we need to check for the ones in the right category.
+      //
+      // We need to ensure that we found _only_ the exact category by checking
+      // it is followed by a dot.
+      if (StringBeginsWith(identifier, mName) &&
+          identifier.CharAt(mName.Length()) == '.') {
+        const char* metricName = &identifierBuf[mName.Length() + 1];
+        aNames.AppendElement()->AssignASCII(metricName);
+      }
+    }
+  }
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/Category.h b/toolkit/components/glean/bindings/Category.h
new file mode 100644
index 0000000000..ce85c71138
--- /dev/null
+++ b/toolkit/components/glean/bindings/Category.h
@@ -0,0 +1,42 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_Category_h
+#define mozilla_glean_Category_h
+
+#include "js/TypeDecls.h"
+#include "nsISupports.h"
+#include "nsTArrayForwardDeclare.h"
+#include "nsWrapperCache.h"
+
+namespace mozilla::glean {
+
+class Category final : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(Category)
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+  nsISupports* GetParentObject() { return nullptr; }
+
+  explicit Category(nsCString&& aName) : mName(aName) {}
+
+  already_AddRefed<nsISupports> NamedGetter(const nsAString& aName,
+                                            bool& aFound);
+  bool NameIsEnumerable(const nsAString& aName);
+  void GetSupportedNames(nsTArray<nsString>& aNames);
+
+ private:
+  nsCString mName;
+
+ protected:
+  virtual ~Category() = default;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_Category_h */
diff --git a/toolkit/components/glean/bindings/Glean.cpp b/toolkit/components/glean/bindings/Glean.cpp
new file mode 100644
index 0000000000..141e17e0f3
--- /dev/null
+++ b/toolkit/components/glean/bindings/Glean.cpp
@@ -0,0 +1,111 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/DOMJSClass.h"
+#include "mozilla/dom/GleanBinding.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/glean/bindings/Glean.h"
+#include "mozilla/glean/bindings/Category.h"
+#include "mozilla/glean/bindings/GleanJSMetricsLookup.h"
+#include "mozilla/glean/bindings/jog/jog_ffi_generated.h"
+#include "mozilla/glean/bindings/jog/JOG.h"
+#include "MainThreadUtils.h"
+#include "js/PropertyAndElement.h"  // JS_DefineProperty
+
+namespace mozilla::glean {
+
+// Whether the runtime-registered metrics should be treated as comprehensive,
+// or additive. If comprehensive, a metric not registered at runtime is a
+// metric that doesn't exist. If additive, a metric not registered at runtime
+// may still exist if it was registered at compile time.
+// If we're supporting Artefact Builds, we treat them as comprehensive.
+// Threading: Must only be read or written to on the main thread.
+static bool gRuntimeMetricsComprehensive = false;
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_0(Glean)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(Glean)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(Glean)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Glean)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+JSObject* Glean::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
+  return dom::GleanImpl_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+// static
+bool Glean::DefineGlean(JSContext* aCx, JS::Handle<JSObject*> aGlobal) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(JS::GetClass(aGlobal)->flags & JSCLASS_DOM_GLOBAL,
+             "Passed object is not a global object!");
+
+  nsIGlobalObject* global = xpc::CurrentNativeGlobal(aCx);
+  if (NS_WARN_IF(!global)) {
+    return false;
+  }
+
+  JS::Rooted<JS::Value> glean(aCx);
+  js::AssertSameCompartment(aCx, aGlobal);
+
+  auto impl = MakeRefPtr<Glean>();
+  if (!dom::GetOrCreateDOMReflector(aCx, impl.get(), &glean)) {
+    return false;
+  }
+
+  return JS_DefineProperty(aCx, aGlobal, "Glean", glean, JSPROP_ENUMERATE);
+}
+
+already_AddRefed<Category> Glean::NamedGetter(const nsAString& aName,
+                                              bool& aFound) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  JOG::EnsureRuntimeMetricsRegistered();
+
+  NS_ConvertUTF16toUTF8 categoryName(aName);
+  if (JOG::HasCategory(categoryName)) {
+    aFound = true;
+    return MakeAndAddRef<Category>(std::move(categoryName));
+  }
+
+  if (gRuntimeMetricsComprehensive) {
+    // This category might be built-in, but since the runtime metrics are
+    // comprehensive, that just signals that the category was removed locally.
+    aFound = false;
+    return nullptr;
+  }
+
+  Maybe<uint32_t> categoryIdx = CategoryByNameLookup(categoryName);
+  if (categoryIdx.isNothing()) {
+    aFound = false;
+    return nullptr;
+  }
+
+  aFound = true;
+  nsDependentCString name(&gCategoryStringTable[categoryIdx.value()]);
+  return MakeAndAddRef<Category>(std::move(name));
+}
+
+bool Glean::NameIsEnumerable(const nsAString& aName) { return false; }
+
+void Glean::GetSupportedNames(nsTArray<nsString>& aNames) {
+  JOG::GetCategoryNames(aNames);
+  if (!JOG::AreRuntimeMetricsComprehensive()) {
+    for (category_entry_t entry : sCategoryByNameLookupEntries) {
+      const char* categoryName = GetCategoryName(entry);
+      aNames.AppendElement()->AssignASCII(categoryName);
+    }
+  }
+}
+
+// static
+void Glean::TestSetRuntimeMetricsComprehensive(bool aIsComprehensive) {
+  MOZ_ASSERT(NS_IsMainThread());
+  gRuntimeMetricsComprehensive = aIsComprehensive;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/Glean.h b/toolkit/components/glean/bindings/Glean.h
new file mode 100644
index 0000000000..4305e68aa7
--- /dev/null
+++ b/toolkit/components/glean/bindings/Glean.h
@@ -0,0 +1,51 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_Glean_h
+#define mozilla_glean_Glean_h
+
+#include "js/TypeDecls.h"
+#include "nsISupports.h"
+#include "nsTArrayForwardDeclare.h"
+#include "nsWrapperCache.h"
+
+namespace mozilla::glean {
+
+class Category;
+
+class Glean final : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(Glean)
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+  nsISupports* GetParentObject() { return nullptr; }
+
+  static bool DefineGlean(JSContext* aCx, JS::Handle<JSObject*> aGlobal);
+
+  already_AddRefed<Category> NamedGetter(const nsAString& aName, bool& aFound);
+  bool NameIsEnumerable(const nsAString& aName);
+  void GetSupportedNames(nsTArray<nsString>& aNames);
+
+  /*
+   * Test-only method.
+   *
+   * Set whether we should treat runtime-registered metrics as the
+   * comprehensive list of all metrics, or whether compile-time-registered
+   * metrics are allowed to count too.
+   *
+   * Allows us to test Artifact Build support flexibly.
+   */
+  static void TestSetRuntimeMetricsComprehensive(bool aIsComprehensive);
+
+ protected:
+  virtual ~Glean() = default;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_Glean */
diff --git a/toolkit/components/glean/bindings/GleanPings.cpp b/toolkit/components/glean/bindings/GleanPings.cpp
new file mode 100644
index 0000000000..5103adb22f
--- /dev/null
+++ b/toolkit/components/glean/bindings/GleanPings.cpp
@@ -0,0 +1,88 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/GleanPings.h"
+
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/DOMJSClass.h"
+#include "mozilla/dom/GleanPingsBinding.h"
+#include "mozilla/glean/bindings/GleanJSPingsLookup.h"
+#include "mozilla/glean/bindings/Ping.h"
+#include "MainThreadUtils.h"
+#include "js/PropertyAndElement.h"  // JS_DefineProperty
+
+namespace mozilla::glean {
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_0(GleanPings)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(GleanPings)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(GleanPings)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(GleanPings)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+JSObject* GleanPings::WrapObject(JSContext* aCx,
+                                 JS::Handle<JSObject*> aGivenProto) {
+  return dom::GleanPingsImpl_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+// static
+bool GleanPings::DefineGleanPings(JSContext* aCx,
+                                  JS::Handle<JSObject*> aGlobal) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(JS::GetClass(aGlobal)->flags & JSCLASS_DOM_GLOBAL,
+             "Passed object is not a global object!");
+
+  nsIGlobalObject* global = xpc::CurrentNativeGlobal(aCx);
+  if (NS_WARN_IF(!global)) {
+    return false;
+  }
+
+  JS::Rooted<JS::Value> gleanPings(aCx);
+  js::AssertSameCompartment(aCx, aGlobal);
+
+  auto impl = MakeRefPtr<GleanPings>();
+  if (!dom::GetOrCreateDOMReflector(aCx, impl.get(), &gleanPings)) {
+    return false;
+  }
+
+  return JS_DefineProperty(aCx, aGlobal, "GleanPings", gleanPings,
+                           JSPROP_ENUMERATE);
+}
+
+already_AddRefed<GleanPing> GleanPings::NamedGetter(const nsAString& aName,
+                                                    bool& aFound) {
+  aFound = false;
+
+  NS_ConvertUTF16toUTF8 pingName(aName);
+
+  JOG::EnsureRuntimeMetricsRegistered();
+
+  Maybe<uint32_t> pingId = JOG::GetPing(pingName);
+  if (pingId.isNothing() && !JOG::AreRuntimeMetricsComprehensive()) {
+    pingId = PingByNameLookup(pingName);
+  }
+
+  if (pingId.isNothing()) {
+    aFound = false;
+    return nullptr;
+  }
+
+  aFound = true;
+  return MakeAndAddRef<GleanPing>(pingId.value());
+}
+
+bool GleanPings::NameIsEnumerable(const nsAString& aName) { return false; }
+
+void GleanPings::GetSupportedNames(nsTArray<nsString>& aNames) {
+  for (uint8_t idx : sPingByNameLookupEntries) {
+    const char* pingName = GetPingName(idx);
+    aNames.AppendElement()->AssignASCII(pingName);
+  }
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/GleanPings.h b/toolkit/components/glean/bindings/GleanPings.h
new file mode 100644
index 0000000000..2dd1ff4b83
--- /dev/null
+++ b/toolkit/components/glean/bindings/GleanPings.h
@@ -0,0 +1,38 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanPings_h
+#define mozilla_glean_GleanPings_h
+
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/glean/bindings/Ping.h"
+#include "nsISupports.h"
+#include "nsWrapperCache.h"
+
+namespace mozilla::glean {
+
+class GleanPings final : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(GleanPings)
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+  nsISupports* GetParentObject() { return nullptr; }
+
+  static bool DefineGleanPings(JSContext* aCx, JS::Handle<JSObject*> aGlobal);
+
+  already_AddRefed<GleanPing> NamedGetter(const nsAString& aName, bool& aFound);
+  bool NameIsEnumerable(const nsAString& aName);
+  void GetSupportedNames(nsTArray<nsString>& aNames);
+
+ protected:
+  virtual ~GleanPings() = default;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanPings */
diff --git a/toolkit/components/glean/bindings/MetricTypes.h b/toolkit/components/glean/bindings/MetricTypes.h
new file mode 100644
index 0000000000..bec4e87ad2
--- /dev/null
+++ b/toolkit/components/glean/bindings/MetricTypes.h
@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_Glean_MetricTypes_h
+#define mozilla_Glean_MetricTypes_h
+
+#include "mozilla/glean/bindings/Boolean.h"
+#include "mozilla/glean/bindings/Counter.h"
+#include "mozilla/glean/bindings/CustomDistribution.h"
+#include "mozilla/glean/bindings/Datetime.h"
+#include "mozilla/glean/bindings/Denominator.h"
+#include "mozilla/glean/bindings/Event.h"
+#include "mozilla/glean/bindings/Labeled.h"
+#include "mozilla/glean/bindings/MemoryDistribution.h"
+#include "mozilla/glean/bindings/Numerator.h"
+#include "mozilla/glean/bindings/Quantity.h"
+#include "mozilla/glean/bindings/Rate.h"
+#include "mozilla/glean/bindings/String.h"
+#include "mozilla/glean/bindings/StringList.h"
+#include "mozilla/glean/bindings/Timespan.h"
+#include "mozilla/glean/bindings/TimingDistribution.h"
+#include "mozilla/glean/bindings/Url.h"
+#include "mozilla/glean/bindings/Uuid.h"
+
+#endif  // mozilla_Glean_MetricTypes_h
diff --git a/toolkit/components/glean/bindings/jog/Cargo.toml b/toolkit/components/glean/bindings/jog/Cargo.toml
new file mode 100644
index 0000000000..c0ef574214
--- /dev/null
+++ b/toolkit/components/glean/bindings/jog/Cargo.toml
@@ -0,0 +1,20 @@
+[package]
+name = "jog"
+version = "0.1.0"
+authors = ["Glean SDK team <glean-team@mozilla.com>"]
+edition = "2021"
+publish = false
+license = "MPL-2.0"
+
+[dependencies]
+fog = { path = "../../api" }
+log = "0.4"
+mozbuild = "0.1"
+nsstring = { path = "../../../../../xpcom/rust/nsstring", optional = true }
+once_cell = "1.2.0"
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+thin-vec = { version = "0.2.1", features = ["gecko-ffi"] }
+
+[features]
+with_gecko = [ "nsstring" ]
diff --git a/toolkit/components/glean/bindings/jog/JOG.cpp b/toolkit/components/glean/bindings/jog/JOG.cpp
new file mode 100644
index 0000000000..164d639016
--- /dev/null
+++ b/toolkit/components/glean/bindings/jog/JOG.cpp
@@ -0,0 +1,221 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/jog/JOG.h"
+
+#include <locale>
+
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/DataMutex.h"
+#include "mozilla/glean/bindings/jog/jog_ffi_generated.h"
+#include "mozilla/Omnijar.h"
+#include "mozilla/Tuple.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsThreadUtils.h"
+#include "nsTHashMap.h"
+#include "nsTHashSet.h"
+
+namespace mozilla::glean {
+
+// Storage
+// Thread Safety: Only used on the main thread.
+StaticAutoPtr<nsTHashSet<nsCString>> gCategories;
+StaticAutoPtr<nsTHashMap<nsCString, uint32_t>> gMetrics;
+StaticAutoPtr<nsTHashMap<nsCString, uint32_t>> gPings;
+
+// static
+bool JOG::HasCategory(const nsACString& aCategoryName) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  return gCategories && gCategories->Contains(aCategoryName);
+}
+
+static Maybe<bool> sFoundAndLoadedJogfile;
+
+// static
+bool JOG::EnsureRuntimeMetricsRegistered(bool aForce) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+#ifdef MOZILLA_OFFICIAL
+  // In the event we're an official build we want there to be no chance we might
+  // accidentally perform I/O on the main thread.
+  return false;
+#endif
+
+  if (sFoundAndLoadedJogfile) {
+    return sFoundAndLoadedJogfile.value();
+  }
+  sFoundAndLoadedJogfile.emplace(false);
+
+  if (!mozilla::IsDevelopmentBuild()) {
+    // Supporting Artifact Builds is a developer-only thing.
+    // We're on the main thread here.
+    // Let's not spend any more time than we need to.
+    return false;
+  }
+  // The metrics we need to process were placed in GreD in jogfile.json
+  // That file was generated by
+  // toolkit/components/glean/build_scripts/glean_parser_ext/jog.py
+  nsCOMPtr<nsIFile> jogfile;
+  if (NS_WARN_IF(NS_FAILED(
+          NS_GetSpecialDirectory(NS_GRE_DIR, getter_AddRefs(jogfile))))) {
+    return false;
+  }
+  if (NS_WARN_IF(NS_FAILED(jogfile->Append(u"jogfile.json"_ns)))) {
+    return false;
+  }
+  bool jogfileExists = false;
+  if (NS_WARN_IF(NS_FAILED(jogfile->Exists(&jogfileExists))) ||
+      !jogfileExists) {
+    return false;
+  }
+
+  // We _could_ register everything here in C++ land,
+  // but let's use Rust because (among other reasons) it's more fun.
+  nsAutoString jogfileString;
+  if (NS_WARN_IF(NS_FAILED(jogfile->GetPath(jogfileString)))) {
+    return false;
+  }
+  sFoundAndLoadedJogfile.emplace(jog::jog_load_jogfile(&jogfileString));
+  return sFoundAndLoadedJogfile.value();
+}
+
+// static
+bool JOG::AreRuntimeMetricsComprehensive() {
+  MOZ_ASSERT(NS_IsMainThread());
+  return sFoundAndLoadedJogfile && sFoundAndLoadedJogfile.value();
+}
+
+// static
+void JOG::GetCategoryNames(nsTArray<nsString>& aNames) {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!gCategories) {
+    return;
+  }
+  for (const auto& category : *gCategories) {
+    aNames.EmplaceBack(NS_ConvertUTF8toUTF16(category));
+  }
+}
+
+// static
+Maybe<uint32_t> JOG::GetMetric(const nsACString& aMetricName) {
+  MOZ_ASSERT(NS_IsMainThread());
+  return !gMetrics ? Nothing() : gMetrics->MaybeGet(aMetricName);
+}
+
+// static
+Maybe<uint32_t> JOG::GetPing(const nsACString& aPingName) {
+  MOZ_ASSERT(NS_IsMainThread());
+  return !gPings ? Nothing() : gPings->MaybeGet(aPingName);
+}
+
+}  // namespace mozilla::glean
+
+// static
+nsCString dottedSnakeToCamel(const nsACString& aSnake) {
+  nsCString camel;
+  bool first = true;
+  for (const nsACString& segment : aSnake.Split('_')) {
+    for (const nsACString& part : segment.Split('.')) {
+      if (first) {
+        first = false;
+        camel.Append(part);
+      } else if (part.Length()) {
+        char lower = part.CharAt(0);
+        if ('a' <= lower && lower <= 'z') {
+          camel.Append(
+              std::toupper(lower, std::locale()));  // append the Capital.
+          camel.Append(part.BeginReading() + 1,
+                       part.Length() - 1);  // append the rest.
+        } else {
+          // Not gonna try to capitalize anything outside a->z.
+          camel.Append(part);
+        }
+      }
+    }
+  }
+  return camel;
+}
+
+// static
+nsCString kebabToCamel(const nsACString& aKebab) {
+  nsCString camel;
+  bool first = true;
+  for (const nsACString& segment : aKebab.Split('-')) {
+    if (first) {
+      first = false;
+      camel.Append(segment);
+    } else if (segment.Length()) {
+      char lower = segment.CharAt(0);
+      if ('a' <= lower && lower <= 'z') {
+        camel.Append(
+            std::toupper(lower, std::locale()));  // append the Capital.
+        camel.Append(segment.BeginReading() + 1,
+                     segment.Length() - 1);  // append the rest.
+      } else {
+        // Not gonna try to capitalize anything outside a->z.
+        camel.Append(segment);
+      }
+    }
+  }
+  return camel;
+}
+
+using mozilla::AppShutdown;
+using mozilla::ShutdownPhase;
+using mozilla::glean::gCategories;
+using mozilla::glean::gMetrics;
+using mozilla::glean::gPings;
+
+extern "C" NS_EXPORT void JOG_RegisterMetric(const nsACString& aCategory,
+                                             const nsACString& aName,
+                                             uint32_t aMetric) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+    return;
+  }
+
+  // aCategory is dotted.snake_case. aName is snake_case.
+  auto categoryCamel = dottedSnakeToCamel(aCategory);
+  auto nameCamel = dottedSnakeToCamel(aName);
+
+  // Register the category
+  if (!gCategories) {
+    gCategories = new nsTHashSet<nsCString>();
+    RunOnShutdown([&] { gCategories = nullptr; },
+                  ShutdownPhase::XPCOMWillShutdown);
+  }
+  gCategories->Insert(categoryCamel);
+
+  // Register the metric
+  if (!gMetrics) {
+    gMetrics = new nsTHashMap<nsCString, uint32_t>();
+    RunOnShutdown([&] { gMetrics = nullptr; },
+                  ShutdownPhase::XPCOMWillShutdown);
+  }
+  gMetrics->InsertOrUpdate(categoryCamel + "."_ns + nameCamel, aMetric);
+}
+
+extern "C" NS_EXPORT void JOG_RegisterPing(const nsACString& aPingName,
+                                           uint32_t aPingId) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+    return;
+  }
+
+  // aPingName is kebab-case. JS expects camelCase.
+  auto pingCamel = kebabToCamel(aPingName);
+
+  // Register the ping
+  if (!gPings) {
+    gPings = new nsTHashMap<nsCString, uint32_t>();
+    RunOnShutdown([&] { gPings = nullptr; }, ShutdownPhase::XPCOMWillShutdown);
+  }
+  gPings->InsertOrUpdate(pingCamel, aPingId);
+}
diff --git a/toolkit/components/glean/bindings/jog/JOG.h b/toolkit/components/glean/bindings/jog/JOG.h
new file mode 100644
index 0000000000..e261d04d88
--- /dev/null
+++ b/toolkit/components/glean/bindings/jog/JOG.h
@@ -0,0 +1,92 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_JOG_h
+#define mozilla_glean_JOG_h
+
+namespace mozilla::glean {
+
+class JOG {
+ public:
+  /**
+   * Returns whether JOG knows about a category by this name
+   *
+   * @param aCategoryName The category name to check.
+   *
+   * @returns true if JOG is aware of a category by the given name at this time
+   */
+  static bool HasCategory(const nsACString& aCategoryName);
+
+  /**
+   * Runs the runtime registrar.
+   *
+   * Locates the runtime metrics file and, if present, loads and processes it.
+   *
+   * Only does any work at all if mozilla::IsDevelopmentBuild()
+   *
+   * **Note:** When this function does something, it is expensive, running
+   * synchronous file I/O to ensure that the registration is complete when this
+   * call returns.
+   *
+   * @param aForce Set to `true` if you want to force the I/O to run. Defaults
+   *        to `false`, which doesn't run the I/O if it's already run and
+   *        returns the previous return value.
+   * @returns whether it found the runtime metrics file and succesfully loaded,
+   *          processed, and registered the described metrics.
+   */
+  static bool EnsureRuntimeMetricsRegistered(bool aForce = false);
+
+  /**
+   * Returns whether, if a metric is absent in the runtime-registered metrics,
+   * you should check the compile-time-registered metrics.
+   *
+   * Runtime-registered metrics can either replace all compile-time-registered
+   * metrics (like in artefact builds) or just be supplementing compile-time-
+   * registered metrics (like addons/dynamic telemetry/etc).
+   *
+   * This is tied to the current state of runtime metric registration. So it
+   * may return false at one time and true later (e.g. if RuntimeRegistrar is
+   * run in between).
+   *
+   * @return true if you should treat the runtime-registered metrics as
+   *         authoritative and comprehensive.
+   */
+  static bool AreRuntimeMetricsComprehensive();
+
+  /**
+   * Adds the runtime-registered metrics' categories to `aNames`.
+   *
+   * @param aNames The list to add the categories' names to.
+   */
+  static void GetCategoryNames(nsTArray<nsString>& aNames);
+
+  /**
+   * Get the metric id+type in a u32 for a named runtime-registered metric.
+   *
+   * Return value's only useful to GleanJSMetricsLookup.h
+   *
+   * @param aMetricName The `myCategory.myName` dotted.camelCase metric name.
+   * @return Nothing() if no metric by that name was registered at runtime.
+   *         Otherwise, the encoded u32 with metric id and metric type id for
+   *         the runtime-registered metric.
+   */
+  static Maybe<uint32_t> GetMetric(const nsACString& aMetricName);
+
+  /**
+   * Get the ping id in a u32 for a named runtime-registered ping.
+   *
+   * Return value's only useful to GleanJSPingsLookup.h
+   *
+   * @param aPingName The ping name.
+   * @return Nothing() if no ping by that name was registered at runtime.
+   *         Otherwise, the id for the runtime-registered ping.
+   */
+  static Maybe<uint32_t> GetPing(const nsACString& aPingName);
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_JOG_h */
diff --git a/toolkit/components/glean/bindings/jog/cbindgen.toml b/toolkit/components/glean/bindings/jog/cbindgen.toml
new file mode 100644
index 0000000000..62139cc6c6
--- /dev/null
+++ b/toolkit/components/glean/bindings/jog/cbindgen.toml
@@ -0,0 +1,26 @@
+header = """/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef mozilla_glean_jog_ffi_generated_h
+#define mozilla_glean_jog_ffi_generated_h
+"""
+trailer = """
+#endif // mozilla_glean_jog_ffi_generated_h
+"""
+autogen_warning = """/* DO NOT MODIFY THIS MANUALLY! This file was generated using cbindgen. */"""
+include_version = true
+braces = "SameLine"
+line_length = 100
+tab_width = 2
+language = "C++"
+namespaces = ["mozilla::glean::jog"]
+includes = ["nsTArray.h", "nsString.h"]
+
+[export.rename]
+"ThinVec" = "nsTArray"
+#"nsCStringRepr" = "nsCString"
+
+[parse]
+#parse_deps = true
+#include = ["fog"]
+#extra_bindings = ["fog"]
diff --git a/toolkit/components/glean/bindings/jog/src/lib.rs b/toolkit/components/glean/bindings/jog/src/lib.rs
new file mode 100644
index 0000000000..885a7a5bbb
--- /dev/null
+++ b/toolkit/components/glean/bindings/jog/src/lib.rs
@@ -0,0 +1,248 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use fog::factory;
+use fog::private::traits::HistogramType;
+use fog::private::{CommonMetricData, Lifetime, MemoryUnit, TimeUnit};
+#[cfg(feature = "with_gecko")]
+use nsstring::{nsACString, nsAString, nsCString};
+use serde::Deserialize;
+use std::collections::HashMap;
+use std::fs::File;
+use std::io::BufReader;
+use thin_vec::ThinVec;
+
+#[derive(Default, Deserialize)]
+struct ExtraMetricArgs {
+    time_unit: Option<TimeUnit>,
+    memory_unit: Option<MemoryUnit>,
+    allowed_extra_keys: Option<Vec<String>>,
+    range_min: Option<u64>,
+    range_max: Option<u64>,
+    bucket_count: Option<u64>,
+    histogram_type: Option<HistogramType>,
+    numerators: Option<Vec<CommonMetricData>>,
+    labels: Option<Vec<String>>,
+}
+
+/// Test-only method.
+///
+/// Registers a metric.
+/// Doesn't check to see if it's been registered before.
+/// Doesn't check that it would pass schema validation if it were a real metric.
+///
+/// `extra_args` is a JSON-encoded string in a form that serde can read into an ExtraMetricArgs.
+///
+/// No effort has been made to make this pleasant to use, since it's for
+/// internal testing only (ie, the testing of JOG itself).
+#[cfg(feature = "with_gecko")]
+#[no_mangle]
+pub extern "C" fn jog_test_register_metric(
+    metric_type: &nsACString,
+    category: &nsACString,
+    name: &nsACString,
+    send_in_pings: &ThinVec<nsCString>,
+    lifetime: &nsACString,
+    disabled: bool,
+    extra_args: &nsACString,
+) -> u32 {
+    log::warn!("Type: {:?}, Category: {:?}, Name: {:?}, SendInPings: {:?}, Lifetime: {:?}, Disabled: {}, ExtraArgs: {}",
+      metric_type, category, name, send_in_pings, lifetime, disabled, extra_args);
+    let metric_type = &metric_type.to_utf8();
+    let category = category.to_string();
+    let name = name.to_string();
+    let send_in_pings = send_in_pings.iter().map(|ping| ping.to_string()).collect();
+    let lifetime = serde_json::from_str(&lifetime.to_utf8())
+        .expect("Lifetime didn't deserialize happily. Is it valid JSON?");
+
+    let extra_args: ExtraMetricArgs = if extra_args.is_empty() {
+        Default::default()
+    } else {
+        serde_json::from_str(&extra_args.to_utf8())
+            .expect("Extras didn't deserialize happily. Are they valid JSON?")
+    };
+    create_and_register_metric(
+        metric_type,
+        category,
+        name,
+        send_in_pings,
+        lifetime,
+        disabled,
+        extra_args,
+    )
+    .expect("Creation/Registration of metric failed") // ok to panic in test-only method
+}
+
+fn create_and_register_metric(
+    metric_type: &str,
+    category: String,
+    name: String,
+    send_in_pings: Vec<String>,
+    lifetime: Lifetime,
+    disabled: bool,
+    extra_args: ExtraMetricArgs,
+) -> Result<u32, Box<dyn std::error::Error>> {
+    let ns_name = nsCString::from(&name);
+    let ns_category = nsCString::from(&category);
+    let metric_id = factory::create_and_register_metric(
+        metric_type,
+        category,
+        name,
+        send_in_pings,
+        lifetime,
+        disabled,
+        extra_args.time_unit,
+        extra_args.memory_unit,
+        extra_args.allowed_extra_keys.or_else(|| Some(Vec::new())),
+        extra_args.range_min,
+        extra_args.range_max,
+        extra_args.bucket_count,
+        extra_args.histogram_type,
+        extra_args.numerators,
+        extra_args.labels,
+    );
+    extern "C" {
+        fn JOG_RegisterMetric(category: &nsACString, name: &nsACString, metric: u32);
+    }
+    if let Ok(metric_id) = metric_id {
+        unsafe {
+            // Safety: We're loaning to C++ data we don't later use.
+            JOG_RegisterMetric(&ns_category, &ns_name, metric_id);
+        }
+    } else {
+        log::warn!(
+            "Could not register metric {}.{} due to {:?}",
+            ns_category,
+            ns_name,
+            metric_id
+        );
+    }
+    metric_id
+}
+
+/// Test-only method.
+///
+/// Registers a ping. Doesn't check to see if it's been registered before.
+/// Doesn't check that it would pass schema validation if it were a real ping.
+#[no_mangle]
+pub extern "C" fn jog_test_register_ping(
+    name: &nsACString,
+    include_client_id: bool,
+    send_if_empty: bool,
+    reason_codes: &ThinVec<nsCString>,
+) -> u32 {
+    let ping_name = name.to_string();
+    let reason_codes = reason_codes
+        .iter()
+        .map(|reason| reason.to_string())
+        .collect();
+    create_and_register_ping(ping_name, include_client_id, send_if_empty, reason_codes)
+        .expect("Creation or registration of ping failed.") // permitted to panic in test-only method.
+}
+
+fn create_and_register_ping(
+    ping_name: String,
+    include_client_id: bool,
+    send_if_empty: bool,
+    reason_codes: Vec<String>,
+) -> Result<u32, Box<dyn std::error::Error>> {
+    let ns_name = nsCString::from(&ping_name);
+    let ping_id = factory::create_and_register_ping(
+        ping_name,
+        include_client_id,
+        send_if_empty,
+        reason_codes,
+    );
+    extern "C" {
+        fn JOG_RegisterPing(name: &nsACString, ping_id: u32);
+    }
+    if let Ok(ping_id) = ping_id {
+        unsafe {
+            // Safety: We're loaning to C++ data we don't later use.
+            JOG_RegisterPing(&ns_name, ping_id);
+        }
+    } else {
+        log::warn!("Could not register ping {} due to {:?}", ns_name, ping_id);
+    }
+    ping_id
+}
+
+/// Test-only method.
+///
+/// Clears all runtime registration storage of registered metrics and pings.
+#[no_mangle]
+pub extern "C" fn jog_test_clear_registered_metrics_and_pings() {}
+
+#[derive(Default, Deserialize)]
+struct Jogfile {
+    metrics: HashMap<String, Vec<MetricDefinitionData>>,
+    pings: Vec<PingDefinitionData>,
+}
+
+#[derive(Default, Deserialize)]
+struct MetricDefinitionData {
+    metric_type: String,
+    name: String,
+    send_in_pings: Vec<String>,
+    lifetime: Lifetime,
+    disabled: bool,
+    #[serde(default)]
+    extra_args: Option<ExtraMetricArgs>,
+}
+
+#[derive(Default, Deserialize)]
+struct PingDefinitionData {
+    name: String,
+    include_client_id: bool,
+    send_if_empty: bool,
+    reason_codes: Option<Vec<String>>,
+}
+
+/// Read the file at the provided location, interpret it as a jogfile,
+/// and register those pings and metrics.
+/// Returns true if we successfully parsed the jogfile. Does not mean
+/// all or any metrics and pings successfully registered,
+/// just that serde managed to deserialize it into metrics and pings and we tried to register them all.
+#[no_mangle]
+pub extern "C" fn jog_load_jogfile(jogfile_path: &nsAString) -> bool {
+    let f = match File::open(jogfile_path.to_string()) {
+        Ok(f) => f,
+        _ => {
+            log::error!("Boo, couldn't open jogfile at {}", jogfile_path.to_string());
+            return false;
+        }
+    };
+    let reader = BufReader::new(f);
+
+    let mut j: Jogfile = match serde_json::from_reader(reader) {
+        Ok(j) => j,
+        Err(e) => {
+            log::error!("Boo, couldn't read jogfile because of: {:?}", e);
+            return false;
+        }
+    };
+    log::trace!("Loaded jogfile. Registering metrics+pings.");
+    for (category, metrics) in j.metrics.drain() {
+        for metric in metrics.into_iter() {
+            let _ = create_and_register_metric(
+                &metric.metric_type,
+                category.to_string(),
+                metric.name,
+                metric.send_in_pings,
+                metric.lifetime,
+                metric.disabled,
+                metric.extra_args.unwrap_or_else(Default::default),
+            );
+        }
+    }
+    for ping in j.pings.into_iter() {
+        let _ = create_and_register_ping(
+            ping.name,
+            ping.include_client_id,
+            ping.send_if_empty,
+            ping.reason_codes.unwrap_or_else(Vec::new),
+        );
+    }
+    true
+}
diff --git a/toolkit/components/glean/bindings/private/Boolean.cpp b/toolkit/components/glean/bindings/private/Boolean.cpp
new file mode 100644
index 0000000000..05520ece6b
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Boolean.cpp
@@ -0,0 +1,78 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Boolean.h"
+
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+#include "Common.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void BooleanMetric::Set(bool aValue) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (scalarId) {
+    Telemetry::ScalarSet(scalarId.extract(), aValue);
+  } else if (IsSubmetricId(mId)) {
+    GetLabeledMirrorLock().apply([&](auto& lock) {
+      auto tuple = lock.ref()->MaybeGet(mId);
+      if (tuple) {
+        Telemetry::ScalarSet(Get<0>(tuple.ref()), Get<1>(tuple.ref()), aValue);
+      }
+    });
+  }
+  fog_boolean_set(mId, int(aValue));
+}
+
+Result<Maybe<bool>, nsCString> BooleanMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_boolean_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_boolean_test_has_value(mId, &aPingName)) {
+    return Maybe<bool>();
+  }
+  return Some(fog_boolean_test_get_value(mId, &aPingName));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanBoolean, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanBoolean, nsIGleanBoolean)
+
+NS_IMETHODIMP
+GleanBoolean::Set(bool aValue) {
+  mBoolean.Set(aValue);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanBoolean::TestGetValue(const nsACString& aStorageName,
+                           JS::MutableHandle<JS::Value> aResult) {
+  auto result = mBoolean.TestGetValue(aStorageName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    aResult.set(JS::BooleanValue(optresult.value()));
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Boolean.h b/toolkit/components/glean/bindings/private/Boolean.h
new file mode 100644
index 0000000000..890820440d
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Boolean.h
@@ -0,0 +1,72 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanBoolean_h
+#define mozilla_glean_GleanBoolean_h
+
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+
+namespace mozilla {
+namespace glean {
+
+namespace impl {
+
+class BooleanMetric {
+ public:
+  constexpr explicit BooleanMetric(uint32_t id) : mId(id) {}
+
+  /**
+   * Set to the specified boolean value.
+   *
+   * @param aValue the value to set.
+   */
+  void Set(bool aValue) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a boolean.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric.
+   */
+  Result<Maybe<bool>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+
+}  // namespace impl
+
+class GleanBoolean final : public nsIGleanBoolean {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANBOOLEAN
+
+  explicit GleanBoolean(uint32_t id) : mBoolean(id){};
+
+ private:
+  virtual ~GleanBoolean() = default;
+
+  const impl::BooleanMetric mBoolean;
+};
+
+}  // namespace glean
+}  // namespace mozilla
+
+#endif /* mozilla_glean_GleanBoolean.h */
diff --git a/toolkit/components/glean/bindings/private/Common.cpp b/toolkit/components/glean/bindings/private/Common.cpp
new file mode 100644
index 0000000000..f84c39c05d
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Common.cpp
@@ -0,0 +1,33 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "Common.h"
+#include "nsComponentManagerUtils.h"
+#include "nsIConsoleService.h"
+#include "nsIScriptError.h"
+#include "nsServiceManagerUtils.h"
+
+namespace mozilla::glean {
+
+// This is copied from TelemetryCommons.cpp (and modified because consoleservice
+// handles threading), but that one is not exported.
+// There's _at least_ a third instance of `LogToBrowserConsole`,
+// but that one is slightly different.
+void LogToBrowserConsole(uint32_t aLogLevel, const nsAString& aMsg) {
+  nsCOMPtr<nsIConsoleService> console(
+      do_GetService("@mozilla.org/consoleservice;1"));
+  if (!console) {
+    NS_WARNING("Failed to log message to console.");
+    return;
+  }
+
+  nsCOMPtr<nsIScriptError> error(do_CreateInstance(NS_SCRIPTERROR_CONTRACTID));
+  error->Init(aMsg, u""_ns, u""_ns, 0, 0, aLogLevel, "chrome javascript"_ns,
+              false /* from private window */, true /* from chrome context */);
+  console->LogMessage(error);
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Common.h b/toolkit/components/glean/bindings/private/Common.h
new file mode 100644
index 0000000000..e3dd7a0a47
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Common.h
@@ -0,0 +1,24 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_Common_h
+#define mozilla_glean_Common_h
+
+#include "nsIScriptError.h"
+
+namespace mozilla::glean {
+
+/**
+ * Dumps a log message to the Browser Console using the provided level.
+ *
+ * @param aLogLevel The level to use when displaying the message in the browser
+ * console (e.g. nsIScriptError::warningFlag, ...).
+ * @param aMsg The text message to print to the console.
+ */
+void LogToBrowserConsole(uint32_t aLogLevel, const nsAString& aMsg);
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_Common_h */
diff --git a/toolkit/components/glean/bindings/private/Counter.cpp b/toolkit/components/glean/bindings/private/Counter.cpp
new file mode 100644
index 0000000000..2a4477b4fc
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Counter.cpp
@@ -0,0 +1,80 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Counter.h"
+
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void CounterMetric::Add(int32_t aAmount) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (aAmount >= 0) {
+    if (scalarId) {
+      Telemetry::ScalarAdd(scalarId.extract(), aAmount);
+    } else if (IsSubmetricId(mId)) {
+      GetLabeledMirrorLock().apply([&](auto& lock) {
+        auto tuple = lock.ref()->MaybeGet(mId);
+        if (tuple && aAmount > 0) {
+          Telemetry::ScalarAdd(Get<0>(tuple.ref()), Get<1>(tuple.ref()),
+                               (uint32_t)aAmount);
+        }
+      });
+    }
+  }
+  fog_counter_add(mId, aAmount);
+}
+
+Result<Maybe<int32_t>, nsCString> CounterMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_counter_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_counter_test_has_value(mId, &aPingName)) {
+    return Maybe<int32_t>();  // can't use Nothing() or templates will fail.
+  }
+  return Some(fog_counter_test_get_value(mId, &aPingName));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanCounter, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanCounter, nsIGleanCounter)
+
+NS_IMETHODIMP
+GleanCounter::Add(int32_t aAmount) {
+  mCounter.Add(aAmount);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanCounter::TestGetValue(const nsACString& aStorageName,
+                           JS::MutableHandle<JS::Value> aResult) {
+  auto result = mCounter.TestGetValue(aStorageName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    aResult.set(JS::Int32Value(optresult.value()));
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Counter.h b/toolkit/components/glean/bindings/private/Counter.h
new file mode 100644
index 0000000000..e1e7190e4e
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Counter.h
@@ -0,0 +1,70 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanCounter_h
+#define mozilla_glean_GleanCounter_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class CounterMetric {
+ public:
+  constexpr explicit CounterMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Increases the counter by `amount`.
+   *
+   * @param aAmount The amount to increase by. Should be positive.
+   */
+  void Add(int32_t aAmount = 1) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as an integer.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<int32_t>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanCounter final : public nsIGleanCounter {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANCOUNTER
+
+  explicit GleanCounter(uint32_t id) : mCounter(id){};
+
+ private:
+  virtual ~GleanCounter() = default;
+
+  const impl::CounterMetric mCounter;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanCounter_h */
diff --git a/toolkit/components/glean/bindings/private/CustomDistribution.cpp b/toolkit/components/glean/bindings/private/CustomDistribution.cpp
new file mode 100644
index 0000000000..4abd0100e7
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/CustomDistribution.cpp
@@ -0,0 +1,125 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/CustomDistribution.h"
+
+#include "Common.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/HistogramGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+#include "nsJSUtils.h"
+#include "nsPrintfCString.h"
+#include "nsString.h"
+#include "js/PropertyAndElement.h"  // JS_DefineProperty
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void CustomDistributionMetric::AccumulateSamples(
+    const nsTArray<uint64_t>& aSamples) const {
+  auto hgramId = HistogramIdForMetric(mId);
+  if (hgramId) {
+    auto id = hgramId.extract();
+    // N.B.: There is an `Accumulate(nsTArray<T>)`, but `T` is `uint32_t` and
+    // we got `uint64_t`s here.
+    for (auto sample : aSamples) {
+      Telemetry::Accumulate(id, sample);
+    }
+  }
+  fog_custom_distribution_accumulate_samples(mId, &aSamples);
+}
+
+void CustomDistributionMetric::AccumulateSamplesSigned(
+    const nsTArray<int64_t>& aSamples) const {
+  auto hgramId = HistogramIdForMetric(mId);
+  if (hgramId) {
+    auto id = hgramId.extract();
+    // N.B.: There is an `Accumulate(nsTArray<T>)`, but `T` is `uint32_t` and
+    // we got `int64_t`s here.
+    for (auto sample : aSamples) {
+      Telemetry::Accumulate(id, sample);
+    }
+  }
+  fog_custom_distribution_accumulate_samples_signed(mId, &aSamples);
+}
+
+Result<Maybe<DistributionData>, nsCString>
+CustomDistributionMetric::TestGetValue(const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_custom_distribution_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_custom_distribution_test_has_value(mId, &aPingName)) {
+    return Maybe<DistributionData>();
+  }
+  nsTArray<uint64_t> buckets;
+  nsTArray<uint64_t> counts;
+  uint64_t sum;
+  fog_custom_distribution_test_get_value(mId, &aPingName, &sum, &buckets,
+                                         &counts);
+  return Some(DistributionData(buckets, counts, sum));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanCustomDistribution, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanCustomDistribution, nsIGleanCustomDistribution)
+
+NS_IMETHODIMP
+GleanCustomDistribution::AccumulateSamples(const nsTArray<int64_t>& aSamples) {
+  mCustomDist.AccumulateSamplesSigned(aSamples);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanCustomDistribution::TestGetValue(const nsACString& aPingName,
+                                      JSContext* aCx,
+                                      JS::MutableHandle<JS::Value> aResult) {
+  auto result = mCustomDist.TestGetValue(aPingName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    // Build return value of the form: { sum: #, values: {bucket1: count1, ...}
+    JS::Rooted<JSObject*> root(aCx, JS_NewPlainObject(aCx));
+    if (!root) {
+      return NS_ERROR_FAILURE;
+    }
+    uint64_t sum = optresult.ref().sum;
+    if (!JS_DefineProperty(aCx, root, "sum", static_cast<double>(sum),
+                           JSPROP_ENUMERATE)) {
+      return NS_ERROR_FAILURE;
+    }
+    JS::Rooted<JSObject*> valuesObj(aCx, JS_NewPlainObject(aCx));
+    if (!valuesObj ||
+        !JS_DefineProperty(aCx, root, "values", valuesObj, JSPROP_ENUMERATE)) {
+      return NS_ERROR_FAILURE;
+    }
+    auto& data = optresult.ref().values;
+    for (const auto& entry : data) {
+      const uint64_t bucket = entry.GetKey();
+      const uint64_t count = entry.GetData();
+      if (!JS_DefineProperty(aCx, valuesObj,
+                             nsPrintfCString("%" PRIu64, bucket).get(),
+                             static_cast<double>(count), JSPROP_ENUMERATE)) {
+        return NS_ERROR_FAILURE;
+      }
+    }
+    aResult.setObject(*root);
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/CustomDistribution.h b/toolkit/components/glean/bindings/private/CustomDistribution.h
new file mode 100644
index 0000000000..1ed9b78788
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/CustomDistribution.h
@@ -0,0 +1,83 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanCustomDistribution_h
+#define mozilla_glean_GleanCustomDistribution_h
+
+#include "mozilla/glean/bindings/DistributionData.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+#include "nsTArray.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class CustomDistributionMetric {
+ public:
+  constexpr explicit CustomDistributionMetric(uint32_t aId) : mId(aId) {}
+
+  /**
+   * Accumulates the provided samples in the metric.
+   *
+   * @param aSamples The vector holding the samples to be recorded by the
+   *                 metric.
+   */
+  void AccumulateSamples(const nsTArray<uint64_t>& aSamples) const;
+
+  /**
+   * Accumulates the provided samples in the metric.
+   *
+   * @param aSamples The vector holding the samples to be recorded by the
+   *                 metric.
+   *
+   * Notes: Discards any negative value in `samples`
+   * and reports an `InvalidValue` error for each of them.
+   */
+  void AccumulateSamplesSigned(const nsTArray<int64_t>& aSamples) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a DistributionData.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<DistributionData>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanCustomDistribution final : public nsIGleanCustomDistribution {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANCUSTOMDISTRIBUTION
+
+  explicit GleanCustomDistribution(uint64_t aId) : mCustomDist(aId){};
+
+ private:
+  virtual ~GleanCustomDistribution() = default;
+
+  const impl::CustomDistributionMetric mCustomDist;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanCustomDistribution_h */
diff --git a/toolkit/components/glean/bindings/private/Datetime.cpp b/toolkit/components/glean/bindings/private/Datetime.cpp
new file mode 100644
index 0000000000..900b8e6a13
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Datetime.cpp
@@ -0,0 +1,124 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Datetime.h"
+
+#include "jsapi.h"
+#include "js/Date.h"
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+#include "prtime.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void DatetimeMetric::Set(const PRExplodedTime* aValue) const {
+  PRExplodedTime exploded;
+  if (!aValue) {
+    PR_ExplodeTime(PR_Now(), PR_LocalTimeParameters, &exploded);
+  } else {
+    exploded = *aValue;
+  }
+
+  auto id = ScalarIdForMetric(mId);
+  if (id) {
+    const uint32_t buflen = 64;  // More than enough for now.
+    char buf[buflen];
+    uint32_t written = PR_FormatTime(buf, buflen, "%FT%T%z", &exploded);
+    if (written > 2 && written < 64) {
+      // Format's still not quite there. Gotta put a `:` between timezone
+      // hours and minutes
+      buf[written] = '\0';
+      buf[written - 1] = buf[written - 2];
+      buf[written - 2] = buf[written - 3];
+      buf[written - 3] = ':';
+      Telemetry::ScalarSet(id.extract(), NS_ConvertASCIItoUTF16(buf));
+    }
+  }
+
+  int32_t offset =
+      exploded.tm_params.tp_gmt_offset + exploded.tm_params.tp_dst_offset;
+  FogDatetime dt{exploded.tm_year,
+                 static_cast<uint32_t>(exploded.tm_month + 1),
+                 static_cast<uint32_t>(exploded.tm_mday),
+                 static_cast<uint32_t>(exploded.tm_hour),
+                 static_cast<uint32_t>(exploded.tm_min),
+                 static_cast<uint32_t>(exploded.tm_sec),
+                 static_cast<uint32_t>(exploded.tm_usec * 1000),
+                 offset};
+  fog_datetime_set(mId, &dt);
+}
+
+Result<Maybe<PRExplodedTime>, nsCString> DatetimeMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_datetime_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_datetime_test_has_value(mId, &aPingName)) {
+    return Maybe<PRExplodedTime>();
+  }
+  FogDatetime ret{0};
+  fog_datetime_test_get_value(mId, &aPingName, &ret);
+  PRExplodedTime pret{0};
+  pret.tm_year = static_cast<PRInt16>(ret.year);
+  pret.tm_month = static_cast<PRInt32>(ret.month - 1);
+  pret.tm_mday = static_cast<PRInt32>(ret.day);
+  pret.tm_hour = static_cast<PRInt32>(ret.hour);
+  pret.tm_min = static_cast<PRInt32>(ret.minute);
+  pret.tm_sec = static_cast<PRInt32>(ret.second);
+  pret.tm_usec = static_cast<PRInt32>(ret.nano / 1000);  // truncated is fine
+  pret.tm_params.tp_gmt_offset = static_cast<PRInt32>(ret.offset_seconds);
+  return Some(std::move(pret));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanDatetime, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanDatetime, nsIGleanDatetime)
+
+NS_IMETHODIMP
+GleanDatetime::Set(PRTime aValue, uint8_t aOptionalArgc) {
+  if (aOptionalArgc == 0) {
+    mDatetime.Set();
+  } else {
+    PRExplodedTime exploded;
+    PR_ExplodeTime(aValue, PR_LocalTimeParameters, &exploded);
+    mDatetime.Set(&exploded);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanDatetime::TestGetValue(const nsACString& aStorageName, JSContext* aCx,
+                            JS::MutableHandle<JS::Value> aResult) {
+  auto result = mDatetime.TestGetValue(aStorageName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    double millis =
+        static_cast<double>(PR_ImplodeTime(optresult.ptr())) / PR_USEC_PER_MSEC;
+    JS::Rooted<JSObject*> root(aCx,
+                               JS::NewDateObject(aCx, JS::TimeClip(millis)));
+    aResult.setObject(*root);
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Datetime.h b/toolkit/components/glean/bindings/private/Datetime.h
new file mode 100644
index 0000000000..4fec93d251
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Datetime.h
@@ -0,0 +1,71 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanDatetime_h
+#define mozilla_glean_GleanDatetime_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+#include "prtime.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class DatetimeMetric {
+ public:
+  constexpr explicit DatetimeMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Set the datetime to the provided value, or the local now.
+   *
+   * @param amount The date value to set.
+   */
+  void Set(const PRExplodedTime* aValue = nullptr) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a PRExplodedTime.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<PRExplodedTime>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanDatetime final : public nsIGleanDatetime {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANDATETIME
+
+  explicit GleanDatetime(uint32_t aId) : mDatetime(aId){};
+
+ private:
+  virtual ~GleanDatetime() = default;
+
+  const impl::DatetimeMetric mDatetime;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanDatetime_h */
diff --git a/toolkit/components/glean/bindings/private/Denominator.cpp b/toolkit/components/glean/bindings/private/Denominator.cpp
new file mode 100644
index 0000000000..e922c4f145
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Denominator.cpp
@@ -0,0 +1,70 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Denominator.h"
+
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void DenominatorMetric::Add(int32_t aAmount) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (scalarId && aAmount >= 0) {
+    Telemetry::ScalarAdd(scalarId.extract(), aAmount);
+  }
+  fog_denominator_add(mId, aAmount);
+}
+
+Result<Maybe<int32_t>, nsCString> DenominatorMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_denominator_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_denominator_test_has_value(mId, &aPingName)) {
+    return Maybe<int32_t>();
+  }
+  return Some(fog_denominator_test_get_value(mId, &aPingName));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanDenominator, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanDenominator, nsIGleanDenominator)
+
+NS_IMETHODIMP
+GleanDenominator::Add(int32_t aAmount) {
+  mDenominator.Add(aAmount);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanDenominator::TestGetValue(const nsACString& aStorageName,
+                               JS::MutableHandle<JS::Value> aResult) {
+  auto result = mDenominator.TestGetValue(aStorageName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    aResult.set(JS::Int32Value(optresult.value()));
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Denominator.h b/toolkit/components/glean/bindings/private/Denominator.h
new file mode 100644
index 0000000000..c96bf17e8d
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Denominator.h
@@ -0,0 +1,70 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanDenominator_h
+#define mozilla_glean_GleanDenominator_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class DenominatorMetric {
+ public:
+  constexpr explicit DenominatorMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Increases the counter by `amount`.
+   *
+   * @param aAmount The amount to increase by. Should be positive.
+   */
+  void Add(int32_t aAmount = 1) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as an integer.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<int32_t>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanDenominator final : public nsIGleanDenominator {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANDENOMINATOR
+
+  explicit GleanDenominator(uint32_t id) : mDenominator(id){};
+
+ private:
+  virtual ~GleanDenominator() = default;
+
+  const impl::DenominatorMetric mDenominator;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanDenominator_h */
diff --git a/toolkit/components/glean/bindings/private/DistributionData.h b/toolkit/components/glean/bindings/private/DistributionData.h
new file mode 100644
index 0000000000..6ff995f222
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/DistributionData.h
@@ -0,0 +1,32 @@
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_DistributionData_h
+#define mozilla_glean_DistributionData_h
+
+#include "nsTHashMap.h"
+
+namespace mozilla::glean {
+
+struct DistributionData final {
+  uint64_t sum;
+  nsTHashMap<nsUint64HashKey, uint64_t> values;
+
+  /**
+   * Create distribution data from the buckets, counts and sum,
+   * as returned by `fog_*_distribution_test_get_value`.
+   */
+  DistributionData(const nsTArray<uint64_t>& aBuckets,
+                   const nsTArray<uint64_t>& aCounts, uint64_t aSum)
+      : sum(aSum) {
+    for (size_t i = 0; i < aBuckets.Length(); ++i) {
+      this->values.InsertOrUpdate(aBuckets[i], aCounts[i]);
+    }
+  }
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_DistributionData_h */
diff --git a/toolkit/components/glean/bindings/private/Event.cpp b/toolkit/components/glean/bindings/private/Event.cpp
new file mode 100644
index 0000000000..d2eb5b3ca6
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Event.cpp
@@ -0,0 +1,183 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Event.h"
+
+#include "Common.h"
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/dom/ToJSValue.h"
+#include "nsIClassInfoImpl.h"
+#include "jsapi.h"
+#include "js/PropertyAndElement.h"  // JS_DefineElement, JS_DefineProperty, JS_Enumerate, JS_GetProperty, JS_GetPropertyById
+#include "nsIScriptError.h"
+
+namespace mozilla::glean {
+
+NS_IMPL_CLASSINFO(GleanEvent, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanEvent, nsIGleanEvent)
+
+NS_IMETHODIMP
+GleanEvent::Record(JS::Handle<JS::Value> aExtra, JSContext* aCx) {
+  if (aExtra.isNullOrUndefined()) {
+    mEvent.Record();
+    return NS_OK;
+  }
+
+  if (!aExtra.isObject()) {
+    LogToBrowserConsole(nsIScriptError::warningFlag,
+                        u"Extras need to be an object"_ns);
+    return NS_OK;
+  }
+
+  nsTArray<nsCString> extraKeys;
+  nsTArray<nsCString> extraValues;
+  CopyableTArray<Telemetry::EventExtraEntry> telExtras;
+
+  JS::Rooted<JSObject*> obj(aCx, &aExtra.toObject());
+  JS::Rooted<JS::IdVector> ids(aCx, JS::IdVector(aCx));
+  if (!JS_Enumerate(aCx, obj, &ids)) {
+    LogToBrowserConsole(nsIScriptError::warningFlag,
+                        u"Failed to enumerate object."_ns);
+    return NS_OK;
+  }
+
+  for (size_t i = 0, n = ids.length(); i < n; i++) {
+    nsAutoJSCString jsKey;
+    if (!jsKey.init(aCx, ids[i])) {
+      LogToBrowserConsole(
+          nsIScriptError::warningFlag,
+          u"Extra dictionary should only contain string keys."_ns);
+      return NS_OK;
+    }
+
+    JS::Rooted<JS::Value> value(aCx);
+    if (!JS_GetPropertyById(aCx, obj, ids[i], &value)) {
+      LogToBrowserConsole(nsIScriptError::warningFlag,
+                          u"Failed to get extra property."_ns);
+      return NS_OK;
+    }
+
+    nsAutoJSCString jsValue;
+    if (value.isString() || (value.isInt32() && value.toInt32() >= 0) ||
+        value.isBoolean()) {
+      if (!jsValue.init(aCx, value)) {
+        LogToBrowserConsole(nsIScriptError::warningFlag,
+                            u"Can't extract extra property"_ns);
+        return NS_OK;
+      }
+    } else if (value.isNullOrUndefined()) {
+      // The extra key is present, but has an empty value.
+      // Treat as though it weren't here at all.
+      continue;
+    } else {
+      LogToBrowserConsole(
+          nsIScriptError::warningFlag,
+          u"Extra properties should have string, bool or non-negative integer values."_ns);
+      return NS_OK;
+    }
+
+    extraKeys.AppendElement(jsKey);
+    extraValues.AppendElement(jsValue);
+    telExtras.EmplaceBack(Telemetry::EventExtraEntry{jsKey, jsValue});
+  }
+
+  // Since this calls the implementation directly, we need to implement GIFFT
+  // here as well as in EventMetric::Record.
+  auto id = EventIdForMetric(mEvent.mId);
+  if (id) {
+    Telemetry::RecordEvent(id.extract(), Nothing(),
+                           telExtras.IsEmpty() ? Nothing() : Some(telExtras));
+  }
+
+  // Calling the implementation directly, because we have a `string->string`
+  // map, not a `T->string` map the C++ API expects.
+  impl::fog_event_record(mEvent.mId, &extraKeys, &extraValues);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanEvent::TestGetValue(const nsACString& aStorageName, JSContext* aCx,
+                         JS::MutableHandle<JS::Value> aResult) {
+  auto resEvents = mEvent.TestGetValue(aStorageName);
+  if (resEvents.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(resEvents.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optEvents = resEvents.unwrap();
+  if (optEvents.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+    return NS_OK;
+  }
+
+  auto events = optEvents.extract();
+
+  auto count = events.Length();
+  JS::Rooted<JSObject*> eventArray(aCx, JS::NewArrayObject(aCx, count));
+  if (NS_WARN_IF(!eventArray)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  for (size_t i = 0; i < count; i++) {
+    auto* value = &events[i];
+
+    JS::Rooted<JSObject*> eventObj(aCx, JS_NewPlainObject(aCx));
+    if (NS_WARN_IF(!eventObj)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    if (!JS_DefineProperty(aCx, eventObj, "timestamp",
+                           (double)value->mTimestamp, JSPROP_ENUMERATE)) {
+      NS_WARNING("Failed to define timestamp for event object.");
+      return NS_ERROR_FAILURE;
+    }
+
+    JS::Rooted<JS::Value> catStr(aCx);
+    if (!dom::ToJSValue(aCx, value->mCategory, &catStr) ||
+        !JS_DefineProperty(aCx, eventObj, "category", catStr,
+                           JSPROP_ENUMERATE)) {
+      NS_WARNING("Failed to define category for event object.");
+      return NS_ERROR_FAILURE;
+    }
+    JS::Rooted<JS::Value> nameStr(aCx);
+    if (!dom::ToJSValue(aCx, value->mName, &nameStr) ||
+        !JS_DefineProperty(aCx, eventObj, "name", nameStr, JSPROP_ENUMERATE)) {
+      NS_WARNING("Failed to define name for event object.");
+      return NS_ERROR_FAILURE;
+    }
+
+    JS::Rooted<JSObject*> extraObj(aCx, JS_NewPlainObject(aCx));
+    if (!JS_DefineProperty(aCx, eventObj, "extra", extraObj,
+                           JSPROP_ENUMERATE)) {
+      NS_WARNING("Failed to define extra for event object.");
+      return NS_ERROR_FAILURE;
+    }
+
+    for (auto pair : value->mExtra) {
+      auto key = mozilla::Get<0>(pair);
+      auto val = mozilla::Get<1>(pair);
+      JS::Rooted<JS::Value> valStr(aCx);
+      if (!dom::ToJSValue(aCx, val, &valStr) ||
+          !JS_DefineProperty(aCx, extraObj, key.Data(), valStr,
+                             JSPROP_ENUMERATE)) {
+        NS_WARNING("Failed to define extra property for event object.");
+        return NS_ERROR_FAILURE;
+      }
+    }
+
+    if (!JS_DefineElement(aCx, eventArray, i, eventObj, JSPROP_ENUMERATE)) {
+      NS_WARNING("Failed to define item in events array.");
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  aResult.setObject(*eventArray);
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Event.h b/toolkit/components/glean/bindings/private/Event.h
new file mode 100644
index 0000000000..111be2cbc2
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Event.h
@@ -0,0 +1,162 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanEvent_h
+#define mozilla_glean_GleanEvent_h
+
+#include "nsIGleanMetrics.h"
+#include "mozilla/glean/bindings/EventGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/Tuple.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+namespace mozilla::glean {
+
+// forward declaration
+class GleanEvent;
+
+namespace impl {
+
+/**
+ * Represents the recorded data for a single event
+ */
+struct RecordedEvent {
+ public:
+  uint64_t mTimestamp;
+  nsCString mCategory;
+  nsCString mName;
+
+  nsTArray<Tuple<nsCString, nsCString>> mExtra;
+};
+
+template <class T>
+class EventMetric {
+  friend class mozilla::glean::GleanEvent;
+
+ public:
+  constexpr explicit EventMetric(uint32_t id) : mId(id) {}
+
+  /**
+   * Record an event.
+   *
+   * @param aExtras The list of (extra key, value) pairs. Allowed extra keys are
+   *                defined in the metric definition.
+   *                If the wrong keys are used or values are too large
+   *                an error is report and no event is recorded.
+   */
+  void Record(const Maybe<T>& aExtras = Nothing()) const {
+    auto id = EventIdForMetric(mId);
+    if (id) {
+      // NB. In case `aExtras` is filled we call `ToFfiExtra`, causing
+      // twice the required allocation. We could be smarter and reuse the data.
+      // But this is GIFFT-only allocation, so wait to be told it's a problem.
+      Maybe<CopyableTArray<Telemetry::EventExtraEntry>> telExtras;
+      if (aExtras) {
+        CopyableTArray<Telemetry::EventExtraEntry> extras;
+        auto serializedExtras = aExtras->ToFfiExtra();
+        auto keys = std::move(Get<0>(serializedExtras));
+        auto values = std::move(Get<1>(serializedExtras));
+        for (size_t i = 0; i < keys.Length(); i++) {
+          extras.EmplaceBack(Telemetry::EventExtraEntry{keys[i], values[i]});
+        }
+        telExtras = Some(extras);
+      }
+      Telemetry::RecordEvent(id.extract(), Nothing(), telExtras);
+    }
+    if (aExtras) {
+      auto extra = aExtras->ToFfiExtra();
+      fog_event_record(mId, &mozilla::Get<0>(extra), &mozilla::Get<1>(extra));
+    } else {
+      nsTArray<nsCString> keys;
+      nsTArray<nsCString> vals;
+      fog_event_record(mId, &keys, &vals);
+    }
+  }
+
+  /**
+   * **Test-only API**
+   *
+   * Get a list of currently stored events for this event metric.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<nsTArray<RecordedEvent>>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const {
+    nsCString err;
+    if (fog_event_test_get_error(mId, &err)) {
+      return Err(err);
+    }
+
+    if (!fog_event_test_has_value(mId, &aPingName)) {
+      return Maybe<nsTArray<RecordedEvent>>();
+    }
+
+    nsTArray<FfiRecordedEvent> events;
+    fog_event_test_get_value(mId, &aPingName, &events);
+
+    nsTArray<RecordedEvent> result;
+    for (const auto& event : events) {
+      auto ev = result.AppendElement();
+      ev->mTimestamp = event.timestamp;
+      ev->mCategory.Append(event.category);
+      ev->mName.Assign(event.name);
+
+      MOZ_ASSERT(event.extras.Length() % 2 == 0);
+      ev->mExtra.SetCapacity(event.extras.Length() / 2);
+      for (unsigned int i = 0; i < event.extras.Length(); i += 2) {
+        // keys & values are interleaved.
+        nsCString key = std::move(event.extras[i]);
+        nsCString value = std::move(event.extras[i + 1]);
+        ev->mExtra.AppendElement(MakeTuple(std::move(key), std::move(value)));
+      }
+    }
+    return Some(std::move(result));
+  }
+
+ private:
+  static const nsCString ExtraStringForKey(uint32_t aKey);
+
+  const uint32_t mId;
+};
+
+}  // namespace impl
+
+struct NoExtraKeys {
+  Tuple<nsTArray<nsCString>, nsTArray<nsCString>> ToFfiExtra() const {
+    nsTArray<nsCString> extraKeys;
+    nsTArray<nsCString> extraValues;
+    return MakeTuple(std::move(extraKeys), std::move(extraValues));
+  }
+};
+
+class GleanEvent final : public nsIGleanEvent {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANEVENT
+
+  explicit GleanEvent(uint32_t id) : mEvent(id){};
+
+ private:
+  virtual ~GleanEvent() = default;
+
+  const impl::EventMetric<NoExtraKeys> mEvent;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanEvent.h */
diff --git a/toolkit/components/glean/bindings/private/Labeled.cpp b/toolkit/components/glean/bindings/private/Labeled.cpp
new file mode 100644
index 0000000000..b01867d729
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Labeled.cpp
@@ -0,0 +1,99 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Labeled.h"
+
+#include "mozilla/dom/GleanBinding.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "mozilla/glean/bindings/GleanJSMetricsLookup.h"
+#include "mozilla/glean/bindings/MetricTypes.h"
+#include "mozilla/UniquePtr.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+template <>
+BooleanMetric Labeled<BooleanMetric>::Get(const nsACString& aLabel) const {
+  auto submetricId = fog_labeled_boolean_get(mId, &aLabel);
+  // If this labeled metric is mirrored, we need to map the submetric id back
+  // to the label string and mirrored scalar so we can mirror its operations.
+  auto mirrorId = ScalarIdForMetric(mId);
+  if (mirrorId) {
+    GetLabeledMirrorLock().apply([&](auto& lock) {
+      auto tuple = MakeTuple<Telemetry::ScalarID, nsString>(
+          mirrorId.extract(), NS_ConvertUTF8toUTF16(aLabel));
+      lock.ref()->InsertOrUpdate(submetricId, std::move(tuple));
+    });
+  }
+  return BooleanMetric(submetricId);
+}
+
+template <>
+CounterMetric Labeled<CounterMetric>::Get(const nsACString& aLabel) const {
+  auto submetricId = fog_labeled_counter_get(mId, &aLabel);
+  // If this labeled metric is mirrored, we need to map the submetric id back
+  // to the label string and mirrored scalar so we can mirror its operations.
+  auto mirrorId = ScalarIdForMetric(mId);
+  if (mirrorId) {
+    GetLabeledMirrorLock().apply([&](auto& lock) {
+      auto tuple = MakeTuple<Telemetry::ScalarID, nsString>(
+          mirrorId.extract(), NS_ConvertUTF8toUTF16(aLabel));
+      lock.ref()->InsertOrUpdate(submetricId, std::move(tuple));
+    });
+  }
+  return CounterMetric(submetricId);
+}
+
+template <>
+StringMetric Labeled<StringMetric>::Get(const nsACString& aLabel) const {
+  auto submetricId = fog_labeled_string_get(mId, &aLabel);
+  // Why no GIFFT map here?
+  // Labeled Strings can't be mirrored. Telemetry has no compatible probe.
+  return StringMetric(submetricId);
+}
+}  // namespace impl
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_0(GleanLabeled)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(GleanLabeled)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(GleanLabeled)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(GleanLabeled)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+JSObject* GleanLabeled::WrapObject(JSContext* aCx,
+                                   JS::Handle<JSObject*> aGivenProto) {
+  return dom::GleanLabeled_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+already_AddRefed<nsISupports> GleanLabeled::NamedGetter(const nsAString& aName,
+                                                        bool& aFound) {
+  auto label = NS_ConvertUTF16toUTF8(aName);
+  aFound = true;
+  uint32_t submetricId = 0;
+  already_AddRefed<nsISupports> submetric =
+      NewSubMetricFromIds(mTypeId, mId, label, &submetricId);
+
+  auto mirrorId = ScalarIdForMetric(mId);
+  if (mirrorId) {
+    GetLabeledMirrorLock().apply([&](auto& lock) {
+      auto tuple = MakeTuple<Telemetry::ScalarID, nsString>(mirrorId.extract(),
+                                                            nsString(aName));
+      lock.ref()->InsertOrUpdate(submetricId, std::move(tuple));
+    });
+  }
+  return submetric;
+}
+
+bool GleanLabeled::NameIsEnumerable(const nsAString& aName) { return false; }
+
+void GleanLabeled::GetSupportedNames(nsTArray<nsString>& aNames) {
+  // We really don't know, so don't do anything.
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Labeled.h b/toolkit/components/glean/bindings/private/Labeled.h
new file mode 100644
index 0000000000..be46b3b56e
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Labeled.h
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_Labeled_h
+#define mozilla_glean_Labeled_h
+
+#include "nsIGleanMetrics.h"
+#include "nsISupports.h"
+#include "nsWrapperCache.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+template <typename T>
+class Labeled {
+ public:
+  constexpr explicit Labeled<T>(uint32_t id) : mId(id) {}
+
+  /**
+   * Gets a specific metric for a given label.
+   *
+   * If a set of acceptable labels were specified in the `metrics.yaml` file,
+   * and the given label is not in the set, it will be recorded under the
+   * special `OTHER_LABEL` label.
+   *
+   * If a set of acceptable labels was not specified in the `metrics.yaml` file,
+   * only the first 16 unique labels will be used.
+   * After that, any additional labels will be recorded under the special
+   * `OTHER_LABEL` label.
+   *
+   * @param aLabel - a snake_case string under 30 characters in length,
+   *                 otherwise the metric will be recorded under the special
+   *                 `OTHER_LABEL` label and an error will be recorded.
+   */
+  T Get(const nsACString& aLabel) const;
+
+ private:
+  const uint32_t mId;
+};
+
+}  // namespace impl
+
+class GleanLabeled final : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(GleanLabeled)
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+  nsISupports* GetParentObject() { return nullptr; }
+
+  explicit GleanLabeled(uint32_t aId, uint32_t aTypeId)
+      : mId(aId), mTypeId(aTypeId){};
+
+  already_AddRefed<nsISupports> NamedGetter(const nsAString& aName,
+                                            bool& aFound);
+  bool NameIsEnumerable(const nsAString& aName);
+  void GetSupportedNames(nsTArray<nsString>& aNames);
+
+ private:
+  virtual ~GleanLabeled() = default;
+
+  const uint32_t mId;
+  const uint32_t mTypeId;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_Labeled_h */
diff --git a/toolkit/components/glean/bindings/private/MemoryDistribution.cpp b/toolkit/components/glean/bindings/private/MemoryDistribution.cpp
new file mode 100644
index 0000000000..41899bf7c1
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/MemoryDistribution.cpp
@@ -0,0 +1,104 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/MemoryDistribution.h"
+
+#include "mozilla/Components.h"
+#include "mozilla/glean/bindings/HistogramGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+#include "nsJSUtils.h"
+#include "nsPrintfCString.h"
+#include "nsString.h"
+#include "js/PropertyAndElement.h"  // JS_DefineProperty
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void MemoryDistributionMetric::Accumulate(size_t aSample) const {
+  auto hgramId = HistogramIdForMetric(mId);
+  if (hgramId) {
+    Telemetry::Accumulate(hgramId.extract(), aSample);
+  }
+  static_assert(sizeof(size_t) <= sizeof(uint64_t),
+                "Memory distribution samples might overflow.");
+  fog_memory_distribution_accumulate(mId, aSample);
+}
+
+Result<Maybe<DistributionData>, nsCString>
+MemoryDistributionMetric::TestGetValue(const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_memory_distribution_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_memory_distribution_test_has_value(mId, &aPingName)) {
+    return Maybe<DistributionData>();
+  }
+  nsTArray<uint64_t> buckets;
+  nsTArray<uint64_t> counts;
+  uint64_t sum;
+  fog_memory_distribution_test_get_value(mId, &aPingName, &sum, &buckets,
+                                         &counts);
+  return Some(DistributionData(buckets, counts, sum));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanMemoryDistribution, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanMemoryDistribution, nsIGleanMemoryDistribution)
+
+NS_IMETHODIMP
+GleanMemoryDistribution::Accumulate(uint64_t aSample) {
+  mMemoryDist.Accumulate(aSample);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanMemoryDistribution::TestGetValue(const nsACString& aPingName,
+                                      JSContext* aCx,
+                                      JS::MutableHandle<JS::Value> aResult) {
+  auto result = mMemoryDist.TestGetValue(aPingName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    // Build return value of the form:
+    // { sum: #, values: {bucket1: count1, ...} }
+    JS::Rooted<JSObject*> root(aCx, JS_NewPlainObject(aCx));
+    if (!root) {
+      return NS_ERROR_FAILURE;
+    }
+    uint64_t sum = optresult.ref().sum;
+    if (!JS_DefineProperty(aCx, root, "sum", static_cast<double>(sum),
+                           JSPROP_ENUMERATE)) {
+      return NS_ERROR_FAILURE;
+    }
+    JS::Rooted<JSObject*> valuesObj(aCx, JS_NewPlainObject(aCx));
+    if (!valuesObj ||
+        !JS_DefineProperty(aCx, root, "values", valuesObj, JSPROP_ENUMERATE)) {
+      return NS_ERROR_FAILURE;
+    }
+    auto& data = optresult.ref().values;
+    for (const auto& entry : data) {
+      const uint64_t bucket = entry.GetKey();
+      const uint64_t count = entry.GetData();
+      if (!JS_DefineProperty(aCx, valuesObj,
+                             nsPrintfCString("%" PRIu64, bucket).get(),
+                             static_cast<double>(count), JSPROP_ENUMERATE)) {
+        return NS_ERROR_FAILURE;
+      }
+    }
+    aResult.setObject(*root);
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/MemoryDistribution.h b/toolkit/components/glean/bindings/private/MemoryDistribution.h
new file mode 100644
index 0000000000..136cdb6c91
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/MemoryDistribution.h
@@ -0,0 +1,74 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanMemoryDistribution_h
+#define mozilla_glean_GleanMemoryDistribution_h
+
+#include "mozilla/glean/bindings/DistributionData.h"
+#include "mozilla/Maybe.h"
+#include "nsIGleanMetrics.h"
+#include "nsTArray.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class MemoryDistributionMetric {
+ public:
+  constexpr explicit MemoryDistributionMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Accumulates the provided sample in the metric.
+   *
+   * @param aSample The sample to be recorded by the metric. The sample is
+   *                assumed to be in the confgured memory unit of the metric.
+   *
+   * Notes: Values bigger than 1 Terabyte (2^40 bytes) are truncated and an
+   * InvalidValue error is recorded.
+   */
+  void Accumulate(size_t aSample) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a DistributionData.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<DistributionData>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanMemoryDistribution final : public nsIGleanMemoryDistribution {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANMEMORYDISTRIBUTION
+
+  explicit GleanMemoryDistribution(uint64_t aId) : mMemoryDist(aId){};
+
+ private:
+  virtual ~GleanMemoryDistribution() = default;
+
+  const impl::MemoryDistributionMetric mMemoryDist;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanMemoryDistribution_h */
diff --git a/toolkit/components/glean/bindings/private/Numerator.cpp b/toolkit/components/glean/bindings/private/Numerator.cpp
new file mode 100644
index 0000000000..79a211773b
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Numerator.cpp
@@ -0,0 +1,89 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Numerator.h"
+
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void NumeratorMetric::AddToNumerator(int32_t aAmount) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (scalarId && aAmount >= 0) {
+    Telemetry::ScalarAdd(scalarId.extract(), u"numerator"_ns, aAmount);
+  }
+  fog_numerator_add_to_numerator(mId, aAmount);
+}
+
+Result<Maybe<std::pair<int32_t, int32_t>>, nsCString>
+NumeratorMetric::TestGetValue(const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_numerator_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_numerator_test_has_value(mId, &aPingName)) {
+    return Maybe<std::pair<int32_t, int32_t>>();
+  }
+  int32_t num = 0;
+  int32_t den = 0;
+  fog_numerator_test_get_value(mId, &aPingName, &num, &den);
+  return Some(std::make_pair(num, den));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanNumerator, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanNumerator, nsIGleanNumerator)
+
+NS_IMETHODIMP
+GleanNumerator::AddToNumerator(int32_t aAmount) {
+  mNumerator.AddToNumerator(aAmount);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanNumerator::TestGetValue(const nsACString& aPingName, JSContext* aCx,
+                             JS::MutableHandle<JS::Value> aResult) {
+  auto result = mNumerator.TestGetValue(aPingName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    // Build return value of the form: { numerator: n, denominator: d }
+    JS::Rooted<JSObject*> root(aCx, JS_NewPlainObject(aCx));
+    if (!root) {
+      return NS_ERROR_FAILURE;
+    }
+    auto pair = optresult.extract();
+    int32_t num = pair.first;
+    int32_t den = pair.second;
+    if (!JS_DefineProperty(aCx, root, "numerator", static_cast<double>(num),
+                           JSPROP_ENUMERATE)) {
+      return NS_ERROR_FAILURE;
+    }
+    if (!JS_DefineProperty(aCx, root, "denominator", static_cast<double>(den),
+                           JSPROP_ENUMERATE)) {
+      return NS_ERROR_FAILURE;
+    }
+    aResult.setObject(*root);
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Numerator.h b/toolkit/components/glean/bindings/private/Numerator.h
new file mode 100644
index 0000000000..66b7eef295
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Numerator.h
@@ -0,0 +1,72 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanNumerator_h
+#define mozilla_glean_GleanNumerator_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+// Actually a RateMetric, but one whose denominator is a CounterMetric external
+// to the RateMetric.
+class NumeratorMetric {
+ public:
+  constexpr explicit NumeratorMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Increases the numerator by `amount`.
+   *
+   * @param aAmount The amount to increase by. Should be positive.
+   */
+  void AddToNumerator(int32_t aAmount = 1) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a pair of integers.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<std::pair<int32_t, int32_t>>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanNumerator final : public nsIGleanNumerator {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANNUMERATOR
+
+  explicit GleanNumerator(uint32_t id) : mNumerator(id){};
+
+ private:
+  virtual ~GleanNumerator() = default;
+
+  const impl::NumeratorMetric mNumerator;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanNumerator_h */
diff --git a/toolkit/components/glean/bindings/private/Ping.cpp b/toolkit/components/glean/bindings/private/Ping.cpp
new file mode 100644
index 0000000000..c341a61148
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Ping.cpp
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Ping.h"
+
+#ifndef MOZ_GLEAN_ANDROID
+#  include "mozilla/AppShutdown.h"
+#  include "mozilla/ClearOnShutdown.h"
+#endif
+#include "mozilla/Components.h"
+#include "nsIClassInfoImpl.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+#ifndef MOZ_GLEAN_ANDROID
+using CallbackMapType = nsTHashMap<uint32_t, PingTestCallback>;
+using MetricIdToCallbackMutex = StaticDataMutex<UniquePtr<CallbackMapType>>;
+static Maybe<MetricIdToCallbackMutex::AutoLock> GetCallbackMapLock() {
+  static MetricIdToCallbackMutex sCallbacks("sCallbacks");
+  auto lock = sCallbacks.Lock();
+  // Test callbacks will continue to work until the end of AppShutdownTelemetry
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+    return Nothing();
+  }
+  if (!*lock) {
+    *lock = MakeUnique<CallbackMapType>();
+    RunOnShutdown(
+        [&] {
+          auto lock = sCallbacks.Lock();
+          *lock = nullptr;  // deletes, see UniquePtr.h
+        },
+        ShutdownPhase::XPCOMWillShutdown);
+  }
+  return Some(std::move(lock));
+}
+#endif
+
+void Ping::Submit(const nsACString& aReason) const {
+#ifdef MOZ_GLEAN_ANDROID
+  Unused << mId;
+#else
+  {
+    GetCallbackMapLock().apply([&](auto& lock) {
+      auto callback = lock.ref()->Extract(mId);
+      if (callback) {
+        callback.extract()(aReason);
+      }
+    });
+  }
+  fog_submit_ping_by_id(mId, &aReason);
+#endif
+}
+
+void Ping::TestBeforeNextSubmit(PingTestCallback&& aCallback) const {
+#ifdef MOZ_GLEAN_ANDROID
+  return;
+#else
+  {
+    GetCallbackMapLock().apply(
+        [&](auto& lock) { lock.ref()->InsertOrUpdate(mId, aCallback); });
+  }
+#endif
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanPing, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanPing, nsIGleanPing)
+
+NS_IMETHODIMP
+GleanPing::Submit(const nsACString& aReason) {
+  mPing.Submit(aReason);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanPing::TestBeforeNextSubmit(nsIGleanPingTestCallback* aCallback) {
+  if (NS_WARN_IF(!aCallback)) {
+    return NS_ERROR_INVALID_ARG;
+  }
+  // Throw the bare ptr into a COM ptr to keep it around in the lambda.
+  nsCOMPtr<nsIGleanPingTestCallback> callback = aCallback;
+  mPing.TestBeforeNextSubmit(
+      [callback](const nsACString& aReason) { callback->Call(aReason); });
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Ping.h b/toolkit/components/glean/bindings/private/Ping.h
new file mode 100644
index 0000000000..6bcd4cb478
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Ping.h
@@ -0,0 +1,83 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_Ping_h
+#define mozilla_glean_Ping_h
+
+#include "mozilla/DataMutex.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "mozilla/Maybe.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+typedef std::function<void(const nsACString& aReason)> PingTestCallback;
+
+namespace impl {
+
+class Ping {
+ public:
+  constexpr explicit Ping(uint32_t aId) : mId(aId) {}
+
+  /**
+   * Collect and submit the ping for eventual upload.
+   *
+   * This will collect all stored data to be included in the ping.
+   * Data with lifetime `ping` will then be reset.
+   *
+   * If the ping is configured with `send_if_empty = false`
+   * and the ping currently contains no content,
+   * it will not be queued for upload.
+   * If the ping is configured with `send_if_empty = true`
+   * it will be queued for upload even if empty.
+   *
+   * Pings always contain the `ping_info` and `client_info` sections.
+   * See [ping
+   * sections](https://mozilla.github.io/glean/book/user/pings/index.html#ping-sections)
+   * for details.
+   *
+   * @param aReason - Optional. The reason the ping is being submitted.
+   *                  Must match one of the configured `reason_codes`.
+   */
+  void Submit(const nsACString& aReason = nsCString()) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Register a callback to be called right before this ping is next submitted.
+   * The provided function is called exactly once before submitting.
+   *
+   * Note: The callback will be called on any call to submit.
+   * A ping may not be sent afterwards, e.g. if the ping is empty and
+   * `send_if_empty` is `false`
+   *
+   * @param aCallback - The callback to call on the next submit.
+   */
+  void TestBeforeNextSubmit(PingTestCallback&& aCallback) const;
+
+ private:
+  const uint32_t mId;
+};
+
+}  // namespace impl
+
+class GleanPing final : public nsIGleanPing {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANPING
+
+  explicit GleanPing(uint32_t aId) : mPing(aId) {}
+
+ private:
+  virtual ~GleanPing() = default;
+
+  const impl::Ping mPing;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_Ping_h */
diff --git a/toolkit/components/glean/bindings/private/Quantity.cpp b/toolkit/components/glean/bindings/private/Quantity.cpp
new file mode 100644
index 0000000000..62591e6c90
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Quantity.cpp
@@ -0,0 +1,74 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Quantity.h"
+
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void QuantityMetric::Set(int64_t aValue) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (scalarId && aValue >= 0) {
+    uint32_t theValue = static_cast<uint32_t>(aValue);
+    if (aValue > std::numeric_limits<uint32_t>::max()) {
+      theValue = std::numeric_limits<uint32_t>::max();
+    }
+    Telemetry::ScalarSet(scalarId.extract(), theValue);
+  }
+  fog_quantity_set(mId, aValue);
+}
+
+Result<Maybe<int64_t>, nsCString> QuantityMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_quantity_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_quantity_test_has_value(mId, &aPingName)) {
+    return Maybe<int64_t>();
+  }
+  return Some(fog_quantity_test_get_value(mId, &aPingName));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanQuantity, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanQuantity, nsIGleanQuantity)
+
+NS_IMETHODIMP
+GleanQuantity::Set(int64_t aValue) {
+  mQuantity.Set(aValue);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanQuantity::TestGetValue(const nsACString& aPingName,
+                            JS::MutableHandle<JS::Value> aResult) {
+  auto result = mQuantity.TestGetValue(aPingName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    aResult.set(JS::DoubleValue(static_cast<double>(optresult.value())));
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Quantity.h b/toolkit/components/glean/bindings/private/Quantity.h
new file mode 100644
index 0000000000..9de1007d10
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Quantity.h
@@ -0,0 +1,68 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanQuantity_h
+#define mozilla_glean_GleanQuantity_h
+
+#include "nsIGleanMetrics.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class QuantityMetric {
+ public:
+  constexpr explicit QuantityMetric(uint32_t id) : mId(id) {}
+
+  /**
+   * Set to the specified value.
+   *
+   * @param aValue the value to set.
+   */
+  void Set(int64_t aValue) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric.
+   */
+  Result<Maybe<int64_t>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+
+}  // namespace impl
+
+class GleanQuantity final : public nsIGleanQuantity {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANQUANTITY
+
+  explicit GleanQuantity(uint32_t id) : mQuantity(id){};
+
+ private:
+  virtual ~GleanQuantity() = default;
+
+  const impl::QuantityMetric mQuantity;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanQuantity.h */
diff --git a/toolkit/components/glean/bindings/private/Rate.cpp b/toolkit/components/glean/bindings/private/Rate.cpp
new file mode 100644
index 0000000000..6bc6ad61c9
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Rate.cpp
@@ -0,0 +1,105 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Rate.h"
+
+#include "jsapi.h"
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/Common.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void RateMetric::AddToNumerator(int32_t aAmount) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (scalarId && aAmount >= 0) {
+    Telemetry::ScalarAdd(scalarId.extract(), u"numerator"_ns, aAmount);
+  }
+  fog_rate_add_to_numerator(mId, aAmount);
+}
+
+void RateMetric::AddToDenominator(int32_t aAmount) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (scalarId && aAmount >= 0) {
+    Telemetry::ScalarAdd(scalarId.extract(), u"denominator"_ns, aAmount);
+  }
+  fog_rate_add_to_denominator(mId, aAmount);
+}
+
+Result<Maybe<std::pair<int32_t, int32_t>>, nsCString> RateMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_rate_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_rate_test_has_value(mId, &aPingName)) {
+    return Maybe<std::pair<int32_t, int32_t>>();
+  }
+  int32_t num = 0;
+  int32_t den = 0;
+  fog_rate_test_get_value(mId, &aPingName, &num, &den);
+  return Some(std::make_pair(num, den));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanRate, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanRate, nsIGleanRate)
+
+NS_IMETHODIMP
+GleanRate::AddToNumerator(int32_t aAmount) {
+  mRate.AddToNumerator(aAmount);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanRate::AddToDenominator(int32_t aAmount) {
+  mRate.AddToDenominator(aAmount);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanRate::TestGetValue(const nsACString& aPingName, JSContext* aCx,
+                        JS::MutableHandle<JS::Value> aResult) {
+  auto result = mRate.TestGetValue(aPingName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    // Build return value of the form: { numerator: n, denominator: d }
+    JS::Rooted<JSObject*> root(aCx, JS_NewPlainObject(aCx));
+    if (!root) {
+      return NS_ERROR_FAILURE;
+    }
+    auto pair = optresult.extract();
+    int32_t num = pair.first;
+    int32_t den = pair.second;
+    if (!JS_DefineProperty(aCx, root, "numerator", static_cast<double>(num),
+                           JSPROP_ENUMERATE)) {
+      return NS_ERROR_FAILURE;
+    }
+    if (!JS_DefineProperty(aCx, root, "denominator", static_cast<double>(den),
+                           JSPROP_ENUMERATE)) {
+      return NS_ERROR_FAILURE;
+    }
+    aResult.setObject(*root);
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Rate.h b/toolkit/components/glean/bindings/private/Rate.h
new file mode 100644
index 0000000000..85e8b4e1d6
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Rate.h
@@ -0,0 +1,77 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanRate_h
+#define mozilla_glean_GleanRate_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class RateMetric {
+ public:
+  constexpr explicit RateMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Increases the numerator by `amount`.
+   *
+   * @param aAmount The amount to increase by. Should be positive.
+   */
+  void AddToNumerator(int32_t aAmount = 1) const;
+
+  /*
+   * Increases the denominator by `amount`.
+   *
+   * @param aAmount The amount to increase by. Should be positive.
+   */
+  void AddToDenominator(int32_t aAmount = 1) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a pair of integers.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<std::pair<int32_t, int32_t>>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanRate final : public nsIGleanRate {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANRATE
+
+  explicit GleanRate(uint32_t id) : mRate(id){};
+
+ private:
+  virtual ~GleanRate() = default;
+
+  const impl::RateMetric mRate;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanRate_h */
diff --git a/toolkit/components/glean/bindings/private/String.cpp b/toolkit/components/glean/bindings/private/String.cpp
new file mode 100644
index 0000000000..bc191a7400
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/String.cpp
@@ -0,0 +1,77 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/String.h"
+
+#include "Common.h"
+#include "jsapi.h"
+#include "js/String.h"
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void StringMetric::Set(const nsACString& aValue) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (scalarId) {
+    Telemetry::ScalarSet(scalarId.extract(), NS_ConvertUTF8toUTF16(aValue));
+  }
+  fog_string_set(mId, &aValue);
+}
+
+Result<Maybe<nsCString>, nsCString> StringMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_string_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_string_test_has_value(mId, &aPingName)) {
+    return Maybe<nsCString>();
+  }
+  nsCString ret;
+  fog_string_test_get_value(mId, &aPingName, &ret);
+  return Some(ret);
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanString, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanString, nsIGleanString)
+
+NS_IMETHODIMP
+GleanString::Set(const nsACString& aValue) {
+  mString.Set(aValue);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanString::TestGetValue(const nsACString& aStorageName, JSContext* aCx,
+                          JS::MutableHandle<JS::Value> aResult) {
+  auto result = mString.TestGetValue(aStorageName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    const NS_ConvertUTF8toUTF16 str(optresult.ref());
+    aResult.set(
+        JS::StringValue(JS_NewUCStringCopyN(aCx, str.Data(), str.Length())));
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/String.h b/toolkit/components/glean/bindings/private/String.h
new file mode 100644
index 0000000000..8c3c6ae05e
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/String.h
@@ -0,0 +1,73 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanString_h
+#define mozilla_glean_GleanString_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class StringMetric {
+ public:
+  constexpr explicit StringMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Set to the specified value.
+   *
+   * Truncates the value if it is longer than 100 bytes and logs an error.
+   * See https://mozilla.github.io/glean/book/user/metrics/string.html#limits.
+   *
+   * @param aValue The string to set the metric to.
+   */
+  void Set(const nsACString& aValue) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a string.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<nsCString>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanString final : public nsIGleanString {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANSTRING
+
+  explicit GleanString(uint32_t aId) : mString(aId){};
+
+ private:
+  virtual ~GleanString() = default;
+
+  const impl::StringMetric mString;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanString_h */
diff --git a/toolkit/components/glean/bindings/private/StringList.cpp b/toolkit/components/glean/bindings/private/StringList.cpp
new file mode 100644
index 0000000000..8882922551
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/StringList.cpp
@@ -0,0 +1,92 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/StringList.h"
+
+#include "Common.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void StringListMetric::Add(const nsACString& aValue) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (scalarId) {
+    Telemetry::ScalarSet(scalarId.extract(), NS_ConvertUTF8toUTF16(aValue),
+                         true);
+  }
+  fog_string_list_add(mId, &aValue);
+}
+
+void StringListMetric::Set(const nsTArray<nsCString>& aValue) const {
+  // Calling `Set` on a mirrored labeled_string is likely an error.
+  // We can't remove keys from the mirror scalar and handle this 'properly',
+  // so you shouldn't use this operation at all.
+  (void)NS_WARN_IF(ScalarIdForMetric(mId).isSome());
+  fog_string_list_set(mId, &aValue);
+}
+
+Result<Maybe<nsTArray<nsCString>>, nsCString> StringListMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_string_list_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_string_list_test_has_value(mId, &aPingName)) {
+    return Maybe<nsTArray<nsCString>>();
+  }
+  nsTArray<nsCString> ret;
+  fog_string_list_test_get_value(mId, &aPingName, &ret);
+  return Some(std::move(ret));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanStringList, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanStringList, nsIGleanStringList)
+
+NS_IMETHODIMP
+GleanStringList::Add(const nsACString& aValue) {
+  mStringList.Add(aValue);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanStringList::Set(const nsTArray<nsCString>& aValue) {
+  mStringList.Set(aValue);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanStringList::TestGetValue(const nsACString& aStorageName, JSContext* aCx,
+                              JS::MutableHandle<JS::Value> aResult) {
+  auto result = mStringList.TestGetValue(aStorageName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    if (!dom::ToJSValue(aCx, optresult.ref(), aResult)) {
+      return NS_ERROR_FAILURE;
+    }
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/StringList.h b/toolkit/components/glean/bindings/private/StringList.h
new file mode 100644
index 0000000000..6b7b9358e2
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/StringList.h
@@ -0,0 +1,84 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanStringList_h
+#define mozilla_glean_GleanStringList_h
+
+#include "mozilla/Maybe.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class StringListMetric {
+ public:
+  constexpr explicit StringListMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Adds a new string to the list.
+   *
+   * Truncates the value if it is longer than 50 bytes and logs an error.
+   *
+   * @param aValue The string to add.
+   */
+  void Add(const nsACString& aValue) const;
+
+  /*
+   * Set to a specific list of strings.
+   *
+   * Truncates any values longer than 50 bytes and logs an error.
+   * Truncates the list if it is over 20 items long.
+   * See
+   * https://mozilla.github.io/glean/book/user/metrics/string_list.html#limits.
+   *
+   * @param aValue The list of strings to set the metric to.
+   */
+  void Set(const nsTArray<nsCString>& aValue) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<nsTArray<nsCString>>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanStringList final : public nsIGleanStringList {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANSTRINGLIST
+
+  explicit GleanStringList(uint32_t aId) : mStringList(aId){};
+
+ private:
+  virtual ~GleanStringList() = default;
+
+  const impl::StringListMetric mStringList;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanStringList_h */
diff --git a/toolkit/components/glean/bindings/private/Timespan.cpp b/toolkit/components/glean/bindings/private/Timespan.cpp
new file mode 100644
index 0000000000..e8377c8fcf
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Timespan.cpp
@@ -0,0 +1,133 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Timespan.h"
+
+#include "Common.h"
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void TimespanMetric::Start() const {
+  auto optScalarId = ScalarIdForMetric(mId);
+  if (optScalarId) {
+    auto scalarId = optScalarId.extract();
+    GetTimesToStartsLock().apply([&](auto& lock) {
+      (void)NS_WARN_IF(lock.ref()->Remove(scalarId));
+      lock.ref()->InsertOrUpdate(scalarId, TimeStamp::Now());
+    });
+  }
+  fog_timespan_start(mId);
+}
+
+void TimespanMetric::Stop() const {
+  auto optScalarId = ScalarIdForMetric(mId);
+  if (optScalarId) {
+    auto scalarId = optScalarId.extract();
+    GetTimesToStartsLock().apply([&](auto& lock) {
+      auto optStart = lock.ref()->Extract(scalarId);
+      if (!NS_WARN_IF(!optStart)) {
+        double delta = (TimeStamp::Now() - optStart.extract()).ToMilliseconds();
+        uint32_t theDelta = static_cast<uint32_t>(delta);
+        if (delta > std::numeric_limits<uint32_t>::max()) {
+          theDelta = std::numeric_limits<uint32_t>::max();
+        } else if (MOZ_UNLIKELY(delta < 0)) {
+          theDelta = 0;
+        }
+        Telemetry::ScalarSet(scalarId, theDelta);
+      }
+    });
+  }
+  fog_timespan_stop(mId);
+}
+
+void TimespanMetric::Cancel() const {
+  auto optScalarId = ScalarIdForMetric(mId);
+  if (optScalarId) {
+    auto scalarId = optScalarId.extract();
+    GetTimesToStartsLock().apply(
+        [&](auto& lock) { lock.ref()->Remove(scalarId); });
+  }
+  fog_timespan_cancel(mId);
+}
+
+void TimespanMetric::SetRaw(uint32_t aDuration) const {
+  auto optScalarId = ScalarIdForMetric(mId);
+  if (optScalarId) {
+    auto scalarId = optScalarId.extract();
+    Telemetry::ScalarSet(scalarId, aDuration);
+  }
+  fog_timespan_set_raw(mId, aDuration);
+}
+
+Result<Maybe<uint64_t>, nsCString> TimespanMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_timespan_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_timespan_test_has_value(mId, &aPingName)) {
+    return Maybe<uint64_t>();
+  }
+  return Some(fog_timespan_test_get_value(mId, &aPingName));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanTimespan, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanTimespan, nsIGleanTimespan)
+
+NS_IMETHODIMP
+GleanTimespan::Start() {
+  mTimespan.Start();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanTimespan::Stop() {
+  mTimespan.Stop();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanTimespan::Cancel() {
+  mTimespan.Cancel();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanTimespan::SetRaw(uint32_t aDuration) {
+  mTimespan.SetRaw(aDuration);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanTimespan::TestGetValue(const nsACString& aStorageName,
+                            JS::MutableHandle<JS::Value> aResult) {
+  auto result = mTimespan.TestGetValue(aStorageName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    aResult.set(JS::DoubleValue(static_cast<double>(optresult.value())));
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Timespan.h b/toolkit/components/glean/bindings/private/Timespan.h
new file mode 100644
index 0000000000..b82a174034
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Timespan.h
@@ -0,0 +1,99 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanTimespan_h
+#define mozilla_glean_GleanTimespan_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class TimespanMetric {
+ public:
+  constexpr explicit TimespanMetric(uint32_t aId) : mId(aId) {}
+
+  /**
+   * Start tracking time for the provided metric.
+   *
+   * This records an error if it’s already tracking time (i.e. start was already
+   * called with no corresponding [stop]): in that case the original
+   * start time will be preserved.
+   */
+  void Start() const;
+
+  /**
+   * Stop tracking time for the provided metric.
+   *
+   * Sets the metric to the elapsed time, but does not overwrite an already
+   * existing value.
+   * This will record an error if no [start] was called or there is an already
+   * existing value.
+   */
+  void Stop() const;
+
+  /**
+   * Abort a previous Start.
+   *
+   * No error will be recorded if no Start was called.
+   */
+  void Cancel() const;
+
+  /**
+   * Explicitly sets the timespan value
+   *
+   * This API should only be used if you cannot make use of
+   * `start`/`stop`/`cancel`.
+   *
+   * @param aDuration The duration of this timespan, in units matching the
+   *        `time_unit` of this metric's definition.
+   */
+  void SetRaw(uint32_t aDuration) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as an integer.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<uint64_t>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanTimespan final : public nsIGleanTimespan {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANTIMESPAN
+
+  explicit GleanTimespan(uint32_t aId) : mTimespan(aId){};
+
+ private:
+  virtual ~GleanTimespan() = default;
+
+  const impl::TimespanMetric mTimespan;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanTimespan_h */
diff --git a/toolkit/components/glean/bindings/private/TimingDistribution.cpp b/toolkit/components/glean/bindings/private/TimingDistribution.cpp
new file mode 100644
index 0000000000..7ec20f94b7
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/TimingDistribution.cpp
@@ -0,0 +1,196 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/TimingDistribution.h"
+
+#include "Common.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/Tuple.h"
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/glean/bindings/HistogramGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+#include "nsJSUtils.h"
+#include "nsPrintfCString.h"
+#include "nsString.h"
+#include "js/PropertyAndElement.h"  // JS_DefineProperty
+
+// Called from within FOG's Rust impl.
+extern "C" NS_EXPORT void GIFFT_TimingDistributionStart(
+    uint32_t aMetricId, mozilla::glean::TimerId aTimerId) {
+  auto mirrorId = mozilla::glean::HistogramIdForMetric(aMetricId);
+  if (mirrorId) {
+    mozilla::glean::GetTimerIdToStartsLock().apply([&](auto& lock) {
+      auto tuple = mozilla::MakeTuple(aMetricId, aTimerId);
+      // It should be all but impossible for anyone to have already inserted
+      // this timer for this metric given the monotonicity of timer ids.
+      (void)NS_WARN_IF(lock.ref()->Remove(tuple));
+      lock.ref()->InsertOrUpdate(tuple, mozilla::TimeStamp::Now());
+    });
+  }
+}
+
+// Called from within FOG's Rust impl.
+extern "C" NS_EXPORT void GIFFT_TimingDistributionStopAndAccumulate(
+    uint32_t aMetricId, mozilla::glean::TimerId aTimerId) {
+  auto mirrorId = mozilla::glean::HistogramIdForMetric(aMetricId);
+  if (mirrorId) {
+    mozilla::glean::GetTimerIdToStartsLock().apply([&](auto& lock) {
+      auto optStart =
+          lock.ref()->Extract(mozilla::MakeTuple(aMetricId, aTimerId));
+      // The timer might not be in the map to be removed if it's already been
+      // cancelled or stop_and_accumulate'd.
+      if (!NS_WARN_IF(!optStart)) {
+        AccumulateTimeDelta(mirrorId.extract(), optStart.extract());
+      }
+    });
+  }
+}
+
+// Called from within FOG's Rust impl.
+extern "C" NS_EXPORT void GIFFT_TimingDistributionAccumulateRawMillis(
+    uint32_t aMetricId, uint32_t aMS) {
+  auto mirrorId = mozilla::glean::HistogramIdForMetric(aMetricId);
+  if (mirrorId) {
+    Accumulate(mirrorId.extract(), aMS);
+  }
+}
+
+// Called from within FOG's Rust impl.
+extern "C" NS_EXPORT void GIFFT_TimingDistributionCancel(
+    uint32_t aMetricId, mozilla::glean::TimerId aTimerId) {
+  auto mirrorId = mozilla::glean::HistogramIdForMetric(aMetricId);
+  if (mirrorId) {
+    mozilla::glean::GetTimerIdToStartsLock().apply([&](auto& lock) {
+      // The timer might not be in the map to be removed if it's already been
+      // cancelled or stop_and_accumulate'd.
+      (void)NS_WARN_IF(
+          !lock.ref()->Remove(mozilla::MakeTuple(aMetricId, aTimerId)));
+    });
+  }
+}
+
+namespace mozilla::glean {
+
+namespace impl {
+
+TimerId TimingDistributionMetric::Start() const {
+  return fog_timing_distribution_start(mId);
+}
+
+void TimingDistributionMetric::StopAndAccumulate(const TimerId&& aId) const {
+  fog_timing_distribution_stop_and_accumulate(mId, aId);
+}
+
+// Intentionally not exposed to JS for lack of use case and a time duration
+// type.
+void TimingDistributionMetric::AccumulateRawDuration(
+    const TimeDuration& aDuration) const {
+  fog_timing_distribution_accumulate_raw_nanos(
+      mId, uint64_t(aDuration.ToMicroseconds() * 1000.00));
+}
+
+void TimingDistributionMetric::Cancel(const TimerId&& aId) const {
+  fog_timing_distribution_cancel(mId, aId);
+}
+
+Result<Maybe<DistributionData>, nsCString>
+TimingDistributionMetric::TestGetValue(const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_timing_distribution_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_timing_distribution_test_has_value(mId, &aPingName)) {
+    return Maybe<DistributionData>();
+  }
+  nsTArray<uint64_t> buckets;
+  nsTArray<uint64_t> counts;
+  uint64_t sum;
+  fog_timing_distribution_test_get_value(mId, &aPingName, &sum, &buckets,
+                                         &counts);
+  return Some(DistributionData(buckets, counts, sum));
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanTimingDistribution, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanTimingDistribution, nsIGleanTimingDistribution)
+
+NS_IMETHODIMP
+GleanTimingDistribution::Start(JSContext* aCx,
+                               JS::MutableHandle<JS::Value> aResult) {
+  if (!dom::ToJSValue(aCx, mTimingDist.Start(), aResult)) {
+    return NS_ERROR_FAILURE;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanTimingDistribution::StopAndAccumulate(uint64_t aId) {
+  mTimingDist.StopAndAccumulate(std::move(aId));
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanTimingDistribution::Cancel(uint64_t aId) {
+  mTimingDist.Cancel(std::move(aId));
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanTimingDistribution::TestGetValue(const nsACString& aPingName,
+                                      JSContext* aCx,
+                                      JS::MutableHandle<JS::Value> aResult) {
+  auto result = mTimingDist.TestGetValue(aPingName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    // Build return value of the form: { sum: #, values: {bucket1: count1,
+    // ...}
+    JS::Rooted<JSObject*> root(aCx, JS_NewPlainObject(aCx));
+    if (!root) {
+      return NS_ERROR_FAILURE;
+    }
+    uint64_t sum = optresult.ref().sum;
+    if (!JS_DefineProperty(aCx, root, "sum", static_cast<double>(sum),
+                           JSPROP_ENUMERATE)) {
+      return NS_ERROR_FAILURE;
+    }
+    JS::Rooted<JSObject*> valuesObj(aCx, JS_NewPlainObject(aCx));
+    if (!valuesObj ||
+        !JS_DefineProperty(aCx, root, "values", valuesObj, JSPROP_ENUMERATE)) {
+      return NS_ERROR_FAILURE;
+    }
+    auto& data = optresult.ref().values;
+    for (const auto& entry : data) {
+      const uint64_t bucket = entry.GetKey();
+      const uint64_t count = entry.GetData();
+      if (!JS_DefineProperty(aCx, valuesObj,
+                             nsPrintfCString("%" PRIu64, bucket).get(),
+                             static_cast<double>(count), JSPROP_ENUMERATE)) {
+        return NS_ERROR_FAILURE;
+      }
+    }
+    aResult.setObject(*root);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanTimingDistribution::TestAccumulateRawMillis(uint64_t aSample) {
+  mTimingDist.AccumulateRawDuration(TimeDuration::FromMilliseconds(aSample));
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/TimingDistribution.h b/toolkit/components/glean/bindings/private/TimingDistribution.h
new file mode 100644
index 0000000000..7c2e69d89e
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/TimingDistribution.h
@@ -0,0 +1,109 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanTimingDistribution_h
+#define mozilla_glean_GleanTimingDistribution_h
+
+#include "mozilla/glean/bindings/DistributionData.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "mozilla/TimeStamp.h"
+#include "nsIGleanMetrics.h"
+#include "nsTArray.h"
+
+namespace mozilla::glean {
+
+typedef uint64_t TimerId;
+
+namespace impl {
+class TimingDistributionMetric {
+ public:
+  constexpr explicit TimingDistributionMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Starts tracking time for the provided metric.
+   *
+   * @returns A unique TimerId for the new timer
+   */
+  TimerId Start() const;
+
+  /*
+   * Stops tracking time for the provided metric and associated timer id.
+   *
+   * Adds a count to the corresponding bucket in the timing distribution.
+   * This will record an error if no `Start` was called on this TimerId or
+   * if this TimerId was used to call `Cancel`.
+   *
+   * @param aId The TimerId to associate with this timing. This allows for
+   *            concurrent timing of events associated with different ids.
+   */
+  void StopAndAccumulate(const TimerId&& aId) const;
+
+  /*
+   * Adds a duration sample to a timing distribution metric.
+   *
+   * Adds a count to the corresponding bucket in the timing distribution.
+   * Prefer Start() and StopAndAccumulate() where possible.
+   * Users of this API are responsible for ensuring the timing source used
+   * to calculate the TimeDuration is monotonic and consistent accross
+   * platforms.
+   *
+   * NOTE: Negative durations are not handled and will saturate to INT64_MAX
+   *       nanoseconds.
+   *
+   * @param aDuration The duration of the sample to add to the distribution.
+   */
+  void AccumulateRawDuration(const TimeDuration& aDuration) const;
+
+  /*
+   * Aborts a previous `Start` call. No error is recorded if no `Start` was
+   * called.
+   *
+   * @param aId The TimerId whose `Start` you wish to abort.
+   */
+  void Cancel(const TimerId&& aId) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a DistributionData.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<DistributionData>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanTimingDistribution final : public nsIGleanTimingDistribution {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANTIMINGDISTRIBUTION
+
+  explicit GleanTimingDistribution(uint64_t aId) : mTimingDist(aId){};
+
+ private:
+  virtual ~GleanTimingDistribution() = default;
+
+  const impl::TimingDistributionMetric mTimingDist;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanTimingDistribution_h */
diff --git a/toolkit/components/glean/bindings/private/Url.cpp b/toolkit/components/glean/bindings/private/Url.cpp
new file mode 100644
index 0000000000..b86c724e17
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Url.cpp
@@ -0,0 +1,77 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Url.h"
+
+#include "Common.h"
+#include "jsapi.h"
+#include "js/String.h"
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void UrlMetric::Set(const nsACString& aValue) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (scalarId) {
+    Telemetry::ScalarSet(scalarId.extract(), NS_ConvertUTF8toUTF16(aValue));
+  }
+  fog_url_set(mId, &aValue);
+}
+
+Result<Maybe<nsCString>, nsCString> UrlMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_url_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_url_test_has_value(mId, &aPingName)) {
+    return Maybe<nsCString>();
+  }
+  nsCString ret;
+  fog_url_test_get_value(mId, &aPingName, &ret);
+  return Some(ret);
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanUrl, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanUrl, nsIGleanUrl)
+
+NS_IMETHODIMP
+GleanUrl::Set(const nsACString& aValue) {
+  mUrl.Set(aValue);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanUrl::TestGetValue(const nsACString& aStorageName, JSContext* aCx,
+                       JS::MutableHandle<JS::Value> aResult) {
+  auto result = mUrl.TestGetValue(aStorageName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    const NS_ConvertUTF8toUTF16 str(optresult.ref());
+    aResult.set(
+        JS::StringValue(JS_NewUCStringCopyN(aCx, str.Data(), str.Length())));
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Url.h b/toolkit/components/glean/bindings/private/Url.h
new file mode 100644
index 0000000000..115eb073f5
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Url.h
@@ -0,0 +1,70 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanUrl_h
+#define mozilla_glean_GleanUrl_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class UrlMetric {
+ public:
+  constexpr explicit UrlMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Set to the specified value.
+   *
+   * @param aValue The stringified Url to set the metric to.
+   */
+  void Set(const nsACString& aValue) const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a string.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<nsCString>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanUrl final : public nsIGleanUrl {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANURL
+
+  explicit GleanUrl(uint32_t aId) : mUrl(aId){};
+
+ private:
+  virtual ~GleanUrl() = default;
+
+  const impl::UrlMetric mUrl;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanUrl_h */
diff --git a/toolkit/components/glean/bindings/private/Uuid.cpp b/toolkit/components/glean/bindings/private/Uuid.cpp
new file mode 100644
index 0000000000..205dc94ec7
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Uuid.cpp
@@ -0,0 +1,89 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/glean/bindings/Uuid.h"
+
+#include "Common.h"
+#include "jsapi.h"
+#include "mozilla/Components.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/glean/bindings/ScalarGIFFTMap.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsIClassInfoImpl.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+void UuidMetric::Set(const nsACString& aValue) const {
+  auto scalarId = ScalarIdForMetric(mId);
+  if (scalarId) {
+    Telemetry::ScalarSet(scalarId.extract(), NS_ConvertUTF8toUTF16(aValue));
+  }
+  fog_uuid_set(mId, &aValue);
+}
+
+void UuidMetric::GenerateAndSet() const {
+  // We don't have the generated value to mirror to the scalar,
+  // so calling this function on a mirrored metric is likely an error.
+  (void)NS_WARN_IF(ScalarIdForMetric(mId).isSome());
+  fog_uuid_generate_and_set(mId);
+}
+
+Result<Maybe<nsCString>, nsCString> UuidMetric::TestGetValue(
+    const nsACString& aPingName) const {
+  nsCString err;
+  if (fog_uuid_test_get_error(mId, &err)) {
+    return Err(err);
+  }
+  if (!fog_uuid_test_has_value(mId, &aPingName)) {
+    return Maybe<nsCString>();
+  }
+  nsCString ret;
+  fog_uuid_test_get_value(mId, &aPingName, &ret);
+  return Some(ret);
+}
+
+}  // namespace impl
+
+NS_IMPL_CLASSINFO(GleanUuid, nullptr, 0, {0})
+NS_IMPL_ISUPPORTS_CI(GleanUuid, nsIGleanUuid)
+
+NS_IMETHODIMP
+GleanUuid::Set(const nsACString& aValue) {
+  mUuid.Set(aValue);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanUuid::GenerateAndSet() {
+  mUuid.GenerateAndSet();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GleanUuid::TestGetValue(const nsACString& aStorageName, JSContext* aCx,
+                        JS::MutableHandle<JS::Value> aResult) {
+  auto result = mUuid.TestGetValue(aStorageName);
+  if (result.isErr()) {
+    aResult.set(JS::UndefinedValue());
+    LogToBrowserConsole(nsIScriptError::errorFlag,
+                        NS_ConvertUTF8toUTF16(result.unwrapErr()));
+    return NS_ERROR_LOSS_OF_SIGNIFICANT_DATA;
+  }
+  auto optresult = result.unwrap();
+  if (optresult.isNothing()) {
+    aResult.set(JS::UndefinedValue());
+  } else {
+    const NS_ConvertUTF8toUTF16 str(optresult.value());
+    aResult.set(
+        JS::StringValue(JS_NewUCStringCopyN(aCx, str.Data(), str.Length())));
+  }
+  return NS_OK;
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/bindings/private/Uuid.h b/toolkit/components/glean/bindings/private/Uuid.h
new file mode 100644
index 0000000000..941ce42540
--- /dev/null
+++ b/toolkit/components/glean/bindings/private/Uuid.h
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanUuid_h
+#define mozilla_glean_GleanUuid_h
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "nsIGleanMetrics.h"
+#include "nsString.h"
+
+namespace mozilla::glean {
+
+namespace impl {
+
+class UuidMetric {
+ public:
+  constexpr explicit UuidMetric(uint32_t aId) : mId(aId) {}
+
+  /*
+   * Sets to the specified value.
+   *
+   * @param aValue The UUID to set the metric to.
+   */
+  void Set(const nsACString& aValue) const;
+
+  /*
+   * Generate a new random UUID and set the metric to it.
+   */
+  void GenerateAndSet() const;
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a hyphenated string.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Result<Maybe<nsCString>, nsCString> TestGetValue(
+      const nsACString& aPingName = nsCString()) const;
+
+ private:
+  const uint32_t mId;
+};
+}  // namespace impl
+
+class GleanUuid final : public nsIGleanUuid {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANUUID
+
+  explicit GleanUuid(uint32_t aId) : mUuid(aId){};
+
+ private:
+  virtual ~GleanUuid() = default;
+
+  const impl::UuidMetric mUuid;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanUuid_h */
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/cpp.py b/toolkit/components/glean/build_scripts/glean_parser_ext/cpp.py
new file mode 100644
index 0000000000..f1ead48669
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/cpp.py
@@ -0,0 +1,136 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""
+Outputter to generate C++ code for metrics.
+"""
+
+import json
+
+import jinja2
+from glean_parser import util
+from util import generate_metric_ids, generate_ping_ids, get_metrics
+
+
+def cpp_datatypes_filter(value):
+    """
+    A Jinja2 filter that renders C++ literals.
+
+    Based on Python's JSONEncoder, but overrides:
+      - lists to array literals {}
+      - strings to "value"
+    """
+
+    class CppEncoder(json.JSONEncoder):
+        def iterencode(self, value):
+            if isinstance(value, list):
+                yield "{"
+                first = True
+                for subvalue in list(value):
+                    if not first:
+                        yield ", "
+                    yield from self.iterencode(subvalue)
+                    first = False
+                yield "}"
+            elif isinstance(value, str):
+                yield '"' + value + '"'
+            else:
+                yield from super().iterencode(value)
+
+    return "".join(CppEncoder().iterencode(value))
+
+
+def type_name(obj):
+    """
+    Returns the C++ type to use for a given metric object.
+    """
+
+    if getattr(obj, "labeled", False):
+        class_name = util.Camelize(obj.type[8:])  # strips "labeled_" off the front.
+        return "Labeled<impl::{}Metric>".format(class_name)
+    generate_enums = getattr(obj, "_generate_enums", [])  # Extra Keys? Reasons?
+    if len(generate_enums):
+        for name, suffix in generate_enums:
+            if not len(getattr(obj, name)) and suffix == "Keys":
+                return util.Camelize(obj.type) + "Metric<NoExtraKeys>"
+            else:
+                # we always use the `extra` suffix,
+                # because we only expose the new event API
+                suffix = "Extra"
+                return "{}Metric<{}>".format(
+                    util.Camelize(obj.type), util.Camelize(obj.name) + suffix
+                )
+    return util.Camelize(obj.type) + "Metric"
+
+
+def extra_type_name(typ: str) -> str:
+    """
+    Returns the corresponding Rust type for event's extra key types.
+    """
+
+    if typ == "boolean":
+        return "bool"
+    elif typ == "string":
+        return "nsCString"
+    elif typ == "quantity":
+        return "uint32_t"
+    else:
+        return "UNSUPPORTED"
+
+
+def output_cpp(objs, output_fd, options={}):
+    """
+    Given a tree of objects, output C++ code to the file-like object `output_fd`.
+
+    :param objs: A tree of objects (metrics and pings) as returned from
+    `parser.parse_objects`.
+    :param output_fd: Writeable file to write the output to.
+    :param options: options dictionary.
+    """
+
+    # Monkeypatch a util.snake_case function for the templates to use
+    util.snake_case = lambda value: value.replace(".", "_").replace("-", "_")
+    # Monkeypatch util.get_jinja2_template to find templates nearby
+
+    def get_local_template(template_name, filters=()):
+        env = jinja2.Environment(
+            loader=jinja2.PackageLoader("cpp", "templates"),
+            trim_blocks=True,
+            lstrip_blocks=True,
+        )
+        env.filters["camelize"] = util.camelize
+        env.filters["Camelize"] = util.Camelize
+        for filter_name, filter_func in filters:
+            env.filters[filter_name] = filter_func
+        return env.get_template(template_name)
+
+    util.get_jinja2_template = get_local_template
+    get_metric_id = generate_metric_ids(objs)
+    get_ping_id = generate_ping_ids(objs)
+
+    if "pings" in objs:
+        template_filename = "cpp_pings.jinja2"
+        if objs.get("tags"):
+            del objs["tags"]
+    else:
+        template_filename = "cpp.jinja2"
+        objs = get_metrics(objs)
+
+    template = util.get_jinja2_template(
+        template_filename,
+        filters=(
+            ("cpp", cpp_datatypes_filter),
+            ("snake_case", util.snake_case),
+            ("type_name", type_name),
+            ("extra_type_name", extra_type_name),
+            ("metric_id", get_metric_id),
+            ("ping_id", get_ping_id),
+            ("Camelize", util.Camelize),
+        ),
+    )
+
+    output_fd.write(template.render(all_objs=objs))
+    output_fd.write("\n")
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/jog.py b/toolkit/components/glean/build_scripts/glean_parser_ext/jog.py
new file mode 100644
index 0000000000..b869ba3d14
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/jog.py
@@ -0,0 +1,201 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""
+Outputter to generate Rust code for metrics.
+"""
+
+import enum
+import json
+import sys
+
+import jinja2
+from glean_parser import util
+from glean_parser.metrics import Rate
+from util import type_ids_and_categories
+
+from js import ID_BITS, PING_INDEX_BITS
+
+# The list of all args to CommonMetricData.
+# No particular order is required, but I have these in common_metric_data.rs
+# order just to be organized.
+# Note that this is util.common_metric_args + "dynamic_label"
+common_metric_data_args = [
+    "name",
+    "category",
+    "send_in_pings",
+    "lifetime",
+    "disabled",
+    "dynamic_label",
+]
+
+# List of all metric-type-specific args that JOG understands.
+known_extra_args = [
+    "time_unit",
+    "memory_unit",
+    "allowed_extra_keys",
+    "reason_codes",
+    "range_min",
+    "range_max",
+    "bucket_count",
+    "histogram_type",
+    "numerators",
+]
+
+# List of all ping-specific args that JOG undertsands.
+known_ping_args = [
+    "name",
+    "include_client_id",
+    "send_if_empty",
+    "reason_codes",
+]
+
+
+def ensure_jog_support_for_args():
+    """
+    glean_parser or the Glean SDK might add new metric/ping args.
+    To ensure JOG doesn't fall behind in support,
+    we check the list of JOG-supported args vs glean_parser's.
+    We fail the build if glean_parser has one or more we haven't seen before.
+    """
+
+    unknown_args = set(util.extra_metric_args) - set(known_extra_args)
+
+    unknown_args |= set(util.ping_args) - set(known_ping_args)
+
+    if len(unknown_args):
+        print(f"Unknown glean_parser args {unknown_args}")
+        print("JOG must be updated to support the new args")
+        sys.exit(1)
+
+
+def load_monkeypatches():
+    """
+    Monkeypatch jinja template loading because we're not glean_parser.
+    We're glean_parser_ext.
+    """
+    # Monkeypatch util.get_jinja2_template to find templates nearby
+    def get_local_template(template_name, filters=()):
+        env = jinja2.Environment(
+            loader=jinja2.PackageLoader("rust", "templates"),
+            trim_blocks=True,
+            lstrip_blocks=True,
+        )
+        env.filters["camelize"] = util.camelize
+        env.filters["Camelize"] = util.Camelize
+        for filter_name, filter_func in filters:
+            env.filters[filter_name] = filter_func
+        return env.get_template(template_name)
+
+    util.get_jinja2_template = get_local_template
+
+
+def output_factory(objs, output_fd, options={}):
+    """
+    Given a tree of objects, output Rust code to the file-like object `output_fd`.
+    Specifically, Rust code that can generate Rust metrics instances.
+
+    :param objs: A tree of objects (metrics and pings) as returned from
+    `parser.parse_objects`.
+    :param output_fd: Writeable file to write the output to.
+    :param options: options dictionary, presently unused.
+    """
+
+    ensure_jog_support_for_args()
+    load_monkeypatches()
+
+    # Get the metric type ids. Must be the same ids generated in js.py
+    metric_types, categories = type_ids_and_categories(objs)
+
+    template = util.get_jinja2_template(
+        "jog_factory.jinja2",
+        filters=(("snake_case", util.snake_case),),
+    )
+
+    output_fd.write(
+        template.render(
+            all_objs=objs,
+            common_metric_data_args=common_metric_data_args,
+            extra_args=util.extra_args,
+            metric_types=metric_types,
+            runtime_metric_bit=ID_BITS - 1,
+            runtime_ping_bit=PING_INDEX_BITS - 1,
+            ID_BITS=ID_BITS,
+        )
+    )
+    output_fd.write("\n")
+
+
+def camel_to_snake(s):
+    assert "_" not in s, "JOG doesn't encode metric typenames with underscores"
+    return "".join(["_" + c.lower() if c.isupper() else c for c in s]).lstrip("_")
+
+
+def output_file(objs, output_fd, options={}):
+    """
+    Given a tree of objects, output them to the file-like object `output_fd`.
+    Specifically, in a format that describes all the metrics and pings defined in objs.
+
+    :param objs: A tree of objects (metrics and pings) as returned from
+                 `parser.parse_objects`.
+                 Presently a dictionary with keys of literals "pings" and "tags"
+                 as well as one key per metric category mapped to lists of
+                 pings, tags, and metrics (respecitvely)
+    :param output_fd: Writeable file to write the output to.
+    :param options: options dictionary, presently unused.
+    """
+
+    ensure_jog_support_for_args()
+
+    jog_data = {"pings": [], "metrics": {}}
+
+    if "tags" in objs:
+        del objs["tags"]  # JOG has no use for tags.
+
+    pings = objs["pings"]
+    del objs["pings"]
+    for ping in pings.values():
+        ping_arg_list = []
+        for arg in known_ping_args:
+            if hasattr(ping, arg):
+                ping_arg_list.append(getattr(ping, arg))
+        jog_data["pings"].append(ping_arg_list)
+
+    def encode(value):
+        if isinstance(value, enum.Enum):
+            return value.name
+        if isinstance(value, Rate):  # `numerators` for an external Denominator metric
+            args = []
+            for arg_name in common_metric_data_args[:-1]:
+                args.append(getattr(value, arg_name))
+
+            # These are deserialized as CommonMetricData.
+            # CMD have a final param JOG never uses: `dynamic_label`
+            # It's optional, so we should be able to omit it, but we'd need to
+            # annotate it with #[serde(default)]... so here we add the sixth
+            # param as None.
+            args.append(None)
+            return args
+        return json.dumps(value)
+
+    for category, metrics in objs.items():
+        dict_cat = jog_data["metrics"].setdefault(category, [])
+        for metric in metrics.values():
+            metric_arg_list = [camel_to_snake(metric.__class__.__name__)]
+            for arg in common_metric_data_args[:-1]:
+                if arg in ["category"]:
+                    continue  # We don't include the category in each metric.
+                metric_arg_list.append(getattr(metric, arg))
+            extra = {}
+            for arg in known_extra_args:
+                if hasattr(metric, arg):
+                    extra[arg] = getattr(metric, arg)
+            if len(extra):
+                metric_arg_list.append(extra)
+            dict_cat.append(metric_arg_list)
+
+    # TODO: Measure the speed gain of removing `indent=2`
+    json.dump(jog_data, output_fd, sort_keys=True, default=encode, indent=2)
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/js.py b/toolkit/components/glean/build_scripts/glean_parser_ext/js.py
new file mode 100644
index 0000000000..cafb179ae5
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/js.py
@@ -0,0 +1,272 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""
+Outputter to generate C++ code for the JavaScript API for metrics.
+
+The code for the JavaScript API is a bit special in that we only generate C++ code,
+string tables and mapping functions.
+The rest is handled by the WebIDL and XPIDL implementation
+that uses this code to look up metrics by name.
+"""
+
+import jinja2
+from glean_parser import util
+from perfecthash import PerfectHash
+from string_table import StringTable
+from util import generate_metric_ids, generate_ping_ids, get_metrics
+
+"""
+We need to store several bits of information in the Perfect Hash Map Entry:
+
+1. An index into the string table to check for string equality with a search key
+   The perfect hash function will give false-positive for non-existent keys,
+   so we need to verify these ourselves.
+2. Type information to instantiate the correct C++ class
+3. The metric's actual ID to lookup the underlying instance.
+4. Whether the metric is a "submetric" (generated per-label for labeled_* metrics)
+5. Whether the metric was registered at runtime
+
+We have 64 bits to play with, so we dedicate:
+
+1. 32 bit to the string table offset. More than enough for a large string table (~60M metrics).
+2. 5 bit for the type. That allows for 32 metric types. We're not even close to that yet.
+3. 25 bit for the metric ID. That allows for 33.5 million metrics. Let's not go there.
+4. 1 bit for signifying that this metric is a submetric
+5. 1 bit for signifying that this metric was registered at runtime
+
+These values are interpolated into the template as well, so changing them here
+ensures the generated C++ code follows.
+If we ever need more bits for a part (e.g. when we add the 33rd metric type),
+we figure out if either the string table indices or the range of possible IDs can be reduced
+and adjust the constants below.
+"""
+ENTRY_WIDTH = 64
+INDEX_BITS = 32
+ID_BITS = 27  # Includes ID_SIGNAL_BITS
+ID_SIGNAL_BITS = 2
+TYPE_BITS = 5
+
+PING_INDEX_BITS = 16
+
+
+def ping_entry(ping_id, ping_string_index):
+    """
+    The 2 pieces of information of a ping encoded into a single 32-bit integer.
+    """
+    assert ping_id < 2 ** (32 - PING_INDEX_BITS)
+    assert ping_string_index < 2 ** PING_INDEX_BITS
+    return ping_id << PING_INDEX_BITS | ping_string_index
+
+
+def create_entry(metric_id, type_id, idx):
+    """
+    The 3 pieces of information of a metric encoded into a single 64-bit integer.
+    """
+    return metric_id << INDEX_BITS | type_id << (INDEX_BITS + ID_BITS) | idx
+
+
+def metric_identifier(category, metric_name):
+    """
+    The metric's unique identifier, including the category and name
+    """
+    return f"{category}.{util.camelize(metric_name)}"
+
+
+def type_name(obj):
+    """
+    Returns the C++ type to use for a given metric object.
+    """
+
+    if getattr(obj, "labeled", False):
+        return "GleanLabeled"
+    return "Glean" + util.Camelize(obj.type)
+
+
+def subtype_name(obj):
+    """
+    Returns the subtype name for labeled metrics.
+    (e.g. 'boolean' for 'labeled_boolean').
+    Returns "" for non-labeled metrics.
+    """
+    if getattr(obj, "labeled", False):
+        type = obj.type[8:]  # strips "labeled_" off the front
+        return "Glean" + util.Camelize(type)
+    return ""
+
+
+def output_js(objs, output_fd, options={}):
+    """
+    Given a tree of objects, output code for the JS API to the file-like object `output_fd`.
+
+    :param objs: A tree of objects (metrics and pings) as returned from
+    `parser.parse_objects`.
+    :param output_fd: Writeable file to write the output to.
+    :param options: options dictionary.
+    """
+
+    # Monkeypatch util.get_jinja2_template to find templates nearby
+
+    def get_local_template(template_name, filters=()):
+        env = jinja2.Environment(
+            loader=jinja2.PackageLoader("js", "templates"),
+            trim_blocks=True,
+            lstrip_blocks=True,
+        )
+        env.filters["Camelize"] = util.Camelize
+        for filter_name, filter_func in filters:
+            env.filters[filter_name] = filter_func
+        return env.get_template(template_name)
+
+    util.get_jinja2_template = get_local_template
+
+    if "pings" in objs:
+        write_pings({"pings": objs["pings"]}, output_fd, "js_pings.jinja2")
+    else:
+        write_metrics(get_metrics(objs), output_fd, "js.jinja2")
+
+
+def write_metrics(objs, output_fd, template_filename):
+    """
+    Given a tree of objects `objs`, output metrics-only code for the JS API to the
+    file-like object `output_fd` using template `template_filename`
+    """
+
+    template = util.get_jinja2_template(
+        template_filename,
+    )
+
+    assert (
+        INDEX_BITS + TYPE_BITS + ID_BITS <= ENTRY_WIDTH
+    ), "INDEX_BITS, TYPE_BITS, or ID_BITS are larger than allowed"
+
+    get_metric_id = generate_metric_ids(objs)
+    # Mapping from a metric's identifier to the entry (metric ID | type id | index)
+    metric_id_mapping = {}
+    categories = []
+
+    category_string_table = StringTable()
+    metric_string_table = StringTable()
+    # Mapping from a type name to its ID
+    metric_type_ids = {}
+
+    for category_name, objs in get_metrics(objs).items():
+        category_name = util.camelize(category_name)
+        id = category_string_table.stringIndex(category_name)
+        categories.append((category_name, id))
+
+        for metric in objs.values():
+            identifier = metric_identifier(category_name, metric.name)
+            metric_type_tuple = (type_name(metric), subtype_name(metric))
+            if metric_type_tuple in metric_type_ids:
+                type_id, _ = metric_type_ids[metric_type_tuple]
+            else:
+                type_id = len(metric_type_ids) + 1
+                metric_type_ids[metric_type_tuple] = (type_id, metric.type)
+
+            idx = metric_string_table.stringIndex(identifier)
+            metric_id = get_metric_id(metric)
+            entry = create_entry(metric_id, type_id, idx)
+            metric_id_mapping[identifier] = entry
+
+    # Create a lookup table for the metric categories only
+    category_string_table = category_string_table.writeToString("gCategoryStringTable")
+    category_map = [(bytearray(category, "ascii"), id) for (category, id) in categories]
+    name_phf = PerfectHash(category_map, 64)
+    category_by_name_lookup = name_phf.cxx_codegen(
+        name="CategoryByNameLookup",
+        entry_type="category_entry_t",
+        lower_entry=lambda x: str(x[1]) + "ul",
+        key_type="const nsACString&",
+        key_bytes="aKey.BeginReading()",
+        key_length="aKey.Length()",
+        return_type="static Maybe<uint32_t>",
+        return_entry="return category_result_check(aKey, entry);",
+    )
+
+    # Create a lookup table for metric's identifiers.
+    metric_string_table = metric_string_table.writeToString("gMetricStringTable")
+    metric_map = [
+        (bytearray(metric_name, "ascii"), metric_id)
+        for (metric_name, metric_id) in metric_id_mapping.items()
+    ]
+    metric_phf = PerfectHash(metric_map, 64)
+    metric_by_name_lookup = metric_phf.cxx_codegen(
+        name="MetricByNameLookup",
+        entry_type="metric_entry_t",
+        lower_entry=lambda x: str(x[1]) + "ull",
+        key_type="const nsACString&",
+        key_bytes="aKey.BeginReading()",
+        key_length="aKey.Length()",
+        return_type="static Maybe<uint32_t>",
+        return_entry="return metric_result_check(aKey, entry);",
+    )
+
+    output_fd.write(
+        template.render(
+            categories=categories,
+            metric_id_mapping=metric_id_mapping,
+            metric_type_ids=metric_type_ids,
+            entry_width=ENTRY_WIDTH,
+            index_bits=INDEX_BITS,
+            id_bits=ID_BITS,
+            type_bits=TYPE_BITS,
+            id_signal_bits=ID_SIGNAL_BITS,
+            category_string_table=category_string_table,
+            category_by_name_lookup=category_by_name_lookup,
+            metric_string_table=metric_string_table,
+            metric_by_name_lookup=metric_by_name_lookup,
+        )
+    )
+    output_fd.write("\n")
+
+
+def write_pings(objs, output_fd, template_filename):
+    """
+    Given a tree of objects `objs`, output pings-only code for the JS API to the
+    file-like object `output_fd` using template `template_filename`
+    """
+
+    template = util.get_jinja2_template(
+        template_filename,
+        filters=(),
+    )
+
+    ping_string_table = StringTable()
+    get_ping_id = generate_ping_ids(objs)
+    # The map of a ping's name to its entry (a combination of a monotonic
+    # integer and its index in the string table)
+    pings = {}
+    for ping_name in objs["pings"].keys():
+        ping_id = get_ping_id(ping_name)
+        ping_name = util.camelize(ping_name)
+        pings[ping_name] = ping_entry(ping_id, ping_string_table.stringIndex(ping_name))
+
+    ping_map = [
+        (bytearray(ping_name, "ascii"), ping_entry)
+        for (ping_name, ping_entry) in pings.items()
+    ]
+    ping_string_table = ping_string_table.writeToString("gPingStringTable")
+    ping_phf = PerfectHash(ping_map, 64)
+    ping_by_name_lookup = ping_phf.cxx_codegen(
+        name="PingByNameLookup",
+        entry_type="ping_entry_t",
+        lower_entry=lambda x: str(x[1]),
+        key_type="const nsACString&",
+        key_bytes="aKey.BeginReading()",
+        key_length="aKey.Length()",
+        return_type="static Maybe<uint32_t>",
+        return_entry="return ping_result_check(aKey, entry);",
+    )
+
+    output_fd.write(
+        template.render(
+            ping_index_bits=PING_INDEX_BITS,
+            ping_by_name_lookup=ping_by_name_lookup,
+            ping_string_table=ping_string_table,
+        )
+    )
+    output_fd.write("\n")
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/run_glean_parser.py b/toolkit/components/glean/build_scripts/glean_parser_ext/run_glean_parser.py
new file mode 100644
index 0000000000..5d70f204e2
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/run_glean_parser.py
@@ -0,0 +1,212 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+from pathlib import Path
+
+import cpp
+import jinja2
+import jog
+import rust
+from glean_parser import lint, parser, translate, util
+from mozbuild.util import FileAvoidWrite
+from util import generate_metric_ids
+
+import js
+
+
+class ParserError(Exception):
+    """Thrown from parse if something goes wrong"""
+
+    pass
+
+
+GIFFT_TYPES = {
+    "Event": ["event"],
+    "Histogram": ["timing_distribution", "memory_distribution", "custom_distribution"],
+    "Scalar": [
+        "boolean",
+        "labeled_boolean",
+        "counter",
+        "labeled_counter",
+        "string",
+        "string_list",
+        "timespan",
+        "uuid",
+        "datetime",
+        "quantity",
+        "rate",
+        "url",
+    ],
+}
+
+
+def get_parser_options(moz_app_version):
+    app_version_major = moz_app_version.split(".", 1)[0]
+    return {
+        "allow_reserved": False,
+        "expire_by_version": int(app_version_major),
+    }
+
+
+def parse(args):
+    """
+    Parse and lint the input files,
+    then return the parsed objects for further processing.
+    """
+
+    # Unfortunately, GeneratedFile appends `flags` directly after `inputs`
+    # instead of listifying either, so we need to pull stuff from a *args.
+    yaml_array = args[:-1]
+    moz_app_version = args[-1]
+
+    input_files = [Path(x) for x in yaml_array]
+
+    options = get_parser_options(moz_app_version)
+
+    return parse_with_options(input_files, options)
+
+
+def parse_with_options(input_files, options):
+    # Derived heavily from glean_parser.translate.translate.
+    # Adapted to how mozbuild sends us a fd, and to expire on versions not dates.
+
+    # Lint the yaml first, then lint the metrics.
+    if lint.lint_yaml_files(input_files, parser_config=options):
+        # Warnings are Errors
+        raise ParserError("linter found problems")
+
+    all_objs = parser.parse_objects(input_files, options)
+    if util.report_validation_errors(all_objs):
+        raise ParserError("found validation errors during parse")
+
+    nits = lint.lint_metrics(all_objs.value, options)
+    if nits is not None and any(nit.check_name != "EXPIRED" for nit in nits):
+        # Treat Warnings as Errors in FOG.
+        # But don't fail the whole build on expired metrics (it blocks testing).
+        raise ParserError("glinter nits found during parse")
+
+    objects = all_objs.value
+
+    translate.transform_metrics(objects)
+
+    return objects, options
+
+
+# Must be kept in sync with the length of `deps` in moz.build.
+DEPS_LEN = 17
+
+
+def main(cpp_fd, *args):
+    def open_output(filename):
+        return FileAvoidWrite(os.path.join(os.path.dirname(cpp_fd.name), filename))
+
+    [js_h_path, rust_path] = args[-2:]
+    args = args[DEPS_LEN:-2]
+    all_objs, options = parse(args)
+
+    cpp.output_cpp(all_objs, cpp_fd, options)
+
+    with open_output(js_h_path) as js_fd:
+        js.output_js(all_objs, js_fd, options)
+
+    with open_output(rust_path) as rust_fd:
+        rust.output_rust(all_objs, rust_fd, options)
+
+
+def gifft_map(output_fd, *args):
+    probe_type = args[-1]
+    args = args[DEPS_LEN:-1]
+    all_objs, options = parse(args)
+
+    # Events also need to output maps from event extra enum to strings.
+    # Sadly we need to generate code for all possible events, not just mirrored.
+    # Otherwise we won't compile.
+    if probe_type == "Event":
+        output_path = Path(os.path.dirname(output_fd.name))
+        with FileAvoidWrite(output_path / "EventExtraGIFFTMaps.cpp") as cpp_fd:
+            output_gifft_map(output_fd, probe_type, all_objs, cpp_fd)
+    else:
+        output_gifft_map(output_fd, probe_type, all_objs, None)
+
+
+def output_gifft_map(output_fd, probe_type, all_objs, cpp_fd):
+    get_metric_id = generate_metric_ids(all_objs)
+    ids_to_probes = {}
+    for category_name, objs in all_objs.items():
+        for metric in objs.values():
+            if (
+                hasattr(metric, "telemetry_mirror")
+                and metric.telemetry_mirror is not None
+            ):
+                info = (metric.telemetry_mirror, f"{category_name}.{metric.name}")
+                if metric.type in GIFFT_TYPES[probe_type]:
+                    if any(
+                        metric.telemetry_mirror == value[0]
+                        for value in ids_to_probes.values()
+                    ):
+                        print(
+                            f"Telemetry mirror {metric.telemetry_mirror} already registered",
+                            file=sys.stderr,
+                        )
+                        sys.exit(1)
+                    ids_to_probes[get_metric_id(metric)] = info
+                # If we don't support a mirror for this metric type: build error.
+                elif not any(
+                    [
+                        metric.type in types_for_probe
+                        for types_for_probe in GIFFT_TYPES.values()
+                    ]
+                ):
+                    print(
+                        f"Glean metric {category_name}.{metric.name} is of type {metric.type}"
+                        " which can't be mirrored (we don't know how).",
+                        file=sys.stderr,
+                    )
+                    sys.exit(1)
+
+    env = jinja2.Environment(
+        loader=jinja2.PackageLoader("run_glean_parser", "templates"),
+        trim_blocks=True,
+        lstrip_blocks=True,
+    )
+    env.filters["snake_case"] = lambda value: value.replace(".", "_").replace("-", "_")
+    env.filters["Camelize"] = util.Camelize
+    template = env.get_template("gifft.jinja2")
+    output_fd.write(
+        template.render(
+            ids_to_probes=ids_to_probes,
+            probe_type=probe_type,
+            id_bits=js.ID_BITS,
+            id_signal_bits=js.ID_SIGNAL_BITS,
+        )
+    )
+    output_fd.write("\n")
+
+    # Events also need to output maps from event extra enum to strings.
+    # Sadly we need to generate code for all possible events, not just mirrored.
+    # Otherwise we won't compile.
+    if probe_type == "Event":
+        template = env.get_template("gifft_events.jinja2")
+        cpp_fd.write(template.render(all_objs=all_objs))
+        cpp_fd.write("\n")
+
+
+def jog_factory(output_fd, *args):
+    args = args[DEPS_LEN:]
+    all_objs, options = parse(args)
+    jog.output_factory(all_objs, output_fd, options)
+
+
+def jog_file(output_fd, *args):
+    args = args[DEPS_LEN:]
+    all_objs, options = parse(args)
+    jog.output_file(all_objs, output_fd, options)
+
+
+if __name__ == "__main__":
+    main(sys.stdout, *sys.argv[1:])
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/rust.py b/toolkit/components/glean/build_scripts/glean_parser_ext/rust.py
new file mode 100644
index 0000000000..a7a38ba68b
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/rust.py
@@ -0,0 +1,272 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""
+Outputter to generate Rust code for metrics.
+"""
+
+import enum
+import json
+
+import jinja2
+from glean_parser import util
+from glean_parser.metrics import Rate
+from util import generate_metric_ids, generate_ping_ids, get_metrics
+
+from js import ID_BITS, ID_SIGNAL_BITS
+
+# The list of all args to CommonMetricData.
+# No particular order is required, but I have these in common_metric_data.rs
+# order just to be organized.
+common_metric_data_args = [
+    "name",
+    "category",
+    "send_in_pings",
+    "lifetime",
+    "disabled",
+    "dynamic_label",
+]
+
+
+def rust_datatypes_filter(value):
+    """
+    A Jinja2 filter that renders Rust literals.
+
+    Based on Python's JSONEncoder, but overrides:
+      - dicts and sets to raise an error
+      - sets to vec![] (used in labels)
+      - enums to become Class::Value
+      - lists to vec![] (used in send_in_pings)
+      - null to None
+      - strings to "value".into()
+      - Rate objects to a CommonMetricData initializer
+        (for external Denominators' Numerators lists)
+    """
+
+    class RustEncoder(json.JSONEncoder):
+        def iterencode(self, value):
+            if isinstance(value, dict):
+                raise ValueError("RustEncoder doesn't know dicts {}".format(str(value)))
+            elif isinstance(value, enum.Enum):
+                yield (value.__class__.__name__ + "::" + util.Camelize(value.name))
+            elif isinstance(value, set):
+                yield from self.iterencode(sorted(list(value)))
+            elif isinstance(value, list):
+                if len(value) > 8 and all(isinstance(v, str) for v in value):
+                    # For large enough sets and lists of strings, we use a single string
+                    # with an array of lengths and convert to a Vec at runtime. This yields
+                    # smaller code, data, and relocations than using vec![].
+                    yield "{"
+                    yield f"""const S: &'static str = "{"".join(value)}";"""
+                    lengths = [len(v) for v in value]
+                    largest = max(lengths)
+                    # Use a type adequate for the largest string.
+                    # In most cases, this will be u8.
+                    len_type = f"u{((largest.bit_length() + 7) // 8) * 8}"
+                    yield f"const LENGTHS: [{len_type}; {len(lengths)}] = {lengths};"
+                    yield "let mut offset = 0;"
+                    yield "LENGTHS.iter().map(|len| {"
+                    yield "  let start = offset;"
+                    yield "  offset += *len as usize;"
+                    yield "  S[start..offset].into()"
+                    yield "}).collect()"
+                    yield "}"
+                else:
+                    yield "vec!["
+                    first = True
+                    for subvalue in list(value):
+                        if not first:
+                            yield ", "
+                        yield from self.iterencode(subvalue)
+                        first = False
+                    yield "]"
+            elif value is None:
+                yield "None"
+            elif isinstance(value, str):
+                yield '"' + value + '".into()'
+            elif isinstance(value, Rate):
+                yield "CommonMetricData {"
+                for arg_name in common_metric_data_args:
+                    if hasattr(value, arg_name):
+                        yield f"{arg_name}: "
+                        yield from self.iterencode(getattr(value, arg_name))
+                        yield ", "
+                yield " ..Default::default()}"
+            else:
+                yield from super().iterencode(value)
+
+    return "".join(RustEncoder().iterencode(value))
+
+
+def ctor(obj):
+    """
+    Returns the scope and name of the constructor to use for a metric object.
+    Necessary because LabeledMetric<T> is constructed using LabeledMetric::new
+    not LabeledMetric<T>::new
+    """
+    if getattr(obj, "labeled", False):
+        return "LabeledMetric::new"
+    return class_name(obj.type) + "::new"
+
+
+def type_name(obj):
+    """
+    Returns the Rust type to use for a given metric or ping object.
+    """
+
+    if getattr(obj, "labeled", False):
+        return "LabeledMetric<Labeled{}>".format(class_name(obj.type))
+    generate_enums = getattr(obj, "_generate_enums", [])  # Extra Keys? Reasons?
+    if len(generate_enums):
+        for name, suffix in generate_enums:
+            if not len(getattr(obj, name)) and suffix == "Keys":
+                return class_name(obj.type) + "<NoExtraKeys>"
+            else:
+                # we always use the `extra` suffix,
+                # because we only expose the new event API
+                suffix = "Extra"
+                return "{}<{}>".format(
+                    class_name(obj.type), util.Camelize(obj.name) + suffix
+                )
+    return class_name(obj.type)
+
+
+def extra_type_name(typ: str) -> str:
+    """
+    Returns the corresponding Rust type for event's extra key types.
+    """
+
+    if typ == "boolean":
+        return "bool"
+    elif typ == "string":
+        return "String"
+    elif typ == "quantity":
+        return "u32"
+    else:
+        return "UNSUPPORTED"
+
+
+def class_name(obj_type):
+    """
+    Returns the Rust class name for a given metric or ping type.
+    """
+    if obj_type == "ping":
+        return "Ping"
+    if obj_type.startswith("labeled_"):
+        obj_type = obj_type[8:]
+    return util.Camelize(obj_type) + "Metric"
+
+
+def extra_keys(allowed_extra_keys):
+    """
+    Returns the &'static [&'static str] ALLOWED_EXTRA_KEYS for impl ExtraKeys
+    """
+    return "&[" + ", ".join(map(lambda key: '"' + key + '"', allowed_extra_keys)) + "]"
+
+
+def output_rust(objs, output_fd, options={}):
+    """
+    Given a tree of objects, output Rust code to the file-like object `output_fd`.
+
+    :param objs: A tree of objects (metrics and pings) as returned from
+    `parser.parse_objects`.
+    :param output_fd: Writeable file to write the output to.
+    :param options: options dictionary, presently unused.
+    """
+
+    # Monkeypatch a util.snake_case function for the templates to use
+    util.snake_case = lambda value: value.replace(".", "_").replace("-", "_")
+    # Monkeypatch util.get_jinja2_template to find templates nearby
+
+    def get_local_template(template_name, filters=()):
+        env = jinja2.Environment(
+            loader=jinja2.PackageLoader("rust", "templates"),
+            trim_blocks=True,
+            lstrip_blocks=True,
+        )
+        env.filters["camelize"] = util.camelize
+        env.filters["Camelize"] = util.Camelize
+        for filter_name, filter_func in filters:
+            env.filters[filter_name] = filter_func
+        return env.get_template(template_name)
+
+    util.get_jinja2_template = get_local_template
+    get_metric_id = generate_metric_ids(objs)
+    get_ping_id = generate_ping_ids(objs)
+
+    # Map from a tuple (const, typ) to an array of tuples (id, path)
+    # where:
+    #   const: The Rust constant name to be used for the lookup map
+    #   typ:   The metric type to be stored in the lookup map
+    #   id:    The numeric metric ID
+    #   path:  The fully qualified path to the metric object in Rust
+    #
+    # This map is only filled for metrics, not for pings.
+    #
+    # Example:
+    #
+    #   ("COUNTERS", "CounterMetric") -> [(1, "test_only::clicks"), ...]
+    objs_by_type = {}
+
+    # Map from a metric ID to the fully qualified path of the event object in Rust.
+    # Required for the special handling of event lookups.
+    #
+    # Example:
+    #
+    #   17 -> "test_only::an_event"
+    events_by_id = {}
+
+    if "pings" in objs:
+        template_filename = "rust_pings.jinja2"
+        objs = {"pings": objs["pings"]}
+    else:
+        template_filename = "rust.jinja2"
+        objs = get_metrics(objs)
+        for category_name, category_value in objs.items():
+            for metric in category_value.values():
+                # The constant is all uppercase and suffixed by `_MAP`
+                const_name = util.snake_case(metric.type).upper() + "_MAP"
+                typ = type_name(metric)
+                key = (const_name, typ)
+
+                metric_name = util.snake_case(metric.name)
+                category_name = util.snake_case(category_name)
+                full_path = f"{category_name}::{metric_name}"
+
+                if metric.type == "event":
+                    events_by_id[get_metric_id(metric)] = full_path
+                    continue
+
+                if key not in objs_by_type:
+                    objs_by_type[key] = []
+                objs_by_type[key].append((get_metric_id(metric), full_path))
+
+    # Now for the modules for each category.
+    template = util.get_jinja2_template(
+        template_filename,
+        filters=(
+            ("rust", rust_datatypes_filter),
+            ("snake_case", util.snake_case),
+            ("type_name", type_name),
+            ("extra_type_name", extra_type_name),
+            ("ctor", ctor),
+            ("extra_keys", extra_keys),
+            ("metric_id", get_metric_id),
+            ("ping_id", get_ping_id),
+        ),
+    )
+
+    output_fd.write(
+        template.render(
+            all_objs=objs,
+            common_metric_data_args=common_metric_data_args,
+            metric_by_type=objs_by_type,
+            extra_args=util.extra_args,
+            events_by_id=events_by_id,
+            submetric_bit=ID_BITS - ID_SIGNAL_BITS,
+        )
+    )
+    output_fd.write("\n")
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/string_table.py b/toolkit/components/glean/build_scripts/glean_parser_ext/string_table.py
new file mode 100644
index 0000000000..1958eef604
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/string_table.py
@@ -0,0 +1,97 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from io import StringIO
+
+
+class StringTable:
+    """Manages a string table and allows C style serialization to a file."""
+
+    def __init__(self):
+        self.current_index = 0
+        self.table = {}
+
+    def c_strlen(self, string):
+        """The length of a string including the null terminating character.
+        :param string: the input string.
+        """
+        return len(string) + 1
+
+    def stringIndex(self, string):
+        """Returns the index in the table of the provided string. Adds the string to
+        the table if it's not there.
+        :param string: the input string.
+        """
+        if string in self.table:
+            return self.table[string]
+        result = self.current_index
+        self.table[string] = result
+        self.current_index += self.c_strlen(string)
+        return result
+
+    def stringIndexes(self, strings):
+        """Returns a list of indexes for the provided list of strings.
+        Adds the strings to the table if they are not in it yet.
+        :param strings: list of strings to put into the table.
+        """
+        return [self.stringIndex(s) for s in strings]
+
+    def writeToString(self, name):
+        """Writes the string table to a string as a C const char array.
+
+        See `writeDefinition` for details
+
+        :param name: the name of the output array.
+        """
+
+        output = StringIO()
+        self.writeDefinition(output, name)
+        return output.getvalue()
+
+    def writeDefinition(self, f, name):
+        """Writes the string table to a file as a C const char array.
+
+        This writes out the string table as one single C char array for memory
+        size reasons, separating the individual strings with '\0' characters.
+        This way we can index directly into the string array and avoid the additional
+        storage costs for the pointers to them (and potential extra relocations for those).
+
+        :param f: the output stream.
+        :param name: the name of the output array.
+        """
+        entries = self.table.items()
+
+        # Avoid null-in-string warnings with GCC and potentially
+        # overlong string constants; write everything out the long way.
+        def explodeToCharArray(string):
+            def toCChar(s):
+                if s == "'":
+                    return "'\\''"
+                return "'%s'" % s
+
+            return ", ".join(map(toCChar, string))
+
+        f.write("#if defined(_MSC_VER) && !defined(__clang__)\n")
+        f.write("const char %s[] = {\n" % name)
+        f.write("#else\n")
+        f.write("constexpr char %s[] = {\n" % name)
+        f.write("#endif\n")
+        for (string, offset) in sorted(entries, key=lambda x: x[1]):
+            if "*/" in string:
+                raise ValueError(
+                    "String in string table contains unexpected sequence '*/': %s"
+                    % string
+                )
+
+            e = explodeToCharArray(string)
+            if e:
+                f.write(
+                    "  /* %5d - \"%s\" */ %s, '\\0',\n"
+                    % (offset, string, explodeToCharArray(string))
+                )
+            else:
+                f.write("  /* %5d - \"%s\" */ '\\0',\n" % (offset, string))
+        f.write("};\n\n")
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/templates/cpp.jinja2 b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/cpp.jinja2
new file mode 100644
index 0000000000..e9fca2a10c
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/cpp.jinja2
@@ -0,0 +1,86 @@
+// -*- mode: C++ -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+{# The rendered source is autogenerated, but this
+Jinja2 template is not. Please file bugs! #}
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_Metrics_h
+#define mozilla_Metrics_h
+
+#include "mozilla/glean/bindings/MetricTypes.h"
+#include "mozilla/Tuple.h"
+#include "mozilla/Maybe.h"
+#include "nsTArray.h"
+#include "nsPrintfCString.h"
+
+namespace mozilla::glean {
+
+{%- macro generate_extra_keys(obj) -%}
+{% for name, suffix in obj["_generate_enums"] %}
+{# we always use the `extra` suffix, because we only expose the new event API #}
+{% set suffix = "Extra" %}
+{% if obj|attr(name)|length %}
+    {% if obj.has_extra_types %}
+    {{ extra_keys_with_types(obj, name, suffix)|indent }}
+    {% else %}
+#error "Untyped event extras not supported. Please annotate event extras with a type. See documentation for details. (Metric: {{obj.category}}.{{obj.name}}, defined in: {{obj.defined_in['filepath']}}:{{obj.defined_in['line']}})"
+    {% endif %}
+{% endif %}
+{% endfor %}
+{%- endmacro -%}
+
+{%- macro extra_keys_with_types(obj, name, suffix) -%}
+struct {{ obj.name|Camelize }}{{ suffix }} {
+  {% for item, type in obj|attr(name) %}
+  mozilla::Maybe<{{type|extra_type_name}}> {{ item|camelize }};
+  {% endfor %}
+
+  Tuple<nsTArray<nsCString>, nsTArray<nsCString>> ToFfiExtra() const {
+    nsTArray<nsCString> extraKeys;
+    nsTArray<nsCString> extraValues;
+    {% for item, type in obj|attr(name) %}
+    if ({{item|camelize}}) {
+      extraKeys.AppendElement()->AssignASCII("{{item}}");
+      {% if type == "string" %}
+      extraValues.EmplaceBack({{item|camelize}}.value());
+      {% elif type == "boolean" %}
+      extraValues.AppendElement()->AssignASCII({{item|camelize}}.value() ? "true" : "false");
+      {% elif type == "quantity" %}
+      extraValues.EmplaceBack(nsPrintfCString("%d", {{item|camelize}}.value()));
+      {% else %}
+#error "Glean: Invalid extra key type for metric {{obj.category}}.{{obj.name}}, defined in: {{obj.defined_in['filepath']}}:{{obj.defined_in['line']}})"
+      {% endif %}
+    }
+    {% endfor %}
+    return MakeTuple(std::move(extraKeys), std::move(extraValues));
+  }
+};
+{%- endmacro %}
+
+struct NoExtraKeys;
+
+{% for category_name, objs in all_objs.items() %}
+namespace {{ category_name|snake_case }} {
+    {% for obj in objs.values() %}
+    /**
+     * generated from {{ category_name }}.{{ obj.name }}
+     */
+    {% if obj|attr("_generate_enums") %}
+{{ generate_extra_keys(obj) }}
+    {%- endif %}
+    /**
+     * {{ obj.description|wordwrap() | replace('\n', '\n     * ') }}
+     */
+    constexpr impl::{{ obj|type_name }} {{obj.name|snake_case }}({{obj|metric_id}});
+
+    {% endfor %}
+}
+{% endfor %}
+
+} // namespace mozilla::glean
+
+#endif // mozilla_Metrics_h
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/templates/cpp_pings.jinja2 b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/cpp_pings.jinja2
new file mode 100644
index 0000000000..f877cb9685
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/cpp_pings.jinja2
@@ -0,0 +1,30 @@
+// -*- mode: C++ -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+{# The rendered source is autogenerated, but this
+Jinja2 template is not. Please file bugs! #}
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_Pings_h
+#define mozilla_glean_Pings_h
+
+#include "mozilla/glean/bindings/Ping.h"
+
+namespace mozilla::glean_pings {
+
+{% for obj in all_objs['pings'].values() %}
+/*
+ * Generated from {{ obj.name }}.
+ *
+ * {{ obj.description|wordwrap() | replace('\n', '\n * ') }}
+ */
+constexpr glean::impl::Ping {{ obj.name|Camelize }}({{ obj.name|ping_id }});
+
+{% endfor %}
+
+}  // namespace mozilla::glean_pings
+
+#endif  // mozilla_glean_Pings_h
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/templates/gifft.jinja2 b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/gifft.jinja2
new file mode 100644
index 0000000000..6df2650b52
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/gifft.jinja2
@@ -0,0 +1,237 @@
+// -*- mode: C++ -*-
+
+/* This file is auto-generated by run_glean_parser.py.
+   It is only for internal use by types in
+   toolkit/components/glean/bindings/private */
+{# The rendered source is autogenerated, but this
+Jinja2 template is not. Please file bugs! #}
+
+#include "mozilla/AppShutdown.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/Tuple.h"
+#include "mozilla/DataMutex.h"
+{% if probe_type == "Scalar" %}
+#include "mozilla/Tuple.h"
+#include "nsClassHashtable.h"
+#include "nsIThread.h"
+#include "nsTHashMap.h"
+{% endif %}
+#include "nsThreadUtils.h"
+
+#ifndef mozilla_glean_{{ probe_type }}GifftMap_h
+#define mozilla_glean_{{ probe_type }}GifftMap_h
+
+namespace mozilla::glean {
+
+using Telemetry::{{ probe_type }}ID;
+
+{% if probe_type == "Histogram" %}
+
+using MetricId = uint32_t; // Same type as in api/src/private/mod.rs
+using TimerId = uint64_t; // Same as in TimingDistribution.h.
+using MetricTimerTuple = Tuple<MetricId, TimerId>;
+class MetricTimerTupleHashKey : public PLDHashEntryHdr {
+ public:
+  using KeyType = const MetricTimerTuple&;
+  using KeyTypePointer = const MetricTimerTuple*;
+
+  explicit MetricTimerTupleHashKey(KeyTypePointer aKey) : mValue(*aKey) {}
+  MetricTimerTupleHashKey(MetricTimerTupleHashKey&& aOther)
+      : PLDHashEntryHdr(std::move(aOther)),
+        mValue(std::move(aOther.mValue)) {}
+  ~MetricTimerTupleHashKey() = default;
+
+  KeyType GetKey() const { return mValue; }
+  bool KeyEquals(KeyTypePointer aKey) const {
+    return Get<0>(*aKey) == Get<0>(mValue) && Get<1>(*aKey) == Get<1>(mValue);
+  }
+
+  static KeyTypePointer KeyToPointer(KeyType aKey) { return &aKey; }
+  static PLDHashNumber HashKey(KeyTypePointer aKey) {
+    // Chosen because this is how nsIntegralHashKey does it.
+    return HashGeneric(Get<0>(*aKey), Get<1>(*aKey));
+  }
+  enum { ALLOW_MEMMOVE = true };
+
+ private:
+  const MetricTimerTuple mValue;
+};
+
+typedef StaticDataMutex<UniquePtr<nsTHashMap<MetricTimerTupleHashKey, TimeStamp>>> TimerToStampMutex;
+static inline Maybe<TimerToStampMutex::AutoLock> GetTimerIdToStartsLock() {
+  static TimerToStampMutex sTimerIdToStarts("sTimerIdToStarts");
+  auto lock = sTimerIdToStarts.Lock();
+  // GIFFT will work up to the end of AppShutdownTelemetry.
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+    return Nothing();
+  }
+  if (!*lock) {
+    *lock = MakeUnique<nsTHashMap<MetricTimerTupleHashKey, TimeStamp>>();
+    RefPtr<nsIRunnable> cleanupFn = NS_NewRunnableFunction(__func__, [&] {
+      if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+        auto lock = sTimerIdToStarts.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+        return;
+      }
+      RunOnShutdown([&] {
+        auto lock = sTimerIdToStarts.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+      }, ShutdownPhase::XPCOMWillShutdown);
+    });
+    // Both getting the main thread and dispatching to it can fail.
+    // In that event we leak. Grab a pointer so we have something to NS_RELEASE
+    // in that case.
+    nsIRunnable* temp = cleanupFn.get();
+    nsCOMPtr<nsIThread> mainThread;
+    if (NS_FAILED(NS_GetMainThread(getter_AddRefs(mainThread)))
+      || NS_FAILED(mainThread->Dispatch(cleanupFn.forget(), nsIThread::DISPATCH_NORMAL))
+    ) {
+      // Failed to dispatch cleanup routine.
+      // First, un-leak the runnable (but only if we actually attempted dispatch)
+      if (!cleanupFn) {
+        NS_RELEASE(temp);
+      }
+      // Next, cleanup immediately, and allow metrics to try again later.
+      *lock = nullptr;
+      return Nothing();
+    }
+  }
+  return Some(std::move(lock));
+}
+{% elif probe_type == "Scalar" %}
+typedef nsUint32HashKey SubmetricIdHashKey;
+typedef nsTHashMap<SubmetricIdHashKey, Tuple<ScalarID, nsString>>
+    SubmetricToLabeledMirrorMapType;
+typedef StaticDataMutex<UniquePtr<SubmetricToLabeledMirrorMapType>>
+    SubmetricToMirrorMutex;
+static inline Maybe<SubmetricToMirrorMutex::AutoLock> GetLabeledMirrorLock() {
+  static SubmetricToMirrorMutex sLabeledMirrors("sLabeledMirrors");
+  auto lock = sLabeledMirrors.Lock();
+  // GIFFT will work up to the end of AppShutdownTelemetry.
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+    return Nothing();
+  }
+  if (!*lock) {
+    *lock = MakeUnique<SubmetricToLabeledMirrorMapType>();
+    RefPtr<nsIRunnable> cleanupFn = NS_NewRunnableFunction(__func__, [&] {
+      if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+        auto lock = sLabeledMirrors.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+        return;
+      }
+      RunOnShutdown([&] {
+        auto lock = sLabeledMirrors.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+      }, ShutdownPhase::XPCOMWillShutdown);
+    });
+    // Both getting the main thread and dispatching to it can fail.
+    // In that event we leak. Grab a pointer so we have something to NS_RELEASE
+    // in that case.
+    nsIRunnable* temp = cleanupFn.get();
+    nsCOMPtr<nsIThread> mainThread;
+    if (NS_FAILED(NS_GetMainThread(getter_AddRefs(mainThread)))
+      || NS_FAILED(mainThread->Dispatch(cleanupFn.forget(), nsIThread::DISPATCH_NORMAL))
+    ) {
+      // Failed to dispatch cleanup routine.
+      // First, un-leak the runnable (but only if we actually attempted dispatch)
+      if (!cleanupFn) {
+        NS_RELEASE(temp);
+      }
+      // Next, cleanup immediately, and allow metrics to try again later.
+      *lock = nullptr;
+      return Nothing();
+    }
+  }
+  return Some(std::move(lock));
+}
+
+namespace {
+class ScalarIDHashKey : public PLDHashEntryHdr {
+ public:
+  typedef const ScalarID& KeyType;
+  typedef const ScalarID* KeyTypePointer;
+
+  explicit ScalarIDHashKey(KeyTypePointer aKey) : mValue(*aKey) {}
+  ScalarIDHashKey(ScalarIDHashKey&& aOther)
+      : PLDHashEntryHdr(std::move(aOther)), mValue(std::move(aOther.mValue)) {}
+  ~ScalarIDHashKey() = default;
+
+  KeyType GetKey() const { return mValue; }
+  bool KeyEquals(KeyTypePointer aKey) const { return *aKey == mValue; }
+
+  static KeyTypePointer KeyToPointer(KeyType aKey) { return &aKey; }
+  static PLDHashNumber HashKey(KeyTypePointer aKey) {
+    return static_cast<std::underlying_type<ScalarID>::type>(*aKey);
+  }
+  enum { ALLOW_MEMMOVE = true };
+
+ private:
+  const ScalarID mValue;
+};
+}  // namespace
+typedef StaticDataMutex<UniquePtr<nsTHashMap<ScalarIDHashKey, TimeStamp>>> TimesToStartsMutex;
+static inline Maybe<TimesToStartsMutex::AutoLock> GetTimesToStartsLock() {
+  static TimesToStartsMutex sTimespanStarts("sTimespanStarts");
+  auto lock = sTimespanStarts.Lock();
+  // GIFFT will work up to the end of AppShutdownTelemetry.
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+    return Nothing();
+  }
+  if (!*lock) {
+    *lock = MakeUnique<nsTHashMap<ScalarIDHashKey, TimeStamp>>();
+    RefPtr<nsIRunnable> cleanupFn = NS_NewRunnableFunction(__func__, [&] {
+      if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+        auto lock = sTimespanStarts.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+        return;
+      }
+      RunOnShutdown([&] {
+        auto lock = sTimespanStarts.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+      }, ShutdownPhase::XPCOMWillShutdown);
+    });
+    // Both getting the main thread and dispatching to it can fail.
+    // In that event we leak. Grab a pointer so we have something to NS_RELEASE
+    // in that case.
+    nsIRunnable* temp = cleanupFn.get();
+    nsCOMPtr<nsIThread> mainThread;
+    if (NS_FAILED(NS_GetMainThread(getter_AddRefs(mainThread)))
+      || NS_FAILED(mainThread->Dispatch(cleanupFn.forget(), nsIThread::DISPATCH_NORMAL))
+    ) {
+      // Failed to dispatch cleanup routine.
+      // First, un-leak the runnable (but only if we actually attempted dispatch)
+      if (!cleanupFn) {
+        NS_RELEASE(temp);
+      }
+      // Next, cleanup immediately, and allow metrics to try again later.
+      *lock = nullptr;
+      return Nothing();
+    }
+  }
+  return Some(std::move(lock));
+}
+
+static inline bool IsSubmetricId(uint32_t aId) {
+  // Submetrics have the 2^{{id_bits - id_signal_bits}} bit set.
+  // (ID_BITS - ID_SIGNAL_BITS, keep it in sync with js.py).
+  return (aId & (1 << {{id_bits - id_signal_bits}})) > 0;
+}
+{% endif %}
+
+static{% if probe_type == "Event" %} inline{% endif %} Maybe<{{ probe_type }}ID> {{ probe_type }}IdForMetric(uint32_t aId) {
+  switch(aId) {
+{% for id, (mirror, metric_name) in ids_to_probes.items() %}
+    case {{ id }}: { // {{ metric_name }}
+      return Some({{ probe_type }}ID::{{ mirror }});
+    }
+{% endfor %}
+    default: {
+      return Nothing();
+    }
+  }
+}
+
+}  // namespace mozilla::glean
+#endif  // mozilla_glean_{{ probe_type }}GifftMaps_h
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/templates/gifft_events.jinja2 b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/gifft_events.jinja2
new file mode 100644
index 0000000000..f32640fc19
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/gifft_events.jinja2
@@ -0,0 +1,52 @@
+// -*- mode: C++ -*-
+
+/* This file is auto-generated by run_glean_parser.py.
+   It is only for internal use by types in
+   toolkit/components/glean/bindings/private */
+{# The rendered source is autogenerated, but this
+Jinja2 template is not. Pleas file bugs! #}
+
+#include "mozilla/glean/bindings/Event.h"
+#include "mozilla/glean/GleanMetrics.h"
+
+namespace mozilla::glean {
+
+template <>
+/*static*/ const nsCString impl::EventMetric<NoExtraKeys>::ExtraStringForKey(uint32_t aKey) {
+  MOZ_ASSERT_UNREACHABLE("What are you doing here? No extra keys!");
+  return ""_ns;
+}
+
+{% for category_name, objs in all_objs.items() %}
+{% for obj in objs.values() %}
+{% if obj|attr("_generate_enums") %}
+{# we always use the `extra` suffix, because we only expose the new event API #}
+{% set suffix = "Extra" %}
+{% for name, _ in obj["_generate_enums"] %}
+{% if obj|attr(name)|length %}
+{% set ns %}{{ category_name|snake_case }}{% endset %}
+{% set type %}{{ obj.name|Camelize }}{{ suffix }}{% endset %}
+template <>
+/*static*/ const nsCString impl::EventMetric<{{ ns }}::{{ type }}>::ExtraStringForKey(uint32_t aKey) {
+  using {{ ns }}::{{ type }};
+  switch (aKey) {
+{% if obj|attr("telemetry_mirror") %}{# Optimization: Do not generate switch if not mirrored #}
+{% for key, _ in obj|attr(name) %}
+    case {{loop.index-1}}: {
+      return "{{ key }}"_ns;
+    }
+{% endfor %}
+{% endif %}
+    default: {
+      MOZ_ASSERT_UNREACHABLE("Impossible event key reached.");
+      return ""_ns;
+    }
+  }
+}
+
+{% endif %}
+{% endfor %}
+{% endif %}
+{% endfor %}
+{% endfor %}
+};  // namespace mozilla::glean
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/templates/jog_factory.jinja2 b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/jog_factory.jinja2
new file mode 100644
index 0000000000..23e5dc4f2b
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/jog_factory.jinja2
@@ -0,0 +1,146 @@
+// -*- mode: Rust -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+{# The rendered source is autogenerated, but this
+Jinja2 template is not. Please file bugs! #}
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/// This file contains factory implementation information for the
+/// JOG Runtime Registration module.
+/// It is responsible for being able to build metrics and pings described at runtime.
+/// It is generated to keep it in sync with how the runtime definitions are defined.
+
+use std::sync::atomic::{AtomicU32, Ordering};
+use crate::private::{
+    CommonMetricData,
+    Lifetime,
+    MemoryUnit,
+    TimeUnit,
+    Ping,
+    LabeledMetric,
+{% for metric_type_name in metric_types.keys() if not metric_type_name.startswith('labeled_') %}
+    {{ metric_type_name|Camelize }}Metric,
+{% endfor %}};
+use crate::private::traits::HistogramType;
+
+pub(crate) static DYNAMIC_METRIC_BIT: u32 = {{runtime_metric_bit}};
+// 2**DYNAMIC_METRIC_BIT + 1 (+1 because we reserve the 0 metric id)
+static NEXT_METRIC_ID: AtomicU32 = AtomicU32::new({{2**runtime_metric_bit + 1}});
+#[cfg(feature = "with_gecko")] // only used in submit_ping_by_id, which is gecko-only.
+pub(crate) static DYNAMIC_PING_BIT: u32 = {{runtime_ping_bit}};
+// 2**DYNAMIC_PING_BIT + 1 (+1 because we reserve the 0 ping id)
+static NEXT_PING_ID: AtomicU32 = AtomicU32::new({{2**runtime_ping_bit + 1}});
+
+pub(crate) mod __jog_metric_maps {
+    use crate::private::MetricId;
+    use crate::private::{
+        Ping,
+        LabeledMetric,
+        NoExtraKeys,
+    {% for metric_type_name in metric_types.keys() %}
+        {{ metric_type_name|Camelize }}Metric,
+    {% endfor %}
+    };
+    use once_cell::sync::Lazy;
+    use std::collections::HashMap;
+    use std::sync::{Arc, RwLock};
+
+{% for metric_type_name in metric_types.keys() if metric_type_name != "event" and not metric_type_name.startswith('labeled_') %}
+    pub static {{ metric_type_name.upper() }}_MAP: Lazy<Arc<RwLock<HashMap<MetricId, {{ metric_type_name|Camelize }}Metric>>>> =
+        Lazy::new(|| Arc::new(RwLock::new(HashMap::new())));
+
+{% endfor %}
+{# Labeled metrics are special because they're LabeledMetric<Labeled{Counter|Boolean|...}Metric> #}
+{% for metric_type_name in metric_types.keys() if metric_type_name.startswith('labeled_') %}
+    pub static {{ metric_type_name.upper() }}_MAP: Lazy<Arc<RwLock<HashMap<MetricId, LabeledMetric<{{ metric_type_name|Camelize }}Metric>>>>> =
+        Lazy::new(|| Arc::new(RwLock::new(HashMap::new())));
+
+{% endfor %}
+    pub static PING_MAP: Lazy<Arc<RwLock<HashMap<u32, Ping>>>> =
+        Lazy::new(|| Arc::new(RwLock::new(HashMap::new())));
+
+{# Event metrics are special because they're EventMetric<K> #}
+    pub static EVENT_MAP: Lazy<Arc<RwLock<HashMap<MetricId, EventMetric<NoExtraKeys>>>>> =
+        Lazy::new(|| Arc::new(RwLock::new(HashMap::new())));
+}
+
+#[derive(Debug)]
+struct MetricTypeNotFoundError(String);
+impl std::error::Error for MetricTypeNotFoundError {}
+impl std::fmt::Display for MetricTypeNotFoundError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(f, "Metric type {} not found", self.0)
+    }
+}
+
+/// Creates and registers a metric, returning its type+id.
+pub fn create_and_register_metric(
+    metric_type: &str,
+{# The rest of these are handrolled because it proved easier than maintaining a
+map of argument name to argument type. I may regret this if I need it again. #}
+{# In order of util.common_metric_args and util.extra_metric_args, because why not. #}
+    category: String,
+    name: String,
+    send_in_pings: Vec<String>,
+    lifetime: Lifetime,
+    disabled: bool,
+    time_unit: Option<TimeUnit>,
+    memory_unit: Option<MemoryUnit>,
+    allowed_extra_keys: Option<Vec<String>>,
+{# Skipping reason_codes since that's a ping thing. #}
+    range_min: Option<u64>,
+    range_max: Option<u64>,
+    bucket_count: Option<u64>,
+    histogram_type: Option<HistogramType>,
+    numerators: Option<Vec<CommonMetricData>>,
+{# And, don't forget the list of acceptable labels for a labeled metric. #}
+    labels: Option<Vec<String>>,
+) -> Result<u32, Box<dyn std::error::Error>> {
+    let metric_id = NEXT_METRIC_ID.fetch_add(1, Ordering::SeqCst);
+    let metric32 = match metric_type {
+{% for metric_type_name, metric_type in metric_types.items() %}
+        "{{ metric_type_name }}" => {
+            let metric = {{ metric_type_name|Camelize if not metric_type_name.startswith('labeled_') else "Labeled"}}Metric::{% if metric_type_name == 'event' %}with_runtime_extra_keys{% else %}new{% endif %}(metric_id.into(), CommonMetricData {
+                {% for arg_name in common_metric_data_args if arg_name in metric_type.args %}
+                {{ arg_name }},
+                {% endfor %}
+                ..Default::default()
+            }
+            {%- for arg_name in metric_type.args if arg_name not in common_metric_data_args -%}
+                , {{ arg_name }}.unwrap()
+            {%- endfor -%}
+            {%- if metric_type_name.startswith('labeled_') -%}
+                , labels
+            {%- endif -%}
+            );
+            let metric32: u32 = ({{metric_type.id}} << {{ID_BITS}}) | metric_id;
+            assert!(
+                __jog_metric_maps::{{metric_type_name.upper()}}_MAP.write()?.insert(metric_id.into(), metric).is_none(),
+                "We should never insert a runtime metric with an already-used id."
+            );
+            metric32
+        }
+{% endfor %}
+        _ => return Err(Box::new(MetricTypeNotFoundError(metric_type.to_string())))
+    };
+    Ok(metric32)
+}
+
+/// Creates and registers a ping, returning its id.
+pub fn create_and_register_ping(
+    ping_name: String,
+    include_client_id: bool,
+    send_if_empty: bool,
+    reason_codes: Vec<String>,
+) -> Result<u32, Box<dyn std::error::Error>> {
+    let ping_id = NEXT_PING_ID.fetch_add(1, Ordering::SeqCst);
+    let ping = Ping::new(ping_name, include_client_id, send_if_empty, reason_codes);
+    assert!(
+        __jog_metric_maps::PING_MAP.write()?.insert(ping_id.into(), ping).is_none(),
+        "We should never insert a runtime ping with an already-used id."
+    );
+    Ok(ping_id)
+}
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/templates/js.jinja2 b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/js.jinja2
new file mode 100644
index 0000000000..b2c9d1031f
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/js.jinja2
@@ -0,0 +1,166 @@
+// -*- mode: C++ -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+{# The rendered source is autogenerated, but this
+Jinja2 template is not. Please file bugs! #}
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_GleanJSMetricsLookup_h
+#define mozilla_GleanJSMetricsLookup_h
+
+#include "mozilla/PerfectHash.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/glean/bindings/MetricTypes.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+
+#define GLEAN_INDEX_BITS ({{index_bits}})
+#define GLEAN_TYPE_BITS ({{type_bits}})
+#define GLEAN_ID_BITS ({{id_bits}})
+#define GLEAN_TYPE_ID(id) ((id) >> GLEAN_ID_BITS)
+#define GLEAN_METRIC_ID(id) ((id) & ((1ULL << GLEAN_ID_BITS) - 1))
+#define GLEAN_OFFSET(entry) (entry & ((1ULL << GLEAN_INDEX_BITS) - 1))
+
+namespace mozilla::glean {
+
+// The category lookup table's entry type
+using category_entry_t = uint32_t;
+// The metric lookup table's entry type
+// This is a bitpacked type with {{index_bits}} bits available to index into
+// the string table, {{type_bits}} bits available to signify the metric type,
+// and the remaining {{id_bits}} bits devoted to {{id_signal_bits}} "signal"
+// bits to signify important characteristics (metric's a labeled metric's
+// submetric, metric's been registered at runtime) and {{id_bits - id_signal_bits}} bits
+// for built-in metric ids.
+// Gives room for {{2 ** (id_bits - id_signal_bits)}} of each combination of
+// characteristics (which hopefully will prove to be enough).
+using metric_entry_t = uint64_t;
+
+static_assert(GLEAN_INDEX_BITS + GLEAN_TYPE_BITS + GLEAN_ID_BITS == sizeof(metric_entry_t) * 8, "Index, Type, and ID bits need to fit into a metric_entry_t");
+static_assert(GLEAN_TYPE_BITS + GLEAN_ID_BITS <= sizeof(uint32_t) * 8, "Metric Types and IDs need to fit into at most 32 bits");
+static_assert({{ categories|length }} < UINT32_MAX, "Too many metric categories generated.");
+static_assert({{ metric_id_mapping|length }} < {{2 ** (id_bits - id_signal_bits)}}, "Too many metrics generated. Need room for {{id_signal_bits}} signal bits.");
+static_assert({{ metric_type_ids|length }} < {{2 ** type_bits}}, "Too many different metric types.");
+
+static already_AddRefed<nsISupports> NewMetricFromId(uint32_t id) {
+  uint32_t typeId = GLEAN_TYPE_ID(id);
+  uint32_t metricId = GLEAN_METRIC_ID(id);
+
+  switch (typeId) {
+    {% for (type_name, subtype_name), (type_id, original_type) in metric_type_ids.items() %}
+    case {{ type_id }}: /* {{ original_type }} */
+    {
+      return MakeAndAddRef<{{type_name}}>(metricId{% if subtype_name|length > 0 %}, {{ type_id }}{% endif %});
+    }
+    {% endfor %}
+    default:
+    MOZ_ASSERT_UNREACHABLE("Invalid type ID reached when trying to instantiate a new metric");
+    return nullptr;
+  }
+}
+
+/**
+ * Create a submetric instance for a labeled metric of the provided type and id for the given label.
+ * Assigns or retrieves an id for the submetric from the SDK.
+ *
+ * @param aParentTypeId - The type of the parent labeled metric identified as a number generated during codegen.
+ *                        Only used to identify which X of LabeledX you are so that X can be created here.
+ * @param aParentMetricId - The metric id for the parent labeled metric.
+ * @param aLabel - The label for the submetric. Might not adhere to the SDK label format.
+ * @param aSubmetricId - an outparam which is assigned the submetric's SDK-generated submetric id.
+ *                       Used only by GIFFT.
+ */
+static already_AddRefed<nsISupports> NewSubMetricFromIds(uint32_t aParentTypeId, uint32_t aParentMetricId, const nsACString& aLabel, uint32_t* aSubmetricId) {
+  switch (aParentTypeId) {
+    {% for (type_name, subtype_name), (type_id, original_type) in metric_type_ids.items() %}
+    {% if subtype_name|length > 0 %}
+    case {{ type_id }}: { /* {{ original_type }} */
+      auto id = impl::fog_{{original_type}}_get(aParentMetricId, &aLabel);
+      *aSubmetricId = id;
+      return MakeAndAddRef<{{subtype_name}}>(id);
+    }
+    {% endif %}
+    {% endfor %}
+    default: {
+      MOZ_ASSERT_UNREACHABLE("Invalid type ID for submetric.");
+      return nullptr;
+    }
+  }
+}
+
+static Maybe<uint32_t> category_result_check(const nsACString& aKey, category_entry_t entry);
+static Maybe<uint32_t> metric_result_check(const nsACString& aKey, metric_entry_t entry);
+
+{{ category_string_table }}
+static_assert(sizeof(gCategoryStringTable) < UINT32_MAX, "Category string table is too large.");
+
+{{ category_by_name_lookup }}
+
+{{ metric_string_table }}
+static_assert(sizeof(gMetricStringTable) < {{2 ** index_bits}}, "Metric string table is too large.");
+
+{{ metric_by_name_lookup }}
+
+/**
+ * Get a category's name from the string table.
+ */
+static const char* GetCategoryName(category_entry_t entry) {
+  MOZ_ASSERT(entry < sizeof(gCategoryStringTable), "Entry identifier offset larger than string table");
+  return &gCategoryStringTable[entry];
+}
+
+/**
+ * Get a metric's identifier from the string table.
+ */
+static const char* GetMetricIdentifier(metric_entry_t entry) {
+  uint32_t offset = GLEAN_OFFSET(entry);
+  MOZ_ASSERT(offset < sizeof(gMetricStringTable), "Entry identifier offset larger than string table");
+  return &gMetricStringTable[offset];
+}
+
+/**
+ * Check that the found entry is pointing to the right key
+ * and return it.
+ * Or return `Nothing()` if the entry was not found.
+ */
+static Maybe<uint32_t> category_result_check(const nsACString& aKey, category_entry_t entry) {
+  if (MOZ_UNLIKELY(entry > sizeof(gCategoryStringTable))) {
+    return Nothing();
+  }
+  if (aKey.EqualsASCII(gCategoryStringTable + entry)) {
+    return Some(entry);
+  }
+  return Nothing();
+}
+
+/**
+ * Check if the found entry index is pointing to the right key
+ * and return the corresponding metric ID.
+ * Or return `Nothing()` if the entry was not found.
+ */
+static Maybe<uint32_t> metric_result_check(const nsACString& aKey, uint64_t entry) {
+  uint32_t metricId = entry >> GLEAN_INDEX_BITS;
+  uint32_t offset = GLEAN_OFFSET(entry);
+
+  if (offset > sizeof(gMetricStringTable)) {
+    return Nothing();
+  }
+
+  if (aKey.EqualsASCII(gMetricStringTable + offset)) {
+    return Some(metricId);
+  }
+
+  return Nothing();
+}
+
+
+#undef GLEAN_INDEX_BITS
+#undef GLEAN_ID_BITS
+#undef GLEAN_TYPE_ID
+#undef GLEAN_METRIC_ID
+#undef GLEAN_OFFSET
+
+} // namespace mozilla::glean
+#endif // mozilla_GleanJSMetricsLookup_h
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/templates/js_pings.jinja2 b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/js_pings.jinja2
new file mode 100644
index 0000000000..85665ec558
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/js_pings.jinja2
@@ -0,0 +1,64 @@
+// -*- mode: C++ -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+{# The rendered source is autogenerated, but this
+Jinja2 template is not. Please file bugs! #}
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_GleanJSPingsLookup_h
+#define mozilla_GleanJSPingsLookup_h
+
+#define GLEAN_PING_INDEX_BITS ({{ping_index_bits}})
+#define GLEAN_PING_ID(entry) ((entry) >> GLEAN_PING_INDEX_BITS)
+#define GLEAN_PING_INDEX(entry) ((entry) & ((1UL << GLEAN_PING_INDEX_BITS) - 1))
+
+namespace mozilla::glean {
+
+// Contains the ping id and the index into the ping string table.
+using ping_entry_t = uint32_t;
+
+static Maybe<uint32_t> ping_result_check(const nsACString& aKey, ping_entry_t aEntry);
+
+{{ ping_string_table }}
+
+{{ ping_by_name_lookup }}
+
+/**
+ * Get a ping's name given its entry from the PHF.
+ */
+static const char* GetPingName(ping_entry_t aEntry) {
+  uint32_t idx = GLEAN_PING_INDEX(aEntry);
+  MOZ_ASSERT(idx < sizeof(gPingStringTable), "Ping index larger than string table");
+  return &gPingStringTable[idx];
+}
+
+/**
+ * Check if the found entry is pointing at the correct ping.
+ * PHF can false-positive a result when the key isn't present, so we check
+ * for a string match. If it fails, return Nothing(). If we found it,
+ * return the ping's id.
+ */
+static Maybe<uint32_t> ping_result_check(const nsACString& aKey, ping_entry_t aEntry) {
+  uint32_t idx = GLEAN_PING_INDEX(aEntry);
+  uint32_t id = GLEAN_PING_ID(aEntry);
+
+  if (MOZ_UNLIKELY(idx > sizeof(gPingStringTable))) {
+    return Nothing();
+  }
+
+  if (aKey.EqualsASCII(&gPingStringTable[idx])) {
+    return Some(id);
+  }
+
+  return Nothing();
+}
+
+#undef GLEAN_PING_INDEX_BITS
+#undef GLEAN_PING_ID
+#undef GLEAN_PING_INDEX
+
+}  // namespace mozilla::glean
+#endif  // mozilla_GleanJSPingsLookup_h
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/templates/rust.jinja2 b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/rust.jinja2
new file mode 100644
index 0000000000..d43d1c3ea0
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/rust.jinja2
@@ -0,0 +1,271 @@
+// -*- mode: Rust -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+{# The rendered source is autogenerated, but this
+Jinja2 template is not. Please file bugs! #}
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+{% macro generate_extra_keys(obj) -%}
+{% for name, _ in obj["_generate_enums"] %}
+{# we always use the `extra` suffix, because we only expose the new event API #}
+{% set suffix = "Extra" %}
+{% if obj|attr(name)|length %}
+    {% if obj.has_extra_types %}
+    {{ extra_keys_with_types(obj, name, suffix)|indent }}
+    {% else %}
+    compile_error!("Untyped event extras not supported. Please annotate event extras with a type. See documentation for details. (Metric: {{obj.category}}.{{obj.name}}, defined in: {{obj.defined_in['filepath']}}:{{obj.defined_in['line']}})");
+    {% endif %}
+{% endif %}
+{% endfor %}
+{%- endmacro -%}
+
+{%- macro extra_keys_with_types(obj, name, suffix) -%}
+#[derive(Default, Debug, Clone, Hash, Eq, PartialEq)]
+pub struct {{ obj.name|Camelize }}{{ suffix }} {
+    {% for item, type in obj|attr(name) %}
+    pub {{ item|snake_case }}: Option<{{type|extra_type_name}}>,
+    {% endfor %}
+}
+
+impl ExtraKeys for {{ obj.name|Camelize }}{{ suffix }} {
+    const ALLOWED_KEYS: &'static [&'static str] = {{ obj.allowed_extra_keys|extra_keys }};
+
+    fn into_ffi_extra(self) -> ::std::collections::HashMap<String, String> {
+      let mut map = ::std::collections::HashMap::new();
+      {% for key, _ in obj|attr(name) %}
+      self.{{key|snake_case}}.and_then(|val| map.insert("{{key|snake_case}}".into(), val.to_string()));
+      {% endfor %}
+      map
+    }
+}
+{%- endmacro -%}
+
+{% for category_name, objs in all_objs.items() %}
+pub mod {{ category_name|snake_case }} {
+    use crate::private::*;
+    use glean::CommonMetricData;
+    #[allow(unused_imports)] // HistogramType might be unusued, let's avoid warnings
+    use glean::HistogramType;
+    use once_cell::sync::Lazy;
+
+    {% for obj in objs.values() %}
+    {% if obj|attr("_generate_enums") %}
+{{ generate_extra_keys(obj) }}
+    {%- endif %}
+    #[allow(non_upper_case_globals)]
+    /// generated from {{ category_name }}.{{ obj.name }}
+    ///
+    /// {{ obj.description|wordwrap() | replace('\n', '\n    /// ') }}
+    pub static {{ obj.name|snake_case }}: Lazy<{{ obj|type_name }}> = Lazy::new(|| {
+        {{ obj|ctor }}({{obj|metric_id}}.into(), CommonMetricData {
+            {% for arg_name in common_metric_data_args if obj[arg_name] is defined %}
+            {{ arg_name }}: {{ obj[arg_name]|rust }},
+            {% endfor %}
+            ..Default::default()
+        }
+        {%- for arg_name in extra_args if obj[arg_name] is defined and arg_name not in common_metric_data_args and arg_name != 'allowed_extra_keys' -%}
+            , {{ obj[arg_name]|rust }}
+        {%- endfor -%}
+        {{ ", " if obj.labeled else ")\n" }}
+        {%- if obj.labeled -%}
+        {%- if obj.labels -%}
+        Some({{ obj.labels|rust }})
+        {%- else -%}
+        None
+        {%- endif -%})
+        {% endif %}
+    });
+
+    {% endfor %}
+}
+{% endfor %}
+
+{% if metric_by_type|length > 0 %}
+#[allow(dead_code)]
+pub(crate) mod __glean_metric_maps {
+    use std::collections::HashMap;
+
+    use crate::metrics::extra_keys_len;
+    use crate::private::*;
+    use once_cell::sync::Lazy;
+
+{% for typ, metrics in metric_by_type.items() %}
+    pub static {{typ.0}}: Lazy<HashMap<MetricId, &Lazy<{{typ.1}}>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity({{metrics|length}});
+        {% for metric in metrics %}
+        map.insert({{metric.0}}.into(), &super::{{metric.1}});
+        {% endfor %}
+        map
+    });
+
+{% endfor %}
+
+    /// Wrapper to record an event based on its metric ID.
+    ///
+    /// # Arguments
+    ///
+    /// * `metric_id` - The metric's ID to look up
+    /// * `extra`     - An map of (extra key id, string) pairs.
+    ///                 The map will be decoded into the appropriate `ExtraKeys` type.
+    /// # Returns
+    ///
+    /// Returns `Ok(())` if the event was found and `record` was called with the given `extra`,
+    /// or an `EventRecordingError::InvalidId` if no event by that ID exists
+    /// or an `EventRecordingError::InvalidExtraKey` if the `extra` map could not be deserialized.
+    pub(crate) fn record_event_by_id(metric_id: u32, extra: HashMap<String, String>) -> Result<(), EventRecordingError> {
+        match metric_id {
+{% for metric_id, event in events_by_id.items() %}
+          {{metric_id}} => {
+              assert!(
+                  extra_keys_len(&super::{{event}}) != 0 || extra.is_empty(),
+                  "No extra keys allowed, but some were passed"
+              );
+
+              super::{{event}}.record_raw(extra);
+              Ok(())
+          }
+{% endfor %}
+           _ => Err(EventRecordingError::InvalidId),
+        }
+    }
+
+    /// Wrapper to record an event based on its metric ID, with a provided timestamp.
+    ///
+    /// # Arguments
+    ///
+    /// * `metric_id` - The metric's ID to look up
+    /// * `timestamp` - The time at which this event was recorded.
+    /// * `extra`     - An map of (extra key id, string) pairs.
+    ///                 The map will be decoded into the appropriate `ExtraKeys` type.
+    /// # Returns
+    ///
+    /// Returns `Ok(())` if the event was found and `record` was called with the given `extra`,
+    /// or an `EventRecordingError::InvalidId` if no event by that ID exists
+    /// or an `EventRecordingError::InvalidExtraKey` if the event doesn't take extra pairs,
+    /// but some are passed in.
+    pub(crate) fn record_event_by_id_with_time(metric_id: MetricId, timestamp: u64, extra: HashMap<String, String>) -> Result<(), EventRecordingError> {
+        match metric_id {
+{% for metric_id, event in events_by_id.items() %}
+          MetricId({{metric_id}}) => {
+              if extra_keys_len(&super::{{event}}) == 0 && !extra.is_empty() {
+                return Err(EventRecordingError::InvalidExtraKey);
+              }
+
+              super::{{event}}.record_with_time(timestamp, extra);
+              Ok(())
+          }
+{% endfor %}
+           _ => Err(EventRecordingError::InvalidId),
+        }
+    }
+
+    /// Wrapper to record an event based on its metric ID.
+    ///
+    /// # Arguments
+    ///
+    /// * `metric_id` - The metric's ID to look up
+    /// * `extra`     - An map of (string, string) pairs.
+    ///                 The map will be decoded into the appropriate `ExtraKeys` types.
+    /// # Returns
+    ///
+    /// Returns `Ok(())` if the event was found and `record` was called with the given `extra`,
+    /// or an `EventRecordingError::InvalidId` if no event by that ID exists
+    /// or an `EventRecordingError::InvalidExtraKey` if the `extra` map could not be deserialized.
+    pub(crate) fn record_event_by_id_with_strings(metric_id: u32, extra: HashMap<String, String>) -> Result<(), EventRecordingError> {
+        match metric_id {
+{% for metric_id, event in events_by_id.items() %}
+          {{metric_id}} => {
+              assert!(
+                  extra_keys_len(&super::{{event}}) != 0 || extra.is_empty(),
+                  "No extra keys allowed, but some were passed"
+              );
+
+              super::{{event}}.record_raw(extra);
+              Ok(())
+          }
+{% endfor %}
+           _ => Err(EventRecordingError::InvalidId),
+        }
+    }
+
+    /// Wrapper to get the currently stored events for event metric.
+    ///
+    /// # Arguments
+    ///
+    /// * `metric_id` - The metric's ID to look up
+    /// * `ping_name` - (Optional) The ping name to look into.
+    ///                 Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// Returns the recorded events or `None` if nothing stored.
+    ///
+    /// # Panics
+    ///
+    /// Panics if no event by the given metric ID could be found.
+    pub(crate) fn event_test_get_value_wrapper(metric_id: u32, ping_name: Option<String>) -> Option<Vec<RecordedEvent>> {
+        match metric_id {
+{% for metric_id, event in events_by_id.items() %}
+           {{metric_id}} => super::{{event}}.test_get_value(ping_name.as_deref()),
+{% endfor %}
+           _ => panic!("No event for metric id {}", metric_id),
+        }
+    }
+
+    /// Check the provided event for errors.
+    ///
+    /// # Arguments
+    ///
+    /// * `metric_id` - The metric's ID to look up
+    /// * `ping_name` - (Optional) The ping name to look into.
+    ///                 Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// Returns a string for the recorded error or `None`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if no event by the given metric ID could be found.
+    #[allow(unused_variables)]
+    pub(crate) fn event_test_get_error(metric_id: u32) -> Option<String> {
+        #[cfg(feature = "with_gecko")]
+        match metric_id {
+{% for metric_id, event in events_by_id.items() %}
+           {{metric_id}} => test_get_errors!(super::{{event}}),
+{% endfor %}
+           _ => panic!("No event for metric id {}", metric_id),
+        }
+
+        #[cfg(not(feature = "with_gecko"))]
+        {
+            return None;
+        }
+    }
+
+    pub(crate) mod submetric_maps {
+        use std::sync::{
+          atomic::AtomicU32,
+          RwLock,
+        };
+        use super::*;
+
+        pub(crate) const SUBMETRIC_BIT: u32 = {{submetric_bit}};
+        pub(crate) static NEXT_LABELED_SUBMETRIC_ID: AtomicU32 = AtomicU32::new((1 << SUBMETRIC_BIT) + 1);
+        pub(crate) static LABELED_METRICS_TO_IDS: Lazy<RwLock<HashMap<(u32, String), u32>>> = Lazy::new(||
+            RwLock::new(HashMap::new())
+        );
+
+{% for typ, metrics in metric_by_type.items() %}
+{% if typ.0 in ('BOOLEAN_MAP', 'COUNTER_MAP', 'STRING_MAP') %}
+        pub static {{typ.0}}: Lazy<RwLock<HashMap<MetricId, Labeled{{typ.1}}>>> = Lazy::new(||
+            RwLock::new(HashMap::new())
+        );
+{% endif %}
+{% endfor%}
+    }
+}
+{% endif %}
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/templates/rust_pings.jinja2 b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/rust_pings.jinja2
new file mode 100644
index 0000000000..a00da2c1bf
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/templates/rust_pings.jinja2
@@ -0,0 +1,59 @@
+// -*- mode: Rust -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+{# The rendered source is autogenerated, but this
+Jinja2 template is not. Please file bugs! #}
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::private::Ping;
+use once_cell::sync::Lazy;
+
+{% for obj in all_objs['pings'].values() %}
+#[allow(non_upper_case_globals)]
+/// {{ obj.description|wordwrap() | replace('\n', '\n/// ') }}
+pub static {{ obj.name|snake_case }}: Lazy<Ping> = Lazy::new(|| {
+    Ping::new(
+        "{{ obj.name }}",
+        {{ obj.include_client_id|rust }},
+        {{ obj.send_if_empty|rust }},
+        {{ obj.reason_codes|rust }},
+    )
+});
+
+{% endfor %}
+
+/// Instantiate each custom ping once to trigger registration.
+#[doc(hidden)]
+pub fn register_pings() {
+    {% for obj in all_objs['pings'].values() %}
+    let _ = &*{{obj.name|snake_case }};
+    {% endfor %}
+}
+
+#[cfg(feature = "with_gecko")]
+pub(crate) fn submit_ping_by_id(id: u32, reason: Option<&str>) {
+    if id & (1 << crate::factory::DYNAMIC_PING_BIT) > 0 {
+        let map = crate::factory::__jog_metric_maps::PING_MAP
+            .read()
+            .expect("Read lock for dynamic ping map was poisoned!");
+        if let Some(ping) = map.get(&id) {
+            ping.submit(reason);
+        } else {
+            // TODO: instrument this error.
+            log::error!("Cannot submit unknown dynamic ping {} by id.", id);
+        }
+        return;
+    }
+    match id {
+{% for obj in all_objs['pings'].values() %}
+        {{ obj.name|ping_id }} => {{ obj.name | snake_case }}.submit(reason),
+{% endfor %}
+        _ => {
+            // TODO: instrument this error.
+            log::error!("Cannot submit unknown ping {} by id.", id);
+        }
+    }
+}
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/util.py b/toolkit/components/glean/build_scripts/glean_parser_ext/util.py
new file mode 100644
index 0000000000..722a3e409c
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/util.py
@@ -0,0 +1,102 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""
+Utility functions for the glean_parser-based code generator
+"""
+import copy
+from typing import Dict, List, Tuple
+
+from glean_parser import util
+
+
+def generate_ping_ids(objs):
+    """
+    Return a lookup function for ping IDs per ping name.
+
+    :param objs: A tree of objects as returned from `parser.parse_objects`.
+    """
+
+    if "pings" not in objs:
+
+        def no_ping_ids_for_you():
+            assert False
+
+        return no_ping_ids_for_you
+
+    # Ping ID 0 is reserved (but unused) right now.
+    ping_id = 1
+
+    ping_id_mapping = {}
+    for ping_name in objs["pings"].keys():
+        ping_id_mapping[ping_name] = ping_id
+        ping_id += 1
+
+    return lambda ping_name: ping_id_mapping[ping_name]
+
+
+def generate_metric_ids(objs):
+    """
+    Return a lookup function for metric IDs per metric object.
+
+    :param objs: A tree of metrics as returned from `parser.parse_objects`.
+    """
+
+    # Metric ID 0 is reserved (but unused) right now.
+    metric_id = 1
+
+    # Mapping from a tuple of (category name, metric name) to the metric's numeric ID
+    metric_id_mapping = {}
+    for category_name, metrics in objs.items():
+        for metric in metrics.values():
+            metric_id_mapping[(category_name, metric.name)] = metric_id
+            metric_id += 1
+
+    return lambda metric: metric_id_mapping[(metric.category, metric.name)]
+
+
+def get_metrics(objs):
+    """
+    Returns *just* the metrics in a set of Glean objects
+    """
+    ret = copy.copy(objs)
+    for category in ["pings", "tags"]:
+        if ret.get(category):
+            del ret[category]
+    return ret
+
+
+def type_ids_and_categories(objs) -> Tuple[Dict[str, Tuple[int, List[str]]], List[str]]:
+    """
+    Iterates over the metrics in objs, constructing two metadata structures:
+     - metric_types: Dict[str, Tuple[int, List[str]]] - map from a metric
+       type (snake_case) to its metric type id and ordered list of arguments.
+     - categories: List[str] - category names (snake_case)
+
+    Is stable across invocations: Will generate same ids for same objs.
+    (If it doesn't, JOG's factory disagreeing with GleanJSMetricsLookup
+    will break the build).
+    Uses the same order of metric args set out in glean_parser.util's
+    common_metric_args and extra_metric_args.
+    (If it didn't, it would supply args in the wrong order to metric type
+    constructors with multiple extra args (e.g. custom_distribution)).
+    """
+    metric_type_ids = {}
+    categories = []
+
+    for category_name, objs in get_metrics(objs).items():
+        categories.append(category_name)
+
+        for metric in objs.values():
+            if metric.type not in metric_type_ids:
+                type_id = len(metric_type_ids) + 1
+                args = util.common_metric_args.copy()
+                for arg_name in util.extra_metric_args:
+                    if hasattr(metric, arg_name):
+                        args.append(arg_name)
+                metric_type_ids[metric.type] = {"id": type_id, "args": args}
+
+    return (metric_type_ids, categories)
diff --git a/toolkit/components/glean/build_scripts/mach_commands.py b/toolkit/components/glean/build_scripts/mach_commands.py
new file mode 100644
index 0000000000..f722d98987
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/mach_commands.py
@@ -0,0 +1,231 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from mach.decorators import Command, CommandArgument
+
+LICENSE_HEADER = """# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+"""
+
+GENERATED_HEADER = """
+### This file was AUTOMATICALLY GENERATED by `./mach update-glean-tags`
+### DO NOT edit it by hand.
+"""
+
+
+@Command(
+    "data-review",
+    category="misc",
+    description="Generate a skeleton data review request form for a given bug's data",
+)
+@CommandArgument(
+    "bug", default=None, nargs="?", type=str, help="bug number or search pattern"
+)
+def data_review(command_context, bug=None):
+    # Get the metrics_index's list of metrics indices
+    # by loading the index as a module.
+    import sys
+    from os import path
+
+    sys.path.append(path.join(path.dirname(__file__), path.pardir))
+    from pathlib import Path
+
+    from glean_parser import data_review
+    from metrics_index import metrics_yamls
+
+    return data_review.generate(
+        bug, [Path(command_context.topsrcdir) / x for x in metrics_yamls]
+    )
+
+
+@Command(
+    "perf-data-review",
+    category="misc",
+    description="Generate a skeleton performance data review request form for a given bug's data",
+)
+@CommandArgument(
+    "bug", default=None, nargs="?", type=str, help="bug number or search pattern"
+)
+def perf_data_review(command_context, bug=None):
+    # Get the metrics_index's list of metrics indices
+    # by loading the index as a module.
+    import sys
+    from os import path
+
+    sys.path.append(path.join(path.dirname(__file__), path.pardir))
+    from metrics_index import metrics_yamls
+
+    sys.path.append(path.dirname(__file__))
+    from pathlib import Path
+
+    import perf_data_review
+
+    return perf_data_review.generate(
+        bug, [Path(command_context.topsrcdir) / x for x in metrics_yamls]
+    )
+
+
+@Command(
+    "update-glean-tags",
+    category="misc",
+    description=(
+        "Creates a list of valid glean tags based on in-tree bugzilla component definitions"
+    ),
+)
+def update_glean_tags(command_context):
+    from pathlib import Path
+
+    import yaml
+    from mozbuild.backend.configenvironment import ConfigEnvironment
+    from mozbuild.frontend.reader import BuildReader
+
+    config = ConfigEnvironment(
+        command_context.topsrcdir,
+        command_context.topobjdir,
+        defines=command_context.defines,
+        substs=command_context.substs,
+    )
+
+    reader = BuildReader(config)
+    bug_components = set()
+    for p in reader.read_topsrcdir():
+        if p.get("BUG_COMPONENT"):
+            bug_components.add(p["BUG_COMPONENT"])
+
+    tags_filename = (Path(__file__).parent / "../tags.yaml").resolve()
+
+    tags = {"$schema": "moz://mozilla.org/schemas/glean/tags/1-0-0"}
+    for bug_component in bug_components:
+        product = bug_component.product.strip()
+        component = bug_component.component.strip()
+        tags["{} :: {}".format(product, component)] = {
+            "description": "The Bugzilla component which applies to this object."
+        }
+
+    open(tags_filename, "w").write(
+        "{}\n{}\n\n".format(LICENSE_HEADER, GENERATED_HEADER)
+        + yaml.dump(tags, width=78, explicit_start=True)
+    )
+
+
+def replace_in_file(path, pattern, replace):
+    """
+    Replace `pattern` with `replace` in the file `path`.
+    The file is modified on disk.
+
+    Returns `True` if exactly one replacement happened.
+    `False` otherwise.
+    """
+
+    import re
+
+    with open(path, "r+") as file:
+        data = file.read()
+        data, subs_made = re.subn(pattern, replace, data, flags=re.MULTILINE)
+
+        file.seek(0)
+        file.write(data)
+        file.truncate()
+
+        if subs_made != 1:
+            return False
+
+    return True
+
+
+def replace_in_file_or_die(path, pattern, replace):
+    """
+    Replace `pattern` with `replace` in the file `path`.
+    The file is modified on disk.
+
+    If not exactly one occurrence of `pattern` was replaced it will exit with exit code 1.
+    """
+
+    import sys
+
+    success = replace_in_file(path, pattern, replace)
+    if not success:
+        print(f"ERROR: Failed to replace one occurrence in {path}")
+        print(f"  Pattern: {pattern}")
+        print(f"  Replace: {replace}")
+        print("File was modified. Check the diff.")
+        sys.exit(1)
+
+
+@Command(
+    "update-glean",
+    category="misc",
+    description="Update Glean to the given version",
+)
+@CommandArgument("version", help="Glean version to upgrade to")
+def update_glean(command_context, version):
+    import textwrap
+    from pathlib import Path
+
+    topsrcdir = Path(command_context.topsrcdir)
+
+    replace_in_file_or_die(
+        topsrcdir / "build.gradle",
+        r'gleanVersion = "[0-9.]+"',
+        f'gleanVersion = "{version}"',
+    )
+    replace_in_file_or_die(
+        topsrcdir / "toolkit" / "components" / "glean" / "Cargo.toml",
+        r'^glean = "[0-9.]+"',
+        f'glean = "{version}"',
+    )
+    replace_in_file_or_die(
+        topsrcdir / "toolkit" / "components" / "glean" / "api" / "Cargo.toml",
+        r'^glean = "[0-9.]+"',
+        f'glean = "{version}"',
+    )
+    replace_in_file_or_die(
+        topsrcdir / "gfx" / "wr" / "webrender" / "Cargo.toml",
+        r'^glean = "[0-9.]+"',
+        f'glean = "{version}"',
+    )
+    replace_in_file_or_die(
+        topsrcdir / "python" / "sites" / "mach.txt",
+        r"glean-sdk==[0-9.]+",
+        f"glean-sdk=={version}",
+    )
+
+    instructions = f"""
+    We've edited the necessary files to require Glean SDK {version}.
+    To ensure it and Firefox's other Rust dependencies are appropriately vendored,
+    please run the following commands:
+
+        cargo update -p glean
+        mach vendor rust --ignore-modified
+
+    `mach vendor rust` may identify version mismatches.
+    Please consult the Updating the Glean SDK docs for assistance:
+    https://firefox-source-docs.mozilla.org/toolkit/components/glean/dev/updating_sdk.html
+
+    Once you resolve these issues and `mach vendor rust` completes successfully,
+    (or if there were no issues in the first place)
+    you will need to certify that the Glean SDK crates are okay to include in
+    Firefox using `mach cargo vet`.
+
+    Please run these commands, reading and following their instructions:
+
+        mach cargo vet certify glean {version}
+        mach cargo vet certify glean-core {version}
+
+    You then get to again run:
+
+      mach vendor rust --ignore-modified
+
+    Then, to update webrender which independently relies on the Glean SDK, run:
+
+        cd gfx/wr
+        cargo update -p glean
+
+    Then, to ensure all is well, build Firefox and run the FOG tests.
+    Instructions can be found here:
+    https://firefox-source-docs.mozilla.org/toolkit/components/glean/dev/testing.html
+    """
+
+    print(textwrap.dedent(instructions))
diff --git a/toolkit/components/glean/build_scripts/perf_data_review.py b/toolkit/components/glean/build_scripts/perf_data_review.py
new file mode 100644
index 0000000000..8c84249a2a
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/perf_data_review.py
@@ -0,0 +1,168 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""
+Produce skeleton Performance Data Review Requests.
+
+This was mostly copies from glean_parser, and should be kept in sync.
+"""
+
+import re
+from pathlib import Path
+from typing import Sequence
+
+from glean_parser import parser, util
+
+
+def generate(
+    bug: str,
+    metrics_files: Sequence[Path],
+) -> int:
+    """
+    Commandline helper for Data Review Request template generation.
+
+    :param bug: pattern to match in metrics' bug_numbers lists.
+    :param metrics_files: List of Path objects to load metrics from.
+    :return: Non-zero if there were any errors.
+    """
+
+    metrics_files = util.ensure_list(metrics_files)
+
+    # Accept any value of expires.
+    parser_options = {
+        "allow_reserved": True,
+        "custom_is_expired": lambda expires: False,
+        "custom_validate_expires": lambda expires: True,
+    }
+    all_objects = parser.parse_objects(metrics_files, parser_options)
+
+    if util.report_validation_errors(all_objects):
+        return 1
+
+    # I tried [\W\Z] but it complained. So `|` it is.
+    reobj = re.compile(f"\\W{bug}\\W|\\W{bug}$")
+    durations = set()
+    responsible_emails = set()
+    metrics_table = ""
+    for category_name, metrics in all_objects.value.items():
+        for metric in metrics.values():
+            if not any([len(reobj.findall(bug)) == 1 for bug in metric.bugs]):
+                continue
+
+            metric_name = util.snake_case(metric.name)
+            category_name = util.snake_case(category_name)
+            one_line_desc = metric.description.replace("\n", " ")
+            sensitivity = ", ".join([s.name for s in metric.data_sensitivity])
+            last_bug = metric.bugs[-1]
+            metrics_table += f"`{category_name}.{metric_name}` | "
+            metrics_table += f"{one_line_desc} | {sensitivity} | {last_bug}\n"
+            if metric.type == "event" and len(metric.allowed_extra_keys):
+                for extra_name, extra_detail in metric.extra_keys.items():
+                    extra_one_line_desc = extra_detail["description"].replace("\n", " ")
+                    metrics_table += f"`{category_name}.{metric_name}#{extra_name}` | "
+                    metrics_table += (
+                        f"{extra_one_line_desc} | {sensitivity} | {last_bug}\n"
+                    )
+
+            durations.add(metric.expires)
+
+            if metric.expires == "never":
+                responsible_emails.update(metric.notification_emails)
+
+    if len(durations) == 1:
+        duration = next(iter(durations))
+        if duration == "never":
+            collection_duration = "This collection will be collected permanently."
+        else:
+            collection_duration = f"This collection has expiry '{duration}'"
+    else:
+        collection_duration = "Parts of this collection expire at different times: "
+        collection_duration += f"{durations}"
+
+    if "never" in durations:
+        collection_duration += "\n" + ", ".join(responsible_emails) + " "
+        collection_duration += "will be responsible for the permanent collections."
+
+    if len(durations) == 0:
+        print(f"I'm sorry, I couldn't find metrics matching the bug number {bug}.")
+        return 1
+
+    # This template is pulled from
+    # https://github.com/mozilla/data-review/blob/main/request.md
+    print(
+        """
+!! Reminder: it is your responsibility to complete and check the correctness of
+!! this automatically-generated request skeleton before requesting Data
+!! Collection Review. See https://wiki.mozilla.org/Data_Collection for details.
+
+DATA REVIEW REQUEST
+1. What questions will you answer with this data?
+
+TODO: Fill this in.
+
+2. Why does Mozilla need to answer these questions? Are there benefits for users?
+   Do we need this information to address product or business requirements?
+
+In order to guarantee the performance of our products, it is vital to monitor
+real-world installs used by real-world users.
+
+3. What alternative methods did you consider to answer these questions?
+   Why were they not sufficient?
+
+Our ability to measure the practical performance impact of changes through CI
+and manual testing is limited. Monitoring the performance of our products in
+the wild among real users is the only way to be sure we have an accurate
+picture.
+
+4. Can current instrumentation answer these questions?
+
+No.
+
+5. List all proposed measurements and indicate the category of data collection for each
+   measurement, using the Firefox data collection categories found on the Mozilla wiki.
+
+Measurement Name | Measurement Description | Data Collection Category | Tracking Bug
+---------------- | ----------------------- | ------------------------ | ------------"""
+    )
+    print(metrics_table)
+    print(
+        """
+6. Please provide a link to the documentation for this data collection which
+   describes the ultimate data set in a public, complete, and accurate way.
+
+This collection is Glean so is documented
+[in the Glean Dictionary](https://dictionary.telemetry.mozilla.org).
+
+7. How long will this data be collected?
+"""
+    )
+    print(collection_duration)
+    print(
+        """
+8. What populations will you measure?
+
+All channels, countries, and locales. No filters.
+
+9. If this data collection is default on, what is the opt-out mechanism for users?
+
+These collections are Glean. The opt-out can be found in the product's preferences.
+
+10. Please provide a general description of how you will analyze this data.
+
+This will be continuously monitored for regression and improvement detection.
+
+11. Where do you intend to share the results of your analysis?
+
+Internal monitoring (GLAM, Redash, Looker, etc.).
+
+12. Is there a third-party tool (i.e. not Telemetry) that you
+    are proposing to use for this data collection?
+
+No.
+"""
+    )
+
+    return 0
diff --git a/toolkit/components/glean/cbindgen.toml b/toolkit/components/glean/cbindgen.toml
new file mode 100644
index 0000000000..d514585ee1
--- /dev/null
+++ b/toolkit/components/glean/cbindgen.toml
@@ -0,0 +1,25 @@
+header = """/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef mozilla_glean_fog_ffi_generated_h
+#define mozilla_glean_fog_ffi_generated_h
+"""
+trailer = """
+#endif // mozilla_glean_fog_ffi_generated_h
+"""
+autogen_warning = """/* DO NOT MODIFY THIS MANUALLY! This file was generated using cbindgen. */"""
+include_version = true
+braces = "SameLine"
+line_length = 100
+tab_width = 2
+language = "C++"
+namespaces = ["mozilla::glean::impl"]
+includes = ["nsTArray.h", "nsString.h"]
+
+[export.rename]
+"ThinVec" = "nsTArray"
+
+[parse]
+parse_deps = true
+include = ["fog"]
+extra_bindings = ["fog"]
diff --git a/toolkit/components/glean/docs/dev/builtin_pings.md b/toolkit/components/glean/docs/dev/builtin_pings.md
new file mode 100644
index 0000000000..cbfff8c559
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/builtin_pings.md
@@ -0,0 +1,13 @@
+# Built-in Pings
+
+FOG embeds the Glean SDK so
+[its documentation on pings is authoritative](https://mozilla.github.io/glean/book/user/pings/index.html).
+The only detail FOG adds is to clarify
+[the "baseline" ping's schedule](https://mozilla.github.io/glean/book/user/pings/baseline.html#scheduling).
+Specifically, in Firefox Desktop, the application is considered
+* "active" when started,
+  or when a user interacts with Firefox after a 20min period of inactivity,
+* "inactive" after the user stops interacting with Firefox after 2min of activity.
+
+For more details about why, see the bug tree around
+[bug 1635242](https://bugzilla.mozilla.org/show_bug.cgi?id=1635242).
diff --git a/toolkit/components/glean/docs/dev/code_organization.md b/toolkit/components/glean/docs/dev/code_organization.md
new file mode 100644
index 0000000000..e943dbfd50
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/code_organization.md
@@ -0,0 +1,56 @@
+# FOG code organization
+
+![Modules of Project FOG](images/fog-modules.svg)
+
+The diagram shows the different modules of Project FOG.
+
+## FOG control
+
+This module is the glue between Firefox and Glean.
+
+* The code lives in `toolkit/components/glean/src`.
+* It is written in Rust.
+* The crate is named `fog_control`.
+* It is not published to crates.io.
+* It is not consumed by other Rust crates inside mozilla-central.
+
+This module is responsible for
+
+* collecting and assembling the [client information](https://mozilla.github.io/glean/book/user/pings/index.html#the-client_info-section)
+* configuring the Glean SDK via the Rust Language Binding
+* watching the Firefox Telemetry data upload preference (`datareporting.healthreport.uploadEnabled`)
+* scheduling builtin pings
+* controling ping upload workers
+* passing IPC buffers
+
+It calls into `glean` (the Glean SDK Rust Language Binding) to:
+
+* configure and initialize Glean
+* toggle `upload_enabled`
+* get upload tasks
+
+It calls into `fog` to:
+
+* pass IPC buffers
+* record to its own metrics
+
+## FOG API
+
+This module provides the user-facing API for Glean inside mozilla-central.
+
+* The code lives in `toolkit/components/glean/api`.
+* It is written in Rust.
+* The crate is named `fog`.
+* It is not published to crates.io.
+* It can be consumed by other Rust crates inside mozilla-central for their Glean usage.
+
+This module is responsible for
+
+* exposing a specific metric API in Rust
+* wrapping metric implementations for handling IPC
+* exposing FFI functionality to implement other language APIs on top.
+  See also [Adding a New Metric Type](new_metric_types.md).
+
+It calls into `glean` (the Glean SDK Rust Language Binding) for:
+
+* metric types (including pings)
diff --git a/toolkit/components/glean/docs/dev/images/fog-modules.svg b/toolkit/components/glean/docs/dev/images/fog-modules.svg
new file mode 100644
index 0000000000..c0271e9f6e
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+++ b/toolkit/components/glean/docs/dev/images/fog-modules.svg
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+<?xml version="1.0" encoding="UTF-8"?>
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
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text-align: left;" pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 118px; height: 1px; padding-top: 280px; margin-left: 411px;"><div style="box-sizing: border-box; font-size: 0; text-align: center; "><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: #000000; line-height: 1.2; pointer-events: all; white-space: normal; word-wrap: normal; ">transfer encoding</div></div></div></foreignObject><text x="470" y="284" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">transfer encoding</text></switch></g><path d="M 470 330 L 470 353.63" fill="none" stroke="#000000" stroke-miterlimit="10" pointer-events="stroke"/><path d="M 470 358.88 L 466.5 351.88 L 470 353.63 L 473.5 351.88 Z" fill="#000000" stroke="#000000" stroke-miterlimit="10" pointer-events="all"/><rect x="410" y="310" width="120" height="20" fill="#f8cecc" stroke="#b85450" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject style="overflow: visible; text-align: left;" pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 118px; height: 1px; padding-top: 320px; margin-left: 411px;"><div style="box-sizing: border-box; font-size: 0; text-align: center; "><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: #000000; line-height: 1.2; pointer-events: all; white-space: normal; word-wrap: normal; ">IPC send</div></div></div></foreignObject><text x="470" y="324" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">IPC send</text></switch></g><path d="M 470 380 L 470 393.63" fill="none" stroke="#000000" stroke-miterlimit="10" pointer-events="stroke"/><path d="M 470 398.88 L 466.5 391.88 L 470 393.63 L 473.5 391.88 Z" fill="#000000" stroke="#000000" stroke-miterlimit="10" pointer-events="all"/><rect x="410" y="360" width="120" height="20" fill="#f8cecc" stroke="#b85450" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject style="overflow: visible; text-align: left;" pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 118px; height: 1px; padding-top: 370px; margin-left: 411px;"><div style="box-sizing: border-box; font-size: 0; text-align: center; "><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: #000000; line-height: 1.2; pointer-events: all; white-space: normal; word-wrap: normal; ">IPC recv</div></div></div></foreignObject><text x="470" y="374" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">IPC recv</text></switch></g><path d="M 470 420 L 470 470 L 296.37 470" fill="none" stroke="#000000" stroke-miterlimit="10" pointer-events="stroke"/><path d="M 291.12 470 L 298.12 466.5 L 296.37 470 L 298.12 473.5 Z" fill="#000000" stroke="#000000" stroke-miterlimit="10" pointer-events="all"/><rect x="410" y="400" width="120" height="20" fill="#dae8fc" stroke="#6c8ebf" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject style="overflow: visible; text-align: left;" pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 118px; height: 1px; padding-top: 410px; margin-left: 411px;"><div style="box-sizing: border-box; font-size: 0; text-align: center; "><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: #000000; line-height: 1.2; pointer-events: all; white-space: normal; word-wrap: normal; ">transfer decoding</div></div></div></foreignObject><text x="470" y="414" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">transfer decoding</text></switch></g><rect x="520" y="230" width="70" height="20" fill="none" stroke="none" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject style="overflow: visible; text-align: left;" pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 68px; height: 1px; padding-top: 240px; margin-left: 521px;"><div style="box-sizing: border-box; font-size: 0; text-align: center; "><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: #000000; line-height: 1.2; pointer-events: all; white-space: normal; word-wrap: normal; ">IPC layer</div></div></div></foreignObject><text x="555" y="244" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">IPC layer</text></switch></g><rect x="100" y="210" width="40" height="20" fill="#f8cecc" stroke="#b85450" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject style="overflow: visible; text-align: left;" pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 38px; height: 1px; padding-top: 220px; margin-left: 101px;"><div style="box-sizing: border-box; font-size: 0; text-align: center; "><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: #000000; line-height: 1.2; pointer-events: all; white-space: normal; word-wrap: normal; "><font style="font-size: 11px">C API</font></div></div></div></foreignObject><text x="120" y="224" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">C API</text></switch></g></g><switch><g requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"/><a transform="translate(0,-5)" href="https://desk.draw.io/support/solutions/articles/16000042487" target="_blank"><text text-anchor="middle" font-size="10px" x="50%" y="100%">Viewer does not support full SVG 1.1</text></a></switch></svg>
\ No newline at end of file
diff --git a/toolkit/components/glean/docs/dev/index.md b/toolkit/components/glean/docs/dev/index.md
new file mode 100644
index 0000000000..334f040ed9
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/index.md
@@ -0,0 +1,15 @@
+# Developing Firefox on Glean
+
+This section of docs is designed to be helpful to people developing FOG.
+If you're not touching code, tests, or documentation in `toolkit/components/glean`,
+and you're not interested in implementation details, you probably want
+[the user docs instead](../user/index).
+
+```{toctree}
+:titlesonly:
+:maxdepth: 1
+:glob:
+
+*
+Glean SDK Source <https://github.com/mozilla/glean/>
+```
diff --git a/toolkit/components/glean/docs/dev/ipc.md b/toolkit/components/glean/docs/dev/ipc.md
new file mode 100644
index 0000000000..b571aa7275
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/ipc.md
@@ -0,0 +1,183 @@
+# Inter-process Communication (IPC)
+
+Firefox Desktop is a multi-process desktop application.
+Code requiring instrumentation may be on any of its processes,
+so FOG provide facilities to do just that.
+
+## Design
+
+The IPC Design of FOG was worked out in
+[bug 1618253](https://bugzilla.mozilla.org/show_bug.cgi?id=1618253).
+
+It centred around a few specific concepts:
+
+### Forbidding Non-Commutative Operations
+
+Because we cannot nicely impose a canonical ordering of metric operations across all processes,
+FOG forbids non-[commutative](https://en.wikipedia.org/wiki/Commutative_property)
+metric operations in some circumstances.
+
+For example,
+`Add()`-ing to a Counter metric works from multiple processes because the order doesn't matter.
+However, given a String metric being `Set()` from multiple processes simultaneously,
+which value should it take?
+
+This ambiguity is not a good foundation to build trust on,
+so we forbid setting a String metric from multiple processes.
+
+#### List of Forbidden Operations
+
+* Boolean's `set` (this is the metric type's only operation)
+* Labeled Boolean's `set` (this is the metric type's only operation)
+* String's `set` (this is the metric type's only operation)
+* Labeled String's `set` (this is the metric type's only operation)
+* String List's `set`
+    * `add` is permitted (order and uniqueness are not guaranteed)
+* Timespan's `start`, `stop`, and `cancel` (these are the metric type's only operations)
+* UUID's `set` and `generateAndSet` (these are the metric type's only operations)
+* Datetime's `set` (this is the metric type's only operation)
+* Quantity's `set` (this is the metric type's only operation)
+
+This list may grow over time as new metric types are added.
+If there's an operation/metric type on this list that you need to use in a non-parent process,
+please reach out
+[on the #glean channel](https://chat.mozilla.org/#/room/#glean:mozilla.org)
+and we'll help you out.
+
+### Process Agnosticism
+
+For metric types that can be used cross-process,
+FOG provides no facility for identifying which process the instrumentation is on.
+
+What this means is that if you accumulate to a
+[Timing Distribution](https://mozilla.github.io/glean/book/user/metrics/timing_distribution.html)
+in multiple processes,
+all the samples from all the processes will be combined in the same metric.
+
+If you wish to distinguish samples from different process types,
+you will need multiple metrics and inline code to select the proper one for the given process.
+For example:
+
+```C++
+if (XRE_GetProcessType() == GeckoProcessType_Default) {
+  mozilla::glean::performance::cache_size.Accumulate(numBytes / 1024);
+} else {
+  mozilla::glean::performance::non_main_process_cache_size.Accumulate(numBytes / 1024);
+}
+```
+
+### Scheduling
+
+FOG makes no guarantee about when non-main-process metric values are sent across IPC.
+FOG will try its best to schedule opportunistically in idle moments,
+and during orderly shutdowns.
+
+There are a few cases where we provide more firm guarantees:
+
+#### Tests
+
+There are test-only APIs in Rust, C++, and Javascript.
+These do not await a flush of child process metric values.
+You can use the test-only method `testFlushAllChildren` on the `FOG`
+XPCOM component to await child data's arrival:
+```js
+await Services.fog.testFlushAllChildren();
+```
+See [the test documentation](testing) for more details on testing FOG.
+For writing tests about instrumentation, see
+[the instrumentation test documentation](../user/instrumentation_tests).
+
+#### Pings
+
+We do not guarantee that non-main-process data has made it into a specific ping.
+
+[Built-in pings](https://mozilla.github.io/glean/book/user/pings/index.html)
+are submitted by the Rust Glean SDK at times FOG doesn't directly control,
+so there may be data not present in the parent process when a built-in ping is submitted.
+We don't anticipate this causing a problem since child-process data that
+"misses" a given ping will be included in the next one.
+
+At this time,
+[Custom Pings](https://mozilla.github.io/glean/book/user/pings/custom.html)
+must be sent in the parent process and have no mechanism
+to schedule their submission for after child-process data arrives in the parent process.
+[bug 1732118](https://bugzilla.mozilla.org/show_bug.cgi?id=1732118)
+tracks the addition of such a mechanism or guarantee.
+
+#### Shutdown
+
+We will make a best effort during an orderly shutdown to flush all pending data in child processes.
+This means a disorderly shutdown (usually a crash)
+may result in child process data being lost.
+
+#### Size
+
+We don't measure or keep an up-to-date calculation of the size of the IPC Payload.
+We do, however, keep a count of the number of times the IPC Payload has been accessed.
+This is used as a (very) conservative estimate of the size of the IPC Payload so we do not exceed the
+[IPC message size limit](https://searchfox.org/mozilla-central/search?q=kMaximumMessageSize).
+
+See [bug 1745660](https://bugzilla.mozilla.org/show_bug.cgi?id=1745660).
+
+### Mechanics
+
+The rough design is that the parent process can request an immediate flush of pending data,
+and each child process can decide to flush its pending data whenever it wishes.
+The former is via `FlushFOGData() returns (ByteBuf)` and the latter via  `FOGData(ByteBuf)`.
+
+Pending Data is a buffer of bytes generated by `bincode` in Rust in the Child,
+handed off to C++, passed over IPC,
+then given back to `bincode` in Rust on the Parent.
+
+Rust is then responsible for turning the pending data into
+[metrics API][glean-metrics] calls on the metrics in the parent process.
+
+#### Supported Process Types
+
+FOG supports messaging between the following types of child process and the parent process:
+* content children (via `PContent`
+  (for now. See [bug 1641989](https://bugzilla.mozilla.org/show_bug.cgi?id=1641989))
+* gmp children (via `PGMP`)
+* gpu children (via `PGPU`)
+* rdd children (via `PRDD`)
+* socket children (via `PSocketProcess`)
+
+See
+[the process model docs](/dom/ipc/process_model.rst)
+for more information about what that means.
+
+### Adding Support for a new Process Type
+
+Adding support for a new process type is a matter of extending the two messages
+mentioned above in "Mechanics" to another process type's protocol (ipdl file).
+
+1. Add two messages to the appropriate sections in `P<ProcessType>.ipdl`
+    * (( **Note:** `PGPU` _should_ be the only ipdl where `parent`
+      means the non-parent/-main/-UI process,
+      but double-check that you get this correct.))
+    * Add `async FOGData(ByteBuf&& aBuf);` to the parent/main/UI process side of things
+      (most often `parent:`).
+    * Add `async FlushFOGData() returns (ByteBuf buf);` to the non-parent/-main/-UI side
+      (most often `child:`).
+2. Implement the protocol endpoints in `P<ProcessType>{Child|Parent}.{h|cpp}`
+    * The message added to the `parent: ` section goes in
+      `P<ProcessType>Parent.{h|cpp}` and vice versa.
+3. Add to `FOGIPC.cpp`'s `FlushAllChildData` code that
+    1. Enumerates all processes of the newly-supported type (there may only be one),
+    2. Calls `SendFlushFOGData on each, and
+    3. Adds the resulting promise to the array.
+4. Add to `FOGIPC.cpp`'s `SendFOGData` the correct `GeckoProcessType_*`
+   enum value, and appropriate code for getting the parent process singleton and calling
+   `SendFOGData` on it.
+5. Add to the fog crate's `register_process_shutdown` function
+   handling for at-shutdown flushing of IPC data.
+   If this isn't added, we will log (but not panic)
+   on the first use of Glean APIs on an unsupported process type.
+    * "Handling" might be an empty block with a comment explaining where to find it
+      (like how `PROCESS_TYPE_DEFAULT` is handled)
+    * Or it might be custom code
+      (like `PROCESS_TYPE_CONTENT`'s)
+6. Add to the documented [list of supported process types](#supported-process-types)
+   the process type you added support for.
+
+[glean-metrics]: https://mozilla.github.io/glean/book/reference/metrics/index.html
diff --git a/toolkit/components/glean/docs/dev/jog.md b/toolkit/components/glean/docs/dev/jog.md
new file mode 100644
index 0000000000..3fb5691593
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/jog.md
@@ -0,0 +1,91 @@
+# Runtime Metric Definition Subsystem: JOG
+
+```{admonition} I'm Sorry
+Why is it caled JOG? Because it's concerned with... run... time.
+```
+
+The normal mechanism for registering metrics,
+for reasons as varied from ease-of-impl to performance,
+happens at compile time.
+However, this doesn't support use cases like
+* [Artifact Builds][artifact-build]
+  (Where only the JavaScript of Firefox Desktop is repackaged at build time,
+  so there is no compile environment)
+* Dynamic Telemetry
+  (A theorized system for instrumenting Firefox Desktop without shipping code)
+* Web Extensions
+  (Or at least the kind that can't or won't use
+  [the Glean JS SDK][glean-js])
+
+Thus we need a subsystem that supports the runtime registration of metrics.
+We call it JOG and it was implemented in [bug 1698184][impl-bug].
+
+## JavaScript Only
+
+Metrics in C++ and Rust are identified by identifiers which we can't swap out at runtime.
+Thus, in order for changes to metrics to be visible to instrumented systems in C++ or Rust, you must compile.
+
+JavaScript, on the other hand, we supply instances to on-demand.
+It not only supports the specific use cases driving this project,
+it's the only environment that can benefit from runtime metric definition in Firefox Desktop.
+
+## Design
+
+The original design was done as part of
+[bug 1662863][design-bug].
+Things have mostly just been refined from there.
+
+## Architecture
+
+We silo as much of the subsystem as we can into the
+`jog` module located in `toolkit/components/glean/bindings/jog/`.
+This includes the metrics construction factory and storage for metrics instances and their names and ids.
+
+Unfortunately, so that the metrics instances can be accessed by FFI,
+the Rust metrics instances created by the `jog` crate are stored within the `fog` crate.
+
+Speaking of FFI, the `jog` crate is using cbindgen to be accessible to C++.
+
+If necessary or pleasant, it is probably possible to do away with the C++ storage,
+moving the category set and metrics id map to Rust and moving information over FFI as needed.
+
+Test methods are run from `nsIFOG` (so we can use them in JS in xpcshell)
+to static `JOG::` functions.
+
+### Build Integration
+
+If JOG detects we're an artifact build (by checking `COMPILE_ENVIRONMENT`),
+it generates `jogfile.json` and ensures it is placed in `GreD`
+(next to the `firefox` binary).
+
+`jogfile.json` includes only the metric and ping information necessary to register them at runtime.
+(It doesn't know about tags or descriptions, just the shapes and names of things)
+
+This file is read the first time JS tries to get a metric category from the
+`Glean` global or a ping from the `GleanPings` global.
+
+Yes, this is on the main thread. Yes, this is synchronous. Yes, this is file I/O.
+
+Since this is a developer build, we think this is worth it to support Artifact Builds.
+
+If we're wrong about this and there are additional conditions we should place JOG under,
+please [contact us][glean-channel].
+
+#### If things get weird, delete `objdir/dist/bin/jogfile.json`
+
+Sometimes, metrics or pings you've added may not appear when you run Firefox.
+For these and other odd cases, the solution is the same:
+delete `jogfile.json` from the `dist/bin` directory of your objdir, then try again.
+
+This shouldn't happen if you keep your artifact and non-artifact objdirs segregated
+(as is good practice).
+
+If, despite doing things properly you still see this or something else odd, then that's a bug.
+Please [file it in Toolkit :: Telemetry][file-bug]
+
+[artifact-build]: https://firefox-source-docs.mozilla.org/contributing/build/artifact_builds.html
+[glean-js]: https://mozilla.github.io/glean/book/user/adding-glean-to-your-project/javascript.html
+[impl-bug]: https://bugzilla.mozilla.org/show_bug.cgi?id=1698184
+[design-bug]: https://bugzilla.mozilla.org/show_bug.cgi?id=1662863
+[glean-channel]: https://chat.mozilla.org/#/room/#glean:mozilla.org
+[file-bug]: https://bugzilla.mozilla.org/enter_bug.cgi?assigned_to=nobody%40mozilla.org&bug_ignored=0&bug_severity=--&bug_status=NEW&bug_type=defect&cf_a11y_review_project_flag=---&cf_fx_iteration=---&cf_fx_points=---&cf_performance_impact=---&cf_status_firefox106=---&cf_status_firefox107=---&cf_status_firefox108=---&cf_status_firefox_esr102=---&cf_status_thunderbird_esr102=---&cf_status_thunderbird_esr91=---&cf_tracking_firefox106=---&cf_tracking_firefox107=---&cf_tracking_firefox108=---&cf_tracking_firefox_esr102=---&cf_tracking_firefox_relnote=---&cf_tracking_thunderbird_esr102=---&cf_tracking_thunderbird_esr91=---&cf_webcompat_priority=---&component=Telemetry&contenttypemethod=list&contenttypeselection=text%2Fplain&defined_groups=1&filed_via=standard_form&flag_type-203=X&flag_type-37=X&flag_type-41=X&flag_type-607=X&flag_type-721=X&flag_type-737=X&flag_type-787=X&flag_type-799=X&flag_type-800=X&flag_type-803=X&flag_type-846=X&flag_type-855=X&flag_type-864=X&flag_type-930=X&flag_type-936=X&flag_type-937=X&flag_type-952=X&form_name=enter_bug&maketemplate=Remember%20values%20as%20bookmarkable%20template&op_sys=Unspecified&priority=--&product=Toolkit&rep_platform=Unspecified&short_desc=Problem%20with%20JOG%3A%20&target_milestone=---&version=unspecified
diff --git a/toolkit/components/glean/docs/dev/local_glean.md b/toolkit/components/glean/docs/dev/local_glean.md
new file mode 100644
index 0000000000..046cf6e79c
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/local_glean.md
@@ -0,0 +1,100 @@
+# Developing with a local Glean build
+
+FOG uses a release version of Glean, as published on [crates.io][cratesio-glean].
+
+For local development and try runs you can replace this Glean implementation with a local or remote version.
+
+1. To tell `mach` where to find your Glean, patch the [top-level `Cargo.toml`][cargo-toml]. E.g. like this:
+
+    ```toml
+    [patches.crates-io]
+    glean = { git = "https://github.com/myfork/glean", branch = "my-feature-branch" }
+    glean-core = { git = "https://github.com/myfork/glean", branch = "my-feature-branch" }
+    ```
+
+    Both crates are required to ensure they are in sync.
+
+    You can specify the exact code to use by `branch`, `tag` or `rev` (Git commit).
+    See the [cargo documentation for details][cargo-doc].
+
+    You can also use a path dependency:
+
+    ```toml
+    [patches.crates-io]
+    glean = { path = "../glean/glean-core/rlb" }
+    glean-core = { path = "../glean/glean-core" }
+    ```
+
+2. If the crate version in the patched repository is not
+   [semver]-compatible with the version required by the
+   `fog` and `fog_control` crates,
+   you need to change the version in the following files to match the ones in your
+   `glean` repo:
+
+    ```
+    toolkit/components/glean/Cargo.toml
+    toolkit/components/glean/api/Cargo.toml
+    ```
+
+    This tells FOG's crates that it needs your local Glean's version.
+
+3. Update the Cargo lockfile:
+
+    ```
+    cargo update -p glean
+    ```
+
+4.  Mozilla's supply-chain management policy requires that third-party software
+    (which includes the Glean SDK because it is distributed as though it is third-party)
+    be audited and certified as safe.
+    Your local Glean SDK probably hasn't been vetted. If you try to vendor right now,
+    `./mach vendor rust` will complain something like:
+
+    ```
+    Vet error: There are some issues with your policy.audit-as-crates-io entries
+    ```
+
+    This is because your local Glean SDK is neither of a version nor is from a source that has been vetted.
+    To allow your local Glean crates to be treated as crates.io-sourced crates for vetting,
+    add the following sections to the top of `supply-chain/config.toml`:
+
+    ```toml
+    [policy.glean]
+    audit-as-crates-io = true
+
+    [policy.glean-core]
+    audit-as-crates-io = true
+    ```
+
+    If your local Glean is of a non-vetted version, you can update `glean` and
+    `glean-core`'s entries in `supply-chain/audits.toml` to the version you're using.
+    If you don't, `./mach vendor rust` will complain and not complete.
+
+    **Note:** Do not attempt to check these changes in.
+    These changes bypass supply chain defenses.
+    `@supply-chain-reviewers` may become cross as they `r-` your patch.
+
+5. Vendor the changed crates:
+
+    ```
+    ./mach vendor rust
+    ```
+
+    **Note:** If you're using a path dependency, `mach vendor rust` doesn't actually change files.
+    Instead it pulls the files directly from the location on disk you specify.
+
+6. Finally, build Firefox:
+
+    ```
+    ./mach build
+    ```
+
+A remote reference works for try runs as well,
+but a path dependency will not.
+
+Please ensure to not land a non-release version of Glean.
+
+[cratesio-glean]: https://crates.io/crates/glean
+[cargo-toml]: https://searchfox.org/mozilla-central/rev/f07a609a76136ef779c65185165ff5ac513cc172/Cargo.toml#76
+[cargo-doc]: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#specifying-dependencies-from-git-repositories
+[semver]: https://semver.org/
diff --git a/toolkit/components/glean/docs/dev/new_metric_types.md b/toolkit/components/glean/docs/dev/new_metric_types.md
new file mode 100644
index 0000000000..c9195b5291
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/new_metric_types.md
@@ -0,0 +1,292 @@
+# Adding a New Metric Type
+
+This document covers how to add a new metric type to FOG.
+You should only have to do this if a new metric type is added to the
+[Glean SDK](https://mozilla.github.io/glean/book/user/metrics/index.html)
+and it is needed in Firefox Desktop.
+
+## IPC
+
+For detailed information about the IPC design,
+including a list of forbidden operations,
+please consult
+[the FOG IPC documentation](ipc.md).
+
+When adding a new metric type, the main IPC considerations are:
+* Which operations are forbidden because they are not commutative?
+    * Most `set`-style operations cannot be reconciled sensibly across multiple processes.
+* If there are non-forbidden operations,
+what partial representation will this metric have in non-main processes?
+Put another way, what shape of storage will this take up in the
+[IPC Payload](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/api/src/ipc.rs)?
+    * For example, Counters can aggregate all partial counts together to a single
+    "partial sum". So
+    [its representation](https://searchfox.org/mozilla-central/rev/803b368879fa332e8e2c1840bf1ec164f7ed2c32/toolkit/components/glean/api/src/ipc.rs#45)
+    in the IPC Payload is just a single number per Counter.
+    * In contrast, Timing Distributions' bucket arrangements are known only to the core,
+    so it can't combine sample counts in child processes.
+    Instead we record durations in the highest resolution (nanos),
+    and send a stream of high-precision samples across IPC.
+
+To implement IPC support in a metric type,
+we split the metric into three pieces:
+1. An umbrella `enum` with the name `MetricTypeMetric`.
+    * It has a `Child` and a `Parent` variant.
+    * It is IPC-aware and is responsible for
+        * If on a non-parent-process,
+        either storing partial representations in the IPC Payload,
+        or logging errors if forbidden non-test APIs are called.
+        (Or panicking if test APIs are called.)
+        * If on the parent process, dispatching API calls on its inner Rust Language Binding metric.
+2. The parent-process implementation is supplied by
+   [the RLB](https://crates.io/crates/glean/).
+    * For testing, it stores the `MetricId` that identifies this particular metric in a cross-process fashion.
+    * For testing, it exposes a `child_metric()` function to create its `Child` equivalent.
+    * For testing and if it supports operations in a non-parent-process,
+      it exposes a `metric_id()` function to access the stored `MetricId`.
+3. The `MetricTypeIpc` is the non-parent-process implementation.
+    * If it does support operations in non-parent processes it stores the
+      `MetricId` that identifies this particular metric in a cross-process fashion.
+
+## Mirrors
+
+FOG can mirror Glean metrics to Telemetry probes via the
+[Glean Interface For Firefox Telemetry](../user/gifft.md).
+
+Can this metric type be mirrored?
+Should it be mirrored?
+
+If so, add an appropriate Telemetry probe for it to mirror to,
+documenting the compatibility in
+[the GIFFT docs](../user/gifft.md).
+
+### GIFFT Tests
+
+If you add a GIFFT mirror, don't forget to test that the mirror works.
+You should be able to do this by adding a task to
+[`toolkit/components/glean/tests/xpcshell/test_GIFFT.js`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/xpcshell/test_GIFFT.js).
+
+### GIFFT C++ State: Typical Locking and Shutdown
+
+Some metric types (`labeled_*`, `timespan`, `timing_distribution`)
+require holding state in C++ to make GIFFT work.
+Pings also hold state to support `testBeforeNextSubmit()`.
+If your new metric type requires state in C++,
+the current state-of-the-art is a `StaticDataMutex`-locked `UniquePtr` to a `nsTHashTable`.
+Access to the inner map is guarded by the lock and is controlled and lazily-instantiated through a single access function.
+[See Ping's `GetCallbackMapLock()`](https://searchfox.org/mozilla-central/source/toolkit/components/glean/bindings/private/Ping.cpp)
+for example.
+
+It is important to clear this state to avoid leaks.
+(See [bug 1752417](https://bugzilla.mozilla.org/show_bug.cgi?id=1752417).)
+However, instrumentation may call metrics APIs at any time.
+
+Therefore, GIFFT explicitly stops supporting these state-requiring operations after the
+[`AppShutdownTelemetry` shutdown phase](https://searchfox.org/mozilla-central/source/xpcom/base/ShutdownPhase.h).
+This is because during the next phase (`XPCOMWillShutdown`) we clear the state.
+
+## Rust
+
+FOG uses the Rust Language Binding APIs (the `glean` crate) with a layer of IPC on top.
+
+The IPC additions and glean-core trait implementations are in the
+[`private` module of the `fog` crate](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/api/src/metrics).
+
+Each metric type gets its own file, mimicking the structure in
+[`glean_core`](https://github.com/mozilla/glean/tree/main/glean-core/src/metrics)
+and [`glean`](https://github.com/mozilla/glean/tree/main/glean-core/rlb/src/private).
+Unless, of course, that metric is a labeled metric type.
+Then the sub metric type gets its own file,
+and you need to add "Labeledness" to it by implementing
+`Sealed` for your new type following the pattern in
+[`api/src/private/labeled.rs`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/api/src/private/labeled.rs).
+
+Every method on the metric type is public for now,
+including test methods,
+and is at least all the methods exposed via the
+[metric traits](https://github.com/mozilla/glean/tree/main/glean-core/src/traits).
+
+To support IPC and the MLA FFI (see below)
+we identify metric instances by MetricId and store them in maps in
+[the `__glean_metric_maps` mod of `metrics.rs`](https://hg.mozilla.org/mozilla-central/toolkit/components/glean/api/src/metrics.rs).
+This work is done by the `rust.py` and `rust(_pings).jinja2` extensions to `glean_parser` found
+[in the `build_scripts/glean_parser_ext/` folder](https://searchfox.org/mozilla-central/source/toolkit/components/glean/build_scripts/glean_parser_ext).
+
+You shouldn't have to edit these files for new metric types,
+as the original modifications to `glean_parser` for this type should already be generating correct code.
+
+### Dealing with Clippy
+
+[Clippy](https://github.com/rust-lang/rust-clippy)
+cannot find the generated Rust metrics maps in `__glean_metric_maps`
+(see [bug 1674728](https://bugzilla.mozilla.org/show_bug.cgi?id=1674728)).
+This means any new metric type that is generating structures via `glean_parser`
+extensions requires you to add a copy of the new map to the clippy-only
+`__glean_metric_maps` at the bottom of
+[the non-generated `metrics.rs`](https://searchfox.org/mozilla-central/source/toolkit/components/glean/api/src/metrics.rs).
+
+### Rust Tests
+
+You should be able to smoke test the basic functionality in Rust unit tests.
+You can do this within the metric type implementation file directly.
+
+## C++ and JS
+
+The C++ and JS APIs are implemented [atop the Rust API](code_organization.md).
+We treat them both together since, though they're different languages,
+they're both implemented in C++ and share much of their implementation.
+
+The overall design is to build the C++ API atop the Multi-Language Architecture's
+(MLA's) FFI, then build the JS API atop the C++ API.
+This allows features like the
+[Glean Interface For Firefox Telemetry (GIFFT)](../user/gifft.md)
+that target only C++ and JS to be more simply implemented in the C++ layer.
+Exceptions to this (where the JS uses the FFI directly) are discouraged.
+
+Each metric type has six pieces you'll need to cover:
+
+### 1. MLA FFI
+
+- Using our convenient macros,
+  define the metric type's Multi-Language Architecture FFI layer above the Rust API in
+  [`api/src/ffi/`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/api/src/ffi/).
+
+### 2. C++ Impl
+
+- Implement a type called `XMetric` (e.g. `CounterMetric`) in `mozilla::glean::impl` in
+  [`bindings/private/`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/bindings/private/).
+    - Its methods should be named the same as the ones in the Rust API, transformed to `CamelCase`.
+    - They should all be public.
+    - Multiplex the FFI's `test_have` and `test_get` functions into a single
+      `TestGetValue` function that returns a
+      `mozilla::Maybe` wrapping the C++ type that best fits the metric type.
+- Include the new metric type in
+  [`bindings/MetricTypes.h`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/bindings/MetricTypes.h).
+- Include the new files in
+  [`moz.build`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/moz.build).
+  The header file should be added to `EXPORTS.mozilla.glean.bindings` and the
+  `.cpp` file should be added to `UNIFIED_SOURCES`.
+
+### 3. IDL
+
+- Duplicate the public API (including its docs) to
+  [`xpcom/nsIGleanMetrics.idl`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/xpcom/nsIGleanMetrics.idl)
+  with the name `nsIGleanX` (e.g. `nsIGleanCounter`).
+    - Inherit from `nsISupports`.
+    - The naming style for members here is `lowerCamelCase`.
+      You'll need a
+      [GUID](https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XPCOM/Generating_GUIDs)
+      because this is XPCOM, but you'll only need the canonical form since we're only exposing to JS.
+    - The `testGetValue` method will return a
+      `jsval` to permit it to return `undefined` when there is no value.
+
+### 4. JS Impl
+
+- Add an `nsIGleanX`-deriving, `XMetric`-owning type called
+  `GleanX` (e.g. `GleanCounter`) in the same header and `.cpp` as `XMetric` in
+  [`bindings/private/`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/bindings/private/).
+    - Don't declare any methods beyond a ctor
+      (takes a `uint32_t` metric id, init-constructs a `impl::XMetric` member)
+      and dtor (`default`): the IDL will do the rest so long as you remember to add
+      `NS_DECL_ISUPPORTS` and `NS_DECL_NSIGLEANX`.
+    - In the definition of `GleanX`, member identifiers are back to
+      `CamelCase` and need macros like `NS_IMETHODIMP`.
+      Delegate operations to the owned `XMetric`, returning
+      `NS_OK` no matter what in non-test methods.
+    - Test-only methods can return `NS_ERROR` codes on failures,
+      but mostly return `NS_OK` and use `undefined` in the
+      `JS::MutableHandleValue` result to signal no value.
+
+### 6. Tests
+
+Two languages means two test suites.
+
+- Add a never-expiring test-only metric of your type to
+  [`test_metrics.yaml`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/test_metrics.yaml).
+    - Feel free to be clever with the name,
+      but be sure to make clear that it is test-only.
+- **C++ Tests (GTest)** - Add a small test case to
+  [`gtest/TestFog.cpp`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/gtest/TestFog.cpp).
+    - For more details, peruse the [testing docs](testing.md).
+- **JS Tests (xpcshell)** - Add a small test case to
+  [`xpcshell/test_Glean.js`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/xpcshell/test_Glean.js)
+  and
+  [`xpcshell/test_JOG.js`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/xpcshell/test_JOG.js).
+  If your metric type has supported IPC operations, also add cases to the `IPC` variants of these test files.
+    - For more details, peruse the [testing docs](testing.md).
+
+### 7. API Documentation
+
+Metric API Documentation is centralized in
+[the Glean SDK Book](https://mozilla.github.io/glean/book/user/metrics/index.html).
+
+You will need to craft a Pull Request against
+[the SDK](https://github.com/mozilla/glean/)
+adding a C++ and JS example to the specific metric type's API docs.
+
+Add a notice at the top of both examples that these APIs are only available in Firefox Desktop:
+````md
+<div data-lang="C++" class="tab">
+
+> **Note**: C++ APIs are only available in Firefox Desktop.
+
+```c++
+#include "mozilla/glean/GleanMetrics.h"
+
+mozilla::glean::category_name::metric_name.Api(args);
+```
+
+There are test APIs available too:
+
+```c++
+#include "mozilla/glean/GleanMetrics.h"
+
+ASSERT_EQ(value, mozilla::glean::category_name::metric_name.TestGetValue().ref());
+```
+</div>
+
+// and again for <div data-lang="JS">
+````
+
+If you're lucky, the Rust API will have already been added.
+Otherwise you'll need to write an example for that one too.
+
+### 8. Labeled metrics (if necessary)
+
+If your new metric type is Labeled, you have more work to do.
+I'm assuming you've already implemented the non-labeled sub metric type following the steps above.
+Now you must add "Labeledness" to it.
+
+There are four pieces to this:
+
+#### FFI
+
+- To add the writeable storage Rust will use to store the dynamically-generated sub metric instances,
+  add your sub metric type's map as a list item in the `submetric_maps` `mod` of
+  [`rust.jinja2`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/build_scripts/glean_parser_ext/templates/rust.jinja2).
+- Following the pattern of the others, add a `fog_{your labeled metric name here}_get()` FFI API to
+  `api/src/ffi/mod.rs`.
+  This is what C++ and JS will use to allocate and retrieve sub metric instances by id.
+
+#### C++
+
+- Following the pattern of the others, add a template specialiation for `Labeled<YourSubMetric>::Get` to
+  [`bindings/private/Labeled.cpp`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/bindings/private/Labeled.cpp).
+  This will ensure C++ consumers can fetch or create sub metric instances.
+
+#### JS
+
+- Already handled for you since the JS types all inherit from `nsISupports`
+  and the JS template knows to add your new type to `NewSubMetricFromIds(...)`
+  (see `GleanLabeled::NamedGetter` if you're curious).
+
+#### Tests
+
+- The labeled variant will need tests the same as Step #6.
+  A tip: be sure to test two labels with different values.
+
+## Python Tests
+
+We have a suite of tests for ensuring code generation generates appropriate code.
+You should add a metric to [that suite](testing.md) for your new metric type.
+You will need to regenerate the expected files.
diff --git a/toolkit/components/glean/docs/dev/preferences.md b/toolkit/components/glean/docs/dev/preferences.md
new file mode 100644
index 0000000000..97a3e91e92
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/preferences.md
@@ -0,0 +1,90 @@
+# Preferences and Defines
+
+## User Preferences
+
+`datareporting.healthreport.uploadEnabled`
+
+This determines whether the Glean SDK is enabled.
+It can be controlled by users via `about:preferences#privacy`.
+If this is set to false from true, we send a
+["deletion-request" ping](https://mozilla.github.io/glean/book/user/pings/deletion_request.html)
+and no data collections will be persisted or reported from that point.
+
+## Test-only Preferences
+
+`telemetry.fog.test.localhost_port`
+
+If set to a value `port` which is greater than 0, pings will be sent to
+`http://localhost:port` instead of `https://incoming.telemetry.mozilla.org`.
+If set to a value `port` which is less than 0, FOG will:
+1) Tell Glean that upload is enabled, even if it isn't.
+2) Take all pings scheduled for upload and drop them on the floor,
+   telling the Glean SDK that it was sent successfully.
+
+This is how you emulate "recording enabled but upload disabled"
+like developer builds have in Firefox Telemetry.
+When switching from `port < 0` to `port >= 0`,
+Glean will be told (if just temporarily) that upload is disabled.
+This clears the stores of recorded-but-not-reported data.
+Defaults to 0.
+
+`telemetry.fog.test.activity_limit`
+`telemetry.fog.test.inactivity_limit`
+
+This pair of prefs control the length of time of activity before inactivity
+(or vice versa)
+needed before FOG informs the SDK's Client Activity API that the client was (in)active.
+Present to allow testing without figuring out how to mock Rust's clock.
+Their values are integer seconds.
+Defaults to 120 (activity), 1200 (inactivity).
+
+## Defines
+
+`MOZ_GLEAN_ANDROID`
+
+If set, recording Glean metrics are a no-op. Glean will not be initialized.
+Only set on Android.
+This define will be removed after we sort out how Android and Geckoview will work
+(see [bug 1670261](https://bugzilla.mozilla.org/show_bug.cgi?id=1670261)).
+It can be queried in C++ via `#ifndef MOZ_GLEAN_ANDROID`,
+and in JS via `AppConstants.MOZ_GLEAN_ANDROID`.
+
+`MOZILLA_OFFICIAL`
+
+If unset, we set a `glean_disable_upload` Rust feature in
+`gkrust` and `gkrust-shared` which is forwarded to `fog_control` as `disable_upload`.
+This feature defaults FOG to an "upload disabled"
+mode where collection on the client proceeds as normal but no ping is sent.
+This mode can be overridden at runtime in two ways:
+* If the ping has a
+  [Debug Tag](https://mozilla.github.io/glean/book/user/debugging/index.html)
+  then it is sent so that it may be inspected in the
+  [Glean Debug Ping Viewer](https://debug-ping-preview.firebaseapp.com/).
+* If the preference `telemetry.fog.test.localhost_port` is set to a value greater than 0,
+  then pings are sent to a server operating locally at that port
+  (even if the ping has a Debug Tag), to enable testing.
+
+Also, if set, [JOG](./jog) is disabled.
+Artifact builds will not exhibit changes to their Glean metrics.
+
+`MOZILLA_OFFICIAL` tends to be set on most builds released to users,
+including builds distributed by Linux distributions.
+It tends to not be set on local developer builds.
+See [bug 1680025](https://bugzilla.mozilla.org/show_bug.cgi?id=1680025) for details.
+
+`COMPILE_ENVIRONMENT`
+
+If `COMPILE_ENVIRONMENT` isn't set in the build config,
+[JOG](./jog) will generate a file for the runtime-registration of metrics and pings.
+This is to support [Artifact Builds](/contributing/build/artifact_builds).
+
+`OS_TARGET`
+
+If not set to `'Android'` we set a `glean_million_queue` Rust feature
+([see gkrust-features.mozbuild][gkrust-features])
+which, when passed to the Glean SDK,
+opts us into a preinit queue that doesn't discard tasks until there are 10^6 of them.
+
+See [bug 1797494](https://bugzilla.mozilla.org/show_bug.cgi?id=1797494) for details.
+
+[gkrust-features]: https://searchfox.org/mozilla-central/source/toolkit/library/rust/gkrust-features.mozbuild
diff --git a/toolkit/components/glean/docs/dev/storage.md b/toolkit/components/glean/docs/dev/storage.md
new file mode 100644
index 0000000000..00464c6173
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/storage.md
@@ -0,0 +1,14 @@
+# Storage
+
+Both FOG and the Glean SDK require some storage in the
+[Firefox Profile Directory](https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Multiple_profiles).
+
+## FOG
+
+At present FOG's storage is limited to its [preferences](preferences.md).
+
+## Glean SDK
+
+The Glean SDK stores things in the
+[Glean Data Directory](https://mozilla.github.io/glean/book/dev/core/internal/directory-structure.html)
+which can be found at `<profile_dir>/datareporting/glean`.
diff --git a/toolkit/components/glean/docs/dev/style_guide.md b/toolkit/components/glean/docs/dev/style_guide.md
new file mode 100644
index 0000000000..c289919f93
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/style_guide.md
@@ -0,0 +1,41 @@
+# FOG Documentation Style Guide
+
+FOG's Documentation is written in Markdown.
+You can find its source at `toolkit/components/glean/docs`.
+
+## Line breaks
+
+We will use [semantic linefeeds]:
+* Break anywhere before 80-100 characters
+* Break after any punctuation when it makes sense
+* Break before or after any markdown when it makes sense
+
+**Tip:** To keep lines narrow, use markdown's [reference link]
+feature whenever it makes sense (or all the time. Up to you.).
+
+## Linking to other documentation
+
+Linking to other external documentation is [easy][reference link].
+Linking to other pieces of documentation in the source docs requires a
+link to the source file in the sphinx tree.
+
+Links can be relative e.g. to link to the [preferences] docs:
+
+```md
+[preferences](preferences.md)
+```
+
+Or they can be absolute e.g. to link to the [Telemetry] docs:
+```md
+[Telemetry](/toolkit/components/telemetry/index.rst)
+```
+
+Sphinx will automagically transform that to an
+appropriately-base-url'd url with a `.html` suffix.
+
+
+[semantic linefeeds]: https://rhodesmill.org/brandon/2012/one-sentence-per-line/
+[reference link]: https://spec.commonmark.org/0.29/#reference-link
+[Telemetry]: /toolkit/components/telemetry/index.rst
+[#firefox-source-docs:mozilla.org]: https://chat.mozilla.org/#/room/#firefox-source-docs:mozilla.org
+[bug 1621950]: https://bugzilla.mozilla.org/show_bug.cgi?id=1621950
diff --git a/toolkit/components/glean/docs/dev/testing.md b/toolkit/components/glean/docs/dev/testing.md
new file mode 100644
index 0000000000..9ce9287a00
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/testing.md
@@ -0,0 +1,246 @@
+# Testing
+
+```{admonition} This documentation is about testing FOG itself
+This document contains information about how FOG tests itself,
+how to add new tests, how and what to log, and stuff like that.
+If you're interested in learning how to test instrumentation you added,
+you'll want to read
+[the instrumetnation testing docs](../user/instrumentation_tests) instead.
+```
+
+Given the multiple API languages, processes, and dependencies,
+testing FOG is a matter of choosing the right tool for the situation.
+
+## One Big Command
+
+To run all the things, here's the tl;dr:
+
+`./mach build && ./mach lint -Ww -o --fix
+&& ./mach lint --linter clippy toolkit/components/glean/api/src
+&& ./mach rusttests && ./mach gtest "FOG*"
+&& python3 ./mach python-test toolkit/components/glean/tests/pytest
+&& ./mach test toolkit/components/glean/tests/xpcshell
+&& ./mach telemetry-tests-client toolkit/components/telemetry/tests/marionette/tests/client/test_fog* --gecko-log "-"
+&& ./mach test toolkit/components/glean/tests/browser
+`
+
+## Logging
+
+An often-overlooked first line of testing is "what do the logs say?".
+To turn on logging for FOG, use any of the following:
+* Run Firefox with `RUST_LOG="fog_control,fog,glean_core"`.
+    * On some platforms this will use terminal colours to indicate log level.
+* Run Firefox with `MOZ_LOG="timestamp,sync,glean::*:5,fog::*:5,fog_control::*:5,glean_core::*:5"`.
+* Set the following prefs:
+    * `logging.config.timestamp` to `true`
+    * `logging.config.sync` to `true`
+    * `logging.fog_control::*` to `5`
+    * `logging.fog::*` to `5`
+    * `logging.glean::*` to `5`
+    * `logging.glean_core::*` to `5`
+    * `logging.config.clear_on_startup` to `false` (or all these prefs will be cleared on startup)
+
+For more information on logging in Gecko, see the
+[Gecko Logging docs](/xpcom/logging).
+
+User-destined logs (of the "You did something wrong" variety) might output to the
+[Browser Console](/devtools-user/browser_console/index)
+if they originate in JS land. Open via
+<kbd>Ctrl</kbd>+<kbd>Shift</kbd>+<kbd>J</kbd>, or
+<kbd>Cmd</kbd>+<kbd>Shift</kbd>+<kbd>J</kbd>.
+
+```{admonition} Note
+At present, Rust logging in non-main processes just doesn't work.
+```
+
+### What to log, and to where?
+
+FOG covers a lot a ground (languages, layers):
+where you are determines what logging you have available.
+
+Here are some common situtations for logging:
+
+#### JS to C++
+
+If your logging is aimed at the user using the JS API
+(e.g. because the type provided isn't convertable to the necessary C++ type)
+then use the Browser Console via
+[FOG's Common's `LogToBrowserConsole`](https://searchfox.org/mozilla-central/rev/d107bc8aeadcc816ba85cb21c1a6a1aac1d4ef9f/toolkit/components/glean/bindings/private/Common.cpp#19).
+
+#### C++
+
+If you are in C++ and didn't come from JS, use `MOZ_LOG` with module `fog`.
+
+#### Rust
+
+Use the logging macros from `log`, e.g. `log::info!` or `log::error!`.
+Remember that, no matter the log level, `log::debug!` and `log::trace!`
+[will not appear in non-debug builds](/testing-rust-code/index.html#gecko-logging)
+
+If you are logging due to a situation caused by and fixable by a developer using the API,
+use `log::error!(...)`. Otherwise, use a quieter level.
+
+## `about:glean`
+
+`about:glean` is a page in a running Firefox that allows you to
+[debug the Glean SDK](https://mozilla.github.io/glean/book/user/debugging/index.html)
+in Firefox Desktop.
+It does this through the displayed user interface (just follow the instructions).
+
+## Linting
+
+To keep in accordance with Mozilla's various and several Coding Styles,
+we rely on `mach lint`.
+
+To lint the code in the "usual" way, automatically fixing where possible, run:
+`./mach lint -Ww -o --fix`
+
+This should keep you from checking in code that will automatically be backed out.
+
+In addition, we need to run the Rust formatter `clippy` on the `fog` crate:
+`./mach lint --linter clippy toolkit/components/glean/api/src`
+
+This will ensure that clippy-only builds will have all the symbols they need to lint our code.
+
+## Rust
+
+Not all of our Rust code can be tested in a single fashion, unfortunately.
+
+### Using `rusttests` (Treeherder symbol `Br` (a build task))
+
+If the crate you're testing has no Gecko symbols you can write standard
+[Rust tests](https://doc.rust-lang.org/book/ch11-01-writing-tests.html).
+
+This supports both unit tests
+(inline in the file under test) and integration tests
+(in the `tests/` folder in the crate root).
+Metric type tests are currently written as unit tests inline in the file,
+as they require access to the metric ID, which should only be exposed in tests.
+
+To run FOG's `rusttests` suite use `mach rusttests`
+
+If the crate uses only a few Gecko symbols, they may use the
+`with_gecko` feature to conditionally use them.
+This allows the crate to test its non-Gecko-adjacent code using Rust tests.
+(You will need to cover the Gecko-adjacent code via another means.)
+
+**Note:** Some FOG rusttests panic on purpose. They print stack traces to stdout.
+If the rusttests fail and you see a stack trace,
+double-check it isn't from a purposefully-panicking test.
+
+**Note:** If a test fails, it is very likely they'll poison the test lock.
+This will cause all subsequent tests that attempt to take the test lock
+(which is all of them)
+to also fail due to `PoisonError`s. They can be safely ignored.
+
+### Using `gtest` (Treeherder symbol `GTest` (a build task))
+
+Because Gecko symbols aren't built for the
+`rusttests` build,
+any test that is written for code that uses Gecko symbols should be written as a
+[`gtest`](https://github.com/google/googletest)
+in `toolkit/components/glean/tests/gtest/`.
+You can write the actual test code in Rust.
+It needs to be accompanied by a C++ GTest that calls a C FFI-exported Rust function.
+See [Testing & Debugging Rust Code](/testing-rust-code/index.md) for more.
+See [`toolkit/components/glean/tests/gtest/TestFog.cpp`](https://searchfox.org/mozilla-central/source/toolkit/components/glean/tests/gtest/TestFog.cpp)
+and [`toolkit/components/glean/tests/gtest/test.rs`](https://searchfox.org/mozilla-central/source/toolkit/components/glean/tests/gtest/test.rs)
+for an example.
+
+By necessity these can only be integration tests against the compiled crate.
+
+**Note:** When adding a new test file, don't forget to add it to
+`toolkit/components/glean/tests/gtest/moz.build` and use the
+`FOG` prefix in your test names
+(e.g. `TEST(FOG, YourTestName) { ... }`).
+
+To run FOG's Rust `gtest` suite use `mach gtest FOG.*`
+
+## Python (Treeherder symbol `py3(fp)` aka `source-test-python-fog`)
+
+The [Glean Parser](https://github.com/mozilla/glean_parser/)
+has been augmented to generate FOG-specific APIs for Glean metrics.
+This augmentation is tested by running:
+
+`mach test toolkit/components/glean/tests/pytest`
+
+These tests require Python 3+.
+If your default Python is Python 2, you may need to instead run:
+
+`python3 mach python-test toolkit/components/glean/tests/pytest`
+
+These tests check the code generator output against known good file contents.
+If you change the code generator the files will need an update.
+Run the test suite with the `UPDATE_EXPECT` environment variable set to do that automatically:
+
+`UPDATE_EXPECT=1 mach test toolkit/components/glean/tests/pytest`
+
+## C++ (Treeherder symbol `GTest` (a build task))
+
+To test the C++ parts of FOG's implementation
+(like metric types)
+you should use `gtest`.
+FOG's `gtest` tests are in
+[`gtest/`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/gtest/).
+
+You can either add a test case to an existing file or add a new file.
+If you add a new file, remember to add it to the
+[`moz.build`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/gtest/moz.build))
+or the test runner won't be able to find it.
+
+All tests should start with `FOG` so that all tests are run with
+`./mach gtest FOG*`.
+
+## JS (Treeherder symbol `X(Xn)` for some number `n`)
+
+To test the JS parts of FOG's implementation
+(like metric types)
+you should use `xpcshell`.
+FOG's `xpcshell` tests are in
+[`xpcshell/`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/xpcshell).
+
+You can either add a test case to an existing file or add a new file.
+If you add a new file, remember to add it to the
+[`xpcshell.ini`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/xpcshell/xpcshell.ini)
+or the test runner will not be able to find it.
+
+To run FOG's JS tests, run:
+`./mach test toolkit/components/glean/tests/xpcshell`
+
+## Non-content-process multiprocess (Browser Chrome Mochitests with Treeherder symbol `M(bcN)` for some number `N`)
+
+To test e.g. the GPU process support you need a full Firefox browser:
+xpcshell doesn't have the flexibility.
+To test that and have access to privileged JS (i.e. `Glean` and `FOG` APIs),
+we use browser-chrome-flavoured mochitests you can find in
+[`browser/`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/browser).
+
+If you need to add a new test file, remember to add it to the
+[`browser.ini`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/glean/tests/browser/browser.ini)
+manifest, or the test runner will not be able to find it.
+
+To run FOG's browser chrome tests, run:
+`./mach test toolkit/components/glean/tests/browser`
+
+## Integration (Marionette, borrowing `telemetry-tests-client` Treeherder symbol `tt(c)`)
+
+To test pings (See [bug 1681742](https://bugzilla.mozilla.org/show_bug.cgi?id=1681742))
+or anything that requires one or more full browsers running,
+we use the `telemetry-tests-client` suite in
+[`toolkit/components/telemetry/tests/marionette/tests/client/`](https://hg.mozilla.org/mozilla-central/file/tip/toolkit/components/telemetry/tests/marionette/tests/client/).
+
+For more information on this suite, look to
+[Firefox Telemetry's Test Documentation](https://firefox-source-docs.mozilla.org/toolkit/components/telemetry/internals/tests.html#integration-tests-telemetry-tests-client-and-telemetry-integration-tests)
+and
+[Marionette's Documentation](/testing/marionette/Testing.md).
+
+To run these integration tests, run:
+`./mach telemetry-tests-client toolkit/components/telemetry/tests/marionette/tests/client/`
+
+To capture the Firefox under test's logs, use the `--gecko-log` parameter.
+For example, to echo to stdout:
+`./mach telemetry-tests-client toolkit/components/telemetry/tests/marionette/tests/client/test_fog* --gecko-log "-"`
+
+**Note:** Running the `tt(c)` suite in this way ignored skip directives in the manifest.
+This means that you might run tests that are not expected to succeed on your platform.
+Check `toolkit/components/telemetry/tests/marionette/tests/client/manifest.ini` for details.
diff --git a/toolkit/components/glean/docs/dev/updating_parser.md b/toolkit/components/glean/docs/dev/updating_parser.md
new file mode 100644
index 0000000000..4609f76a80
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/updating_parser.md
@@ -0,0 +1,52 @@
+# Updating glean_parser
+
+Project FOG uses the `glean_parser` to generate code from metric definitions.
+It depends on [glean-parser] from pypi.org
+
+[glean-parser]: https://pypi.org/project/glean-parser/
+
+To update the in-tree glean-parser change the version in `third_party/python/requirements.in`,
+then run
+
+```
+./mach vendor python
+```
+
+```{note}
+**Important**: the glean_parser and all of its dependencies must support Python 3.5, as discussed here.
+This is the minimum version supported by mach and installed on the CI images for running tests.
+This is enforced by the version ranges declared in the Python installation manifest.
+```
+
+## Version mismatch of the Python dependencies
+
+The logic for handling version mismatches is very similar to the one for the Rust crates.
+See [Updating the Glean SDK](updating_sdk.md) for details.
+However, updating Python packages also requires to think about Python 3.5 (and Python 2, still) compatibility.
+
+## Keeping versions in sync
+
+The Glean SDK and `glean_parser` are currently released as separate projects.
+However each Glean SDK release requires a specific `glean_parser` version.
+When updating one or the other ensure versions stay compatible.
+You can find the currently used `glean_parser` version in the Glean SDK source tree, e.g. in [sdk_generator.sh].
+
+[sdk_generator.sh]: https://github.com/mozilla/glean/blob/main/glean-core/ios/sdk_generator.sh#L28
+
+## Using a local `glean_parser` development version
+
+To test out a new `glean_parser` in mozilla-central follow these steps:
+
+1. Remove `glean_parser` from the user-wide virtual environment.
+   This can be found in a path like `~/.mozbuild/srcdirs/gecko-f5e3b9c6ded5/_virtualenvs/mach/lib/python3.10/site-packages/glean_parser`
+   Note that the `gecko-f5e3b9c6ded5` part will be different depending on your local checkout.
+   Remove all directories and files mentioning `glean_parser`
+2. Remove `glean_parser` from the build virtual enviromment.
+   This can be found in `$MOZ_OBJDIR/_virtualenvs/common/lib/python3.6/site-packages/glean_parser`.
+   Note that `$MOZ_OBJDIR` depends on your local mozconfig configuration.
+   Remove all directories and files mentioning `glean_parser`
+3. Copy the local `glean_parser` checkout into `third_party/python/glean_parser`.
+   E.g. `cp ~/code/glean_parser $GECKO/third_party/python/glean_parser`.
+
+You should now be able to build `mozilla-central` and it will use the modified `glean_parser`.
+You can make further edits in `$GECKO/third_party/python/glean_parser`.
diff --git a/toolkit/components/glean/docs/dev/updating_sdk.md b/toolkit/components/glean/docs/dev/updating_sdk.md
new file mode 100644
index 0000000000..fafec08d39
--- /dev/null
+++ b/toolkit/components/glean/docs/dev/updating_sdk.md
@@ -0,0 +1,48 @@
+# Updating the Glean SDK
+
+Project FOG uses the Glean SDK published as the [`glean`][glean-crate]
+and [`glean-core`][glean-core] crates on crates.io.
+
+[glean-crate]: https://crates.io/crates/glean
+[glean-core]: https://crates.io/crates/glean-core
+
+These two crates' versions are included in several places in mozilla-central.
+To update them all, you should use the command
+`mach update-glean <version, like "54.1.0">`.
+
+This is a semi-manual process.
+Please pay attention to the output of `mach update-glean` for instructions,
+and follow them closely.
+
+## Version mismatches of Rust dependencies
+
+Other crates that are already vendored might require a different version of the same dependencies that the Glean SDK requires.
+The general strategy for Rust dependencies is to keep one single version of the dependency in-tree
+(see [comment #8 in bug 1591555](https://bugzilla.mozilla.org/show_bug.cgi?id=1591555#c8)).
+This might be hard to do in reality since some dependencies might require tweaks in order to work.
+The following strategy can be followed to decide on version mismatches:
+
+* If the versions only **differ by the patch version**, Cargo will keep the vendored version,
+  unless some other dependency pinned specific patch versions;
+  assuming it doesn’t break the Glean SDK;
+  if it does, follow the next steps;
+* If the version of the **vendored dependency is newer** (greater major or minor version) than the version required by the Glean SDK,
+  [file a bug in the Glean SDK component][glean-bug] to get Glean to require the same version;
+    * You will have to abandon updating the Glean SDK to this version.
+      You will have to wait for Glean SDK to update its dependency and for a new Glean SDK release.
+      Then you will have to update to that new Glean SDK version.
+* If the version of the **vendored dependency is older** (lower major or minor version), consider updating the vendored version to the newer one;
+  seek review from the person who vendored that dependency in the first place;
+  if that is not possible or breaks mozilla-central build, then consider keeping both versions vendored in-tree; please note that this option will probably only be approved for small crates,
+  and will require updating the `TOLERATED_DUPES` list in `mach vendor`
+  (instructions are provided as you go).
+
+## Keeping versions in sync
+
+The Glean SDK and `glean_parser` are currently released as separate projects.
+However each Glean SDK release requires a specific `glean_parser` version.
+When updating one or the other ensure versions stay compatible.
+You can find the currently used `glean_parser` version in the Glean SDK source tree, e.g. in [sdk_generator.sh].
+
+[sdk_generator.sh]: https://github.com/mozilla/glean/blob/main/glean-core/ios/sdk_generator.sh#L28
+[glean-bug]: https://bugzilla.mozilla.org/enter_bug.cgi?product=Data+Platform+and+Tools&component=Glean%3A+SDK&priority=P3&status_whiteboard=%5Btelemetry%3Aglean-rs%3Am%3F%5D
diff --git a/toolkit/components/glean/docs/index.md b/toolkit/components/glean/docs/index.md
new file mode 100644
index 0000000000..c9d8f42eb4
--- /dev/null
+++ b/toolkit/components/glean/docs/index.md
@@ -0,0 +1,30 @@
+# Firefox on Glean (FOG)
+
+Firefox on Glean (FOG) is the name of the layer that integrates the
+[Glean SDK][glean-sdk] into
+[Firefox Desktop](https://www.firefox.com/).
+
+The [Glean SDK][glean-sdk]
+is a data collection library built by Mozilla for use in its products.
+Like [Telemetry][telemetry], it can be used to
+(in accordance with our [Privacy Policy][privacy-policy])
+send anonymous usage statistics to Mozilla in order to make better decisions.
+
+If you have any questions,
+please reach out to the team on
+[#glean:mozilla.org][glean-matrix].
+
+```{toctree}
+:titlesonly:
+:maxdepth: 2
+:glob:
+
+user/index
+dev/index
+```
+
+[telemetry]: ../telemetry/index
+[glean-sdk]: https://github.com/mozilla/glean/
+[book-of-glean]: https://mozilla.github.io/glean/book/index.html
+[privacy-policy]: https://www.mozilla.org/privacy/
+[glean-matrix]: https://chat.mozilla.org/#/room/#glean:mozilla.org
diff --git a/toolkit/components/glean/docs/user/getting_started.md b/toolkit/components/glean/docs/user/getting_started.md
new file mode 100644
index 0000000000..50b955bced
--- /dev/null
+++ b/toolkit/components/glean/docs/user/getting_started.md
@@ -0,0 +1,97 @@
+# Getting Started with Firefox on Glean (FOG)
+
+This documentation is designed to be helpful to those who are
+* New to data collection in Firefox Desktop,
+* Experienced with data collection in Firefox Desktop, but not the Glean kind
+* Those who are just interested in a refresher.
+
+## What is FOG?
+
+Firefox on Glean (FOG) is the library that brings
+[the Glean SDK](https://mozilla.github.io/glean/book/index.html),
+Mozilla's modern data collection system,
+to Firefox Desktop.
+
+FOG's code is in `toolkit/components/glean` and is considered part of the
+`Toolkit :: Telemetry` [module][modules].
+Bugs against FOG can be [filed][file-fog-bugs]
+in Bugzilla in the `Toolkit` product and the `Telemetry` component.
+(No bugs about adding new instrumentation, please.
+You can file those in the components that you want instrumented.)
+You can find folks who can help answer your questions about FOG in
+* [#glean:mozilla.org](https://chat.mozilla.org/#/room/#glean:mozilla.org)
+* [#telemetry:mozilla.org](https://chat.mozilla.org/#/room/#telemetry:mozilla.org)
+* Slack#data-help
+
+On top of the usual things Glean embedders supply
+(user engagement monitoring, network upload configuration, data upload preference watching, ...)
+FOG supplies Firefox-Desktop-specific things:
+* Privileged JS API
+* C++ API
+* IPC
+* Test Preferences
+* Support for `xpcshell`, browser-chrome mochitests, GTests, and rusttests
+* `about:glean`
+* ...and more.
+
+## What do I need to know about Glean?
+
+You use the APIs supplied by the Glean SDK to instrument Mozilla projects.
+
+The unit of instrumentation is the **metric**.
+Recording the number of times a user opens a new tab? That's a metric.
+Timing how long each JS garbage collector pass takes? Also a metric.
+
+Glean has documentation about
+[how to add a new metric][add-a-metric]
+that you should follow to learn how to add a metric to instrument Firefox Desktop.
+There are some [peculiarities specific to Firefox Desktop](new_definitions_file)
+that you'll wish to review as well.
+Don't forget to get [Data Collection Review][data-review]
+for any new or expanded data collections in mozilla projects.
+
+By adding a metric you've told the Glean SDK what shape of instrumentation you want.
+And by using the metric's APIs to instrument your code,
+you've put your interesting data into that metric.
+But how does the data leave Firefox Desktop and make it to Mozilla's Data Pipeline?
+
+Batches of related metrics are collected into **pings**
+which are submitted according to their specific schedules.
+If you don't say otherwise, any non-`event`-metric will be sent in the
+[built-in Glean "metrics" ping][metrics-ping] about once a day.
+(`event` metrics are sent in [the "events" ping][events-ping]
+more frequently than that).
+
+With data being sent to Mozilla's Data Pipeline, how do you analyse it?
+
+That's an impossible question to answer completely without knowing a _lot_ about what questions you want to answer.
+However, in general, if you want to see what data is being collected by your instrumentation,
+[go to its page in Glean Dictionary][glean-dictionary]
+and you'll find links and information there about how to proceed.
+
+## Where do I learn more?
+
+Here in the [FOG User Documentation](./index) you will find FOG-specific details like
+[how to write instrumentation tests](instrumentation_tests), or
+[how to use Glean APIs to mirror data to Telemetry](gifft).
+
+Most of what you should have to concern yourself with, as an instrumentor,
+is documented in [the Book of Glean](https://mozilla.github.io/glean/book/index.html).
+Such as its [illuminating glossary][glean-glossary],
+the [list of all metric types][metrics-types],
+or the index of our long-running blog series [This Week in Glean][twig-index].
+
+And for anything else you need help with, please find us in
+[#glean:mozilla.org](https://chat.mozilla.org/#/room/#glean:mozilla.org).
+We'll be happy to help you learn more about FOG and Glean.
+
+[add-a-metric]: https://mozilla.github.io/glean/book/user/metrics/adding-new-metrics.html
+[metrics-ping]: https://mozilla.github.io/glean/book/user/pings/metrics.html
+[events-ping]: https://mozilla.github.io/glean/book/user/pings/events.html
+[modules]: https://wiki.mozilla.org/Modules/All
+[data-review]: https://wiki.mozilla.org/Data_Collection
+[glean-dictionary]: https://dictionary.telemetry.mozilla.org/
+[glean-glossary]: https://mozilla.github.io/glean/book/appendix/glossary.html
+[twig-index]: https://mozilla.github.io/glean/book/appendix/twig.html
+[metrics-types]: https://mozilla.github.io/glean/book/reference/metrics/index.html
+[file-fog-bugs]: https://bugzilla.mozilla.org/enter_bug.cgi?product=Toolkit&component=Telemetry
diff --git a/toolkit/components/glean/docs/user/gifft.md b/toolkit/components/glean/docs/user/gifft.md
new file mode 100644
index 0000000000..892805f5c0
--- /dev/null
+++ b/toolkit/components/glean/docs/user/gifft.md
@@ -0,0 +1,223 @@
+# Glean Interface For Firefox Telemetry (GIFFT)
+
+To make Migration from Firefox Telemetry to Glean easier,
+the C++ and JS Glean API can be configured
+(on a metric-by-metric basis)
+to mirror data collection to both the Glean metric and a Telemetry probe.
+
+GIFFT should ideally be used only when the data you require for analysis still mostly lives in Telemetry,
+and should be removed promptly when no longer needed.
+Instrumentors are encouraged to have the Telemetry mirror probe expire within six versions.
+(As always you can renew an expiring probe if you're still using it,
+but this will help us get closer to the time when we eventually turn Telemetry off.)
+
+**Note:** GIFFT only works for data provided via C++ or JS.
+Rust Glean metrics APIs will not mirror to Telemetry as Telemetry does not have a Rust API.
+
+**Note:** Using the Glean API replaces the Telemetry API.
+Do not use any mix of the two APIs for the same probe.
+
+## How to Mirror a Glean Metric to a Firefox Telemetry Probe
+
+For the mirror to work, you need three things:
+* A compatible Glean metric (defined in a `metrics.yaml`)
+* A compatible Telemetry probe
+  (defined in `Histograms.json`, `Scalars.yaml`, or `Events.yaml`)
+* A `telemetry_mirror` property on the Glean metric definition identifying the Telemetry probe
+
+### Compatibility
+
+This compatibility table explains which Telemetry probe types can be mirrors for which Glean metric types:
+
+| Glean Metric Type | Telementry Probe Type |
+| ----------------- | --------------------- |
+| [boolean](https://mozilla.github.io/glean/book/user/metrics/boolean.html) | [Scalar of kind: boolean](/toolkit/components/telemetry/collection/scalars.rst) |
+| [labeled_boolean](https://mozilla.github.io/glean/book/user/metrics/labeled_booleans.html) | [Keyed scalar of kind: boolean](/toolkit/components/telemetry/collection/scalars.rst) |
+| [counter](https://mozilla.github.io/glean/book/user/metrics/counter.html) | [Scalar of kind: uint](/toolkit/components/telemetry/collection/scalars.rst) |
+| [labeled_counter](https://mozilla.github.io/glean/book/user/metrics/labeled_counters.html) | [Keyed Scalar of kind: uint](/toolkit/components/telemetry/collection/scalars.rst) |
+| [string](https://mozilla.github.io/glean/book/user/metrics/string.html) | [Scalar of kind: string](/toolkit/components/telemetry/collection/scalars.rst) |
+| [labeled_string](https://mozilla.github.io/glean/book/user/metrics/labeled_strings.html) | *No Supported Telemetry Type* |
+| [string_list](https://mozilla.github.io/glean/book/user/metrics/string_list.html) | [Keyed Scalar of kind: boolean](/toolkit/components/telemetry/collection/scalars.rst). The keys are the strings. The values are all `true`. Calling `Set` on the labeled_string is not mirrored (since there's no way to remove keys from a keyed scalar of kind boolean). Doing so will log a warning. |
+| [timespan](https://mozilla.github.io/glean/book/user/metrics/timespan.html) | [Scalar of kind: uint](/toolkit/components/telemetry/collection/scalars.rst). The value is in units of milliseconds. |
+| [timing_distribution](https://mozilla.github.io/glean/book/user/metrics/timing_distribution.html) | [Histogram of kind "linear" or "exponential"](/toolkit/components/telemetry/collection/histograms.rst#exponential). Samples will be in units of milliseconts. |
+| [memory_distribution](https://mozilla.github.io/glean/book/user/metrics/memory_distribution.html) | [Histogram of kind "linear" or "exponential"](/toolkit/components/telemetry/collection/histograms.rst#exponential). Samples will be in `memory_unit` units. |
+| [custom_distribution](https://mozilla.github.io/glean/book/user/metrics/custom_distribution.html) | [Histogram of kind "linear" or "exponential"](/toolkit/components/telemetry/collection/histograms.rst#exponential). Samples will be used as is. Ensure the bucket count and range match. |
+| [uuid](https://mozilla.github.io/glean/book/user/metrics/uuid.html) | [Scalar of kind: string](/toolkit/components/telemetry/collection/scalars.rst). Value will be in canonical 8-4-4-4-12 format. Value is not guaranteed to be valid, and invalid values may be present in the mirrored scalar while the uuid metric remains empty. Calling `GenerateAndSet` on the uuid is not mirrored, and will log a warning. |
+| [url](https://mozilla.github.io/glean/book/user/metrics/url.html) | [Scalar of kind: string](/toolkit/components/telemetry/collection/scalars.rst). The stringified Url will be cropped to the maximum length allowed by the legacy type. |
+| [datetime](https://mozilla.github.io/glean/book/user/metrics/datetime.html) | [Scalar of kind: string](/toolkit/components/telemetry/collection/scalars.rst). Value will be in ISO8601 format. |
+| [events](https://mozilla.github.io/glean/book/user/metrics/event.html) | [Events](/toolkit/components/telemetry/collection/events.rst). The `value` field will be left empty.  |
+| [quantity](https://mozilla.github.io/glean/book/user/metrics/quantity.html) | [Scalar of kind: uint](/toolkit/components/telemetry/collection/scalars.rst) |
+| [rate](https://mozilla.github.io/glean/book/user/metrics/rate.html) | [Keyed Scalar of kind: uint](/toolkit/components/telemetry/collection/scalars.rst). The keys are "numerator" and "denominator". Does not work for `rate` metrics with external denominators. |
+
+### The `telemetry_mirror` property in `metrics.yaml`
+
+You must use the C++ enum identifier of the Histogram, Scalar, or Event being mirrored to:
+* For Histograms, the Telemetry C++ enum identifier is the histogram's name
+    * e.g. The C++ enum identifier for `WR_RENDERER_TIME` is
+      `WR_RENDERER_TIME` (see {searchfox}`gfx/metrics.yaml`)
+* For Scalars, the Telemetry C++ enum identifier is the Scalar category and name in
+  `SCREAMING_SNAKE_CASE` with any `.` replaced with `_`
+    * e.g. The enum identifier for `extensions.startupCache.load_time` is
+      `EXTENSIONS_STARTUPCACHE_LOAD_TIME` (see {searchfox}`toolkit/components/extensions/metrics.yaml`)
+* For Events, the Telemetry C++ enum identifier is the Event category, method, and object
+  rendered in `Snakey_CamelCase`.
+    * e.g. The enum identifier for `page_load.toplevel#content` is
+      `Page_load_Toplevel_Content` (see {searchfox}`dom/metrics.yaml`)
+
+If you use the wrong enum identifier, this will manifest as a build error.
+
+If you are having trouble finding the correct conjugation for the mirror Telemetry probe,
+you can find the specific value in the list of all Telemetry C++ enum identifiers in
+`<objdir>/toolkit/components/telemetry/Telemetry{Histogram|Scalar|Event}Enums.h`.
+(Choose the file appropriate to the type of the Telemetry mirror.)
+
+## Artifact Build Support
+
+Sadly, GIFFT does not support Artifact builds.
+You must build Firefox when you add the mirrored metric so the C++ enum value is present,
+even if you only use the metric from Javascript.
+
+## Analysis Gotchas
+
+Firefox Telemetry and the Glean SDK are very different.
+Though GIFFT bridges the differences as best it can,
+there are many things it cannot account for.
+
+These are a few of the ways that differences between Firefox Telemetry and the Glean SDK might manifest as anomalies during analysis.
+
+### Processes, Products, and Channels
+
+Like Firefox on Glean itself,
+GIFFT doesn't know what process, product, or channel it is recording in.
+Telemetry does, and imposes restrictions on which probes can be recorded to and when.
+
+Ensure that the following fields in any Telemetry mirror's definition aren't too restrictive for your use:
+* `record_in_processes`
+* `products`
+* `release_channel_collection`/`releaseChannelCollection`
+
+A mismatch won't result in an error.
+If you, for example,
+record to a Glean metric in a release channel that the Telemetry mirror probe doesn't permit,
+then the Glean metric will have a value and the Telemetry mirror probe won't.
+
+Also recall that Telemetry probes split their values across processes.
+[Glean metrics do not](../dev/ipc.md).
+This may manifest as curious anomalies when comparing the Glean metric to its Telemetry mirror probe.
+Ensure your analyses are aggregating Telemetry values from all processes,
+or define and use process-specific Glean metrics and Telemetry mirror probes to keep things separate.
+
+### Pings
+
+Glean and Telemetry both send their built-in pings on their own schedules.
+This means the values present in these pings may not agree since they reflect state at different time.
+
+For example, if you are measuring "Number of Monitors" with a
+[`quantity`](https://mozilla.github.io/glean/book/user/metrics/quantity.html)
+sent by default in the Glean "metrics" ping mirrored to a
+[Scalar of kind: uint](/toolkit/components/telemetry/collection/scalars.rst)
+sent by default in the Telemetry "main" ping,
+then if the user plugs in a second monitor between midnight
+(when Telemetry "main" pings with reason "daily" are sent) and 4AM
+(when Glean "metrics" pings with reason "today" are sent),
+the value in the `quantity` will be `2`
+while the value in the Scalar of kind: uint will be `1`.
+
+If the metric or mirrored probe are sent in Custom pings,
+the schedules could line up exactly or be entirely unrelated.
+
+### Labels
+
+Labeled metrics supported by GIFFT
+(`labeled_boolean` and `labeled_counter`)
+adhere to the Glean SDK's
+[label format](https://mozilla.github.io/glean/book/user/metrics/index.html#label-format).
+
+Keyed Scalars, on the other hand, do not have a concept of an "Invalid key".
+Firefox Telemetry will accept just about any sequence of bytes as a key.
+
+This means that a label deemed invalid by the Glean SDK may appear in the mirrored probe's data.
+For example, using `InvalidLabel` as a label that doesn't conform to the format
+(it has upper-case letters)
+see that the `labeled_boolean` metric
+[correctly ascribes it to `__other__`](https://mozilla.github.io/glean/book/user/metrics/index.html#labeled-metrics)
+whereas the mirrored Keyed Scalar with kind boolean stores and retrieves it without change:
+```js
+Glean.testOnly.mirrorsForLabeledBools.InvalidLabel.set(true);
+Assert.equal(true, Glean.testOnly.mirrorsForLabeledBools.__other__.testGetValue());
+let snapshot = Services.telemetry.getSnapshotForKeyedScalars().parent;
+Assert.equal(true, snapshot["telemetry.test.mirror_for_labeled_bool"]["InvalidLabel"]);
+```
+
+### Telemetry Events
+
+A Glean event can be mirrored to a Telemetry Event.
+Telemetry Events must be enabled before they can be recorded to via the API
+`Telemetry.setEventRecordingEnabled(category, enable);`.
+If the Telemetry Event isn't enabled,
+recording to the Glean event will still work,
+and the event will be Summarized in Telemetry as all disabled events are.
+
+See
+[the Telemetry Event docs](/toolkit/components/telemetry/collection/events.rst)
+for details on how disabled Telemetry Events behave.
+
+### Numeric Values
+
+The arguments and storage formats for Glean's numeric types
+(`counter`, `labeled_counter`, `quantity`, `rate`, and `timespan`)
+are different from Telemetry's numeric type
+(Scalar of kind `uint`).
+
+This results in a few notable differences.
+
+#### Saturation and Overflow
+
+`counter`, `labeled_counter`, and `rate` metrics are stored as 32-bit signed values.
+`quantity` metrics are stored as 64-bit signed values.
+`timing_distribution` samples can be 64-bit signed values.
+All of these Glean numeric metric types saturate at their maximum representable value,
+or according to the Limits section of the Glean metric type documentation.
+
+Scalars of kind `uint` are stored as 32-bit unsigned values.
+They will overflow if they exceed the value $2^{32} - 1$.
+
+If a Glean numeric type saturates, it will record an error of type `invalid_overflow`.
+In your analyses please check for these errors.
+
+#### Quantity Value Over-size
+
+Values greater than $2^{32} - 1$ passed to a `quantity` metric's
+`set()` method will be clamped to $2^{32} - 1$ before being passed to the metric's Telemetry mirror.
+
+#### Negative Values
+
+Values less than 0 passed to any numeric metric type's API will not be passed on to the Telemetry mirror.
+This avoids small negative numbers being cast into a stunningly large numbers,
+and keeps the Telemetry mirror's value closer to that of the Glean metric.
+
+#### Long Time Spans
+
+If the number of milliseconds between calls to a
+`timespan` metric's `start()` and `stop()` methods exceeds $2^{32} - 1$,
+the value passed to the metric's Telemetry mirror will be clamped to $2^{32} - 1$.
+
+The same happens for samples in `timing_distribution` metrics:
+values passed to the Telemetry mirror histogram will saturate at $2^{32} - 1$
+until they get past $2^{64}$ when they'll overflow.
+
+### App Shutdown
+
+Telemetry only works up to
+[`ShutdownPhase::AppShutdownTelemetry` aka `profile-before-change-telemetry`][app-shutdown].
+Telemetry data recorded after that phase just aren't persisted.
+
+FOG _presently_ shuts down Glean in a later phase,
+and so is able to collect data deeper into shutdown.
+(The particular phase is not presently something anyone's asked us to guarantee,
+so that's why I'm not being precise.)
+
+What this means is that, for data recorded later in shutdown,
+Glean will report more complete information than Telemetry will.
+
+[app-shutdown]: https://searchfox.org/mozilla-central/source/xpcom/base/AppShutdown.cpp#57
diff --git a/toolkit/components/glean/docs/user/index.md b/toolkit/components/glean/docs/user/index.md
new file mode 100644
index 0000000000..79b4163a44
--- /dev/null
+++ b/toolkit/components/glean/docs/user/index.md
@@ -0,0 +1,17 @@
+# Using Firefox on Glean
+
+This section of docs is designed to be helpful to people instrumenting Firefox Desktop.
+You may wish to begin with the [Getting Started](./getting_started.md) docs.
+Or, if you're already acquainted with Glean concepts and what FOG is,
+you might want to know [how to migrate a piece of Firefox Telemetry to Glean](migration).
+
+```{toctree}
+:titlesonly:
+:maxdepth: 1
+:glob:
+
+getting_started
+new_definitions_file
+*
+Glean SDK Documentation <https://mozilla.github.io/glean/book/index.html>
+```
diff --git a/toolkit/components/glean/docs/user/instrumentation_tests.md b/toolkit/components/glean/docs/user/instrumentation_tests.md
new file mode 100644
index 0000000000..ed28c6d4e8
--- /dev/null
+++ b/toolkit/components/glean/docs/user/instrumentation_tests.md
@@ -0,0 +1,224 @@
+# Writing Instrumentation Tests
+
+```{admonition} Old Glean Proverb
+If it's important enough to be instrumented, it's important enough to be tested.
+```
+
+All metrics and pings in the Glean SDK have [well-documented APIs for testing][glean-metrics-apis].
+You'll want to familiarize yourself with `TestGetValue()`
+(here's [an example JS (xpcshell) test of some metrics][metrics-xpcshell-test])
+for metrics and
+[`TestBeforeNextSubmit()`][test-before-next-submit]
+(here's [an example C++ (gtest) test of a custom ping][ping-gtest])
+for pings.
+
+All test APIs are available in all three of FOG's supported languages:
+Rust, C++, and JavaScript.
+
+But how do you get into a position where you can even call these test APIs?
+How do they fit in with Firefox Desktop's testing frameworks?
+
+## Manual Testing and Debugging
+
+The Glean SDK has [debugging capabilities][glean-debug]
+for manually verifying that instrumentation makes it to Mozilla's Data Pipeline.
+Firefox Desktop supports these via environment variables _and_
+via the interface on `about:glean`.
+
+This is all well and good for getting a good sense check that things are going well _now_,
+but in order to check that everything stays good through the future,
+you're going to want to write some automated tests.
+
+## General Things To Bear In Mind
+
+* You may see values from previous tests persist across tests because the profile directory was shared between test cases.
+    * You can reset Glean before your test by calling
+      `Services.fog.testResetFOG()` (in JS).
+    * You shouldn't have to do this in C++ or Rust since there you should use the
+      `FOGFixture` test fixture.
+* If your metric is based on timing (`timespan`, `timing_distribution`),
+  do not expect to be able to assert the correct timing value.
+  Glean does a lot of timing for you deep in the SDK, so unless you mock the system's monotonic clock,
+  do not expect the values to be predictable.
+    * Instead, check that a value is `> 0` or that the number of samples is expected.
+    * You might be able to assert that the value is at least as much as a known, timed value,
+    but beware of rounding.
+* Errors in instrumentation APIs do not panic, throw, or crash.
+  But Glean remembers that the errors happened.
+    * Test APIs, on the other hand, are permitted
+      (some may say "encouraged")
+      to panic, throw, or crash on bad behaviour.
+    * If you call a test API and it panics, throws, or crashes,
+      that means your instrumentation did something wrong.
+      Check your test logs for details about what went awry.
+
+## The Usual Test Format
+
+Instrumentation tests tend to follow the same three-part format:
+1) Assert no value in the metric
+2) Express behaviour
+3) Assert correct value in the metric
+
+Your choice of test suite will depend on how the instrumented behaviour can be expressed.
+
+
+## `xpcshell` Tests
+
+If the instrumented behaviour is on the main or content process and can be called from privileged JS,
+`xpcshell` is an excellent choice.
+
+`xpcshell` is so minimal an environment, however, that
+(pending [bug 1756055](https://bugzilla.mozilla.org/show_bug.cgi?id=1756055))
+you'll need to manually tell it you need two things:
+1) A profile directory
+2) An initialized FOG
+
+```js
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_setup(function test_setup() {
+  // FOG needs a profile directory to put its data in.
+  do_get_profile();
+
+  // FOG needs to be initialized in order for data to flow.
+  Services.fog.initializeFOG();
+});
+```
+
+From there, just follow The Usual Test Format:
+
+```js
+add_task(function test_instrumentation() {
+  // 1) Assert no value
+  Assert.equal(undefined, Glean.myMetricCategory.myMetricName.testGetValue());
+
+  // 2) Express behaviour
+  // ...<left as an exercise to the reader>...
+
+  // 3) Assert correct value
+  Assert.equal(kValue, Glean.myMetricCategory.myMetricName.testGetValue());
+});
+```
+
+If your new instrumentation includes a new custom ping,
+there are two small additions to The Usual Test Format:
+
+* 1.1) Call `testBeforeNextSubmit` _before_ your ping is submitted.
+  The callback you register in `testBeforeNextSubmit`
+  is called synchronously with the call to the ping's `submit()`.
+* 3.1) Check that the ping actually was submitted.
+  If all your Asserts are inside `testBeforeNextSubmit`'s closure,
+  another way this test could pass is by not running any of them.
+
+```js
+add_task(function test_custom_ping() {
+  // 1) Assert no value
+  Assert.equal(undefined, Glean.myMetricCategory.myMetricName.testGetValue());
+
+  // 1.1) Set up Step 3.
+  let submitted = false;
+  GleanPings.myPing.testBeforeNextSubmit(reason => {
+    submitted = true;
+    // 3) Assert correct value
+    Assert.equal(kExpectedReason, reason, "Reason of submitted ping must match.");
+    Assert.equal(kExpectedMetricValue, Glean.myMetricCategory.myMetricName.testGetValue());
+  });
+
+  // 2) Express behaviour that sends a ping with expected reason and contents
+  // ...<left as an exercise to the reader>...
+
+  // 3.1) Check that the ping actually was submitted.
+  Assert.ok(submitted, "Ping was submitted, callback was called.");
+});
+```
+
+(( We acknowledge that this isn't the most ergonomic form.
+Please follow
+[bug 1756637](https://bugzilla.mozilla.org/show_bug.cgi?id=1756637)
+for updates on a better design and implementation for ping tests. ))
+
+## mochitest
+
+`browser-chrome`-flavoured mochitests can be tested very similarly to `xpcshell`.
+
+Prefer `xpcshell` and only use mochitests if you cannot express the behaviour in `xpcshell`.
+This can happen, for example, if the behaviour happens on a non-main process.
+
+### IPC
+
+All test APIs must be called on the main process
+(they'll assert otherwise).
+But your instrumentation might be on any process, so how do you test it?
+
+In this case there's a slight addition to the Usual Test Format:
+1) Assert no value in the metric
+2) Express behaviour
+3) _Flush all pending FOG IPC operations with `Services.fog.testFlushAllChildren()`_
+4) Assert correct value in the metric.
+
+## GTests/Google Tests
+
+Please make use of the `FOGFixture` fixture when writing your tests, like:
+
+```cpp
+TEST_F(FOGFixture, MyTestCase) {
+  // 1) Assert no value
+  ASSERT_EQ(mozilla::Nothing(),
+            my_metric_category::my_metric_name.TestGetValue());
+
+  // 2) Express behaviour
+  // ...<left as an exercise to the reader>...
+
+  // 3) Assert correct value
+  ASSERT_EQ(kValue,
+            my_metric_category::my_metric_name.TestGetValue().unwrap().ref());
+}
+```
+
+The fixture will take care of ensuring storage is reset between tests.
+
+## Rust `rusttests`
+
+The general-purpose
+[Testing & Debugging Rust Code in Firefox](/testing-rust-code/index)
+is a good thing to review first.
+
+Unfortunately, FOG requires gecko
+(to tell it where the profile dir is, and other things),
+which means we need to use the
+[GTest + FFI approach](/testing-rust-code/index.html#gtests)
+where GTest is the runner and Rust is just the language the test is written in.
+
+This means your test will look like a GTest like this:
+
+```cpp
+extern "C" void Rust_MyRustTest();
+TEST_F(FOGFixture, MyRustTest) { Rust_MyRustTest(); }
+```
+
+Plus a Rust test like this:
+
+```rust
+#[no_mangle]
+pub extern "C" fn Rust_MyRustTest() {
+    // 1) Assert no value
+    assert_eq!(None,
+               fog::metrics::my_metric_category::my_metric_name.test_get_value(None));
+
+    // 2) Express behaviour
+    // ...<left as an exercise to the reader>...
+
+    // 3) Assert correct value
+    assert_eq!(Some(value),
+               fog::metrics::my_metric_category::my_metric_name.test_get_value(None));
+}
+```
+
+[glean-metrics-apis]: https://mozilla.github.io/glean/book/reference/metrics/index.html
+[metrics-xpcshell-test]: https://searchfox.org/mozilla-central/rev/66e59131c1c76fe486424dc37f0a8a399ca874d4/toolkit/mozapps/update/tests/unit_background_update/test_backgroundupdate_glean.js#28
+[ping-gtest]: https://searchfox.org/mozilla-central/rev/66e59131c1c76fe486424dc37f0a8a399ca874d4/toolkit/components/glean/tests/gtest/TestFog.cpp#232
+[test-before-next-submit]: https://mozilla.github.io/glean/book/reference/pings/index.html#testbeforenextsubmit
+[glean-debug]: https://mozilla.github.io/glean/book/reference/debug/index.html
diff --git a/toolkit/components/glean/docs/user/migration.md b/toolkit/components/glean/docs/user/migration.md
new file mode 100644
index 0000000000..f3c86a182b
--- /dev/null
+++ b/toolkit/components/glean/docs/user/migration.md
@@ -0,0 +1,909 @@
+# Migrating Firefox Telemetry to Glean
+
+This guide aims to help you migrate individual data collections from
+[Firefox Telemetry](/toolkit/components/telemetry/index.rst)
+to
+[Glean][book-of-glean] via [Firefox on Glean](../index.md).
+
+This is intended to be a reference to help you fill out your
+[migration worksheet][migration-worksheet],
+or for mentally translating Telemetry concepts to Glean ones.
+
+```{contents}
+```
+
+## General Things To Bear In Mind
+
+You should familiarize yourself with
+[the guide on adding new metrics to Firefox Desktop](new_definitions_file.md).
+Its advice stacks with the advice included in this guide as
+(once you've figured out what kind) you will indeed be adding new metrics.
+
+There are some other broad topics specific to migrating Firefox Telemetry stuff to Glean stuff:
+
+### Process-Agnosticism: No more `record_in_processes` field
+
+Glean (and thus FOG) [doesn't know anything about processes][ipc-dev-doc]
+except what it has to in order to ensure all the data makes it to the parent process.
+Firefox Telemetry cared very much about which process was collecting which specific data,
+keeping them separate.
+
+If you collect data in multiple processes and wish to keep data from each process type separate,
+you will need to provide this separation yourself.
+
+Please see [this dev doc][ipc-dev-doc] for an example of how to do that.
+
+### Channel-Agnosticism: No more `release_channel_collection: opt-out`
+
+FOG doesn't make a differentiation between pre-release Firefox and release Firefox,
+except inasmuch as is necessary to put the correct channel in `client_info.app_channel`.
+
+This means all data is collected in all build configurations.
+
+If you wish or are required to only collect your data in pre-release Firefox,
+please avail yourself of the `EARLY_BETA_OR_EARLIER` `#define` or `AppConstant`.
+
+### File-level Product Inclusion/Exclusion: No more `products` field
+
+Glean determines which metrics are recorded in which products via
+[a dependency tree][repositories-yaml].
+This means FOG doesn't distinguish between products at the per-product level.
+
+If some of your metrics are recorded in different sets of products
+(e.g. some of your metrics are collected in both Firefox Desktop _and_ Firefox for Android,
+but others are Firefox Desktop-specific)
+you must separate them into separate [definitions files](new_definitions_file.md).
+
+### Many Definitions Files
+
+Each component is expected to own and care for its own
+[metrics definitions files](new_definitions_file.md).
+There is no centralized `Histograms.json` or `Scalars.yaml` or `Events.yaml`.
+
+Instead the component being instrumented will have its own `metrics.yaml`
+(and `pings.yaml` for any [Custom Pings][custom-pings])
+in which you will define the data.
+
+See [this guide](new_definitions_file.md) for details.
+
+### Testing
+
+Firefox Telemetry had very uneven support for testing instrumentation code.
+FOG has much better support. Anywhere you can instrument is someplace you can test.
+
+It's as simple as calling `testGetValue`.
+
+All migrated collections are expected to be tested.
+If you can't test them, then you'd better have an exceptionally good reason why not.
+
+For more details, please peruse the
+[instrumentation testing docs](instrumentation_tests).
+
+## Which Glean Metric Type Should I Use?
+
+Glean uses higher-level metric types than Firefox Telemetry does.
+This complicates migration as something that is "just a number"
+in Firefox Telemetry might map to any number of Glean metric types.
+
+Please choose the most specific metric type that solves your problem.
+This'll make analysis easier as
+1. Others will know more about how to analyse the metric from more specific types.
+2. Tooling will be able to present only relevant operations for more specific types.
+
+Example:
+> In Firefox Telemetry I record the number of monitors attached to the computer that Firefox Desktop is running on.
+> I could record this number as a [`string`][string-metric], a [`counter`][counter-metric],
+> or a [`quantity`][quantity-metric].
+> The `string` is an obvious trap. It doesn't even have the correct data type (string vs number).
+> But is it a `counter` or `quantity`?
+> If you pay attention to this guide you'll learn that `counter`s are used to accumulate sums of information,
+> whereas `quantity` metrics are used to record specific values.
+> The "sum" of monitors over time doesn't make sense, so `counter` is out.
+> `quantity` is the correct choice.
+
+## Histograms
+
+[Histograms][telemetry-histograms]
+are the oldest Firefox Telemetry data type, and as such they've accumulated
+([ha!][histogram-accumulate]) the most ways of being used.
+
+### Scalar Values in Histograms: kind `flag` and `count`
+
+If you have a Histogram that records exactly one value,
+please scroll down and look at the migration guide for the relevant Scalar:
+* For Histograms of kind `flag` see "Scalars of kind `bool`"
+* For Histograms of kind `count` see "Scalars of kind `uint`"
+
+### Continuous Distributions: kind `linear` and `exponential`
+
+If the Histogram you wish to migrate is formed of multiple buckets that together form a single continuous range
+(like you have buckets 1-5, 6-10, 11-19, and 20-50 - they form the range 1-50),
+then you will want a "distribution" metric type in Glean.
+Which kind of "distribution" metric type depends on what the samples are.
+
+#### Timing samples - Use Glean's `timing_distribution`
+
+The most common type of continuous distribution in Firefox Telemetry is a histogram of timing samples like
+[`GC_MS`][gc-ms].
+
+In Glean this sort of data is recorded using a
+[`timing-distribution`][timing-distribution-metric] metric type.
+
+You will no longer need to worry about the range of values or number or distribution of buckets
+(represented by the `low`, `high`, `n_buckets`, or `kind` in your Histogram's definition).
+Glean uses a [clever automatic bucketing algorithm][timing-distribution-metric] instead.
+
+So for a Histogram that records timing samples like this:
+
+```
+  "GC_MS": {
+    "record_in_processes": ["main", "content"],
+    "products": ["firefox", "geckoview_streaming"],
+    "alert_emails": ["dev-telemetry-gc-alerts@mozilla.org", "jcoppeard@mozilla.com"],
+    "expires_in_version": "never",
+    "releaseChannelCollection": "opt-out",
+    "kind": "exponential",
+    "high": 10000,
+    "n_buckets": 50,
+    "bug_numbers": [1636419],
+    "description": "Time spent running JS GC (ms)"
+  },
+```
+
+You will migrate to a `timing_distibution` metric type like this:
+
+```yaml
+js:
+  gc:
+    type: timing_distribution
+    time_unit: millisecond
+    description: |
+      Time spent running the Javascript Garbage Collector.
+      Migrated from Firefox Telemetry's `GC_MS`.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1636419
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1636419#c8
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - dev-telemetry-gc-alerts@mozilla.org
+      - jcoppeard@mozilla.com
+    expires: never
+```
+
+**GIFFT:** This type of collection is mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+
+#### Memory Samples - Use Glean's `memory_distribution`
+
+Another common content of `linear` or `exponential`
+Histograms in Firefox Telemetry is memory samples.
+For example, [`MEMORY_TOTAL`][memory-total]'s samples are in kilobytes.
+
+In Glean this sort of data is recorded using a
+[`memory-distribution`][memory-distribution-metric] metric type.
+
+You will no longer need to worry about the range of values or number or distribution of buckets
+(represented by the `low`, `high`, `n_buckets`, or `kind` in your Histogram's definition).
+Glean uses a [clever automatic bucketing algorithm][memory-distribution-metric] instead.
+
+So for a Histogram that records memory samples like this:
+
+```
+  "MEMORY_TOTAL": {
+    "record_in_processes": ["main"],
+    "products": ["firefox", "thunderbird"],
+    "alert_emails": ["memshrink-telemetry-alerts@mozilla.com", "amccreight@mozilla.com"],
+    "bug_numbers": [1198209, 1511918],
+    "expires_in_version": "never",
+    "kind": "exponential",
+    "low": 32768,
+    "high": 16777216,
+    "n_buckets": 100,
+    "description": "Total Memory Across All Processes (KB)",
+    "releaseChannelCollection": "opt-out"
+  },
+```
+
+You will migrate to a `memory_distribution` metric type like this:
+
+```yaml
+memory:
+  total:
+    type: memory_distribution
+    memory_unit: kilobyte
+    description: |
+      The total memory allocated across all processes.
+      Migrated from Telemetry's `MEMORY_TOTAL`.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1198209
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1511918
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1511918#c9
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - memshrink-telemetry-alerts@mozilla.com
+      - amccreight@mozilla.com
+    expires: never
+```
+
+**GIFFT:** This type of collection is mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+
+#### Percentage Samples - Comment on bug 1657467
+
+A very common Histogram in Firefox Desktop is a distribution of percentage samples.
+[For example, `GC_SLICE_DURING_IDLE`][gc-idle].
+
+Glean doesn't currently have a good metric type for this.
+But we [intend to add one][new-metric-percent].
+If you are migrating a collection of this type,
+please add a comment to the bug detailing which probe you are migrating,
+and when you need it migrated by.
+We'll prioritize adding this metric type accordingly.
+
+#### Other - Use Glean's `custom_distribution`
+
+Continuous Distribution Histograms have been around long enough to have gotten weird.
+If you're migrating one of those histograms with units like
+["square root of pixels times milliseconds"][checkerboard-severity],
+we have a "catch all" metric type for you: [Custom Distribution][custom-distribution-metric].
+
+Sadly, you'll have to care about the bucketing algorithm and bucket ranges for this one.
+So for a Histogram with artisinal samples like:
+
+```
+  "CHECKERBOARD_SEVERITY": {
+    "record_in_processes": ["main", "content", "gpu"],
+    "products": ["firefox", "fennec", "geckoview_streaming"],
+    "alert_emails": ["gfx-telemetry-alerts@mozilla.com", "botond@mozilla.com"],
+    "bug_numbers": [1238040, 1539309, 1584109],
+    "releaseChannelCollection": "opt-out",
+    "expires_in_version": "never",
+    "kind": "exponential",
+    "high": 1073741824,
+    "n_buckets": 50,
+    "description": "Opaque measure of the severity of a checkerboard event"
+  },
+```
+
+You will migrate it to a `custom_distribution` like:
+
+```yaml
+gfx.checkerboard:
+  severity:
+    type: custom_distribution
+    range_max: 1073741824
+    bucket_count: 50
+    histogram_type: exponential
+    unit: Opaque unit
+    description: >
+      An opaque measurement of the severity of a checkerboard event.
+      This doesn't have units, it's just useful for comparing two checkerboard
+      events to see which one is worse, for some implementation-specific
+      definition of "worse". The larger the value, the worse the
+      checkerboarding.
+      Migrated from Telemetry's `CHECKERBOARD_SEVERITY`.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1238040
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1539309
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1584109
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1584109#c1
+    notification_emails:
+      - gfx-telemetry-alerts@mozilla.com
+      - botond@mozilla.com
+    data_sensitivity:
+      - technical
+    expires: never
+```
+
+**TODO [Bug 1677447](https://bugzilla.mozilla.org/show_bug.cgi?id=1677447):**
+Custom Distributions aren't yet implemented in FOG. We're working on it.
+When they're done we'll see if they'll support GIFFT like the other distributions.
+
+#### Keyed Histograms with Continuous Sample Distributions - Ask on #glean:mozilla.org for assistance
+
+Glean doesn't currently have a good metric type for keyed continuous distributions
+like video play time keyed by codec.
+Please [reach out to us][glean-matrix] to explain your use-case.
+We will help you either work within what Glean currently affords or
+[design a new metric type for you][new-metric-type].
+
+### Discrete Distributions: kind `categorical`, `enumerated`, or `boolean` - Use Glean's `labeled_counter`
+
+If the samples don't fall in a continuous range and instead fall into a known number of buckets,
+Glean provides the [Labeled Counter][labeled-counter-metric] for these cases.
+
+Simply enumerate the discrete categories as `labels` in the `labeled_counter`.
+
+For example, for a Histogram of kind `categorical` like:
+
+```
+  "AVIF_DECODE_RESULT": {
+    "record_in_processes": ["main", "content"],
+    "products": ["firefox", "geckoview_streaming"],
+    "alert_emails": ["cchang@mozilla.com", "jbauman@mozilla.com"],
+    "expires_in_version": "never",
+    "releaseChannelCollection": "opt-out",
+    "kind": "categorical",
+    "labels": [
+      "success",
+      "parse_error",
+      "no_primary_item",
+      "decode_error",
+      "size_overflow",
+      "out_of_memory",
+      "pipe_init_error",
+      "write_buffer_error",
+      "alpha_y_sz_mismatch",
+      "alpha_y_bpc_mismatch"
+    ],
+    "description": "Decode result of AVIF image",
+    "bug_numbers": [1670827]
+  },
+```
+
+You would migrate to a `labeled_counter` like:
+
+```yaml
+avif:
+  decode_result:
+    type: labeled_counter,
+    description: |
+      Each AVIF image's decode result.
+      Migrated from Telemetry's `AVIF_DECODE_RESULT`.
+    labels:
+      - success
+      - parse_error
+      - no_primary_item
+      - decode_error
+      - size_overflow
+      - out_of_memory
+      - pipe_init_error
+      - write_buffer_error
+      - alpha_y_sz_mismatch
+      - alpha_y_bpc_mismatch
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1670827
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1670827#c9
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - cchang@mozilla.com
+      - jbauman@mozilla.com
+    expires: never
+```
+
+**N.B:** Glean Labels have a strict regex.
+You may have to transform some categories to
+`snake_case` so that they're safe for the data pipeline.
+
+**GIFFT:** This type of collection is mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+**N.B.:** This will mirror back as a Keyed Scalar of kind `uint`,
+not as any kind of Histogram,
+so your original un-migrated histogram cannot be used as the mirror.
+
+#### Keyed Histograms with Discrete Sample Distributions: `"keyed": true` and kind `categorical`, `enumerated`, or `boolean` - Comment on bug 1657470
+
+Glean doesn't currently have a good metric type for this.
+But we [intend to add one][new-metric-keyed-categorical].
+If you are migrating a collection of this type,
+please add a comment to the bug detailing which probe you are migrating,
+and when you need it migrated by.
+We'll prioritize adding this metric type accordingly.
+
+## Scalars
+
+[Scalars][telemetry-scalars] are low-level individual data collections with a variety of uses.
+
+### Scalars of `kind: uint` that you call `scalarAdd` on - Use Glean's `counter`
+
+The most common kind of Scalar is of `kind: uint`.
+The most common use of such a scalar is to repeatedly call `scalarAdd`
+on it as countable things happen.
+
+The Glean metric type for countable things is [the `counter` metric type][counter-metric].
+
+So for a Scalar like this:
+
+```yaml
+script.preloader:
+  mainthread_recompile:
+    bug_numbers:
+      - 1364235
+    description:
+      How many times we ended up recompiling a script from the script preloader
+      on the main thread.
+    expires: "100"
+    keyed: false
+    kind: uint
+    notification_emails:
+      - dothayer@mozilla.com
+      - plawless@mozilla.com
+    release_channel_collection: opt-out
+    products:
+      - 'firefox'
+      - 'fennec'
+    record_in_processes:
+      - 'main'
+      - 'content'
+```
+
+You will migrate to a `counter` metric type like this:
+
+```yaml
+script.preloader:
+  mainthread_recompile:
+    type: counter
+    description: |
+      How many times we ended up recompiling a script from the script preloader
+      on the main thread.
+      Migrated from Telemetry's `script.preloader.mainthread_recompile`.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1364235
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1364235#c25
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - dothayer@mozilla.com
+      - plawless@mozilla.com
+    expires: "100"
+```
+
+**GIFFT:** This type of collection is mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+
+#### Keyed Scalars of `kind: uint` that you call `scalarAdd` on - Use Glean's `labeled_counter`
+
+Another very common use of Scalars is to have a Keyed Scalar of
+`kind: uint`. This was often used to track UI usage.
+
+This is supported by the [Glean `labeled_counter` metric type][labeled-counter-metric].
+
+So for a Keyed Scalar of `kind: uint` like this:
+
+```yaml
+urlbar:
+  tips:
+    bug_numbers:
+      - 1608461
+    description: >
+      A keyed uint recording how many times particular tips are shown in the
+      Urlbar and how often their confirm and help buttons are pressed.
+    expires: never
+    kind: uint
+    keyed: true
+    notification_emails:
+      - email@example.com
+    release_channel_collection: opt-out
+    products:
+      - 'firefox'
+    record_in_processes:
+      - main
+```
+
+You would migrate it to a `labeled_counter` like this:
+
+```yaml
+urlbar:
+  tips:
+    type: labeled_counter
+    description: >
+      A keyed uint recording how many times particular tips are shown in the
+      Urlbar and how often their confirm and help buttons are pressed.
+      Migrated from Telemetry's `urlbar.tips`.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1608461
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1608461#c42
+    data_sensitivity:
+      - interaction
+    expires: never
+    notification_emails:
+      - email@example.com
+```
+
+Now, if your Keyed Scalar has a list of known keys,
+you should provide it to the `labeled_counter` using the `labels` property like so:
+
+```yaml
+urlbar:
+  tips:
+    type: labeled_counter
+    labels:
+      - tabtosearch_onboard_shown
+      - tabtosearch_shown
+      - searchtip_onboard_shown
+    ...
+```
+
+**N.B:** Glean Labels have a strict regex.
+You may have to transform some categories to
+`snake_case` so that they're safe for the data pipeline.
+
+**GIFFT:** This type of collection is mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+
+### Scalars of `kind: uint` that you call `scalarSet` on - Use Glean's `quantity`
+
+Distinct from counts which are partial sums,
+Scalars of `kind: uint` that you _set_ could contain just about anything.
+The best metric type depends on the type of data you're setting
+(See "Other Scalar-ish types" for some possibilities).
+
+If it's a numerical value you are setting, chances are you will be best served by
+[Glean's `quantity` metric type][quantity-metric].
+
+For a such a quantitative Scalar like:
+
+```yaml
+gfx.display:
+  primary_height:
+    bug_numbers:
+      - 1594145
+    description: >
+      Height of the primary display, takes device rotation into account.
+    expires: never
+    kind: uint
+    notification_emails:
+      - gfx-telemetry-alerts@mozilla.com
+      - ktaeleman@mozilla.com
+    products:
+      - 'geckoview_streaming'
+    record_in_processes:
+      - 'main'
+    release_channel_collection: opt-out
+```
+
+You would migrate it to a `quantity` like:
+
+```yaml
+gfx.display:
+  primary_height:
+    type: quantity
+    unit: pixels
+    description: >
+      Height of the primary display, takes device rotation into account.
+      Migrated from Telemetry's `gfx.display.primary_height`.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1594145
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1687219
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1594145#c4
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - gfx-telemetry-alerts@mozilla.com
+    expires: never
+```
+
+Note the required `unit` property.
+
+**GIFFT:** This type of collection is mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+
+**IPC Note:** Due to `set` not being a [commutative operation][ipc-docs], using `quantity`
+on non-parent processes is forbidden.
+This is a restriction that favours correctness over friendliness,
+which we may revisit if enough use cases require it.
+Please [contact us][glean-matrix] if you'd like us to do so.
+
+#### Keyed Scalars of `kind: uint` that you call `scalarSet` on - Ask on #glean:mozilla.org for assistance
+
+Glean doesn't currently have a good metric type for keyed quantities.
+Please [reach out to us][glean-matrix] to explain your use-case.
+We will help you either work within what Glean currently affords or
+[design a new metric type for you][new-metric-type].
+
+### Scalars of `kind: uint` that you call `scalarSetMaximum` or some combination of operations on - Ask on #glean:mozilla.org for assistance
+
+Glean doesn't currently have a good metric type for dealing with maximums,
+or for dealing with values you both count and set.
+Please [reach out to us][glean-matrix] to explain your use-case.
+We will help you either work within what Glean currently affords or
+[design a new metric type for you][new-metric-type].
+
+### Scalars of `kind: string` - Use Glean's `string`
+
+If your string value is a unique identifier, then consider
+[Glean's `uuid` metric type][uuid-metric] first.
+
+If the string scalar value doesn't fit that or any other more specific metric type,
+then [Glean's `string` metric type][string-metric] will do.
+
+For a Scalar of `kind: string` like:
+
+```yaml
+widget:
+  gtk_version:
+    bug_numbers:
+      - 1670145
+    description: >
+      The version of Gtk 3 in use.
+    kind: string
+    expires: never
+    notification_emails:
+      - layout-telemetry-alerts@mozilla.com
+    release_channel_collection: opt-out
+    products:
+      - 'firefox'
+    record_in_processes:
+      - 'main'
+```
+
+You will migrate it to a `string` metric like:
+
+```yaml
+widget:
+  gtk_version:
+    type: string
+    description: >
+      The version of Gtk 3 in use.
+      Migrated from Telemetry's `widget.gtk_version`.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1670145
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1670145#c7
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - layout-telemetry-alerts@mozilla.com
+    expires: never
+```
+
+**GIFFT:** This type of collection is mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+
+**IPC Note:** Due to `set` not being a [commutative operation][ipc-docs], using `string`
+on non-parent processes is forbidden.
+This is a restriction that favours correctness over friendliness,
+which we may revisit if enough use cases require it.
+Please [contact us][glean-matrix] if you'd like us to do so.
+
+### Scalars of `kind: boolean` - Use Glean's `boolean`
+
+If you need to store a simple true/false,
+[Glean's `boolean` metric type][boolean-metric] is likely best.
+
+If you have more that just `true` and `false` to store,
+you may prefer a `labeled_counter`.
+
+For a Scalar of `kind: boolean` like:
+
+```yaml
+widget:
+  dark_mode:
+    bug_numbers:
+      - 1601846
+    description: >
+      Whether the OS theme is dark.
+    expires: never
+    kind: boolean
+    notification_emails:
+      - layout-telemetry-alerts@mozilla.com
+      - cmccormack@mozilla.com
+    release_channel_collection: opt-out
+    products:
+      - 'firefox'
+      - 'fennec'
+    record_in_processes:
+      - 'main'
+```
+
+You would migrate to a `boolean` metric type like:
+
+```yaml
+widget:
+  dark_mode:
+    type: boolean
+    description: >
+      Whether the OS theme is dark.
+      Migrated from Telemetry's `widget.dark_mode`.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1601846
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1601846#c5
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - layout-telemetry-alerts@mozilla.com
+      - cmccormack@mozilla.com
+    expires: never
+```
+
+**GIFFT:** This type of collection is mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+
+**IPC Note:** Due to `set` not being a [commutative operation][ipc-docs], using `boolean`
+on non-parent processes is forbidden.
+This is a restriction that favours correctness over friendliness,
+which we may revisit if enough use cases require it.
+Please [contact us][glean-matrix] if you'd like us to do so.
+
+#### Keyed Scalars of `kind: boolean` - Use Glean's `labeled_boolean`
+
+If you have multiple related true/false values, you may have put them in a
+Keyed Scalar of `kind: boolean`.
+
+The best match for this is
+[Glean's `labeled_boolean` metric type][labeled-boolean-metric].
+
+For a Keyed Scalar of `kind: boolean` like:
+
+```yaml
+devtools.tool:
+  registered:
+    bug_numbers:
+      - 1447302
+      - 1503568
+      - 1587985
+    description: >
+      Recorded on enable tool checkbox check/uncheck in Developer Tools options
+      panel. Boolean stating if the tool was enabled or disabled by the user.
+      Keyed by tool id. Current default tools with their id's are defined in
+      https://searchfox.org/mozilla-central/source/devtools/client/definitions.js
+    expires: never
+    kind: boolean
+    keyed: true
+    notification_emails:
+      - dev-developer-tools@lists.mozilla.org
+      - accessibility@mozilla.com
+    release_channel_collection: opt-out
+    products:
+      - 'firefox'
+      - 'fennec'
+    record_in_processes:
+      - 'main'
+```
+
+You would migrate to a `labeled_boolean` like:
+
+```yaml
+devtools.tool:
+  registered:
+    type: labeled_boolean
+    description: >
+      Recorded on enable tool checkbox check/uncheck in Developer Tools options
+      panel. Boolean stating if the tool was enabled or disabled by the user.
+      Migrated from Telemetry's `devtools.tool`.
+    labels:
+      - options
+      - inspector
+      - webconsole
+      - jsdebugger
+      - styleeditor
+      - performance
+      - memory
+      - netmonitor
+      - storage
+      - dom
+      - accessibility
+      - application
+      - dark
+      - light
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1447302
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1503568
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1587985
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1447302#c17
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1503568#c3
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1587985#c5
+    data_sensitivity:
+      - interaction
+    notification_emails:
+      - dev-developer-tools@lists.mozilla.org
+      - accessibility@mozilla.com
+    expires: never
+```
+
+**N.B:** Glean Labels have a strict regex.
+You may have to transform some categories to
+`snake_case` so that they're safe for the data pipeline.
+
+**GIFFT:** This type of collection is mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+
+**IPC Note:** Due to `set` not being a [commutative operation][ipc-docs], using `labeled_boolean`
+on non-parent processes is forbidden.
+This is a restriction that favours correctness over friendliness,
+which we may revisit if enough use cases require it.
+Please [contact us][glean-matrix] if you'd like us to do so.
+
+### Other Scalar-ish types: `rate`, `timespan`, `datetime`, `uuid`
+
+The Glean SDK provides some very handy higher-level metric types for specific data.
+If your data
+* Is two or more numbers that are related (like failure count vs total count),
+  then consider the [Glean `rate` metric type][rate-metric].
+* Is a single duration or span of time (like how long Firefox takes to start),
+  then consider the [Glean `timespan` metric type][timespan-metric].
+* Is a single point in time (like the most recent sync time),
+  then consider the [Glean `datetime` metric type][datetime-metric].
+* Is a unique identifier (like a session id),
+  then consider the [Glean `uuid` metric type][uuid-metric].
+
+**GIFFT:** These types of collection are mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+
+## Events - Use Glean's `event`
+
+[Telemetry Events][telemetry-events]
+are a lesser-used form of data collection in Firefox Desktop.
+Glean aimed to remove some of the stumbling blocks facing instrumentors when using events
+in the [Glean `event` metric type][event-metric]:
+
+* Don't worry about enabling event categories.
+  In Glean all `events` are always on.
+* No more event `name`.
+  Events in Glean follow the same `category.name.metric_name`
+  naming structure that other metrics do.
+* No more `method`/`object`/`value`.
+  Events in Glean are just their identifier and an `extras` key/value dictionary.
+
+Since the two Event types aren't that analogous you will need to decide if your event
+* Prefers to put its `method`/`object`/`value` in the `extras` dictionary
+* Prefers to fold its `method`/`object`/`value` into its identifier
+
+**GIFFT:** Events are mirrorable back to Firefox Telemetry via the
+[Glean Interface For Firefox Telemetry][gifft].
+See [the guide][gifft] for instructions.
+
+## Other: Environment, Crash Annotations, Use Counters, Etc - Ask on #glean:mozilla.org for assistance
+
+Telemetry has a lot of collection subsystems build adjacent to those already mentioned.
+We have solutions for the common ones,
+but they are entirely dependent on the specific use case.
+Please [reach out to us][glean-matrix] to explain it to us so we can help you either
+work within what Glean currently affords or
+[design a new metric type for you][new-metric-type].
+
+[book-of-glean]: https://mozilla.github.io/glean/book/index.html
+[gc-ms]: https://glam.telemetry.mozilla.org/firefox/probe/gc_ms/explore
+[histogram-accumulate]: https://searchfox.org/mozilla-central/rev/d59bdea4956040e16113b05296c56867f761735b/toolkit/components/telemetry/core/Telemetry.h#61
+[ipc-docs]: ../dev/ipc.md
+[gifft]: gifft.md
+[memory-total]: https://glam.telemetry.mozilla.org/firefox/probe/memory_total/explore
+[migration-worksheet]: https://docs.google.com/spreadsheets/d/1uEK7zSIJDcGGmof9NywP5AwaovVQCv_Bm3iNqibtESI/edit#gid=0
+[boolean-metric]: https://mozilla.github.io/glean/book/reference/metrics/boolean.html
+[labeled-boolean-metric]: https://mozilla.github.io/glean/book/reference/metrics/labeled_booleans.html
+[counter-metric]: https://mozilla.github.io/glean/book/reference/metrics/counter.html
+[labeled-counter-metric]: https://mozilla.github.io/glean/book/reference/metrics/labeled_counters.html
+[string-metric]: https://mozilla.github.io/glean/book/reference/metrics/string.html
+[labeled-string-metric]: https://mozilla.github.io/glean/book/reference/metrics/labeled_strings.html
+[timespan-metric]: https://mozilla.github.io/glean/book/reference/metrics/timespan.html
+[timing-distribution-metric]: https://mozilla.github.io/glean/book/reference/metrics/timing_distribution.html
+[memory-distribution-metric]: https://mozilla.github.io/glean/book/reference/metrics/memory_distribution.html
+[uuid-metric]: https://mozilla.github.io/glean/book/reference/metrics/uuid.html
+[datetime-metric]: https://mozilla.github.io/glean/book/reference/metrics/datetime.html
+[event-metric]: https://mozilla.github.io/glean/book/reference/metrics/event.html
+[custom-distribution-metric]: https://mozilla.github.io/glean/book/reference/metrics/custom_distribution.html
+[quantity-metric]: https://mozilla.github.io/glean/book/reference/metrics/quantity.html
+[rate-metric]: https://mozilla.github.io/glean/book/reference/metrics/rate.html
+[ipc-dev-doc]: ../dev/ipc.md
+[gc-idle]: https://glam.telemetry.mozilla.org/firefox/probe/gc_slice_during_idle/explore
+[new-metric-keyed-categorical]: https://bugzilla.mozilla.org/show_bug.cgi?id=1657470
+[new-metric-percent]: https://bugzilla.mozilla.org/show_bug.cgi?id=1657467
+[new-metric-type]: https://wiki.mozilla.org/Glean/Adding_or_changing_Glean_metric_types
+[glean-matrix]: https://chat.mozilla.org/#/room/#glean:mozilla.org
+[checkerboard-severity]: https://searchfox.org/mozilla-central/rev/d59bdea4956040e16113b05296c56867f761735b/gfx/layers/apz/src/CheckerboardEvent.cpp#44
+[telemetry-events]: /toolkit/components/telemetry/collection/events.rst
+[telemetry-scalars]: /toolkit/components/telemetry/collection/scalars.rst
+[telemetry-histograms]: /toolkit/components/telemetry/collection/histograms.rst
+[repositories-yaml]: https://github.com/mozilla/probe-scraper/blob/main/repositories.yaml
diff --git a/toolkit/components/glean/docs/user/new_definitions_file.md b/toolkit/components/glean/docs/user/new_definitions_file.md
new file mode 100644
index 0000000000..976f34b209
--- /dev/null
+++ b/toolkit/components/glean/docs/user/new_definitions_file.md
@@ -0,0 +1,107 @@
+# New Metrics and Pings
+
+To add a new metric or ping to Firefox Desktop you should follow the
+[Glean SDK documentation on the subject](https://mozilla.github.io/glean/book/user/adding-new-metrics.html),
+with some few twists we detail herein:
+
+## IPC
+
+Firefox Desktop is made of multiple processes.
+You can record data from any process in Firefox Desktop
+[subject to certain conditions](../dev/ipc.md).
+
+If you will be recording data to this metric in multiple processes,
+you should make yourself aware of those conditions.
+
+## Where do I Define new Metrics and Pings?
+
+Metrics and pings are defined in their definitions files
+(`metrics.yaml` or `pings.yaml`, respectively).
+But where can you find `metrics.yaml` or `pings.yaml`?
+
+If you're not the first person in your component to ask that question,
+the answer is likely "in the root of your component".
+Look for the definitions files near to where you are instrumenting your code.
+Or you can look in
+`toolkit/components/glean/metrics_index.py`
+to see the list of all currently-known definitions files.
+
+If you _are_ the first person in your component to ask that question,
+you get to choose where to start them!
+We recommend adding them in the root of your component, next to a `moz.build`.
+Be sure to link to this document at the top of the file!
+It contains many useful tidbits of information that anyone adding new metrics should know.
+Preferably, use this blank template to get started,
+substituting your component's `product :: component` tag from
+[the list](https://searchfox.org/mozilla-central/source/toolkit/components/glean/tags.yaml):
+
+```yaml
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Adding a new metric? We have docs for that!
+# https://firefox-source-docs.mozilla.org/toolkit/components/glean/user/new_definitions_file.html
+
+---
+$schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
+$tags:
+  - 'Your Product :: Your Component'
+
+```
+
+If you add a new definitions file, be sure to edit
+`toolkit/components/glean/metrics_index.py`,
+adding your definitions files to the Python lists therein.
+If you don't, no API will be generated for your metrics and your build will fail.
+You will have to decide which products your metrics will be used in.
+For code that's also used in other Gecko-based products (Firefox Desktop, Firefox for Android, Focus for Android), use `gecko_metrics`.
+For Desktop-only instrumentation use `firefox_desktop_metrics`.
+For other products use their respective lists.
+
+Changes to `metrics_index.py` are automatically reflected in the data pipeline once a day
+using the [fog-updater automation in probe-scraper](https://github.com/mozilla/probe-scraper/tree/main/fog-updater).
+Data will not show up in datasets and tools until this happens.
+If something is unclear or data is not showing up in time you will need to file a bug in
+`Data Platform and Tools :: General`.
+
+If you have any questions, be sure to ask on
+[the #glean channel](https://chat.mozilla.org/#/room/#glean:mozilla.org).
+
+**Note:** Do _not_ use `toolkit/components/glean/metrics.yaml`
+or `toolkit/components/glean/pings.yaml`.
+These are for metrics instrumenting the code under `toolkit/components/glean`
+and are not general-purpose locations for adding metrics and pings.
+
+## How does Expiry Work?
+
+In FOG,
+unlike in other Glean-SDK-using projects,
+metrics expire based on Firefox application version.
+This is to allow metrics to be valid over the entire life of an application version,
+whether that is the 4-6 weeks of usual releases or the 13 months of ESR releases.
+
+There are three values accepted in the `expires` field of `metrics.yaml`s for FOG:
+* `"X"` (where `X` is the major portion of a Firefox Desktop version) -
+  The metric will be expired when the `MOZ_APP_VERSION` reaches or exceeds `X`.
+  (For example, when the Firefox Version is `88.0a1`,
+  all metrics marked with `expires: "88"` or lower will be expired.)
+  This is the recommended form for all new metrics to ensure they stop recording when they stop being relevant.
+* `expired` - For marking a metric as manually expired.
+  Not usually used, but sometimes helpful for internal tests.
+* `never` - For marking a metric as part of a permanent data collection.
+  Metrics marked with `never` must have
+  [instrumentation tests](instrumentation_tests).
+
+For more information on what expiry means and the
+`metrics.yaml` format, see
+[the Glean SDK docs](https://mozilla.github.io/glean/book/user/metric-parameters.html)
+on this subject. Some quick facts:
+
+* Data collected to expired metrics is not recorded or sent.
+* Recording to expired metrics is not an error at runtime.
+* Expired metrics being in a `metrics.yaml` is a linting error in `glean_parser`.
+* Expired (and non-expired) metrics that are no longer useful should be promptly removed from your `metrics.yaml`.
+  This reduces the size and improves the performance of Firefox
+  (and speeds up the Firefox build process)
+  by decreasing the amount of code that needs to be generated.
diff --git a/toolkit/components/glean/ipc/FOGIPC.cpp b/toolkit/components/glean/ipc/FOGIPC.cpp
new file mode 100644
index 0000000000..20258498f8
--- /dev/null
+++ b/toolkit/components/glean/ipc/FOGIPC.cpp
@@ -0,0 +1,545 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FOGIPC.h"
+
+#include <limits>
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "mozilla/glean/GleanMetrics.h"
+#include "mozilla/dom/BrowsingContextGroup.h"
+#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/DocGroup.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/gfx/GPUChild.h"
+#include "mozilla/gfx/GPUParent.h"
+#include "mozilla/gfx/GPUProcessManager.h"
+#include "mozilla/Hal.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/net/SocketProcessChild.h"
+#include "mozilla/net/SocketProcessParent.h"
+#include "mozilla/ProcInfo.h"
+#include "mozilla/RDDChild.h"
+#include "mozilla/RDDParent.h"
+#include "mozilla/RDDProcessManager.h"
+#include "mozilla/ipc/UtilityProcessChild.h"
+#include "mozilla/ipc/UtilityProcessManager.h"
+#include "mozilla/ipc/UtilityProcessParent.h"
+#include "mozilla/ipc/UtilityProcessSandboxing.h"
+#include "mozilla/Unused.h"
+#include "GMPPlatform.h"
+#include "GMPServiceParent.h"
+#include "nsIClassifiedChannel.h"
+#include "nsIXULRuntime.h"
+#include "nsTArray.h"
+#include "nsThreadUtils.h"
+
+using mozilla::dom::ContentParent;
+using mozilla::gfx::GPUChild;
+using mozilla::gfx::GPUProcessManager;
+using mozilla::ipc::ByteBuf;
+using mozilla::ipc::UtilityProcessChild;
+using mozilla::ipc::UtilityProcessManager;
+using mozilla::ipc::UtilityProcessParent;
+using FlushFOGDataPromise = mozilla::dom::ContentParent::FlushFOGDataPromise;
+
+namespace geckoprofiler::markers {
+
+using namespace mozilla;
+
+struct ProcessingTimeMarker {
+  static constexpr Span<const char> MarkerTypeName() {
+    return MakeStringSpan("ProcessingTime");
+  }
+  static void StreamJSONMarkerData(baseprofiler::SpliceableJSONWriter& aWriter,
+                                   int64_t aDiffMs,
+                                   const ProfilerString8View& aType,
+                                   const ProfilerString8View& aTrackerType) {
+    aWriter.IntProperty("time", aDiffMs);
+    aWriter.StringProperty("label", aType);
+    if (aTrackerType.Length() > 0) {
+      aWriter.StringProperty("tracker", aTrackerType);
+    }
+  }
+  static MarkerSchema MarkerTypeDisplay() {
+    using MS = MarkerSchema;
+    MS schema{MS::Location::MarkerChart, MS::Location::MarkerTable};
+    schema.AddKeyLabelFormat("time", "Recorded Time", MS::Format::Milliseconds);
+    schema.AddKeyLabelFormat("tracker", "Tracker Type", MS::Format::String);
+    schema.SetTooltipLabel("{marker.name} - {marker.data.label}");
+    schema.SetTableLabel(
+        "{marker.name} - {marker.data.label}: {marker.data.time}");
+    return schema;
+  }
+};
+
+}  // namespace geckoprofiler::markers
+
+namespace mozilla::glean {
+
+#ifdef NIGHTLY_BUILD
+// The 2 following static global variables are set within RecordPowerMetrics
+// so that RecordThreadCpuUse can avoid computing the Glean process type
+// (matching a label of per_process_type_labels).
+// This is useful because RecordThreadCpuUse will either be called in a loop
+// for every thread (recomputing the process type for every thread would be
+// expensive), or will be called off main thread when a thread is unregisters
+// itself (some APIs needed to compute the process type might not be available
+// off main thread).
+// It is fine to call RecordThreadCpuUse during startup before the first
+// RecordPowerMetrics call. In that case the parent process will be recorded
+// as inactive, and other processes will be ignored (content processes start
+// in the 'prealloc' type for which we don't record per-thread CPU use data).
+using LabeledCounterMetric = const impl::Labeled<impl::CounterMetric>;
+static Atomic<LabeledCounterMetric*> gCpuTimePerThreadMetric(nullptr);
+static Atomic<LabeledCounterMetric*> gWakeupsPerThreadMetric(nullptr);
+
+// These 2 macros are only meant to reduce code duplication, there is no
+// requirement of the 2 variables being set atomically as a single value.
+#  define SET_PER_THREAD_CPU_METRICS(aProcessType)                    \
+    gCpuTimePerThreadMetric = &power_cpu_ms_per_thread::aProcessType; \
+    gWakeupsPerThreadMetric = &power_wakeups_per_thread::aProcessType;
+
+#  define RESET_PER_THREAD_CPU_METRICS() \
+    gCpuTimePerThreadMetric = nullptr;   \
+    gWakeupsPerThreadMetric = nullptr;
+
+void RecordThreadCpuUse(const nsACString& aThreadName, uint64_t aCpuTimeMs,
+                        uint64_t aWakeCount) {
+  // Copy the values of the atomics to local variables so that we don't have to
+  // worry about other threads changing them during the execution of this
+  // function.
+  LabeledCounterMetric* cpuTimeMetric = gCpuTimePerThreadMetric;
+  LabeledCounterMetric* wakeupsMetric = gWakeupsPerThreadMetric;
+
+  if (!cpuTimeMetric || !wakeupsMetric) {
+    if (XRE_IsParentProcess()) {
+      // The metrics can be null for the parent process during startup,
+      // and we want to record during that time.
+      SET_PER_THREAD_CPU_METRICS(parent_inactive);
+      cpuTimeMetric = gCpuTimePerThreadMetric;
+      wakeupsMetric = gWakeupsPerThreadMetric;
+      if (!cpuTimeMetric || !wakeupsMetric) {
+        return;
+      }
+    } else {
+      // We are not interested in per-thread CPU use data for the current
+      // process type.
+      return;
+    }
+  }
+
+  nsAutoCString threadName(aThreadName);
+  for (size_t i = 0; i < threadName.Length(); ++i) {
+    const char c = threadName.CharAt(i);
+
+    // Valid characters.
+    if ((c >= '0' && c <= '9') || (c >= 'a' && c <= 'z') || c == '-' ||
+        c == '_') {
+      continue;
+    }
+
+    // Should only use lower case characters
+    if (c >= 'A' && c <= 'Z') {
+      threadName.SetCharAt(c + ('a' - 'A'), i);
+      continue;
+    }
+
+    // Replace everything else with _
+    threadName.SetCharAt('_', i);
+  }
+
+  if (aCpuTimeMs != 0 &&
+      MOZ_LIKELY(aCpuTimeMs < std::numeric_limits<int32_t>::max())) {
+    cpuTimeMetric->Get(threadName).Add(int32_t(aCpuTimeMs));
+  }
+
+  if (aWakeCount != 0 &&
+      MOZ_LIKELY(aWakeCount < std::numeric_limits<int32_t>::max())) {
+    wakeupsMetric->Get(threadName).Add(int32_t(aWakeCount));
+  }
+}
+#else  // ifdef NIGHTLY_BUILD
+#  define SET_PER_THREAD_CPU_METRICS(aProcessType)
+#  define RESET_PER_THREAD_CPU_METRICS()
+#endif
+
+void GetTrackerType(nsAutoCString& aTrackerType) {
+  using namespace mozilla::dom;
+  uint32_t trackingFlags =
+      (nsIClassifiedChannel::CLASSIFIED_CRYPTOMINING |
+       nsIClassifiedChannel::CLASSIFIED_FINGERPRINTING |
+       nsIClassifiedChannel::CLASSIFIED_TRACKING |
+       nsIClassifiedChannel::CLASSIFIED_TRACKING_AD |
+       nsIClassifiedChannel::CLASSIFIED_TRACKING_ANALYTICS |
+       nsIClassifiedChannel::CLASSIFIED_TRACKING_SOCIAL);
+  AutoTArray<RefPtr<BrowsingContextGroup>, 5> bcGroups;
+  BrowsingContextGroup::GetAllGroups(bcGroups);
+  for (auto& bcGroup : bcGroups) {
+    AutoTArray<DocGroup*, 5> docGroups;
+    bcGroup->GetDocGroups(docGroups);
+    for (auto* docGroup : docGroups) {
+      for (Document* doc : *docGroup) {
+        nsCOMPtr<nsIClassifiedChannel> classifiedChannel =
+            do_QueryInterface(doc->GetChannel());
+        if (classifiedChannel) {
+          uint32_t classificationFlags =
+              classifiedChannel->GetThirdPartyClassificationFlags();
+          trackingFlags &= classificationFlags;
+          if (!trackingFlags) {
+            return;
+          }
+        }
+      }
+    }
+  }
+
+  // The if-elseif-else chain works because the tracker types listed here are
+  // currently mutually exclusive and should be maintained that way by policy.
+  if (trackingFlags == nsIClassifiedChannel::CLASSIFIED_TRACKING_AD) {
+    aTrackerType = "ad";
+  } else if (trackingFlags ==
+             nsIClassifiedChannel::CLASSIFIED_TRACKING_ANALYTICS) {
+    aTrackerType = "analytics";
+  } else if (trackingFlags ==
+             nsIClassifiedChannel::CLASSIFIED_TRACKING_SOCIAL) {
+    aTrackerType = "social";
+  } else if (trackingFlags == nsIClassifiedChannel::CLASSIFIED_CRYPTOMINING) {
+    aTrackerType = "cryptomining";
+  } else if (trackingFlags == nsIClassifiedChannel::CLASSIFIED_FINGERPRINTING) {
+    aTrackerType = "fingerprinting";
+  } else if (trackingFlags == nsIClassifiedChannel::CLASSIFIED_TRACKING) {
+    // CLASSIFIED_TRACKING means we were not able to identify the type of
+    // classification.
+    aTrackerType = "unknown";
+  }
+}
+
+void RecordPowerMetrics() {
+  static uint64_t previousCpuTime = 0, previousGpuTime = 0;
+
+  uint64_t cpuTime, newCpuTime = 0;
+  if (NS_SUCCEEDED(GetCpuTimeSinceProcessStartInMs(&cpuTime)) &&
+      cpuTime > previousCpuTime) {
+    newCpuTime = cpuTime - previousCpuTime;
+  }
+
+  uint64_t gpuTime, newGpuTime = 0;
+  // Avoid loading gdi32.dll for the Socket process where the GPU is never used.
+  if (!XRE_IsSocketProcess() &&
+      NS_SUCCEEDED(GetGpuTimeSinceProcessStartInMs(&gpuTime)) &&
+      gpuTime > previousGpuTime) {
+    newGpuTime = gpuTime - previousGpuTime;
+  }
+
+  if (!newCpuTime && !newGpuTime) {
+    // Nothing to record.
+    return;
+  }
+
+  // Compute the process type string.
+  nsAutoCString type(XRE_GetProcessTypeString());
+  nsAutoCString trackerType;
+  if (XRE_IsContentProcess()) {
+    auto* cc = dom::ContentChild::GetSingleton();
+    if (cc) {
+      type.Assign(dom::RemoteTypePrefix(cc->GetRemoteType()));
+      if (StringBeginsWith(type, WEB_REMOTE_TYPE)) {
+        type.AssignLiteral("web");
+        switch (cc->GetProcessPriority()) {
+          case hal::PROCESS_PRIORITY_BACKGROUND:
+            type.AppendLiteral(".background");
+            SET_PER_THREAD_CPU_METRICS(content_background);
+            break;
+          case hal::PROCESS_PRIORITY_FOREGROUND:
+            type.AppendLiteral(".foreground");
+            SET_PER_THREAD_CPU_METRICS(content_foreground);
+            break;
+          case hal::PROCESS_PRIORITY_BACKGROUND_PERCEIVABLE:
+            type.AppendLiteral(".background-perceivable");
+            RESET_PER_THREAD_CPU_METRICS();
+            break;
+          default:
+            RESET_PER_THREAD_CPU_METRICS();
+            break;
+        }
+      }
+      GetTrackerType(trackerType);
+    } else {
+      RESET_PER_THREAD_CPU_METRICS();
+    }
+  } else if (XRE_IsParentProcess()) {
+    if (nsContentUtils::GetUserIsInteracting()) {
+      type.AssignLiteral("parent.active");
+      SET_PER_THREAD_CPU_METRICS(parent_active);
+    } else {
+      type.AssignLiteral("parent.inactive");
+      SET_PER_THREAD_CPU_METRICS(parent_inactive);
+    }
+    hal::WakeLockInformation info;
+    GetWakeLockInfo(u"video-playing"_ns, &info);
+    if (info.numLocks() != 0 && info.numHidden() < info.numLocks()) {
+      type.AppendLiteral(".playing-video");
+    } else {
+      GetWakeLockInfo(u"audio-playing"_ns, &info);
+      if (info.numLocks()) {
+        type.AppendLiteral(".playing-audio");
+      }
+    }
+  } else if (XRE_IsGPUProcess()) {
+    SET_PER_THREAD_CPU_METRICS(gpu_process);
+  } else {
+    RESET_PER_THREAD_CPU_METRICS();
+  }
+
+  if (newCpuTime) {
+    // The counters are reset at least once a day. Assuming all cores are used
+    // continuously, an int32 can hold the data for 24.85 cores.
+    // This should be fine for now, but may overflow in the future.
+    // Bug 1751277 tracks a newer, bigger counter.
+    int32_t nNewCpuTime = int32_t(newCpuTime);
+    if (newCpuTime < std::numeric_limits<int32_t>::max()) {
+      power::total_cpu_time_ms.Add(nNewCpuTime);
+      power::cpu_time_per_process_type_ms.Get(type).Add(nNewCpuTime);
+      if (!trackerType.IsEmpty()) {
+        power::cpu_time_per_tracker_type_ms.Get(trackerType).Add(nNewCpuTime);
+      }
+    } else {
+      power::cpu_time_bogus_values.Add(1);
+    }
+    PROFILER_MARKER("Process CPU Time", OTHER, {}, ProcessingTimeMarker,
+                    nNewCpuTime, type, trackerType);
+    previousCpuTime += newCpuTime;
+  }
+
+  if (newGpuTime) {
+    int32_t nNewGpuTime = int32_t(newGpuTime);
+    if (newGpuTime < std::numeric_limits<int32_t>::max()) {
+      power::total_gpu_time_ms.Add(nNewGpuTime);
+      power::gpu_time_per_process_type_ms.Get(type).Add(nNewGpuTime);
+    } else {
+      power::gpu_time_bogus_values.Add(1);
+    }
+    PROFILER_MARKER("Process GPU Time", OTHER, {}, ProcessingTimeMarker,
+                    nNewGpuTime, type, trackerType);
+    previousGpuTime += newGpuTime;
+  }
+
+  profiler_record_wakeup_count(type);
+}
+
+/**
+ * Flush your data ASAP, either because the parent process is asking you to
+ * or because the process is about to shutdown.
+ *
+ * @param aResolver - The function you need to call with the bincoded,
+ *                    serialized payload that the Rust impl hands you.
+ */
+void FlushFOGData(std::function<void(ipc::ByteBuf&&)>&& aResolver) {
+  // Record power metrics right before data is sent to the parent.
+  RecordPowerMetrics();
+
+  ByteBuf buf;
+  uint32_t ipcBufferSize = impl::fog_serialize_ipc_buf();
+  bool ok = buf.Allocate(ipcBufferSize);
+  if (!ok) {
+    return;
+  }
+  uint32_t writtenLen = impl::fog_give_ipc_buf(buf.mData, buf.mLen);
+  if (writtenLen != ipcBufferSize) {
+    return;
+  }
+  aResolver(std::move(buf));
+}
+
+/**
+ * Called by FOG on the parent process when it wants to flush all its
+ * children's data.
+ * @param aResolver - The function that'll be called with the results.
+ */
+void FlushAllChildData(
+    std::function<void(nsTArray<ipc::ByteBuf>&&)>&& aResolver) {
+  auto timerId = fog_ipc::flush_durations.Start();
+
+  nsTArray<ContentParent*> parents;
+  ContentParent::GetAll(parents);
+  nsTArray<RefPtr<FlushFOGDataPromise>> promises;
+  for (auto* parent : parents) {
+    promises.EmplaceBack(parent->SendFlushFOGData());
+  }
+
+  if (GPUProcessManager* gpuManager = GPUProcessManager::Get()) {
+    if (GPUChild* gpuChild = gpuManager->GetGPUChild()) {
+      promises.EmplaceBack(gpuChild->SendFlushFOGData());
+    }
+  }
+
+  if (RDDProcessManager* rddManager = RDDProcessManager::Get()) {
+    if (RDDChild* rddChild = rddManager->GetRDDChild()) {
+      promises.EmplaceBack(rddChild->SendFlushFOGData());
+    }
+  }
+
+  if (net::SocketProcessParent* socketParent =
+          net::SocketProcessParent::GetSingleton()) {
+    promises.EmplaceBack(socketParent->SendFlushFOGData());
+  }
+
+  {
+    RefPtr<mozilla::gmp::GeckoMediaPluginServiceParent> gmps(
+        mozilla::gmp::GeckoMediaPluginServiceParent::GetSingleton());
+    // There can be multiple Gecko Media Plugin processes, but iterating
+    // through them requires locking a mutex and the IPCs need to be sent
+    // from a different thread, so it's better to let the
+    // GeckoMediaPluginServiceParent code do it for us.
+    gmps->SendFlushFOGData(promises);
+  }
+
+  if (RefPtr<UtilityProcessManager> utilityManager =
+          UtilityProcessManager::GetIfExists()) {
+    for (RefPtr<UtilityProcessParent>& parent :
+         utilityManager->GetAllProcessesProcessParent()) {
+      promises.EmplaceBack(parent->SendFlushFOGData());
+    }
+  }
+
+  if (promises.Length() == 0) {
+    // No child processes at the moment. Resolve synchronously.
+    fog_ipc::flush_durations.Cancel(std::move(timerId));
+    nsTArray<ipc::ByteBuf> results;
+    aResolver(std::move(results));
+    return;
+  }
+
+  // If fog.ipc.flush_failures ever gets too high:
+  // TODO: Don't throw away resolved data if some of the promises reject.
+  // (not sure how, but it'll mean not using ::All... maybe a custom copy of
+  // AllPromiseHolder? Might be impossible outside MozPromise.h)
+  FlushFOGDataPromise::All(GetCurrentSerialEventTarget(), promises)
+      ->Then(GetCurrentSerialEventTarget(), __func__,
+             [aResolver = std::move(aResolver), timerId](
+                 FlushFOGDataPromise::AllPromiseType::ResolveOrRejectValue&&
+                     aValue) {
+               fog_ipc::flush_durations.StopAndAccumulate(std::move(timerId));
+               if (aValue.IsResolve()) {
+                 aResolver(std::move(aValue.ResolveValue()));
+               } else {
+                 fog_ipc::flush_failures.Add(1);
+                 nsTArray<ipc::ByteBuf> results;
+                 aResolver(std::move(results));
+               }
+             });
+}
+
+/**
+ * A child process has sent you this buf as a treat.
+ * @param buf - a bincoded serialized payload that the Rust impl understands.
+ */
+void FOGData(ipc::ByteBuf&& buf) {
+  fog_ipc::buffer_sizes.Accumulate(buf.mLen);
+  impl::fog_use_ipc_buf(buf.mData, buf.mLen);
+}
+
+/**
+ * Called by FOG on a child process when it wants to send a buf to the parent.
+ * @param buf - a bincoded serialized payload that the Rust impl understands.
+ */
+void SendFOGData(ipc::ByteBuf&& buf) {
+  switch (XRE_GetProcessType()) {
+    case GeckoProcessType_Content:
+      mozilla::dom::ContentChild::GetSingleton()->SendFOGData(std::move(buf));
+      break;
+    case GeckoProcessType_GMPlugin: {
+      mozilla::gmp::SendFOGData(std::move(buf));
+    } break;
+    case GeckoProcessType_GPU:
+      Unused << mozilla::gfx::GPUParent::GetSingleton()->SendFOGData(
+          std::move(buf));
+      break;
+    case GeckoProcessType_RDD:
+      Unused << mozilla::RDDParent::GetSingleton()->SendFOGData(std::move(buf));
+      break;
+    case GeckoProcessType_Socket:
+      Unused << net::SocketProcessChild::GetSingleton()->SendFOGData(
+          std::move(buf));
+      break;
+    case GeckoProcessType_Utility:
+      Unused << ipc::UtilityProcessChild::GetSingleton()->SendFOGData(
+          std::move(buf));
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unsuppored process type");
+  }
+}
+
+/**
+ * Called on the parent process to ask all child processes for data,
+ * sending it all down into Rust to be used.
+ */
+RefPtr<GenericPromise> FlushAndUseFOGData() {
+  // Record power metrics on the parent before sending requests to child
+  // processes.
+  RecordPowerMetrics();
+
+  RefPtr<GenericPromise::Private> ret = new GenericPromise::Private(__func__);
+  std::function<void(nsTArray<ByteBuf> &&)> resolver =
+      [ret](nsTArray<ByteBuf>&& bufs) {
+        for (ByteBuf& buf : bufs) {
+          FOGData(std::move(buf));
+        }
+        ret->Resolve(true, __func__);
+      };
+  FlushAllChildData(std::move(resolver));
+  return ret;
+}
+
+void TestTriggerMetrics(uint32_t aProcessType,
+                        const RefPtr<dom::Promise>& promise) {
+  switch (aProcessType) {
+    case nsIXULRuntime::PROCESS_TYPE_GMPLUGIN: {
+      RefPtr<mozilla::gmp::GeckoMediaPluginServiceParent> gmps(
+          mozilla::gmp::GeckoMediaPluginServiceParent::GetSingleton());
+      gmps->TestTriggerMetrics()->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [promise]() { promise->MaybeResolveWithUndefined(); },
+          [promise]() { promise->MaybeRejectWithUndefined(); });
+    } break;
+    case nsIXULRuntime::PROCESS_TYPE_GPU:
+      gfx::GPUProcessManager::Get()->TestTriggerMetrics()->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [promise]() { promise->MaybeResolveWithUndefined(); },
+          [promise]() { promise->MaybeRejectWithUndefined(); });
+      break;
+    case nsIXULRuntime::PROCESS_TYPE_RDD:
+      RDDProcessManager::Get()->TestTriggerMetrics()->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [promise]() { promise->MaybeResolveWithUndefined(); },
+          [promise]() { promise->MaybeRejectWithUndefined(); });
+      break;
+    case nsIXULRuntime::PROCESS_TYPE_SOCKET:
+      Unused << net::SocketProcessParent::GetSingleton()
+                    ->SendTestTriggerMetrics()
+                    ->Then(
+                        GetCurrentSerialEventTarget(), __func__,
+                        [promise]() { promise->MaybeResolveWithUndefined(); },
+                        [promise]() { promise->MaybeRejectWithUndefined(); });
+      break;
+    case nsIXULRuntime::PROCESS_TYPE_UTILITY:
+      Unused << ipc::UtilityProcessManager::GetSingleton()
+                    ->GetProcessParent(ipc::SandboxingKind::GENERIC_UTILITY)
+                    ->SendTestTriggerMetrics()
+                    ->Then(
+                        GetCurrentSerialEventTarget(), __func__,
+                        [promise]() { promise->MaybeResolveWithUndefined(); },
+                        [promise]() { promise->MaybeRejectWithUndefined(); });
+      break;
+    default:
+      promise->MaybeRejectWithUndefined();
+      break;
+  }
+}
+
+}  // namespace mozilla::glean
diff --git a/toolkit/components/glean/ipc/FOGIPC.h b/toolkit/components/glean/ipc/FOGIPC.h
new file mode 100644
index 0000000000..3701f71838
--- /dev/null
+++ b/toolkit/components/glean/ipc/FOGIPC.h
@@ -0,0 +1,102 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef FOGIPC_h__
+#define FOGIPC_h__
+
+#include <functional>
+
+#include "mozilla/Maybe.h"
+#include "mozilla/MozPromise.h"
+#include "nsTArrayForwardDeclare.h"
+
+namespace mozilla {
+namespace ipc {
+class ByteBuf;
+}  // namespace ipc
+}  // namespace mozilla
+
+// This module provides the interface for FOG to communicate between processes.
+
+namespace mozilla {
+namespace glean {
+
+/**
+ * The parent process is asking you to flush your data ASAP.
+ *
+ * @param aResolver - The function you need to call with the bincoded,
+ *                    serialized payload that the Rust impl hands you.
+ */
+void FlushFOGData(std::function<void(ipc::ByteBuf&&)>&& aResolver);
+
+/**
+ * Called by FOG on the parent process when it wants to flush all its
+ * children's data.
+ * @param aResolver - The function that'll be called with the results.
+ */
+void FlushAllChildData(
+    std::function<void(nsTArray<ipc::ByteBuf>&&)>&& aResolver);
+
+/**
+ * A child process has sent you this buf as a treat.
+ * @param buf - a bincoded serialized payload that the Rust impl understands.
+ */
+void FOGData(ipc::ByteBuf&& buf);
+
+/**
+ * Called by FOG on a child process when it wants to send a buf to the parent.
+ * @param buf - a bincoded serialized payload that the Rust impl understands.
+ */
+void SendFOGData(ipc::ByteBuf&& buf);
+
+/**
+ * Called on the parent process to ask all child processes for data,
+ * sending it all down into Rust to be used.
+ *
+ * @returns a Promise that resolves when the data has made it to the parent.
+ */
+RefPtr<GenericPromise> FlushAndUseFOGData();
+
+/**
+ * ** Test-only Method **
+ *
+ * Trigger GMP, GPU, RDD or Socket process test instrumentation.
+ *
+ * @param processType - one of the PROCESS_TYPE_* constants from nsIXULRuntime.
+ * @param promise - a promise that will be resolved when the data has made it to
+ *                  the target process.
+ */
+void TestTriggerMetrics(uint32_t processType,
+                        const RefPtr<dom::Promise>& promise);
+
+#ifdef NIGHTLY_BUILD
+/**
+ * This function records the CPU activity (CPU time used and wakeup count)
+ * of a specific thread. It is called only by profiler code, either multiple
+ * times in a row when RecordPowerMetrics asks the profiler to record
+ * the wakeup counts of all threads, or once when a thread is unregistered.
+ *
+ * @param aThreadName The name of the thread for which the CPU data is being
+ *                    recorded.
+ *                    The name will be converted to lower case, and characters
+ *                    that are not valid for glean labels will be replaced with
+ *                    '_'. The resulting name should be part of the
+ *                    per_thread_labels static list of labels defined in
+ *                    toolkit/components/processtools/metrics.yaml.
+ * @param aCpuTimeMs CPU time in miliseconds since the last time CPU use data
+ *                   was recorded for this thread.
+ * @param aWakeCount How many times the thread woke up since the previous time
+ *                   CPU use data was recorded for this thread.
+ */
+void RecordThreadCpuUse(const nsACString& aThreadName, uint64_t aCpuTimeMs,
+                        uint64_t aWakeCount);
+#endif
+
+void RecordPowerMetrics();
+
+}  // namespace glean
+}  // namespace mozilla
+
+#endif  // FOGIPC_h__
diff --git a/toolkit/components/glean/ipc/Support.cpp b/toolkit/components/glean/ipc/Support.cpp
new file mode 100644
index 0000000000..479b9b42b0
--- /dev/null
+++ b/toolkit/components/glean/ipc/Support.cpp
@@ -0,0 +1,74 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This file is for support functions for the Rust IPC module.
+// Some information just isn't available to Rust and must be made available over
+// FFI.
+#include "FOGIPC.h"
+#include "mozilla/AppShutdown.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Unused.h"
+#include "nsThreadUtils.h"
+
+using mozilla::AppShutdown;
+using mozilla::RunOnShutdown;
+using mozilla::ShutdownPhase;
+using mozilla::Unused;
+using mozilla::glean::FlushFOGData;
+using mozilla::glean::SendFOGData;
+using mozilla::ipc::ByteBuf;
+
+extern "C" {
+void FOG_RegisterContentChildShutdown() {
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed)) {
+    return;
+  }
+
+  // If there is no main thread (too early in startup or too late in shutdown),
+  // there's nothing we can do but log.
+  bool failed =
+      NS_FAILED(NS_DispatchToMainThread(NS_NewRunnableFunction(__func__, [] {
+        // By the time the main thread dispatched this, it may already be too
+        // late.
+        if (AppShutdown::IsInOrBeyond(ShutdownPhase::AppShutdownConfirmed)) {
+          return;
+        }
+        RunOnShutdown(
+            [] {
+              FlushFOGData(
+                  [](ByteBuf&& aBuf) { SendFOGData(std::move(aBuf)); });
+            },
+            ShutdownPhase::AppShutdownConfirmed);
+      })));
+  if (failed) {
+    NS_WARNING(
+        "Failed to register FOG content child shutdown flush. "
+        "Will lose shutdown data and leak a runnable.");
+    mozilla::glean::fog_ipc::shutdown_registration_failures.Add(1);
+  }
+}
+
+int FOG_GetProcessType() { return XRE_GetProcessType(); }
+
+/**
+ * Called from FOG IPC in Rust when the IPC Payload might be getting full.
+ * We should probably flush before we reach the max IPC message size.
+ */
+void FOG_IPCPayloadFull() {
+  // NS_DispatchToMainThread can leak the runnable (bug 1787589), so let's be
+  // sure not to create it too late in shutdown.
+  // We choose XPCOMShutdown to match gFOG->Shutdown().
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMShutdown)) {
+    return;
+  }
+  // FOG IPC must happen on the main thread until bug 1641989.
+  // If there is no main thread (too early in startup or too late in shutdown),
+  // there's nothing we can do but log.
+  Unused << NS_WARN_IF(NS_FAILED(NS_DispatchToMainThread(
+      NS_NewRunnableFunction("FOG IPC Payload getting full", [] {
+        FlushFOGData([](ByteBuf&& aBuf) { SendFOGData(std::move(aBuf)); });
+      }))));
+}
+}
diff --git a/toolkit/components/glean/metrics.yaml b/toolkit/components/glean/metrics.yaml
new file mode 100644
index 0000000000..40961c5297
--- /dev/null
+++ b/toolkit/components/glean/metrics.yaml
@@ -0,0 +1,137 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is for Internal FOG Use Only.
+# Please don't add anything here unless you have the permission of a
+# Telemetry Module Peer.
+
+---
+$schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
+$tags:
+  - 'Toolkit :: Telemetry'
+
+fog:
+  initialization:
+    type: timespan
+    time_unit: nanosecond
+    description: |
+      Time the FOG initialization takes.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1662123
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1662123#c3
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - jrediger@mozilla.com
+      - glean-team@mozilla.com
+    expires: never
+
+  failed_idle_registration:
+    type: boolean
+    lifetime: application
+    description: |
+      True if we failed to register with the idle service. Absent otherwise.
+      Means IPC probably isn't working well.
+      Child-process data will likely be absent, or incomplete.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694739
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694739#c5
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - chutten@mozilla.com
+      - glean-team@mozilla.com
+    expires: never
+
+fog.ipc:
+  replay_failures:
+    type: counter
+    description: |
+      The number of times the ipc buffer failed to be replayed in the
+      parent process.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1664461
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1664461
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - chutten@mozilla.com
+      - glean-team@mozilla.com
+    expires: never
+
+  buffer_sizes:
+    type: memory_distribution
+    memory_unit: byte
+    description: |
+      The number and size of the IPC buffers being received over FOG IPC.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694739
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694739#c5
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - chutten@mozilla.com
+      - glean-team@mozilla.com
+    expires: never
+
+  flush_durations:
+    type: timing_distribution
+    time_unit: microsecond
+    description: |
+      The length of time between asking the child processes for their
+      IPC buffers and all of them being received by the parent.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694739
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694739#c5
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - chutten@mozilla.com
+      - glean-team@mozilla.com
+    expires: never
+
+  flush_failures:
+    type: counter
+    description: |
+      The number of times we failed to flush all non-parent-process data,
+      throwing even partial results into the trash.
+      If this number is high, we might consider writing custom `MozPromise`-
+      handling code instead of using `MozPromise::All`.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1729026
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1729026
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - chutten@mozilla.com
+      - glean-team@mozilla.com
+    expires: never
+
+  shutdown_registration_failures:
+    type: counter
+    description: |
+      The number of times we tried to register shutdown flush routines for
+      content child processes, and failed (probably because there was no main
+      thread).
+      As a result there may be data loss from content child processes.
+      Large or rising number of clients experiencing this indicates we should
+      perhaps refactor content child shutdown in FOG to try harder to register
+      flush operations.
+      Will likely be obsoleted by bug 1641989.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1766977
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1766977
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - chutten@mozilla.com
+      - glean-team@mozilla.com
+    expires: never
diff --git a/toolkit/components/glean/metrics_index.py b/toolkit/components/glean/metrics_index.py
new file mode 100644
index 0000000000..fc6cf9cb09
--- /dev/null
+++ b/toolkit/components/glean/metrics_index.py
@@ -0,0 +1,102 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# ATTENTION: Changes to this file will need to be reflected in probe-scraper[1].
+# This should happen automatically once a day.
+# If something is unclear or data is not showing up in time
+# you will need to file a bug in Data Platform and Tools :: General.
+#
+# [1] https://github.com/mozilla/probe-scraper
+
+# Metrics that are sent by Gecko and everyone using Gecko
+# (Firefox Desktop, Firefox for Android, Focus for Android, etc.).
+# Order is lexicographical, enforced by t/c/glean/tests/pytest/test_yaml_indices.py
+gecko_metrics = [
+    "browser/base/content/metrics.yaml",
+    "dom/media/metrics.yaml",
+    "dom/media/webrtc/metrics.yaml",
+    "dom/metrics.yaml",
+    "gfx/metrics.yaml",
+    "netwerk/metrics.yaml",
+    "netwerk/protocol/http/metrics.yaml",
+    "toolkit/components/cookiebanners/metrics.yaml",
+    "toolkit/components/glean/metrics.yaml",
+    "toolkit/components/pdfjs/metrics.yaml",
+    "toolkit/components/processtools/metrics.yaml",
+]
+
+# Metrics that are sent by Firefox Desktop
+# Order is lexicographical, enforced by t/c/glean/tests/pytest/test_yaml_indices.py
+firefox_desktop_metrics = [
+    "browser/components/metrics.yaml",
+    "browser/components/newtab/metrics.yaml",
+    "browser/components/search/metrics.yaml",
+    "browser/components/urlbar/metrics.yaml",
+    "browser/modules/metrics.yaml",
+    "toolkit/components/extensions/metrics.yaml",
+    "toolkit/components/nimbus/metrics.yaml",
+    "toolkit/components/search/metrics.yaml",
+    "toolkit/components/telemetry/dap/metrics.yaml",
+    "toolkit/components/telemetry/metrics.yaml",
+    "toolkit/xre/metrics.yaml",
+]
+
+# Metrics that are sent by the Firefox Desktop Background Update Task
+# Order is lexicographical, enforced by t/c/glean/tests/pytest/test_yaml_indices.py
+background_update_metrics = [
+    "toolkit/mozapps/update/metrics.yaml",
+]
+
+# Test metrics
+# Order is lexicographical, enforced by t/c/glean/tests/pytest/test_yaml_indices.py
+test_metrics = [
+    "toolkit/components/glean/tests/test_metrics.yaml",
+]
+
+# The list of all Glean metrics.yaml files, relative to the top src dir.
+# ONLY TO BE MODIFIED BY FOG PEERS!
+metrics_yamls = (
+    gecko_metrics + firefox_desktop_metrics + background_update_metrics + test_metrics
+)
+
+# Pings that are sent by Gecko and everyone using Gecko
+# (Firefox Desktop, Firefox for Android, Focus for Android, etc.).
+# Order is lexicographical, enforced by t/c/glean/tests/pytest/test_yaml_indices.py
+gecko_pings = [
+    "dom/pings.yaml",
+    "toolkit/components/glean/pings.yaml",
+]
+
+# Pings that are sent by Firefox Desktop.
+# Order is lexicographical, enforced by t/c/glean/tests/pytest/test_yaml_indices.py
+firefox_desktop_pings = [
+    "browser/components/newtab/pings.yaml",
+    "toolkit/components/telemetry/pings.yaml",
+]
+
+# Pings that are sent by the Firefox Desktop Background Update Task
+# Order is lexicographical, enforced by t/c/glean/tests/pytest/test_yaml_indices.py
+background_update_pings = [
+    "toolkit/mozapps/update/pings.yaml",
+]
+
+# Test pings
+# Order is lexicographical, enforced by t/c/glean/tests/pytest/test_yaml_indices.py
+test_pings = [
+    "toolkit/components/glean/tests/test_pings.yaml",
+]
+
+# The list of all Glean pings.yaml files, relative to the top src dir.
+# ONLY TO BE MODIFIED BY FOG PEERS!
+pings_yamls = gecko_pings + firefox_desktop_pings + background_update_pings + test_pings
+
+# The list of tags that are allowed in the above to files, and their
+# descriptions. Currently we restrict to a set scraped from bugzilla
+# (via `./mach update-glean-tags`)
+# Order is lexicographical, enforced by t/c/glean/tests/pytest/test_yaml_indices.py
+tags_yamls = [
+    "toolkit/components/glean/tags.yaml",
+]
diff --git a/toolkit/components/glean/moz.build b/toolkit/components/glean/moz.build
new file mode 100644
index 0000000000..4af10cdc0a
--- /dev/null
+++ b/toolkit/components/glean/moz.build
@@ -0,0 +1,213 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+SPHINX_TREES["/toolkit/components/glean"] = "docs"
+
+# Needed so that we can include IPC things.
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+EXPORTS.mozilla += [
+    "ipc/FOGIPC.h",
+]
+
+EXPORTS.mozilla.glean += [
+    "!GleanMetrics.h",
+    "!GleanPings.h",
+]
+
+EXPORTS.mozilla.glean.bindings += [
+    "!EventGIFFTMap.h",
+    "!GleanJSMetricsLookup.h",
+    "!GleanJSPingsLookup.h",
+    "!HistogramGIFFTMap.h",
+    "!ScalarGIFFTMap.h",
+    "bindings/Category.h",
+    "bindings/Glean.h",
+    "bindings/GleanPings.h",
+    "bindings/MetricTypes.h",
+    "bindings/private/Boolean.h",
+    "bindings/private/Common.h",
+    "bindings/private/Counter.h",
+    "bindings/private/CustomDistribution.h",
+    "bindings/private/Datetime.h",
+    "bindings/private/Denominator.h",
+    "bindings/private/DistributionData.h",
+    "bindings/private/Event.h",
+    "bindings/private/Labeled.h",
+    "bindings/private/MemoryDistribution.h",
+    "bindings/private/Numerator.h",
+    "bindings/private/Ping.h",
+    "bindings/private/Quantity.h",
+    "bindings/private/Rate.h",
+    "bindings/private/String.h",
+    "bindings/private/StringList.h",
+    "bindings/private/Timespan.h",
+    "bindings/private/TimingDistribution.h",
+    "bindings/private/Url.h",
+    "bindings/private/Uuid.h",
+]
+
+EXPORTS.mozilla.glean.bindings.jog += [
+    "bindings/jog/JOG.h",
+]
+
+if CONFIG["COMPILE_ENVIRONMENT"]:
+    EXPORTS.mozilla.glean += [
+        "!fog_ffi_generated.h",
+    ]
+
+    EXPORTS.mozilla.glean.bindings.jog += [
+        "!jog_ffi_generated.h",
+    ]
+
+    CbindgenHeader("fog_ffi_generated.h", inputs=["/toolkit/components/glean"])
+    CbindgenHeader(
+        "jog_ffi_generated.h", inputs=["/toolkit/components/glean/bindings/jog"]
+    )
+
+UNIFIED_SOURCES += [
+    "bindings/Category.cpp",
+    "bindings/Glean.cpp",
+    "bindings/GleanPings.cpp",
+    "bindings/jog/JOG.cpp",
+    "bindings/private/Boolean.cpp",
+    "bindings/private/Common.cpp",
+    "bindings/private/Counter.cpp",
+    "bindings/private/CustomDistribution.cpp",
+    "bindings/private/Datetime.cpp",
+    "bindings/private/Denominator.cpp",
+    "bindings/private/Event.cpp",
+    "bindings/private/Labeled.cpp",
+    "bindings/private/MemoryDistribution.cpp",
+    "bindings/private/Numerator.cpp",
+    "bindings/private/Ping.cpp",
+    "bindings/private/Quantity.cpp",
+    "bindings/private/Rate.cpp",
+    "bindings/private/String.cpp",
+    "bindings/private/StringList.cpp",
+    "bindings/private/Timespan.cpp",
+    "bindings/private/TimingDistribution.cpp",
+    "bindings/private/Url.cpp",
+    "bindings/private/Uuid.cpp",
+    "ipc/FOGIPC.cpp",
+    "ipc/Support.cpp",
+]
+
+SOURCES += [
+    "!EventExtraGIFFTMaps.cpp",
+]
+
+# Provides us the list of dependent metrics|pings.yaml.
+include("metrics_index.py")
+# GeneratedFile's `inputs` are relative to our dir.
+# The yamls arrays are relative to topsrcdir, so we need to transform:
+metrics_yamls = ["../../../" + x for x in metrics_yamls]
+pings_yamls = ["../../../" + x for x in pings_yamls]
+tags_yamls = ["../../../" + x for x in tags_yamls]
+# If you change the length of this deps list, update DEPS_LEN in run_glean_parser.py
+deps = [
+    "metrics_index.py",
+    "build_scripts/glean_parser_ext/cpp.py",
+    "build_scripts/glean_parser_ext/jog.py",
+    "build_scripts/glean_parser_ext/js.py",
+    "build_scripts/glean_parser_ext/run_glean_parser.py",
+    "build_scripts/glean_parser_ext/rust.py",
+    "build_scripts/glean_parser_ext/string_table.py",
+    "build_scripts/glean_parser_ext/util.py",
+    "build_scripts/glean_parser_ext/templates/cpp.jinja2",
+    "build_scripts/glean_parser_ext/templates/cpp_pings.jinja2",
+    "build_scripts/glean_parser_ext/templates/gifft.jinja2",
+    "build_scripts/glean_parser_ext/templates/gifft_events.jinja2",
+    "build_scripts/glean_parser_ext/templates/jog_factory.jinja2",
+    "build_scripts/glean_parser_ext/templates/js.jinja2",
+    "build_scripts/glean_parser_ext/templates/js_pings.jinja2",
+    "build_scripts/glean_parser_ext/templates/rust.jinja2",
+    "build_scripts/glean_parser_ext/templates/rust_pings.jinja2",
+]
+
+GeneratedFile(
+    "GleanMetrics.h",
+    "GleanJSMetricsLookup.h",
+    "api/src/metrics.rs",
+    script="build_scripts/glean_parser_ext/run_glean_parser.py",
+    flags=[CONFIG["MOZ_APP_VERSION"], "GleanJSMetricsLookup.h", "api/src/metrics.rs"],
+    inputs=deps + metrics_yamls + tags_yamls,
+)
+
+GeneratedFile(
+    "GleanPings.h",
+    "GleanJSPingsLookup.h",
+    "api/src/pings.rs",
+    script="build_scripts/glean_parser_ext/run_glean_parser.py",
+    flags=[CONFIG["MOZ_APP_VERSION"], "GleanJSPingsLookup.h", "api/src/pings.rs"],
+    inputs=deps + pings_yamls + tags_yamls,
+)
+
+# Glean Interface For Firefox Telemetry Maps from Glean MetricId to Telemetry ProbeId
+# We split it one map per header to avoid unused function warnings on build.
+GeneratedFile(
+    "EventGIFFTMap.h",
+    script="build_scripts/glean_parser_ext/run_glean_parser.py",
+    entry_point="gifft_map",
+    flags=[CONFIG["MOZ_APP_VERSION"], "Event"],
+    inputs=deps + metrics_yamls + tags_yamls,
+)
+
+GeneratedFile(
+    "HistogramGIFFTMap.h",
+    script="build_scripts/glean_parser_ext/run_glean_parser.py",
+    entry_point="gifft_map",
+    flags=[CONFIG["MOZ_APP_VERSION"], "Histogram"],
+    inputs=deps + metrics_yamls + tags_yamls,
+)
+
+GeneratedFile(
+    "ScalarGIFFTMap.h",
+    script="build_scripts/glean_parser_ext/run_glean_parser.py",
+    entry_point="gifft_map",
+    flags=[CONFIG["MOZ_APP_VERSION"], "Scalar"],
+    inputs=deps + metrics_yamls + tags_yamls,
+)
+
+# JOG provides both the Rust factory for building runtime-registered metrics
+# and pings _and_ the YAML file used at runtime to register those metrics and
+# pings for Artifact Builds.
+# The factory lives inside the `fog` crate to avoid a circular dependency.
+GeneratedFile(
+    "api/src/factory.rs",
+    script="build_scripts/glean_parser_ext/run_glean_parser.py",
+    entry_point="jog_factory",
+    flags=[CONFIG["MOZ_APP_VERSION"]],
+    inputs=deps + pings_yamls + metrics_yamls + tags_yamls,
+)
+
+# Only generate jogfile.json in Artifact Builds since
+# its presence triggers main-thread I/O (!MOZILLA_OFFICIAL builds only).
+if not CONFIG["COMPILE_ENVIRONMENT"]:
+    GeneratedFile(
+        "jogfile.json",
+        script="build_scripts/glean_parser_ext/run_glean_parser.py",
+        entry_point="jog_file",
+        flags=[CONFIG["MOZ_APP_VERSION"]],
+        inputs=deps + pings_yamls + metrics_yamls + tags_yamls,
+    )
+    # Once generated, it needs to be placed in GreD so it can be found.
+    FINAL_TARGET_FILES += ["!jogfile.json"]
+
+DIRS += [
+    "tests",  # Must be in DIRS, not TEST_DIRS or python-test won't find it.
+    "xpcom",
+]
+
+with Files("docs/**"):
+    SCHEDULES.exclusive = ["docs"]
+
+with Files("**"):
+    BUG_COMPONENT = ("Toolkit", "Telemetry")
+
+REQUIRES_UNIFIED_BUILD = True
diff --git a/toolkit/components/glean/pings.yaml b/toolkit/components/glean/pings.yaml
new file mode 100644
index 0000000000..d4710a47c2
--- /dev/null
+++ b/toolkit/components/glean/pings.yaml
@@ -0,0 +1,13 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file defines the pings that are recorded by the Glean SDK. They are
+# automatically converted to platform-specific code at build time using the
+# `glean_parser` PyPI package.
+
+# This file is presently for Internal FOG Use Only.
+# You should not add pings here until probably about January of 2021.
+
+---
+$schema: moz://mozilla.org/schemas/glean/pings/2-0-0
diff --git a/toolkit/components/glean/src/init/mod.rs b/toolkit/components/glean/src/init/mod.rs
new file mode 100644
index 0000000000..5bf217e081
--- /dev/null
+++ b/toolkit/components/glean/src/init/mod.rs
@@ -0,0 +1,330 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use std::env;
+use std::ffi::CString;
+use std::ops::DerefMut;
+use std::path::PathBuf;
+
+#[cfg(target_os = "android")]
+use nserror::NS_ERROR_NOT_IMPLEMENTED;
+use nserror::{nsresult, NS_ERROR_FAILURE};
+use nsstring::{nsACString, nsCString, nsString};
+use xpcom::interfaces::{nsIFile, nsIPrefService, nsIProperties, nsIXULAppInfo, nsIXULRuntime};
+use xpcom::{RefPtr, XpCom};
+
+use glean::{ClientInfoMetrics, Configuration};
+
+#[cfg(not(target_os = "android"))]
+mod upload_pref;
+#[cfg(not(target_os = "android"))]
+mod user_activity;
+#[cfg(not(target_os = "android"))]
+mod viaduct_uploader;
+
+#[cfg(not(target_os = "android"))]
+use upload_pref::UploadPrefObserver;
+#[cfg(not(target_os = "android"))]
+use user_activity::UserActivityObserver;
+#[cfg(not(target_os = "android"))]
+use viaduct_uploader::ViaductUploader;
+
+/// Project FOG's entry point.
+///
+/// This assembles client information and the Glean configuration and then initializes the global
+/// Glean instance.
+#[cfg(not(target_os = "android"))]
+#[no_mangle]
+pub extern "C" fn fog_init(
+    data_path_override: &nsACString,
+    app_id_override: &nsACString,
+) -> nsresult {
+    let upload_enabled = static_prefs::pref!("datareporting.healthreport.uploadEnabled");
+    let recording_enabled = static_prefs::pref!("telemetry.fog.test.localhost_port") < 0;
+    let uploader = Some(Box::new(ViaductUploader) as Box<dyn glean::net::PingUploader>);
+
+    fog_init_internal(
+        data_path_override,
+        app_id_override,
+        upload_enabled || recording_enabled,
+        uploader,
+    )
+    .into()
+}
+
+/// Project FOG's entry point on Android.
+///
+/// This assembles client information and the Glean configuration and then initializes the global
+/// Glean instance.
+/// It always enables upload and set no uploader.
+/// This should only be called in test scenarios.
+/// In normal use Glean should be initialized and controlled by the Glean Kotlin SDK.
+#[cfg(target_os = "android")]
+#[no_mangle]
+pub extern "C" fn fog_init(
+    data_path_override: &nsACString,
+    app_id_override: &nsACString,
+) -> nsresult {
+    // On Android always enable Glean upload.
+    let upload_enabled = true;
+    // Don't set up an uploader.
+    let uploader = None;
+
+    fog_init_internal(
+        data_path_override,
+        app_id_override,
+        upload_enabled,
+        uploader,
+    )
+    .into()
+}
+
+fn fog_init_internal(
+    data_path_override: &nsACString,
+    app_id_override: &nsACString,
+    upload_enabled: bool,
+    uploader: Option<Box<dyn glean::net::PingUploader>>,
+) -> Result<(), nsresult> {
+    fog::metrics::fog::initialization.start();
+
+    log::debug!("Initializing FOG.");
+
+    setup_observers()?;
+
+    let (mut conf, client_info) = build_configuration(data_path_override, app_id_override)?;
+
+    conf.upload_enabled = upload_enabled;
+    conf.uploader = uploader;
+
+    // If we're operating in automation without any specific source tags to set,
+    // set the tag "automation" so any pings that escape don't clutter the tables.
+    // See https://mozilla.github.io/glean/book/user/debugging/index.html#enabling-debugging-features-through-environment-variables
+    if env::var("MOZ_AUTOMATION").is_ok() && env::var("GLEAN_SOURCE_TAGS").is_err() {
+        log::info!("In automation, setting 'automation' source tag.");
+        glean::set_source_tags(vec!["automation".to_string()]);
+        log::info!("In automation, disabling MPS to avoid 4am issues.");
+        conf.use_core_mps = false;
+    }
+
+    log::debug!("Configuration: {:#?}", conf);
+
+    // Register all custom pings before we initialize.
+    fog::pings::register_pings();
+
+    glean::initialize(conf, client_info);
+
+    fog::metrics::fog::initialization.stop();
+
+    Ok(())
+}
+
+fn build_configuration(
+    data_path_override: &nsACString,
+    app_id_override: &nsACString,
+) -> Result<(Configuration, ClientInfoMetrics), nsresult> {
+    let data_path_str = if data_path_override.is_empty() {
+        get_data_path()?
+    } else {
+        data_path_override.to_utf8().to_string()
+    };
+    let data_path = PathBuf::from(&data_path_str);
+
+    let (app_build, app_display_version, channel) = get_app_info()?;
+
+    let client_info = ClientInfoMetrics {
+        app_build,
+        app_display_version,
+        channel: Some(channel),
+    };
+    log::debug!("Client Info: {:#?}", client_info);
+
+    const SERVER: &str = "https://incoming.telemetry.mozilla.org";
+    let localhost_port = static_prefs::pref!("telemetry.fog.test.localhost_port");
+    let server = if localhost_port > 0 {
+        format!("http://localhost:{}", localhost_port)
+    } else {
+        String::from(SERVER)
+    };
+
+    // In the event that this isn't "firefox.desktop", we don't use core's MPS.
+    let mut use_core_mps = false;
+    let application_id = if app_id_override.is_empty() {
+        use_core_mps = true;
+        "firefox.desktop".to_string()
+    } else {
+        app_id_override.to_utf8().to_string()
+    };
+
+    let configuration = Configuration {
+        upload_enabled: false,
+        data_path,
+        application_id,
+        max_events: None,
+        delay_ping_lifetime_io: true,
+        server_endpoint: Some(server),
+        uploader: None,
+        use_core_mps,
+    };
+
+    Ok((configuration, client_info))
+}
+
+#[cfg(not(target_os = "android"))]
+fn setup_observers() -> Result<(), nsresult> {
+    if let Err(e) = UploadPrefObserver::begin_observing() {
+        log::error!(
+            "Could not observe data upload pref. Abandoning FOG init due to {:?}",
+            e
+        );
+        return Err(e);
+    }
+
+    if let Err(e) = UserActivityObserver::begin_observing() {
+        log::error!(
+            "Could not observe user activity. Abandoning FOG init due to {:?}",
+            e
+        );
+        return Err(e);
+    }
+
+    Ok(())
+}
+
+#[cfg(target_os = "android")]
+fn setup_observers() -> Result<(), nsresult> {
+    // No observers are set up on Android.
+    Ok(())
+}
+
+/// Construct and return the data_path from the profile dir, or return an error.
+fn get_data_path() -> Result<String, nsresult> {
+    let dir_svc: RefPtr<nsIProperties> = match xpcom::components::Directory::service() {
+        Ok(ds) => ds,
+        _ => return Err(NS_ERROR_FAILURE),
+    };
+    let mut profile_dir = xpcom::GetterAddrefs::<nsIFile>::new();
+    unsafe {
+        dir_svc
+            .Get(
+                cstr!("ProfD").as_ptr(),
+                &nsIFile::IID,
+                profile_dir.void_ptr(),
+            )
+            .to_result()?;
+    }
+    let profile_dir = profile_dir.refptr().ok_or(NS_ERROR_FAILURE)?;
+    let mut profile_path = nsString::new();
+    unsafe {
+        (*profile_dir).GetPath(&mut *profile_path).to_result()?;
+    }
+    let profile_path = String::from_utf16(&profile_path[..]).map_err(|_| NS_ERROR_FAILURE)?;
+    let data_path = profile_path + "/datareporting/glean";
+    Ok(data_path)
+}
+
+/// Return a tuple of the build_id, app version, and build channel.
+/// If the XUL Runtime isn't a XULAppInfo (e.g. in xpcshell),
+/// build_id ad app_version will be "unknown".
+/// Other problems result in an error being returned instead.
+fn get_app_info() -> Result<(String, String, String), nsresult> {
+    let xul: RefPtr<nsIXULRuntime> =
+        xpcom::components::XULRuntime::service().map_err(|_| NS_ERROR_FAILURE)?;
+
+    let pref_service: RefPtr<nsIPrefService> =
+        xpcom::components::Preferences::service().map_err(|_| NS_ERROR_FAILURE)?;
+    let branch = xpcom::getter_addrefs(|p| {
+        // Safe because:
+        //  * `null` is explicitly allowed per documentation
+        //  * `p` is a valid outparam guaranteed by `getter_addrefs`
+        unsafe { pref_service.GetDefaultBranch(std::ptr::null(), p) }
+    })?;
+    let pref_name = CString::new("app.update.channel").map_err(|_| NS_ERROR_FAILURE)?;
+    let mut channel = nsCString::new();
+    // Safe because:
+    //  * `branch` is non-null (otherwise `getter_addrefs` would've been `Err`
+    //  * `pref_name` exists so a pointer to it is valid for the life of the function
+    //  * `channel` exists so a pointer to it is valid, and it can be written to
+    unsafe {
+        if (*branch)
+            .GetCharPref(pref_name.as_ptr(), channel.deref_mut() as *mut nsACString)
+            .to_result()
+            .is_err()
+        {
+            channel = "unknown".into();
+        }
+    }
+
+    let app_info = match xul.query_interface::<nsIXULAppInfo>() {
+        Some(ai) => ai,
+        // In e.g. xpcshell the XULRuntime isn't XULAppInfo.
+        // We still want to return sensible values so tests don't explode.
+        _ => {
+            return Ok((
+                "unknown".to_owned(),
+                "unknown".to_owned(),
+                channel.to_string(),
+            ))
+        }
+    };
+
+    let mut build_id = nsCString::new();
+    unsafe {
+        app_info.GetAppBuildID(&mut *build_id).to_result()?;
+    }
+
+    let mut version = nsCString::new();
+    unsafe {
+        app_info.GetVersion(&mut *version).to_result()?;
+    }
+
+    Ok((
+        build_id.to_string(),
+        version.to_string(),
+        channel.to_string(),
+    ))
+}
+
+/// **TEST-ONLY METHOD**
+/// Resets FOG and the underlying Glean SDK, clearing stores.
+#[cfg(not(target_os = "android"))]
+#[no_mangle]
+pub extern "C" fn fog_test_reset(
+    data_path_override: &nsACString,
+    app_id_override: &nsACString,
+) -> nsresult {
+    fog_test_reset_internal(data_path_override, app_id_override).into()
+}
+
+// Split out into its own function so I could use `?`
+#[cfg(not(target_os = "android"))]
+fn fog_test_reset_internal(
+    data_path_override: &nsACString,
+    app_id_override: &nsACString,
+) -> Result<(), nsresult> {
+    let (mut conf, client_info) = build_configuration(data_path_override, app_id_override)?;
+
+    let upload_enabled = static_prefs::pref!("datareporting.healthreport.uploadEnabled");
+    let recording_enabled = static_prefs::pref!("telemetry.fog.test.localhost_port") < 0;
+    conf.upload_enabled = upload_enabled || recording_enabled;
+
+    // Don't accidentally send "main" pings during tests.
+    conf.use_core_mps = false;
+
+    // I'd prefer to reuse the uploader, but it gets moved into Glean so we build anew.
+    conf.uploader = Some(Box::new(ViaductUploader) as Box<dyn glean::net::PingUploader>);
+
+    glean::test_reset_glean(conf, client_info, true);
+    Ok(())
+}
+
+/// **TEST-ONLY METHOD**
+/// Does nothing on Android. Returns NS_ERROR_NOT_IMPLEMENTED.
+#[cfg(target_os = "android")]
+#[no_mangle]
+pub extern "C" fn fog_test_reset(
+    _data_path_override: &nsACString,
+    _app_id_override: &nsACString,
+) -> nsresult {
+    NS_ERROR_NOT_IMPLEMENTED
+}
diff --git a/toolkit/components/glean/src/init/upload_pref.rs b/toolkit/components/glean/src/init/upload_pref.rs
new file mode 100644
index 0000000000..737230c16c
--- /dev/null
+++ b/toolkit/components/glean/src/init/upload_pref.rs
@@ -0,0 +1,99 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use std::ffi::CStr;
+use std::os::raw::c_char;
+use std::sync::atomic::{AtomicBool, Ordering};
+
+use nserror::{nsresult, NS_ERROR_FAILURE, NS_OK};
+use nsstring::{nsACString, nsCStr};
+use xpcom::{
+    interfaces::{nsIPrefBranch, nsISupports},
+    RefPtr,
+};
+
+/// Whether the current value of the localhost testing pref is permitting
+/// metric recording (even if upload is disabled).
+static RECORDING_ENABLED: AtomicBool = AtomicBool::new(false);
+
+// Partially cargo-culted from https://searchfox.org/mozilla-central/rev/598e50d2c3cd81cd616654f16af811adceb08f9f/security/manager/ssl/cert_storage/src/lib.rs#1192
+#[xpcom(implement(nsIObserver), atomic)]
+pub(crate) struct UploadPrefObserver {}
+
+#[allow(non_snake_case)]
+impl UploadPrefObserver {
+    pub(crate) fn begin_observing() -> Result<(), nsresult> {
+        // Ensure we begin with the correct current value of RECORDING_ENABLED.
+        let recording_enabled = static_prefs::pref!("telemetry.fog.test.localhost_port") < 0;
+        RECORDING_ENABLED.store(recording_enabled, Ordering::SeqCst);
+
+        // SAFETY: Everything here is self-contained.
+        //
+        // * We allocate the pref observer, created by the xpcom macro
+        // * We query the pref service and bail out if it doesn't exist.
+        // * We create a nsCStr from a static string.
+        // * We control all input to `AddObserverImpl`
+        unsafe {
+            let pref_obs = Self::allocate(InitUploadPrefObserver {});
+            let pref_branch: RefPtr<nsIPrefBranch> =
+                xpcom::components::Preferences::service().map_err(|_| NS_ERROR_FAILURE)?;
+            let pref_nscstr =
+                &nsCStr::from("datareporting.healthreport.uploadEnabled") as &nsACString;
+            (*pref_branch)
+                .AddObserverImpl(pref_nscstr, pref_obs.coerce(), false)
+                .to_result()?;
+            let pref_nscstr = &nsCStr::from("telemetry.fog.test.localhost_port") as &nsACString;
+            (*pref_branch)
+                .AddObserverImpl(pref_nscstr, pref_obs.coerce(), false)
+                .to_result()?;
+        }
+
+        Ok(())
+    }
+
+    unsafe fn Observe(
+        &self,
+        _subject: *const nsISupports,
+        topic: *const c_char,
+        pref_name: *const u16,
+    ) -> nserror::nsresult {
+        let topic = CStr::from_ptr(topic).to_str().unwrap();
+        // Conversion utf16 to utf8 is messy.
+        // We should only ever observe changes to one of the two prefs we want,
+        // but just to be on the safe side let's assert.
+
+        // cargo-culted from https://searchfox.org/mozilla-central/rev/598e50d2c3cd81cd616654f16af811adceb08f9f/security/manager/ssl/cert_storage/src/lib.rs#1606-1612
+        // (with a little transformation)
+        let len = (0..).take_while(|&i| *pref_name.offset(i) != 0).count(); // find NUL.
+        let slice = std::slice::from_raw_parts(pref_name, len);
+        let pref_name = match String::from_utf16(slice) {
+            Ok(name) => name,
+            Err(_) => return NS_ERROR_FAILURE,
+        };
+        log::info!("Observed {:?}, {:?}", topic, pref_name);
+        debug_assert!(topic == "nsPref:changed");
+        debug_assert!(
+            pref_name == "datareporting.healthreport.uploadEnabled"
+                || pref_name == "telemetry.fog.test.localhost_port"
+        );
+
+        let upload_enabled = static_prefs::pref!("datareporting.healthreport.uploadEnabled");
+        let recording_enabled = static_prefs::pref!("telemetry.fog.test.localhost_port") < 0;
+        log::info!(
+            "New upload_enabled {}, recording_enabled {}",
+            upload_enabled,
+            recording_enabled
+        );
+        if RECORDING_ENABLED.load(Ordering::SeqCst) && !recording_enabled {
+            // Whenever the test pref goes from permitting recording to forbidding it,
+            // ensure Glean is told to wipe the stores.
+            // This may send a "deletion-request" ping for a client_id that's never sent
+            // any other pings.
+            glean::set_upload_enabled(false);
+        }
+        RECORDING_ENABLED.store(recording_enabled, Ordering::SeqCst);
+        glean::set_upload_enabled(upload_enabled || recording_enabled);
+        NS_OK
+    }
+}
diff --git a/toolkit/components/glean/src/init/user_activity.rs b/toolkit/components/glean/src/init/user_activity.rs
new file mode 100644
index 0000000000..dbafeca4e8
--- /dev/null
+++ b/toolkit/components/glean/src/init/user_activity.rs
@@ -0,0 +1,129 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use std::ffi::CStr;
+use std::os::raw::c_char;
+use std::sync::{
+    atomic::{AtomicBool, Ordering},
+    RwLock,
+};
+use std::time::{Duration, Instant};
+
+use nserror::{nsresult, NS_ERROR_FAILURE, NS_OK};
+use xpcom::{
+    interfaces::{nsIObserverService, nsISupports},
+    RefPtr,
+};
+
+// Partially cargo-culted from UploadPrefObserver.
+#[xpcom(implement(nsIObserver), atomic)]
+pub(crate) struct UserActivityObserver {
+    last_edge: RwLock<Instant>,
+    was_active: AtomicBool,
+}
+
+/// Listens to Firefox Desktop's `user-interaction-(in)active` topics,
+/// debouncing them before calling into the Glean SDK Client Activity API.
+/// See
+/// [the docs](https://firefox-source-docs.mozilla.org/toolkit/components/glean/builtin_pings.html)
+/// for more info.
+#[allow(non_snake_case)]
+impl UserActivityObserver {
+    pub(crate) fn begin_observing() -> Result<(), nsresult> {
+        // First and foremost, even if we can't get the ObserverService,
+        // init always means client activity.
+        glean::handle_client_active();
+
+        // SAFETY: Everything here is self-contained.
+        //
+        // * We allocate the activity observer, created by the xpcom macro
+        // * We create cstr from a static string.
+        // * We control all input to `AddObserver`
+        unsafe {
+            let activity_obs = Self::allocate(InitUserActivityObserver {
+                last_edge: RwLock::new(Instant::now()),
+                was_active: AtomicBool::new(false),
+            });
+            let obs_service: RefPtr<nsIObserverService> =
+                xpcom::components::Observer::service().map_err(|_| NS_ERROR_FAILURE)?;
+            let rv = obs_service.AddObserver(
+                activity_obs.coerce(),
+                cstr!("user-interaction-active").as_ptr(),
+                false,
+            );
+            if !rv.succeeded() {
+                return Err(rv);
+            }
+            let rv = obs_service.AddObserver(
+                activity_obs.coerce(),
+                cstr!("user-interaction-inactive").as_ptr(),
+                false,
+            );
+            if !rv.succeeded() {
+                return Err(rv);
+            }
+        }
+        Ok(())
+    }
+
+    unsafe fn Observe(
+        &self,
+        _subject: *const nsISupports,
+        topic: *const c_char,
+        _data: *const u16,
+    ) -> nserror::nsresult {
+        match CStr::from_ptr(topic).to_str() {
+            Ok("user-interaction-active") => self.handle_active(),
+            Ok("user-interaction-inactive") => self.handle_inactive(),
+            _ => NS_OK,
+        }
+    }
+
+    fn handle_active(&self) -> nserror::nsresult {
+        let was_active = self.was_active.swap(true, Ordering::SeqCst);
+        if !was_active {
+            let inactivity = self
+                .last_edge
+                .read()
+                .expect("Edge lock poisoned.")
+                .elapsed();
+            // We only care after a certain period of inactivity (default 20min).
+            let limit = static_prefs::pref!("telemetry.fog.test.inactivity_limit");
+            if inactivity >= Duration::from_secs(limit.into()) {
+                log::info!(
+                    "User triggers core activity after {}s!",
+                    inactivity.as_secs()
+                );
+                glean::handle_client_active();
+            }
+            let mut edge = self.last_edge.write().expect("Edge lock poisoned.");
+            *edge = Instant::now();
+        }
+        NS_OK
+    }
+
+    fn handle_inactive(&self) -> nserror::nsresult {
+        let was_active = self.was_active.swap(false, Ordering::SeqCst);
+        // This is actually always so. Inactivity is only notified once.
+        if was_active {
+            let activity = self
+                .last_edge
+                .read()
+                .expect("Edge lock poisoned.")
+                .elapsed();
+            // We only care after a certain period of activity (default 2min).
+            let limit = static_prefs::pref!("telemetry.fog.test.activity_limit");
+            if activity >= Duration::from_secs(limit.into()) {
+                log::info!(
+                    "User triggers core inactivity after {}s!",
+                    activity.as_secs()
+                );
+                glean::handle_client_inactive();
+            }
+            let mut edge = self.last_edge.write().expect("Edge lock poisoned.");
+            *edge = Instant::now();
+        }
+        NS_OK
+    }
+}
diff --git a/toolkit/components/glean/src/init/viaduct_uploader.rs b/toolkit/components/glean/src/init/viaduct_uploader.rs
new file mode 100644
index 0000000000..381567b488
--- /dev/null
+++ b/toolkit/components/glean/src/init/viaduct_uploader.rs
@@ -0,0 +1,64 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+use glean::net::{PingUploader, UploadResult};
+use url::Url;
+use viaduct::{Error::*, Request};
+
+/// An uploader that uses [Viaduct](https://github.com/mozilla/application-services/tree/main/components/viaduct).
+#[derive(Debug)]
+pub(crate) struct ViaductUploader;
+
+impl PingUploader for ViaductUploader {
+    /// Uploads a ping to a server.
+    ///
+    /// # Arguments
+    ///
+    /// * `url` - the URL path to upload the data to.
+    /// * `body` - the serialized text data to send.
+    /// * `headers` - a vector of tuples containing the headers to send with
+    ///   the request, i.e. (Name, Value).
+    fn upload(&self, url: String, body: Vec<u8>, headers: Vec<(String, String)>) -> UploadResult {
+        log::trace!("FOG Ping Uploader uploading to {}", url);
+        let url_clone = url.clone();
+        let result: std::result::Result<UploadResult, viaduct::Error> = (move || {
+            let debug_tagged = headers.iter().any(|(name, _)| name == "X-Debug-ID");
+            let localhost_port = static_prefs::pref!("telemetry.fog.test.localhost_port");
+            if localhost_port < 0
+                || (localhost_port == 0 && !debug_tagged && cfg!(feature = "disable_upload"))
+            {
+                log::info!("FOG Ping uploader faking success");
+                return Ok(UploadResult::http_status(200));
+            }
+            let parsed_url = Url::parse(&url_clone)?;
+
+            log::info!("FOG Ping uploader uploading to {:?}", parsed_url);
+
+            let mut req = Request::post(parsed_url.clone()).body(body.clone());
+            for (header_key, header_value) in &headers {
+                req = req.header(header_key.to_owned(), header_value)?;
+            }
+
+            log::trace!("FOG Ping Uploader sending ping to {}", parsed_url);
+            let res = req.send()?;
+            Ok(UploadResult::http_status(res.status as i32))
+        })();
+        log::trace!(
+            "FOG Ping Uploader completed uploading to {} (Result {:?})",
+            url,
+            result
+        );
+        match result {
+            Ok(result) => result,
+            Err(NonTlsUrl | UrlError(_)) => UploadResult::unrecoverable_failure(),
+            Err(
+                RequestHeaderError(_)
+                | BackendError(_)
+                | NetworkError(_)
+                | BackendNotInitialized
+                | SetBackendError,
+            ) => UploadResult::recoverable_failure(),
+        }
+    }
+}
diff --git a/toolkit/components/glean/src/lib.rs b/toolkit/components/glean/src/lib.rs
new file mode 100644
index 0000000000..e74fc106d1
--- /dev/null
+++ b/toolkit/components/glean/src/lib.rs
@@ -0,0 +1,193 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+//! Firefox on Glean (FOG) is the name of the layer that integrates the [Glean SDK][glean-sdk] into Firefox Desktop.
+//! It is currently being designed and implemented.
+//!
+//! The [Glean SDK][glean-sdk] is a data collection library built by Mozilla for use in its products.
+//! Like [Telemetry][telemetry], it can be used to
+//! (in accordance with our [Privacy Policy][privacy-policy])
+//! send anonymous usage statistics to Mozilla in order to make better decisions.
+//!
+//! Documentation can be found online in the [Firefox Source Docs][docs].
+//!
+//! [glean-sdk]: https://github.com/mozilla/glean/
+//! [book-of-glean]: https://mozilla.github.io/glean/book/index.html
+//! [privacy-policy]: https://www.mozilla.org/privacy/
+//! [docs]: https://firefox-source-docs.mozilla.org/toolkit/components/glean/
+
+// No one is currently using the Glean SDK, so let's export it, so we know it gets
+// compiled.
+pub extern crate fog;
+
+use nserror::{nsresult, NS_ERROR_FAILURE, NS_OK};
+use nsstring::{nsACString, nsCString};
+use thin_vec::ThinVec;
+
+#[macro_use]
+extern crate cstr;
+#[cfg_attr(not(target_os = "android"), macro_use)]
+extern crate xpcom;
+
+mod init;
+
+pub use init::fog_init;
+
+#[no_mangle]
+pub extern "C" fn fog_shutdown() {
+    glean::shutdown();
+}
+
+#[no_mangle]
+pub extern "C" fn fog_register_pings() {
+    fog::pings::register_pings();
+}
+
+static mut PENDING_BUF: Vec<u8> = Vec::new();
+
+// IPC serialization/deserialization methods
+// Crucially important that the first two not be called on multiple threads.
+
+/// Only safe if only called on a single thread (the same single thread you call
+/// fog_give_ipc_buf on).
+#[no_mangle]
+pub unsafe extern "C" fn fog_serialize_ipc_buf() -> usize {
+    if let Some(buf) = fog::ipc::take_buf() {
+        PENDING_BUF = buf;
+        PENDING_BUF.len()
+    } else {
+        PENDING_BUF = vec![];
+        0
+    }
+}
+
+/// Only safe if called on a single thread (the same single thread you call
+/// fog_serialize_ipc_buf on), and if buf points to an allocated buffer of at
+/// least buf_len bytes.
+#[no_mangle]
+pub unsafe extern "C" fn fog_give_ipc_buf(buf: *mut u8, buf_len: usize) -> usize {
+    let pending_len = PENDING_BUF.len();
+    if buf.is_null() || buf_len < pending_len {
+        return 0;
+    }
+    std::ptr::copy_nonoverlapping(PENDING_BUF.as_ptr(), buf, pending_len);
+    PENDING_BUF = Vec::new();
+    pending_len
+}
+
+/// Only safe if buf points to an allocated buffer of at least buf_len bytes.
+/// No ownership is transfered to Rust by this method: caller owns the memory at
+/// buf before and after this call.
+#[no_mangle]
+pub unsafe extern "C" fn fog_use_ipc_buf(buf: *const u8, buf_len: usize) {
+    let slice = std::slice::from_raw_parts(buf, buf_len);
+    let res = fog::ipc::replay_from_buf(slice);
+    if res.is_err() {
+        log::warn!("Unable to replay ipc buffer. This will result in data loss.");
+        fog::metrics::fog_ipc::replay_failures.add(1);
+    }
+}
+
+/// Sets the debug tag for pings assembled in the future.
+/// Returns an error result if the provided value is not a valid tag.
+#[no_mangle]
+pub extern "C" fn fog_set_debug_view_tag(value: &nsACString) -> nsresult {
+    let result = glean::set_debug_view_tag(&value.to_string());
+    if result {
+        return NS_OK;
+    } else {
+        return NS_ERROR_FAILURE;
+    }
+}
+
+/// Submits a ping by name.
+#[no_mangle]
+pub extern "C" fn fog_submit_ping(ping_name: &nsACString) -> nsresult {
+    glean::submit_ping_by_name(&ping_name.to_string(), None);
+    NS_OK
+}
+
+/// Turns ping logging on or off.
+/// Returns an error if the logging failed to be configured.
+#[no_mangle]
+pub extern "C" fn fog_set_log_pings(value: bool) -> nsresult {
+    glean::set_log_pings(value);
+    NS_OK
+}
+
+/// Flushes ping-lifetime data to the db when delay_ping_lifetime_io is true.
+#[no_mangle]
+pub extern "C" fn fog_persist_ping_lifetime_data() -> nsresult {
+    glean::persist_ping_lifetime_data();
+    NS_OK
+}
+
+/// Indicate that an experiment is running.
+/// Glean will add an experiment annotation which is sent with pings.
+/// This information is not persisted between runs.
+///
+/// See [`glean_core::Glean::set_experiment_active`].
+#[no_mangle]
+pub extern "C" fn fog_set_experiment_active(
+    experiment_id: &nsACString,
+    branch: &nsACString,
+    extra_keys: &ThinVec<nsCString>,
+    extra_values: &ThinVec<nsCString>,
+) {
+    assert_eq!(
+        extra_keys.len(),
+        extra_values.len(),
+        "Experiment extra keys and values differ in length."
+    );
+    let extra = if extra_keys.len() == 0 {
+        None
+    } else {
+        Some(
+            extra_keys
+                .iter()
+                .zip(extra_values.iter())
+                .map(|(k, v)| (k.to_string(), v.to_string()))
+                .collect(),
+        )
+    };
+    glean::set_experiment_active(experiment_id.to_string(), branch.to_string(), extra);
+}
+
+/// Indicate that an experiment is no longer running.
+///
+/// See [`glean_core::Glean::set_experiment_inactive`].
+#[no_mangle]
+pub extern "C" fn fog_set_experiment_inactive(experiment_id: &nsACString) {
+    glean::set_experiment_inactive(experiment_id.to_string());
+}
+
+/// TEST ONLY FUNCTION
+///
+/// Returns true if the identified experiment is active.
+#[no_mangle]
+pub extern "C" fn fog_test_is_experiment_active(experiment_id: &nsACString) -> bool {
+    glean::test_is_experiment_active(experiment_id.to_string())
+}
+
+/// TEST ONLY FUNCTION
+///
+/// Fills `branch`, `extra_keys`, and `extra_values` with the identified experiment's data.
+/// Panics if the identified experiment isn't active.
+#[no_mangle]
+pub extern "C" fn fog_test_get_experiment_data(
+    experiment_id: &nsACString,
+    branch: &mut nsACString,
+    extra_keys: &mut ThinVec<nsCString>,
+    extra_values: &mut ThinVec<nsCString>,
+) {
+    let data = glean::test_get_experiment_data(experiment_id.to_string());
+    if let Some(data) = data {
+        branch.assign(&data.branch);
+        if let Some(extra) = data.extra {
+            let (data_keys, data_values): (Vec<_>, Vec<_>) = extra.iter().unzip();
+            extra_keys.extend(data_keys.into_iter().map(|key| key.into()));
+            extra_values.extend(data_values.into_iter().map(|value| value.into()));
+        }
+    }
+}
diff --git a/toolkit/components/glean/tags.yaml b/toolkit/components/glean/tags.yaml
new file mode 100644
index 0000000000..4fadce4c94
--- /dev/null
+++ b/toolkit/components/glean/tags.yaml
@@ -0,0 +1,531 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+### This file was AUTOMATICALLY GENERATED by `./mach update-glean-tags`
+### DO NOT edit it by hand.
+
+
+---
+$schema: moz://mozilla.org/schemas/glean/tags/1-0-0
+'Cloud Services :: Firefox: Common':
+  description: The Bugzilla component which applies to this object.
+'Conduit :: mots':
+  description: The Bugzilla component which applies to this object.
+'Core :: Audio/Video':
+  description: The Bugzilla component which applies to this object.
+'Core :: Audio/Video: GMP':
+  description: The Bugzilla component which applies to this object.
+'Core :: Audio/Video: MediaStreamGraph':
+  description: The Bugzilla component which applies to this object.
+'Core :: Audio/Video: Playback':
+  description: The Bugzilla component which applies to this object.
+'Core :: Audio/Video: Recording':
+  description: The Bugzilla component which applies to this object.
+'Core :: Audio/Video: cubeb':
+  description: The Bugzilla component which applies to this object.
+'Core :: AutoConfig (Mission Control Desktop)':
+  description: The Bugzilla component which applies to this object.
+'Core :: CSS Parsing and Computation':
+  description: The Bugzilla component which applies to this object.
+'Core :: CSS Transitions and Animations':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Animation':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Bindings (WebIDL)':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: CSS Object Model':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Content Processes':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Copy & Paste and Drag & Drop':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Core & HTML':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Device Interfaces':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Editor':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Events':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: File':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Forms':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Geolocation':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: HTML Parser':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Navigation':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Networking':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Performance':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Push Notifications':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Security':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Selection':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Serializers':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Service Workers':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Streams':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: UI Events & Focus Handling':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Web Authentication':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Web Payments':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: Workers':
+  description: The Bugzilla component which applies to this object.
+'Core :: DOM: postMessage':
+  description: The Bugzilla component which applies to this object.
+'Core :: Disability Access APIs':
+  description: The Bugzilla component which applies to this object.
+'Core :: Gecko Profiler':
+  description: The Bugzilla component which applies to this object.
+'Core :: General':
+  description: The Bugzilla component which applies to this object.
+'Core :: Graphics':
+  description: The Bugzilla component which applies to this object.
+'Core :: Graphics: Canvas2D':
+  description: The Bugzilla component which applies to this object.
+'Core :: Graphics: CanvasWebGL':
+  description: The Bugzilla component which applies to this object.
+'Core :: Graphics: ImageLib':
+  description: The Bugzilla component which applies to this object.
+'Core :: Graphics: Text':
+  description: The Bugzilla component which applies to this object.
+'Core :: Graphics: WebGPU':
+  description: The Bugzilla component which applies to this object.
+'Core :: Graphics: WebRender':
+  description: The Bugzilla component which applies to this object.
+'Core :: Hardware Abstraction Layer (HAL)':
+  description: The Bugzilla component which applies to this object.
+'Core :: IPC':
+  description: The Bugzilla component which applies to this object.
+'Core :: Internationalization':
+  description: The Bugzilla component which applies to this object.
+'Core :: JavaScript Engine':
+  description: The Bugzilla component which applies to this object.
+'Core :: JavaScript Engine: JIT':
+  description: The Bugzilla component which applies to this object.
+'Core :: JavaScript: GC':
+  description: The Bugzilla component which applies to this object.
+'Core :: JavaScript: Internationalization API':
+  description: The Bugzilla component which applies to this object.
+'Core :: JavaScript: Standard Library':
+  description: The Bugzilla component which applies to this object.
+'Core :: JavaScript: WebAssembly':
+  description: The Bugzilla component which applies to this object.
+'Core :: Javascript: Web Assembly':
+  description: The Bugzilla component which applies to this object.
+'Core :: Javascript: WebAssembly':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Block and Inline':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Columns':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Flexbox':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Floats':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Form Controls':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Generated Content, Lists, and Counters':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Grid':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Images, Video, and HTML Frames':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Positioned':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Ruby':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Scrolling and Overflow':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Tables':
+  description: The Bugzilla component which applies to this object.
+'Core :: Layout: Text and Fonts':
+  description: The Bugzilla component which applies to this object.
+'Core :: Localization':
+  description: The Bugzilla component which applies to this object.
+'Core :: MFBT':
+  description: The Bugzilla component which applies to this object.
+'Core :: MathML':
+  description: The Bugzilla component which applies to this object.
+'Core :: Memory Allocator':
+  description: The Bugzilla component which applies to this object.
+'Core :: Networking':
+  description: The Bugzilla component which applies to this object.
+'Core :: Networking: Cache':
+  description: The Bugzilla component which applies to this object.
+'Core :: Networking: Cookies':
+  description: The Bugzilla component which applies to this object.
+'Core :: Networking: DNS':
+  description: The Bugzilla component which applies to this object.
+'Core :: Networking: File':
+  description: The Bugzilla component which applies to this object.
+'Core :: Networking: HTTP':
+  description: The Bugzilla component which applies to this object.
+'Core :: Networking: JAR':
+  description: The Bugzilla component which applies to this object.
+'Core :: Networking: WebSockets':
+  description: The Bugzilla component which applies to this object.
+'Core :: Panning and Zooming':
+  description: The Bugzilla component which applies to this object.
+'Core :: Performance':
+  description: The Bugzilla component which applies to this object.
+'Core :: Permission Manager':
+  description: The Bugzilla component which applies to this object.
+'Core :: Preferences: Backend':
+  description: The Bugzilla component which applies to this object.
+'Core :: Printing: Output':
+  description: The Bugzilla component which applies to this object.
+'Core :: Privacy: Anti-Tracking':
+  description: The Bugzilla component which applies to this object.
+'Core :: SVG':
+  description: The Bugzilla component which applies to this object.
+'Core :: Security':
+  description: The Bugzilla component which applies to this object.
+'Core :: Security: CAPS':
+  description: The Bugzilla component which applies to this object.
+'Core :: Security: PSM':
+  description: The Bugzilla component which applies to this object.
+'Core :: Security: Process Sandboxing':
+  description: The Bugzilla component which applies to this object.
+'Core :: Spelling checker':
+  description: The Bugzilla component which applies to this object.
+'Core :: Storage: Cache API':
+  description: The Bugzilla component which applies to this object.
+'Core :: Storage: IndexedDB':
+  description: The Bugzilla component which applies to this object.
+'Core :: Storage: Quota Manager':
+  description: The Bugzilla component which applies to this object.
+'Core :: Storage: localStorage & sessionStorage':
+  description: The Bugzilla component which applies to this object.
+'Core :: String':
+  description: The Bugzilla component which applies to this object.
+'Core :: Web Audio':
+  description: The Bugzilla component which applies to this object.
+'Core :: Web Painting':
+  description: The Bugzilla component which applies to this object.
+'Core :: Web Speech':
+  description: The Bugzilla component which applies to this object.
+'Core :: WebRTC':
+  description: The Bugzilla component which applies to this object.
+'Core :: WebRTC: Audio/Video':
+  description: The Bugzilla component which applies to this object.
+'Core :: WebRTC: Networking':
+  description: The Bugzilla component which applies to this object.
+'Core :: WebRTC: Signaling':
+  description: The Bugzilla component which applies to this object.
+'Core :: WebVR':
+  description: The Bugzilla component which applies to this object.
+'Core :: Widget':
+  description: The Bugzilla component which applies to this object.
+'Core :: Widget: Cocoa':
+  description: The Bugzilla component which applies to this object.
+'Core :: Widget: Gtk':
+  description: The Bugzilla component which applies to this object.
+'Core :: Widget: Win32':
+  description: The Bugzilla component which applies to this object.
+'Core :: Window Management':
+  description: The Bugzilla component which applies to this object.
+'Core :: XML':
+  description: The Bugzilla component which applies to this object.
+'Core :: XPCOM':
+  description: The Bugzilla component which applies to this object.
+'Core :: XPConnect':
+  description: The Bugzilla component which applies to this object.
+'Core :: XSLT':
+  description: The Bugzilla component which applies to this object.
+'Core :: XUL':
+  description: The Bugzilla component which applies to this object.
+'Core :: js-ctypes':
+  description: The Bugzilla component which applies to this object.
+'Core :: mozglue':
+  description: The Bugzilla component which applies to this object.
+'Developer Infrastructure :: Lint and Formatting':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Accessibility Tools':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Console':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: DOM':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Debugger':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Framework':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: General':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Inspector':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Inspector: Animations':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Inspector: Changes':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Inspector: Compatibility':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Inspector: Layout':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Inspector: Rules':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: JSON Viewer':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Memory':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Netmonitor':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Performance Tools (Profiler/Timeline)':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Responsive Design Mode':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Shared Components':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Source Editor':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Storage Inspector':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: Style Editor':
+  description: The Bugzilla component which applies to this object.
+'DevTools :: about:debugging':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Address Bar':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Bookmarks & History':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Distributions':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Downloads Panel':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Enterprise Policies':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: File Handling':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Firefox Accounts':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: General':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Headless':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Installer':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Keyboard Navigation':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Menus':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Messaging System':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Migration':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: New Tab Page':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Nimbus Desktop Client':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Normandy Client':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: PDF Viewer':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Page Info Window':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Pocket':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Preferences':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Private Browsing':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Protections UI':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Remote Settings Client':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Screenshots':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Search':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Security':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Services Automation':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Session Restore':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Shell Integration':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Site Identity':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Site Permissions':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Sync':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Tabbed Browser':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Theme':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Toolbars and Customization':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Tours':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: Translation':
+  description: The Bugzilla component which applies to this object.
+'Firefox :: about:logins':
+  description: The Bugzilla component which applies to this object.
+'Firefox Build System :: Bootstrap Configuration':
+  description: The Bugzilla component which applies to this object.
+'Firefox Build System :: General':
+  description: The Bugzilla component which applies to this object.
+'Firefox Build System :: Generated Documentation':
+  description: The Bugzilla component which applies to this object.
+'Firefox Build System :: Mach Core':
+  description: The Bugzilla component which applies to this object.
+'Firefox Build System :: Source Code Analysis':
+  description: The Bugzilla component which applies to this object.
+'Firefox Build System :: Task Configuration':
+  description: The Bugzilla component which applies to this object.
+'Firefox Build System :: Try':
+  description: The Bugzilla component which applies to this object.
+'GeckoView :: General':
+  description: The Bugzilla component which applies to this object.
+'Localization Infrastructure and Tools :: Fluent Migration':
+  description: The Bugzilla component which applies to this object.
+'Localization Infrastructure and Tools :: General':
+  description: The Bugzilla component which applies to this object.
+'Localization Infrastructure and Tools :: compare-locales':
+  description: The Bugzilla component which applies to this object.
+'NSPR :: NSPR':
+  description: The Bugzilla component which applies to this object.
+'NSS :: Libraries':
+  description: The Bugzilla component which applies to this object.
+'Release Engineering :: General':
+  description: The Bugzilla component which applies to this object.
+'Release Engineering :: Release Automation: Updates':
+  description: The Bugzilla component which applies to this object.
+'Remote Protocol :: Agent':
+  description: The Bugzilla component which applies to this object.
+'Remote Protocol :: CDP':
+  description: The Bugzilla component which applies to this object.
+'Remote Protocol :: WebDriver BiDi':
+  description: The Bugzilla component which applies to this object.
+'Taskcluster :: General':
+  description: The Bugzilla component which applies to this object.
+'Taskcluster :: Platform Libraries':
+  description: The Bugzilla component which applies to this object.
+'Testing :: CPPUnitTest':
+  description: The Bugzilla component which applies to this object.
+'Testing :: Code Coverage':
+  description: The Bugzilla component which applies to this object.
+'Testing :: Firefox UI Tests':
+  description: The Bugzilla component which applies to this object.
+'Testing :: GTest':
+  description: The Bugzilla component which applies to this object.
+'Testing :: General':
+  description: The Bugzilla component which applies to this object.
+'Testing :: Marionette':
+  description: The Bugzilla component which applies to this object.
+'Testing :: Mochitest':
+  description: The Bugzilla component which applies to this object.
+'Testing :: Mozbase':
+  description: The Bugzilla component which applies to this object.
+'Testing :: Mozbase Rust':
+  description: The Bugzilla component which applies to this object.
+'Testing :: Python Test':
+  description: The Bugzilla component which applies to this object.
+'Testing :: Reftest':
+  description: The Bugzilla component which applies to this object.
+'Testing :: XPCShell Harness':
+  description: The Bugzilla component which applies to this object.
+'Testing :: geckodriver':
+  description: The Bugzilla component which applies to this object.
+'Testing :: mozperftest':
+  description: The Bugzilla component which applies to this object.
+'Testing :: web-platform-tests':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Add-ons Manager':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Application Update':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Async Tooling':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Autocomplete':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Background Tasks':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Blocklist Implementation':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Crash Reporting':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Data Sanitization':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Downloads API':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: FeatureGate':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Find Toolbar':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Form Autofill':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Form Manager':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: General':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: NSIS Installer':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Notifications and Alerts':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: OS.File':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Password Manager':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Performance Monitoring':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Picture-in-Picture':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Places':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Preferences':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Printing':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Reader Mode':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Safe Browsing':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Startup and Profile System':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Storage':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Telemetry':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Themes':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: Video/Audio Controls':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: View Source':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: XUL Widgets':
+  description: The Bugzilla component which applies to this object.
+'Toolkit :: about:memory':
+  description: The Bugzilla component which applies to this object.
+'Web Compatibility :: Tooling & Investigations':
+  description: The Bugzilla component which applies to this object.
+'WebExtensions :: General':
+  description: The Bugzilla component which applies to this object.
+'WebExtensions :: Request Handling':
+  description: The Bugzilla component which applies to this object.
+'WebExtensions :: Storage':
+  description: The Bugzilla component which applies to this object.
+'WebExtensions :: Themes':
+  description: The Bugzilla component which applies to this object.
+'WebExtensions :: Untriaged':
+  description: The Bugzilla component which applies to this object.
+'mozilla.org :: Licensing':
+  description: The Bugzilla component which applies to this object.
+'mozilla.org :: MozillaBuild':
+  description: The Bugzilla component which applies to this object.
diff --git a/toolkit/components/glean/tests/browser/browser.ini b/toolkit/components/glean/tests/browser/browser.ini
new file mode 100644
index 0000000000..eae3f38730
--- /dev/null
+++ b/toolkit/components/glean/tests/browser/browser.ini
@@ -0,0 +1,19 @@
+# Please keep test files lexicographically sorted, with whitespace between.
+[DEFAULT]
+support-files =
+
+[browser_event_leak.js]
+
+[browser_fog_gmp.js]
+support-files = empty_file.html
+
+[browser_fog_gpu.js]
+
+[browser_fog_rdd.js]
+support-files = small-shot.ogg
+
+[browser_fog_socket.js]
+
+[browser_fog_utility.js]
+
+[browser_labeled_gifft.js]
diff --git a/toolkit/components/glean/tests/browser/browser_event_leak.js b/toolkit/components/glean/tests/browser/browser_event_leak.js
new file mode 100644
index 0000000000..1e69f17064
--- /dev/null
+++ b/toolkit/components/glean/tests/browser/browser_event_leak.js
@@ -0,0 +1,26 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async () => {
+  Services.fog.testResetFOG(); // Needed for TV which reuses profiles on repeat
+  Assert.equal(
+    undefined,
+    Glean.testOnlyIpc.eventWithExtra.testGetValue(),
+    "Nothing to begin with"
+  );
+  Glean.testOnlyIpc.eventWithExtra.record({
+    extra1: "Some extra string",
+    extra2: 42,
+    extra3_longer_name: false,
+  });
+  Assert.equal(
+    1,
+    Glean.testOnlyIpc.eventWithExtra.testGetValue().length,
+    "One event? One event."
+  );
+
+  // AND NOW, FOR THE TRUE TEST:
+  // Will this leak memory all over the place?
+});
diff --git a/toolkit/components/glean/tests/browser/browser_fog_gmp.js b/toolkit/components/glean/tests/browser/browser_fog_gmp.js
new file mode 100644
index 0000000000..4219605eea
--- /dev/null
+++ b/toolkit/components/glean/tests/browser/browser_fog_gmp.js
@@ -0,0 +1,84 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Return a web-based URL for a given file based on the testing directory.
+ * @param {String} fileName
+ *        file that caller wants its web-based url
+ */
+function GetTestWebBasedURL(fileName) {
+  return (
+    getRootDirectory(gTestPath).replace(
+      "chrome://mochitests/content",
+      "https://example.org"
+    ) + fileName
+  );
+}
+
+add_task(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [["media.eme.enabled", true]],
+  });
+
+  await BrowserTestUtils.withNewTab(
+    GetTestWebBasedURL("empty_file.html"),
+    async function(browser) {
+      await SpecialPowers.spawn(browser, [], async function() {
+        try {
+          let config = [
+            {
+              initDataTypes: ["webm"],
+              videoCapabilities: [{ contentType: 'video/webm; codecs="vp9"' }],
+            },
+          ];
+          let access = await content.navigator.requestMediaKeySystemAccess(
+            "org.w3.clearkey",
+            config
+          );
+
+          content.mediaKeys = await access.createMediaKeys();
+          info("got media keys, which should ensure a GMP process exists");
+        } catch (ex) {
+          ok(false, ex.toString());
+        }
+      });
+
+      ok(
+        (await ChromeUtils.requestProcInfo()).children.some(
+          p => p.type == "gmpPlugin"
+        ),
+        "Found the GMP process."
+      );
+
+      Services.fog.testResetFOG();
+
+      is(
+        undefined,
+        Glean.testOnlyIpc.aCounter.testGetValue(),
+        "Ensure we begin without value."
+      );
+
+      await TestUtils.waitForCondition(async () => {
+        try {
+          await Services.fog.testTriggerMetrics(
+            Ci.nsIXULRuntime.PROCESS_TYPE_GMPLUGIN
+          );
+          return true;
+        } catch (e) {
+          info(e);
+          return false;
+        }
+      }, "waiting until we can successfully send the TestTriggerMetrics IPC.");
+
+      await Services.fog.testFlushAllChildren();
+
+      is(
+        Glean.testOnlyIpc.aCounter.testGetValue(),
+        Ci.nsIXULRuntime.PROCESS_TYPE_GMPLUGIN,
+        "Ensure the GMP-process-set value shows up in the parent process."
+      );
+    }
+  );
+});
diff --git a/toolkit/components/glean/tests/browser/browser_fog_gpu.js b/toolkit/components/glean/tests/browser/browser_fog_gpu.js
new file mode 100644
index 0000000000..da0e699c20
--- /dev/null
+++ b/toolkit/components/glean/tests/browser/browser_fog_gpu.js
@@ -0,0 +1,34 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async () => {
+  if (
+    !(await ChromeUtils.requestProcInfo()).children.some(p => p.type == "gpu")
+  ) {
+    ok(
+      true,
+      'No GPU process? No test. Try again with --setpref "layers.gpu-process.force-enabled=true".'
+    );
+    return;
+  }
+  ok(true, "GPU Process found: Let's test.");
+
+  Services.fog.testResetFOG();
+
+  is(
+    undefined,
+    Glean.testOnlyIpc.aCounter.testGetValue(),
+    "Ensure we begin without value."
+  );
+
+  await Services.fog.testTriggerMetrics(Ci.nsIXULRuntime.PROCESS_TYPE_GPU);
+  await Services.fog.testFlushAllChildren();
+
+  is(
+    Glean.testOnlyIpc.aCounter.testGetValue(),
+    Ci.nsIXULRuntime.PROCESS_TYPE_GPU,
+    "Ensure the GPU-process-set value shows up in the parent process."
+  );
+});
diff --git a/toolkit/components/glean/tests/browser/browser_fog_rdd.js b/toolkit/components/glean/tests/browser/browser_fog_rdd.js
new file mode 100644
index 0000000000..caf9a6db1f
--- /dev/null
+++ b/toolkit/components/glean/tests/browser/browser_fog_rdd.js
@@ -0,0 +1,63 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/**
+ * Return a web-based URL for a given file based on the testing directory.
+ * @param {String} fileName
+ *        file that caller wants its web-based url
+ */
+function GetTestWebBasedURL(fileName) {
+  return (
+    getRootDirectory(gTestPath).replace(
+      "chrome://mochitests/content",
+      "http://example.org"
+    ) + fileName
+  );
+}
+
+add_task(async () => {
+  await SpecialPowers.pushPrefEnv({
+    set: [["media.rdd-process.enabled", true]],
+  });
+
+  let url = GetTestWebBasedURL("small-shot.ogg");
+  info(
+    `Opening ${url} in a new tab to trigger the creation of the RDD process`
+  );
+  let tab = BrowserTestUtils.addTab(gBrowser, url);
+
+  await TestUtils.waitForCondition(
+    async () =>
+      (await ChromeUtils.requestProcInfo()).children.some(p => p.type == "rdd"),
+    "waiting to find RDD process."
+  );
+
+  Services.fog.testResetFOG();
+
+  is(
+    undefined,
+    Glean.testOnlyIpc.aCounter.testGetValue(),
+    "Ensure we begin without value."
+  );
+
+  await TestUtils.waitForCondition(async () => {
+    try {
+      await Services.fog.testTriggerMetrics(Ci.nsIXULRuntime.PROCESS_TYPE_RDD);
+      return true;
+    } catch (e) {
+      return false;
+    }
+  }, "waiting until we can successfully send the TestTriggerMetrics IPC.");
+
+  await Services.fog.testFlushAllChildren();
+
+  is(
+    Glean.testOnlyIpc.aCounter.testGetValue(),
+    Ci.nsIXULRuntime.PROCESS_TYPE_RDD,
+    "Ensure the RDD-process-set value shows up in the parent process."
+  );
+
+  BrowserTestUtils.removeTab(tab);
+});
diff --git a/toolkit/components/glean/tests/browser/browser_fog_socket.js b/toolkit/components/glean/tests/browser/browser_fog_socket.js
new file mode 100644
index 0000000000..4ca4f085a1
--- /dev/null
+++ b/toolkit/components/glean/tests/browser/browser_fog_socket.js
@@ -0,0 +1,33 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async () => {
+  if (
+    !(await ChromeUtils.requestProcInfo()).children.some(
+      p => p.type == "socket"
+    )
+  ) {
+    ok(true, "No Socket process? No test.");
+    return;
+  }
+  ok(true, "Socket process found: Let's test.");
+
+  Services.fog.testResetFOG();
+
+  is(
+    undefined,
+    Glean.testOnlyIpc.aCounter.testGetValue(),
+    "Ensure we begin without value."
+  );
+
+  await Services.fog.testTriggerMetrics(Ci.nsIXULRuntime.PROCESS_TYPE_SOCKET);
+  await Services.fog.testFlushAllChildren();
+
+  is(
+    Glean.testOnlyIpc.aCounter.testGetValue(),
+    Ci.nsIXULRuntime.PROCESS_TYPE_SOCKET,
+    "Ensure the Socket-process-set value shows up in the parent process."
+  );
+});
diff --git a/toolkit/components/glean/tests/browser/browser_fog_utility.js b/toolkit/components/glean/tests/browser/browser_fog_utility.js
new file mode 100644
index 0000000000..aaea9cfb42
--- /dev/null
+++ b/toolkit/components/glean/tests/browser/browser_fog_utility.js
@@ -0,0 +1,37 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(async () => {
+  const utilityProcessTest = Cc[
+    "@mozilla.org/utility-process-test;1"
+  ].createInstance(Ci.nsIUtilityProcessTest);
+  await utilityProcessTest
+    .startProcess()
+    .then(async () => {
+      Services.fog.testResetFOG();
+
+      is(
+        undefined,
+        Glean.testOnlyIpc.aCounter.testGetValue(),
+        "Ensure we begin without value."
+      );
+
+      await Services.fog.testTriggerMetrics(
+        Ci.nsIXULRuntime.PROCESS_TYPE_UTILITY
+      );
+      await Services.fog.testFlushAllChildren();
+
+      is(
+        Glean.testOnlyIpc.aCounter.testGetValue(),
+        Ci.nsIXULRuntime.PROCESS_TYPE_UTILITY,
+        "Ensure the utility-process-set value shows up in the parent process."
+      );
+    })
+    .catch(async () => {
+      ok(false, "Cannot start Utility process?");
+    });
+
+  await utilityProcessTest.stopProcess();
+});
diff --git a/toolkit/components/glean/tests/browser/browser_labeled_gifft.js b/toolkit/components/glean/tests/browser/browser_labeled_gifft.js
new file mode 100644
index 0000000000..2203424e82
--- /dev/null
+++ b/toolkit/components/glean/tests/browser/browser_labeled_gifft.js
@@ -0,0 +1,50 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+function keyedScalarValue(aScalarName) {
+  let snapshot = Services.telemetry.getSnapshotForKeyedScalars();
+  return "parent" in snapshot ? snapshot.parent[aScalarName] : undefined;
+}
+
+add_task(async () => {
+  Assert.equal(
+    undefined,
+    Glean.testOnlyIpc.aLabeledCounter.a_label.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.testOnlyIpc.aLabeledCounter.a_label.add(1);
+  Glean.testOnlyIpc.aLabeledCounter.another_label.add(2);
+  Assert.equal(1, Glean.testOnlyIpc.aLabeledCounter.a_label.testGetValue());
+  Assert.equal(
+    2,
+    Glean.testOnlyIpc.aLabeledCounter.another_label.testGetValue()
+  );
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.testOnlyIpc.aLabeledCounter.__other__.testGetValue()
+  );
+  Glean.testOnlyIpc.aLabeledCounter.InvalidLabel.add(3);
+  Assert.throws(
+    () => Glean.testOnlyIpc.aLabeledCounter.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Can't get the value when you're error'd"
+  );
+
+  let value = keyedScalarValue(
+    "telemetry.test.another_mirror_for_labeled_counter"
+  );
+  Assert.deepEqual(
+    {
+      a_label: 1,
+      another_label: 2,
+      InvalidLabel: 3,
+    },
+    value
+  );
+
+  // AND NOW, FOR THE TRUE TEST:
+  // Will this leak memory all over the place?
+});
diff --git a/toolkit/components/glean/tests/browser/empty_file.html b/toolkit/components/glean/tests/browser/empty_file.html
new file mode 100644
index 0000000000..af8440ac16
--- /dev/null
+++ b/toolkit/components/glean/tests/browser/empty_file.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="UTF-8">
+  </head>
+  <body>
+    This page is intentionally left blank.
+  </body>
+</html>
diff --git a/toolkit/components/glean/tests/browser/small-shot.ogg b/toolkit/components/glean/tests/browser/small-shot.ogg
new file mode 100644
index 0000000000..1a41623f81
--- /dev/null
+++ b/toolkit/components/glean/tests/browser/small-shot.ogg
diff --git a/toolkit/components/glean/tests/gtest/Cargo.toml b/toolkit/components/glean/tests/gtest/Cargo.toml
new file mode 100644
index 0000000000..914efad469
--- /dev/null
+++ b/toolkit/components/glean/tests/gtest/Cargo.toml
@@ -0,0 +1,14 @@
+[package]
+name = "fog-gtest"
+version = "0.1.0"
+authors = ["glean-team@mozilla.com"]
+license = "MPL-2.0"
+description = "Tests for the FOG crate"
+
+[dependencies]
+fog = { path = "../../api" }
+jog = { path = "../../bindings/jog" }
+nsstring = { path = "../../../../../xpcom/rust/nsstring" }
+
+[lib]
+path = "test.rs"
diff --git a/toolkit/components/glean/tests/gtest/FOGFixture.h b/toolkit/components/glean/tests/gtest/FOGFixture.h
new file mode 100644
index 0000000000..da3c6fc123
--- /dev/null
+++ b/toolkit/components/glean/tests/gtest/FOGFixture.h
@@ -0,0 +1,23 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+
+#ifndef FOGFixture_h_
+#define FOGFixture_h_
+
+#include "gtest/gtest.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "nsString.h"
+
+using namespace mozilla::glean::impl;
+
+class FOGFixture : public ::testing::Test {
+ protected:
+  FOGFixture() = default;
+  virtual void SetUp() {
+    nsCString empty;
+    ASSERT_EQ(NS_OK, fog_test_reset(&empty, &empty));
+  }
+};
+
+#endif  // FOGFixture_h_
diff --git a/toolkit/components/glean/tests/gtest/TestFog.cpp b/toolkit/components/glean/tests/gtest/TestFog.cpp
new file mode 100644
index 0000000000..c3dd1a7914
--- /dev/null
+++ b/toolkit/components/glean/tests/gtest/TestFog.cpp
@@ -0,0 +1,378 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "FOGFixture.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "mozilla/glean/GleanMetrics.h"
+#include "mozilla/glean/GleanPings.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Result.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/Tuple.h"
+#include "nsTArray.h"
+
+#include "mozilla/Preferences.h"
+#include "mozilla/Unused.h"
+#include "nsString.h"
+#include "prtime.h"
+
+using mozilla::Preferences;
+using namespace mozilla::glean;
+using namespace mozilla::glean::impl;
+
+#define DATA_PREF "datareporting.healthreport.uploadEnabled"
+
+extern "C" {
+// This function is called by the rust code in test.rs if a non-fatal test
+// failure occurs.
+void GTest_FOG_ExpectFailure(const char* aMessage) {
+  EXPECT_STREQ(aMessage, "");
+}
+}
+
+TEST_F(FOGFixture, BuiltinPingsRegistered) {
+  Preferences::SetInt("telemetry.fog.test.localhost_port", -1);
+  nsAutoCString metricsPingName("metrics");
+  nsAutoCString baselinePingName("baseline");
+  nsAutoCString eventsPingName("events");
+  ASSERT_EQ(NS_OK, fog_submit_ping(&metricsPingName));
+  ASSERT_EQ(NS_OK, fog_submit_ping(&baselinePingName));
+  ASSERT_EQ(NS_OK, fog_submit_ping(&eventsPingName));
+}
+
+TEST_F(FOGFixture, TestCppCounterWorks) {
+  mozilla::glean::test_only::bad_code.Add(42);
+
+  ASSERT_EQ(42, mozilla::glean::test_only::bad_code.TestGetValue("test-ping"_ns)
+                    .unwrap()
+                    .value());
+  // And test that the ping name's optional, while you're at it:
+  ASSERT_EQ(42, test_only::bad_code.TestGetValue().unwrap().value());
+}
+
+TEST_F(FOGFixture, TestCppStringWorks) {
+  auto kValue = "cheez!"_ns;
+  mozilla::glean::test_only::cheesy_string.Set(kValue);
+
+  ASSERT_STREQ(kValue.get(), mozilla::glean::test_only::cheesy_string
+                                 .TestGetValue("test-ping"_ns)
+                                 .unwrap()
+                                 .value()
+                                 .get());
+}
+
+TEST_F(FOGFixture, TestCppTimespanWorks) {
+  mozilla::glean::test_only::can_we_time_it.Start();
+  PR_Sleep(PR_MillisecondsToInterval(10));
+  mozilla::glean::test_only::can_we_time_it.Stop();
+
+  ASSERT_TRUE(
+      mozilla::glean::test_only::can_we_time_it.TestGetValue("test-ping"_ns)
+          .unwrap()
+          .value() > 0);
+}
+
+TEST_F(FOGFixture, TestCppUuidWorks) {
+  nsCString kTestUuid("decafdec-afde-cafd-ecaf-decafdecafde");
+  test_only::what_id_it.Set(kTestUuid);
+  ASSERT_STREQ(kTestUuid.get(),
+               test_only::what_id_it.TestGetValue("test-ping"_ns)
+                   .unwrap()
+                   .value()
+                   .get());
+
+  test_only::what_id_it.GenerateAndSet();
+  // Since we generate v4 UUIDs, and the first character of the third group
+  // isn't 4, this won't ever collide with kTestUuid.
+  ASSERT_STRNE(kTestUuid.get(),
+               test_only::what_id_it.TestGetValue("test-ping"_ns)
+                   .unwrap()
+                   .value()
+                   .get());
+}
+
+TEST_F(FOGFixture, TestCppBooleanWorks) {
+  mozilla::glean::test_only::can_we_flag_it.Set(false);
+
+  ASSERT_EQ(false, mozilla::glean::test_only::can_we_flag_it
+                       .TestGetValue("test-ping"_ns)
+                       .unwrap()
+                       .value());
+}
+
+MATCHER_P(BitEq, x, "bit equal") {
+  static_assert(sizeof(x) == sizeof(arg));
+  return std::memcmp(&arg, &x, sizeof(x)) == 0;
+}
+
+TEST_F(FOGFixture, TestCppDatetimeWorks) {
+  PRExplodedTime date{0, 35, 10, 12, 6, 10, 2020, 0, 0, {5 * 60 * 60, 0}};
+  test_only::what_a_date.Set(&date);
+
+  auto received = test_only::what_a_date.TestGetValue("test-ping"_ns).unwrap();
+  ASSERT_THAT(received.value(), BitEq(date));
+}
+
+using mozilla::MakeTuple;
+using mozilla::Some;
+using mozilla::Tuple;
+using mozilla::glean::test_only_ipc::AnEventExtra;
+using mozilla::glean::test_only_ipc::EventWithExtraExtra;
+
+TEST_F(FOGFixture, TestCppEventWorks) {
+  test_only_ipc::no_extra_event.Record();
+  ASSERT_TRUE(test_only_ipc::no_extra_event.TestGetValue("store1"_ns)
+                  .unwrap()
+                  .isSome());
+
+  AnEventExtra extra = {.extra1 = Some("can set extras"_ns)};
+  test_only_ipc::an_event.Record(Some(extra));
+  auto optEvents = test_only_ipc::an_event.TestGetValue("store1"_ns).unwrap();
+  ASSERT_TRUE(optEvents.isSome());
+
+  auto events = optEvents.extract();
+  ASSERT_EQ(1UL, events.Length());
+  ASSERT_STREQ("test_only.ipc", events[0].mCategory.get());
+  ASSERT_STREQ("an_event", events[0].mName.get());
+  ASSERT_EQ(1UL, events[0].mExtra.Length());
+  ASSERT_STREQ("extra1", mozilla::Get<0>(events[0].mExtra[0]).get());
+  ASSERT_STREQ("can set extras", mozilla::Get<1>(events[0].mExtra[0]).get());
+}
+
+TEST_F(FOGFixture, TestCppEventsWithDifferentExtraTypes) {
+  EventWithExtraExtra extra = {.extra1 = Some("can set extras"_ns),
+                               .extra2 = Some(37),
+                               .extra3LongerName = Some(false)};
+  test_only_ipc::event_with_extra.Record(Some(extra));
+  auto optEvents =
+      test_only_ipc::event_with_extra.TestGetValue("store1"_ns).unwrap();
+  ASSERT_TRUE(optEvents.isSome());
+
+  auto events = optEvents.extract();
+  ASSERT_EQ(1UL, events.Length());
+
+  // The list of extra key/value pairs can be in any order.
+  ASSERT_EQ(3UL, events[0].mExtra.Length());
+  for (auto extra : events[0].mExtra) {
+    auto key = mozilla::Get<0>(extra);
+    auto value = mozilla::Get<1>(extra);
+
+    if (key == "extra1"_ns) {
+      ASSERT_STREQ("can set extras", value.get());
+    } else if (key == "extra2"_ns) {
+      ASSERT_STREQ("37", value.get());
+    } else if (key == "extra3_longer_name"_ns) {
+      ASSERT_STREQ("false", value.get());
+    } else {
+      ASSERT_TRUE(false)
+      << "Invalid extra item recorded.";
+    }
+  }
+}
+
+TEST_F(FOGFixture, TestCppMemoryDistWorks) {
+  test_only::do_you_remember.Accumulate(7);
+  test_only::do_you_remember.Accumulate(17);
+
+  DistributionData data =
+      test_only::do_you_remember.TestGetValue("test-ping"_ns).unwrap().ref();
+  // Sum is in bytes, test_only::do_you_remember is in megabytes. So
+  // multiplication ahoy!
+  ASSERT_EQ(data.sum, 24UL * 1024 * 1024);
+  for (const auto& entry : data.values) {
+    const uint64_t bucket = entry.GetKey();
+    const uint64_t count = entry.GetData();
+    ASSERT_TRUE(count == 0 ||
+                (count == 1 && (bucket == 17520006 || bucket == 7053950)))
+    << "Only two occupied buckets";
+  }
+}
+
+TEST_F(FOGFixture, TestCppCustomDistWorks) {
+  test_only_ipc::a_custom_dist.AccumulateSamples({7, 268435458});
+
+  DistributionData data =
+      test_only_ipc::a_custom_dist.TestGetValue("store1"_ns).unwrap().ref();
+  ASSERT_EQ(data.sum, 7UL + 268435458);
+  for (const auto& entry : data.values) {
+    const uint64_t bucket = entry.GetKey();
+    const uint64_t count = entry.GetData();
+    ASSERT_TRUE(count == 0 ||
+                (count == 1 && (bucket == 1 || bucket == 268435456)))
+    << "Only two occupied buckets";
+  }
+}
+
+TEST_F(FOGFixture, TestCppPings) {
+  test_only::one_ping_one_bool.Set(false);
+  const auto& ping = mozilla::glean_pings::OnePingOnly;
+  bool submitted = false;
+  ping.TestBeforeNextSubmit([&submitted](const nsACString& aReason) {
+    submitted = true;
+    ASSERT_EQ(false,
+              test_only::one_ping_one_bool.TestGetValue().unwrap().ref());
+  });
+  ping.Submit();
+  ASSERT_TRUE(submitted)
+  << "Must have actually called the lambda.";
+}
+
+TEST_F(FOGFixture, TestCppStringLists) {
+  auto kValue = "cheez!"_ns;
+  auto kValue2 = "cheezier!"_ns;
+  auto kValue3 = "cheeziest."_ns;
+
+  nsTArray<nsCString> cheezList;
+  cheezList.EmplaceBack(kValue);
+  cheezList.EmplaceBack(kValue2);
+
+  test_only::cheesy_string_list.Set(cheezList);
+
+  auto val = test_only::cheesy_string_list.TestGetValue().unwrap().value();
+  // Note: This is fragile if the order is ever not preserved.
+  ASSERT_STREQ(kValue.get(), val[0].get());
+  ASSERT_STREQ(kValue2.get(), val[1].get());
+
+  test_only::cheesy_string_list.Add(kValue3);
+
+  val = test_only::cheesy_string_list.TestGetValue().unwrap().value();
+  ASSERT_STREQ(kValue3.get(), val[2].get());
+}
+
+TEST_F(FOGFixture, TestCppTimingDistWorks) {
+  auto id1 = test_only::what_time_is_it.Start();
+  auto id2 = test_only::what_time_is_it.Start();
+  PR_Sleep(PR_MillisecondsToInterval(5));
+  auto id3 = test_only::what_time_is_it.Start();
+  test_only::what_time_is_it.Cancel(std::move(id1));
+  PR_Sleep(PR_MillisecondsToInterval(5));
+  test_only::what_time_is_it.StopAndAccumulate(std::move(id2));
+  test_only::what_time_is_it.StopAndAccumulate(std::move(id3));
+
+  DistributionData data =
+      test_only::what_time_is_it.TestGetValue().unwrap().ref();
+  const uint64_t NANOS_IN_MILLIS = 1e6;
+
+  // bug 1701847 - Sleeps don't necessarily round up as you'd expect.
+  // Give ourselves a 40000ns (0.04ms) window to be off on fast machines.
+  const uint64_t EPSILON = 40000;
+
+  // We don't know exactly how long those sleeps took, only that it was at
+  // least 15ms total.
+  ASSERT_GT(data.sum, (uint64_t)(15 * NANOS_IN_MILLIS) - EPSILON);
+
+  // We also can't guarantee the buckets, but we can guarantee two samples.
+  uint64_t sampleCount = 0;
+  for (const auto& value : data.values.Values()) {
+    sampleCount += value;
+  }
+  ASSERT_EQ(sampleCount, (uint64_t)2);
+}
+
+TEST_F(FOGFixture, TestLabeledBooleanWorks) {
+  ASSERT_EQ(mozilla::Nothing(),
+            test_only::mabels_like_balloons.Get("hot_air"_ns)
+                .TestGetValue()
+                .unwrap());
+  test_only::mabels_like_balloons.Get("hot_air"_ns).Set(true);
+  test_only::mabels_like_balloons.Get("helium"_ns).Set(false);
+  ASSERT_EQ(true, test_only::mabels_like_balloons.Get("hot_air"_ns)
+                      .TestGetValue()
+                      .unwrap()
+                      .ref());
+  ASSERT_EQ(false, test_only::mabels_like_balloons.Get("helium"_ns)
+                       .TestGetValue()
+                       .unwrap()
+                       .ref());
+}
+
+TEST_F(FOGFixture, TestLabeledCounterWorks) {
+  ASSERT_EQ(mozilla::Nothing(),
+            test_only::mabels_kitchen_counters.Get("marble"_ns)
+                .TestGetValue()
+                .unwrap());
+  test_only::mabels_kitchen_counters.Get("marble"_ns).Add(1);
+  test_only::mabels_kitchen_counters.Get("laminate"_ns).Add(2);
+  ASSERT_EQ(1, test_only::mabels_kitchen_counters.Get("marble"_ns)
+                   .TestGetValue()
+                   .unwrap()
+                   .ref());
+  ASSERT_EQ(2, test_only::mabels_kitchen_counters.Get("laminate"_ns)
+                   .TestGetValue()
+                   .unwrap()
+                   .ref());
+}
+
+TEST_F(FOGFixture, TestLabeledStringWorks) {
+  ASSERT_EQ(mozilla::Nothing(),
+            test_only::mabels_balloon_strings.Get("twine"_ns)
+                .TestGetValue()
+                .unwrap());
+  test_only::mabels_balloon_strings.Get("twine"_ns).Set("seems acceptable"_ns);
+  test_only::mabels_balloon_strings.Get("parachute_cord"_ns)
+      .Set("preferred"_ns);
+  ASSERT_STREQ("seems acceptable",
+               test_only::mabels_balloon_strings.Get("twine"_ns)
+                   .TestGetValue()
+                   .unwrap()
+                   .ref()
+                   .get());
+  ASSERT_STREQ("preferred",
+               test_only::mabels_balloon_strings.Get("parachute_cord"_ns)
+                   .TestGetValue()
+                   .unwrap()
+                   .ref()
+                   .get());
+}
+
+TEST_F(FOGFixture, TestCppQuantityWorks) {
+  // This joke only works in base 13.
+  const uint32_t kValue = 6 * 9;
+  mozilla::glean::test_only::meaning_of_life.Set(kValue);
+
+  ASSERT_EQ(kValue, mozilla::glean::test_only::meaning_of_life.TestGetValue()
+                        .unwrap()
+                        .value());
+}
+
+TEST_F(FOGFixture, TestCppRateWorks) {
+  // 1) Standard rate with internal denominator
+  const int32_t kNum = 22;
+  const int32_t kDen = 7;  // because I like pi, even just approximately.
+
+  test_only_ipc::irate.AddToNumerator(kNum);
+  test_only_ipc::irate.AddToDenominator(kDen);
+  auto value = test_only_ipc::irate.TestGetValue().unwrap();
+  ASSERT_EQ(kNum, value.ref().first);
+  ASSERT_EQ(kDen, value.ref().second);
+
+  // 2) Rate with external denominator
+  test_only_ipc::rate_with_external_denominator.AddToNumerator(kNum);
+  test_only_ipc::an_external_denominator.Add(kDen);
+  value = test_only_ipc::rate_with_external_denominator.TestGetValue().unwrap();
+  ASSERT_EQ(kNum, value.ref().first);
+  ASSERT_EQ(kDen, value.ref().second);
+  ASSERT_EQ(
+      kDen,
+      test_only_ipc::an_external_denominator.TestGetValue().unwrap().extract());
+}
+
+TEST_F(FOGFixture, TestCppUrlWorks) {
+  auto kValue = "https://example.com/fog/gtest"_ns;
+  mozilla::glean::test_only_ipc::a_url.Set(kValue);
+
+  ASSERT_STREQ(kValue.get(),
+               mozilla::glean::test_only_ipc::a_url.TestGetValue("store1"_ns)
+                   .unwrap()
+                   .value()
+                   .get());
+}
+
+extern "C" void Rust_TestRustInGTest();
+TEST_F(FOGFixture, TestRustInGTest) { Rust_TestRustInGTest(); }
+
+extern "C" void Rust_TestJogfile();
+TEST_F(FOGFixture, TestJogfile) { Rust_TestJogfile(); }
diff --git a/toolkit/components/glean/tests/gtest/moz.build b/toolkit/components/glean/tests/gtest/moz.build
new file mode 100644
index 0000000000..329604e929
--- /dev/null
+++ b/toolkit/components/glean/tests/gtest/moz.build
@@ -0,0 +1,16 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+if not CONFIG["MOZ_GLEAN_ANDROID"]:
+    UNIFIED_SOURCES += [
+        "TestFog.cpp",
+    ]
+
+    TEST_HARNESS_FILES.gtest += ["../pytest/jogfile_output"]
+
+FINAL_LIBRARY = "xul-gtest"
+
+REQUIRES_UNIFIED_BUILD = True
diff --git a/toolkit/components/glean/tests/gtest/test.rs b/toolkit/components/glean/tests/gtest/test.rs
new file mode 100644
index 0000000000..f84454b266
--- /dev/null
+++ b/toolkit/components/glean/tests/gtest/test.rs
@@ -0,0 +1,52 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+extern crate nsstring;
+use nsstring::nsString;
+
+fn nonfatal_fail(msg: String) {
+    extern "C" {
+        fn GTest_FOG_ExpectFailure(message: *const ::std::os::raw::c_char);
+    }
+    unsafe {
+        let msg = ::std::ffi::CString::new(msg).unwrap();
+        GTest_FOG_ExpectFailure(msg.as_ptr());
+    }
+}
+
+/// This macro checks if the expression evaluates to true,
+/// and causes a non-fatal GTest test failure if it doesn't.
+macro_rules! expect {
+    ($x:expr) => {
+        match (&$x) {
+            true => {}
+            false => nonfatal_fail(format!(
+                "check failed: (`{}`) at {}:{}",
+                stringify!($x),
+                file!(),
+                line!()
+            )),
+        }
+    };
+}
+
+#[no_mangle]
+pub extern "C" fn Rust_TestRustInGTest() {
+    // Just a smoke test, we show here how tests might work that both
+    // a) Are in Rust, and
+    // b) Require Gecko
+    // This demonstration doesn't actually require Gecko. But we pretend it
+    // does so we remember how to do this rust-in-gtest pattern.
+    fog::metrics::test_only::bad_code.add(12);
+    expect!(fog::metrics::test_only::bad_code.test_get_value(None) == Some(12));
+}
+
+#[no_mangle]
+pub extern "C" fn Rust_TestJogfile() {
+    // Ensure that the generated jogfile in t/c/g/tests/pytest
+    // (which is installed nearby using TEST_HARNESS_FILES)
+    // can be consumed by JOG's inner workings
+    //
+    // If it can't, that's perhaps a sign that the inner workings need to be updated.
+    expect!(jog::jog_load_jogfile(&nsString::from("jogfile_output")));
+}
diff --git a/toolkit/components/glean/tests/moz.build b/toolkit/components/glean/tests/moz.build
new file mode 100644
index 0000000000..e7de2c3b66
--- /dev/null
+++ b/toolkit/components/glean/tests/moz.build
@@ -0,0 +1,16 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+PYTHON_UNITTEST_MANIFESTS += ["pytest/python.ini"]
+
+TEST_DIRS += ["gtest"]
+
+XPCSHELL_TESTS_MANIFESTS += ["xpcshell/xpcshell.ini"]
+
+BROWSER_CHROME_MANIFESTS += ["browser/browser.ini"]
+
+with Files("**"):
+    BUG_COMPONENT = ("Toolkit", "Telemetry")
diff --git a/toolkit/components/glean/tests/pytest/expect_helper.py b/toolkit/components/glean/tests/pytest/expect_helper.py
new file mode 100644
index 0000000000..543ef04026
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/expect_helper.py
@@ -0,0 +1,34 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import inspect
+import os
+
+
+def expect(path, actual):
+    """
+    Assert that the content of the file at `path` contains `actual`.
+
+    If the environment variable `UPDATE_EXPECT` is set, the path content is updated to `actual`.
+    This allows to update the file contents easily.
+    """
+
+    callerframerecord = inspect.stack()[1]
+    frame = callerframerecord[0]
+    info = inspect.getframeinfo(frame)
+    msg = f"""
+Unexpected content in {path} (at {info.filename}:{info.lineno})
+
+If the code generation was changed,
+run the test suite again with `UPDATE_EXPECT=1` set to update the test files.
+""".strip()
+
+    if "UPDATE_EXPECT" in os.environ:
+        with open(path, "w") as file:
+            file.write(actual)
+
+    expected = None
+    with open(path, "r") as file:
+        expected = file.read()
+    assert actual == expected, msg
diff --git a/toolkit/components/glean/tests/pytest/gifft_output_Event b/toolkit/components/glean/tests/pytest/gifft_output_Event
new file mode 100644
index 0000000000..565fcca59d
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/gifft_output_Event
@@ -0,0 +1,38 @@
+// -*- mode: C++ -*-
+
+/* This file is auto-generated by run_glean_parser.py.
+   It is only for internal use by types in
+   toolkit/components/glean/bindings/private */
+
+#include "mozilla/AppShutdown.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/Tuple.h"
+#include "mozilla/DataMutex.h"
+#include "nsThreadUtils.h"
+
+#ifndef mozilla_glean_EventGifftMap_h
+#define mozilla_glean_EventGifftMap_h
+
+namespace mozilla::glean {
+
+using Telemetry::EventID;
+
+
+static inline Maybe<EventID> EventIdForMetric(uint32_t aId) {
+  switch(aId) {
+    case 17: { // test.nested.event_metric
+      return Some(EventID::EventMetric_EnumNames_AreStrange);
+    }
+    case 18: { // test.nested.event_metric_with_extra
+      return Some(EventID::EventMetric_EnumName_WithExtra);
+    }
+    default: {
+      return Nothing();
+    }
+  }
+}
+
+}  // namespace mozilla::glean
+#endif  // mozilla_glean_EventGifftMaps_h
diff --git a/toolkit/components/glean/tests/pytest/gifft_output_EventExtra b/toolkit/components/glean/tests/pytest/gifft_output_EventExtra
new file mode 100644
index 0000000000..f5f2671d99
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/gifft_output_EventExtra
@@ -0,0 +1,35 @@
+// -*- mode: C++ -*-
+
+/* This file is auto-generated by run_glean_parser.py.
+   It is only for internal use by types in
+   toolkit/components/glean/bindings/private */
+
+#include "mozilla/glean/bindings/Event.h"
+#include "mozilla/glean/GleanMetrics.h"
+
+namespace mozilla::glean {
+
+template <>
+/*static*/ const nsCString impl::EventMetric<NoExtraKeys>::ExtraStringForKey(uint32_t aKey) {
+  MOZ_ASSERT_UNREACHABLE("What are you doing here? No extra keys!");
+  return ""_ns;
+}
+
+template <>
+/*static*/ const nsCString impl::EventMetric<test_nested::EventMetricWithExtraExtra>::ExtraStringForKey(uint32_t aKey) {
+  using test_nested::EventMetricWithExtraExtra;
+  switch (aKey) {
+    case 0: {
+      return "an_extra_key"_ns;
+    }
+    case 1: {
+      return "another_extra_key"_ns;
+    }
+    default: {
+      MOZ_ASSERT_UNREACHABLE("Impossible event key reached.");
+      return ""_ns;
+    }
+  }
+}
+
+};  // namespace mozilla::glean
diff --git a/toolkit/components/glean/tests/pytest/gifft_output_Histogram b/toolkit/components/glean/tests/pytest/gifft_output_Histogram
new file mode 100644
index 0000000000..ef01708dfe
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/gifft_output_Histogram
@@ -0,0 +1,113 @@
+// -*- mode: C++ -*-
+
+/* This file is auto-generated by run_glean_parser.py.
+   It is only for internal use by types in
+   toolkit/components/glean/bindings/private */
+
+#include "mozilla/AppShutdown.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/Tuple.h"
+#include "mozilla/DataMutex.h"
+#include "nsThreadUtils.h"
+
+#ifndef mozilla_glean_HistogramGifftMap_h
+#define mozilla_glean_HistogramGifftMap_h
+
+namespace mozilla::glean {
+
+using Telemetry::HistogramID;
+
+
+using MetricId = uint32_t; // Same type as in api/src/private/mod.rs
+using TimerId = uint64_t; // Same as in TimingDistribution.h.
+using MetricTimerTuple = Tuple<MetricId, TimerId>;
+class MetricTimerTupleHashKey : public PLDHashEntryHdr {
+ public:
+  using KeyType = const MetricTimerTuple&;
+  using KeyTypePointer = const MetricTimerTuple*;
+
+  explicit MetricTimerTupleHashKey(KeyTypePointer aKey) : mValue(*aKey) {}
+  MetricTimerTupleHashKey(MetricTimerTupleHashKey&& aOther)
+      : PLDHashEntryHdr(std::move(aOther)),
+        mValue(std::move(aOther.mValue)) {}
+  ~MetricTimerTupleHashKey() = default;
+
+  KeyType GetKey() const { return mValue; }
+  bool KeyEquals(KeyTypePointer aKey) const {
+    return Get<0>(*aKey) == Get<0>(mValue) && Get<1>(*aKey) == Get<1>(mValue);
+  }
+
+  static KeyTypePointer KeyToPointer(KeyType aKey) { return &aKey; }
+  static PLDHashNumber HashKey(KeyTypePointer aKey) {
+    // Chosen because this is how nsIntegralHashKey does it.
+    return HashGeneric(Get<0>(*aKey), Get<1>(*aKey));
+  }
+  enum { ALLOW_MEMMOVE = true };
+
+ private:
+  const MetricTimerTuple mValue;
+};
+
+typedef StaticDataMutex<UniquePtr<nsTHashMap<MetricTimerTupleHashKey, TimeStamp>>> TimerToStampMutex;
+static inline Maybe<TimerToStampMutex::AutoLock> GetTimerIdToStartsLock() {
+  static TimerToStampMutex sTimerIdToStarts("sTimerIdToStarts");
+  auto lock = sTimerIdToStarts.Lock();
+  // GIFFT will work up to the end of AppShutdownTelemetry.
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+    return Nothing();
+  }
+  if (!*lock) {
+    *lock = MakeUnique<nsTHashMap<MetricTimerTupleHashKey, TimeStamp>>();
+    RefPtr<nsIRunnable> cleanupFn = NS_NewRunnableFunction(__func__, [&] {
+      if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+        auto lock = sTimerIdToStarts.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+        return;
+      }
+      RunOnShutdown([&] {
+        auto lock = sTimerIdToStarts.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+      }, ShutdownPhase::XPCOMWillShutdown);
+    });
+    // Both getting the main thread and dispatching to it can fail.
+    // In that event we leak. Grab a pointer so we have something to NS_RELEASE
+    // in that case.
+    nsIRunnable* temp = cleanupFn.get();
+    nsCOMPtr<nsIThread> mainThread;
+    if (NS_FAILED(NS_GetMainThread(getter_AddRefs(mainThread)))
+      || NS_FAILED(mainThread->Dispatch(cleanupFn.forget(), nsIThread::DISPATCH_NORMAL))
+    ) {
+      // Failed to dispatch cleanup routine.
+      // First, un-leak the runnable (but only if we actually attempted dispatch)
+      if (!cleanupFn) {
+        NS_RELEASE(temp);
+      }
+      // Next, cleanup immediately, and allow metrics to try again later.
+      *lock = nullptr;
+      return Nothing();
+    }
+  }
+  return Some(std::move(lock));
+}
+
+static Maybe<HistogramID> HistogramIdForMetric(uint32_t aId) {
+  switch(aId) {
+    case 12: { // test.timing_distribution_metric
+      return Some(HistogramID::SOME_TIME_HISTOGRAM_MS);
+    }
+    case 13: { // test.memory_distribution_metric
+      return Some(HistogramID::SOME_MEM_HISTOGRAM_KB);
+    }
+    case 14: { // test.custom_distribution_metric
+      return Some(HistogramID::SOME_LINEAR_HISTOGRAM);
+    }
+    default: {
+      return Nothing();
+    }
+  }
+}
+
+}  // namespace mozilla::glean
+#endif  // mozilla_glean_HistogramGifftMaps_h
diff --git a/toolkit/components/glean/tests/pytest/gifft_output_Scalar b/toolkit/components/glean/tests/pytest/gifft_output_Scalar
new file mode 100644
index 0000000000..0e79e4d00d
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/gifft_output_Scalar
@@ -0,0 +1,189 @@
+// -*- mode: C++ -*-
+
+/* This file is auto-generated by run_glean_parser.py.
+   It is only for internal use by types in
+   toolkit/components/glean/bindings/private */
+
+#include "mozilla/AppShutdown.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/Tuple.h"
+#include "mozilla/DataMutex.h"
+#include "mozilla/Tuple.h"
+#include "nsClassHashtable.h"
+#include "nsIThread.h"
+#include "nsTHashMap.h"
+#include "nsThreadUtils.h"
+
+#ifndef mozilla_glean_ScalarGifftMap_h
+#define mozilla_glean_ScalarGifftMap_h
+
+namespace mozilla::glean {
+
+using Telemetry::ScalarID;
+
+typedef nsUint32HashKey SubmetricIdHashKey;
+typedef nsTHashMap<SubmetricIdHashKey, Tuple<ScalarID, nsString>>
+    SubmetricToLabeledMirrorMapType;
+typedef StaticDataMutex<UniquePtr<SubmetricToLabeledMirrorMapType>>
+    SubmetricToMirrorMutex;
+static inline Maybe<SubmetricToMirrorMutex::AutoLock> GetLabeledMirrorLock() {
+  static SubmetricToMirrorMutex sLabeledMirrors("sLabeledMirrors");
+  auto lock = sLabeledMirrors.Lock();
+  // GIFFT will work up to the end of AppShutdownTelemetry.
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+    return Nothing();
+  }
+  if (!*lock) {
+    *lock = MakeUnique<SubmetricToLabeledMirrorMapType>();
+    RefPtr<nsIRunnable> cleanupFn = NS_NewRunnableFunction(__func__, [&] {
+      if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+        auto lock = sLabeledMirrors.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+        return;
+      }
+      RunOnShutdown([&] {
+        auto lock = sLabeledMirrors.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+      }, ShutdownPhase::XPCOMWillShutdown);
+    });
+    // Both getting the main thread and dispatching to it can fail.
+    // In that event we leak. Grab a pointer so we have something to NS_RELEASE
+    // in that case.
+    nsIRunnable* temp = cleanupFn.get();
+    nsCOMPtr<nsIThread> mainThread;
+    if (NS_FAILED(NS_GetMainThread(getter_AddRefs(mainThread)))
+      || NS_FAILED(mainThread->Dispatch(cleanupFn.forget(), nsIThread::DISPATCH_NORMAL))
+    ) {
+      // Failed to dispatch cleanup routine.
+      // First, un-leak the runnable (but only if we actually attempted dispatch)
+      if (!cleanupFn) {
+        NS_RELEASE(temp);
+      }
+      // Next, cleanup immediately, and allow metrics to try again later.
+      *lock = nullptr;
+      return Nothing();
+    }
+  }
+  return Some(std::move(lock));
+}
+
+namespace {
+class ScalarIDHashKey : public PLDHashEntryHdr {
+ public:
+  typedef const ScalarID& KeyType;
+  typedef const ScalarID* KeyTypePointer;
+
+  explicit ScalarIDHashKey(KeyTypePointer aKey) : mValue(*aKey) {}
+  ScalarIDHashKey(ScalarIDHashKey&& aOther)
+      : PLDHashEntryHdr(std::move(aOther)), mValue(std::move(aOther.mValue)) {}
+  ~ScalarIDHashKey() = default;
+
+  KeyType GetKey() const { return mValue; }
+  bool KeyEquals(KeyTypePointer aKey) const { return *aKey == mValue; }
+
+  static KeyTypePointer KeyToPointer(KeyType aKey) { return &aKey; }
+  static PLDHashNumber HashKey(KeyTypePointer aKey) {
+    return static_cast<std::underlying_type<ScalarID>::type>(*aKey);
+  }
+  enum { ALLOW_MEMMOVE = true };
+
+ private:
+  const ScalarID mValue;
+};
+}  // namespace
+typedef StaticDataMutex<UniquePtr<nsTHashMap<ScalarIDHashKey, TimeStamp>>> TimesToStartsMutex;
+static inline Maybe<TimesToStartsMutex::AutoLock> GetTimesToStartsLock() {
+  static TimesToStartsMutex sTimespanStarts("sTimespanStarts");
+  auto lock = sTimespanStarts.Lock();
+  // GIFFT will work up to the end of AppShutdownTelemetry.
+  if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+    return Nothing();
+  }
+  if (!*lock) {
+    *lock = MakeUnique<nsTHashMap<ScalarIDHashKey, TimeStamp>>();
+    RefPtr<nsIRunnable> cleanupFn = NS_NewRunnableFunction(__func__, [&] {
+      if (AppShutdown::IsInOrBeyond(ShutdownPhase::XPCOMWillShutdown)) {
+        auto lock = sTimespanStarts.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+        return;
+      }
+      RunOnShutdown([&] {
+        auto lock = sTimespanStarts.Lock();
+        *lock = nullptr;  // deletes, see UniquePtr.h
+      }, ShutdownPhase::XPCOMWillShutdown);
+    });
+    // Both getting the main thread and dispatching to it can fail.
+    // In that event we leak. Grab a pointer so we have something to NS_RELEASE
+    // in that case.
+    nsIRunnable* temp = cleanupFn.get();
+    nsCOMPtr<nsIThread> mainThread;
+    if (NS_FAILED(NS_GetMainThread(getter_AddRefs(mainThread)))
+      || NS_FAILED(mainThread->Dispatch(cleanupFn.forget(), nsIThread::DISPATCH_NORMAL))
+    ) {
+      // Failed to dispatch cleanup routine.
+      // First, un-leak the runnable (but only if we actually attempted dispatch)
+      if (!cleanupFn) {
+        NS_RELEASE(temp);
+      }
+      // Next, cleanup immediately, and allow metrics to try again later.
+      *lock = nullptr;
+      return Nothing();
+    }
+  }
+  return Some(std::move(lock));
+}
+
+static inline bool IsSubmetricId(uint32_t aId) {
+  // Submetrics have the 2^25 bit set.
+  // (ID_BITS - ID_SIGNAL_BITS, keep it in sync with js.py).
+  return (aId & (1 << 25)) > 0;
+}
+
+static Maybe<ScalarID> ScalarIdForMetric(uint32_t aId) {
+  switch(aId) {
+    case 1: { // test.boolean_metric
+      return Some(ScalarID::SOME_BOOL_SCALAR);
+    }
+    case 2: { // test.labeled_boolean_metric
+      return Some(ScalarID::SOME_KEYED_BOOL_SCALAR);
+    }
+    case 3: { // test.labeled_boolean_metric_labels
+      return Some(ScalarID::SOME_OTHER_KEYED_BOOL_SCALAR);
+    }
+    case 4: { // test.counter_metric
+      return Some(ScalarID::SOME_UINT_SCALAR);
+    }
+    case 5: { // test.labeled_counter_metric
+      return Some(ScalarID::SOME_KEYED_UINT_SCALAR);
+    }
+    case 6: { // test.labeled_counter_metric_labels
+      return Some(ScalarID::SOME_OTHER_KEYED_UINT_SCALAR);
+    }
+    case 7: { // test.string_metric
+      return Some(ScalarID::SOME_STRING_SCALAR);
+    }
+    case 10: { // test.string_list_metric
+      return Some(ScalarID::YET_ANOTHER_KEYED_BOOL_SCALAR);
+    }
+    case 11: { // test.timespan_metric
+      return Some(ScalarID::SOME_OTHER_UINT_SCALAR);
+    }
+    case 15: { // test.nested.uuid_metric
+      return Some(ScalarID::SOME_OTHER_STRING_SCALAR);
+    }
+    case 16: { // test.nested.datetime_metric
+      return Some(ScalarID::SOME_STILL_OTHER_STRING_SCALAR);
+    }
+    case 19: { // test.nested.quantity_metric
+      return Some(ScalarID::TELEMETRY_TEST_MIRROR_FOR_QUANTITY);
+    }
+    default: {
+      return Nothing();
+    }
+  }
+}
+
+}  // namespace mozilla::glean
+#endif  // mozilla_glean_ScalarGifftMaps_h
diff --git a/toolkit/components/glean/tests/pytest/jogfile_output b/toolkit/components/glean/tests/pytest/jogfile_output
new file mode 100644
index 0000000000..7a38cc2fc0
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/jogfile_output
@@ -0,0 +1,287 @@
+{
+  "metrics": {
+    "test": [
+      [
+        "boolean",
+        "boolean_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "labeled_boolean",
+        "labeled_boolean_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "labeled_boolean",
+        "labeled_boolean_metric_labels",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "counter",
+        "counter_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "labeled_counter",
+        "labeled_counter_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "labeled_counter",
+        "labeled_counter_metric_labels",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "string",
+        "string_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "labeled_string",
+        "labeled_string_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "labeled_string",
+        "labeled_string_metric_labels",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "string_list",
+        "string_list_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "timespan",
+        "timespan_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false,
+        {
+          "time_unit": "millisecond"
+        }
+      ],
+      [
+        "timing_distribution",
+        "timing_distribution_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false,
+        {
+          "time_unit": "nanosecond"
+        }
+      ],
+      [
+        "memory_distribution",
+        "memory_distribution_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false,
+        {
+          "memory_unit": "kilobyte"
+        }
+      ],
+      [
+        "custom_distribution",
+        "custom_distribution_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false,
+        {
+          "bucket_count": 100,
+          "histogram_type": "linear",
+          "range_max": 100,
+          "range_min": 0
+        }
+      ]
+    ],
+    "test.nested": [
+      [
+        "uuid",
+        "uuid_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false
+      ],
+      [
+        "datetime",
+        "datetime_metric",
+        [
+          "metrics"
+        ],
+        "application",
+        false,
+        {
+          "time_unit": "millisecond"
+        }
+      ],
+      [
+        "event",
+        "event_metric",
+        [
+          "events"
+        ],
+        "ping",
+        false,
+        {
+          "allowed_extra_keys": []
+        }
+      ],
+      [
+        "event",
+        "event_metric_with_extra",
+        [
+          "events"
+        ],
+        "ping",
+        false,
+        {
+          "allowed_extra_keys": [
+            "an_extra_key",
+            "another_extra_key"
+          ]
+        }
+      ],
+      [
+        "quantity",
+        "quantity_metric",
+        [
+          "metrics"
+        ],
+        "ping",
+        false
+      ],
+      [
+        "rate",
+        "rate_metric",
+        [
+          "metrics"
+        ],
+        "ping",
+        false
+      ],
+      [
+        "rate",
+        "rate_with_external_denominator",
+        [
+          "metrics"
+        ],
+        "ping",
+        false
+      ],
+      [
+        "denominator",
+        "external_denominator",
+        [
+          "metrics"
+        ],
+        "ping",
+        false,
+        {
+          "numerators": [
+            [
+              "rate_with_external_denominator",
+              "test.nested",
+              [
+                "metrics"
+              ],
+              "ping",
+              false,
+              null
+            ]
+          ]
+        }
+      ]
+    ]
+  },
+  "pings": [
+    [
+      "not-baseline",
+      true,
+      false,
+      [
+        "background",
+        "dirty_startup",
+        "foreground"
+      ]
+    ],
+    [
+      "not-metrics",
+      true,
+      false,
+      [
+        "overdue",
+        "reschedule",
+        "today",
+        "tomorrow",
+        "upgrade"
+      ]
+    ],
+    [
+      "not-events",
+      true,
+      false,
+      [
+        "background",
+        "max_capacity",
+        "startup"
+      ]
+    ],
+    [
+      "not-deletion-request",
+      true,
+      true,
+      []
+    ]
+  ]
+}
\ No newline at end of file
diff --git a/toolkit/components/glean/tests/pytest/metrics_expires_versions_test.yaml b/toolkit/components/glean/tests/pytest/metrics_expires_versions_test.yaml
new file mode 100644
index 0000000000..ea73a6465e
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/metrics_expires_versions_test.yaml
@@ -0,0 +1,84 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is FOR TESTING PURPOSES ONLY.
+
+---
+$schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
+
+test:
+  expired1:
+    type: boolean
+    expires: 41
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1664306
+    data_reviews:
+      - https://example.com
+    no_lint:
+      - EXPIRED
+
+  expired2:
+    type: labeled_boolean
+    expires: 42
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1664306
+    data_reviews:
+      - https://example.com
+    no_lint:
+      - EXPIRED
+
+  unexpired:
+    type: labeled_boolean
+    expires: 100
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1664306
+    data_reviews:
+      - https://example.com
+    labels:
+      - one_label
+      - two_labels
+
+  never:
+    type: string
+    expires: never
+    description: A never-expiring metric
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1664306
+    data_reviews:
+      - https://example.com
+
+  always:
+    type: string
+    expires: expired
+    description: An already-expired metric
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1664306
+    data_reviews:
+      - https://example.com
+    no_lint:
+      - EXPIRED
diff --git a/toolkit/components/glean/tests/pytest/metrics_test.yaml b/toolkit/components/glean/tests/pytest/metrics_test.yaml
new file mode 100644
index 0000000000..8b4a7404f1
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/metrics_test.yaml
@@ -0,0 +1,369 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file defines the metrics that are recorded by the Glean SDK. They are
+# automatically converted to platform-specific code at build time using the
+# `glean_parser` PyPI package.
+
+# This file is presently for Internal FOG Use Only.
+# You should not add metrics here until probably about January of 2021.
+# If you're looking for the metrics.yaml for Geckoveiw Streaming Telemetry,
+# you can find that one in toolkit/components/telemetry/geckoview/streaming.
+
+---
+$schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
+
+test:
+  boolean_metric:
+    type: boolean
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: SOME_BOOL_SCALAR
+
+  labeled_boolean_metric:
+    type: labeled_boolean
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: SOME_KEYED_BOOL_SCALAR
+
+  labeled_boolean_metric_labels:
+    type: labeled_boolean
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    labels:
+      - one_label
+      - two_labels
+      - three_labels
+      - four_labels
+      - five_labels
+      - six_labels
+      - seven_labels
+      - eight_labels
+      - nine_labels
+      - ten_labels
+    telemetry_mirror: SOME_OTHER_KEYED_BOOL_SCALAR
+
+  counter_metric:
+    type: counter
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: SOME_UINT_SCALAR
+
+  labeled_counter_metric:
+    type: labeled_counter
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: SOME_KEYED_UINT_SCALAR
+
+  labeled_counter_metric_labels:
+    type: labeled_counter
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    labels:
+      - one_label
+      - two_labels
+    telemetry_mirror: SOME_OTHER_KEYED_UINT_SCALAR
+
+  string_metric:
+    type: string
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: SOME_STRING_SCALAR
+
+  labeled_string_metric:
+    type: labeled_string
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+
+  labeled_string_metric_labels:
+    type: labeled_string
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    labels:
+      - one_label
+      - two_labels
+
+  string_list_metric:
+    type: string_list
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: YET_ANOTHER_KEYED_BOOL_SCALAR
+
+  timespan_metric:
+    type: timespan
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: SOME_OTHER_UINT_SCALAR
+
+  timing_distribution_metric:
+    type: timing_distribution
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: SOME_TIME_HISTOGRAM_MS
+
+  memory_distribution_metric:
+    type: memory_distribution
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    memory_unit: kilobyte
+    telemetry_mirror: SOME_MEM_HISTOGRAM_KB
+
+  custom_distribution_metric:
+    type: custom_distribution
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    range_min: 0
+    range_max: 100
+    bucket_count: 100
+    histogram_type: linear
+    telemetry_mirror: SOME_LINEAR_HISTOGRAM
+
+test.nested:
+  uuid_metric:
+    type: uuid
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: SOME_OTHER_STRING_SCALAR
+
+  datetime_metric:
+    type: datetime
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: application
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: SOME_STILL_OTHER_STRING_SCALAR
+
+  event_metric:
+    type: event
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: ping
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: EventMetric_EnumNames_AreStrange
+
+  event_metric_with_extra:
+    type: event
+    expires: never
+    description: |
+      A multi-line
+      description
+    lifetime: ping
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1635260/
+    data_reviews:
+      - https://example.com
+    extra_keys:
+      an_extra_key:
+        type: string
+        description: An extra key description
+      another_extra_key:
+        type: string
+        description: Another extra key description
+    telemetry_mirror: EventMetric_EnumName_WithExtra
+
+  quantity_metric:
+    type: quantity
+    unit: someunit
+    expires: never
+    description: |
+      A multi-line
+      description
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1704846/
+    data_reviews:
+      - https://example.com
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_QUANTITY
+
+  rate_metric:
+    type: rate
+    expires: never
+    description: |
+      A multi-line
+      description
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1704846/
+    data_reviews:
+      - https://example.com
+
+  rate_with_external_denominator:
+    type: rate
+    denominator_metric: test.nested.external_denominator
+    expires: never
+    description: |
+      A multi-line
+      description
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1704846/
+    data_reviews:
+      - https://example.com
+
+  external_denominator:
+    type: counter
+    expires: never
+    description: |
+      A multi-line
+      description
+    notification_emails:
+      - glean-team@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/1704846/
+    data_reviews:
+      - https://example.com
diff --git a/toolkit/components/glean/tests/pytest/metrics_test_output b/toolkit/components/glean/tests/pytest/metrics_test_output
new file mode 100644
index 0000000000..9bb1438306
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/metrics_test_output
@@ -0,0 +1,693 @@
+// -*- mode: Rust -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+pub mod test {
+    use crate::private::*;
+    use glean::CommonMetricData;
+    #[allow(unused_imports)] // HistogramType might be unusued, let's avoid warnings
+    use glean::HistogramType;
+    use once_cell::sync::Lazy;
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.boolean_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static boolean_metric: Lazy<BooleanMetric> = Lazy::new(|| {
+        BooleanMetric::new(1.into(), CommonMetricData {
+            name: "boolean_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        })
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.labeled_boolean_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static labeled_boolean_metric: Lazy<LabeledMetric<LabeledBooleanMetric>> = Lazy::new(|| {
+        LabeledMetric::new(2.into(), CommonMetricData {
+            name: "labeled_boolean_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, None)
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.labeled_boolean_metric_labels
+    ///
+    /// A multi-line
+    /// description
+    pub static labeled_boolean_metric_labels: Lazy<LabeledMetric<LabeledBooleanMetric>> = Lazy::new(|| {
+        LabeledMetric::new(3.into(), CommonMetricData {
+            name: "labeled_boolean_metric_labels".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, Some({const S: &'static str = "eight_labelsfive_labelsfour_labelsnine_labelsone_labelseven_labelssix_labelsten_labelsthree_labelstwo_labels";const LENGTHS: [u8; 10] = [12, 11, 11, 11, 9, 12, 10, 10, 12, 10];let mut offset = 0;LENGTHS.iter().map(|len| {  let start = offset;  offset += *len as usize;  S[start..offset].into()}).collect()}))
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.counter_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static counter_metric: Lazy<CounterMetric> = Lazy::new(|| {
+        CounterMetric::new(4.into(), CommonMetricData {
+            name: "counter_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        })
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.labeled_counter_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static labeled_counter_metric: Lazy<LabeledMetric<LabeledCounterMetric>> = Lazy::new(|| {
+        LabeledMetric::new(5.into(), CommonMetricData {
+            name: "labeled_counter_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, None)
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.labeled_counter_metric_labels
+    ///
+    /// A multi-line
+    /// description
+    pub static labeled_counter_metric_labels: Lazy<LabeledMetric<LabeledCounterMetric>> = Lazy::new(|| {
+        LabeledMetric::new(6.into(), CommonMetricData {
+            name: "labeled_counter_metric_labels".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, Some(vec!["one_label".into(), "two_labels".into()]))
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.string_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static string_metric: Lazy<StringMetric> = Lazy::new(|| {
+        StringMetric::new(7.into(), CommonMetricData {
+            name: "string_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        })
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.labeled_string_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static labeled_string_metric: Lazy<LabeledMetric<LabeledStringMetric>> = Lazy::new(|| {
+        LabeledMetric::new(8.into(), CommonMetricData {
+            name: "labeled_string_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, None)
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.labeled_string_metric_labels
+    ///
+    /// A multi-line
+    /// description
+    pub static labeled_string_metric_labels: Lazy<LabeledMetric<LabeledStringMetric>> = Lazy::new(|| {
+        LabeledMetric::new(9.into(), CommonMetricData {
+            name: "labeled_string_metric_labels".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, Some(vec!["one_label".into(), "two_labels".into()]))
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.string_list_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static string_list_metric: Lazy<StringListMetric> = Lazy::new(|| {
+        StringListMetric::new(10.into(), CommonMetricData {
+            name: "string_list_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        })
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.timespan_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static timespan_metric: Lazy<TimespanMetric> = Lazy::new(|| {
+        TimespanMetric::new(11.into(), CommonMetricData {
+            name: "timespan_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, TimeUnit::Millisecond)
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.timing_distribution_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static timing_distribution_metric: Lazy<TimingDistributionMetric> = Lazy::new(|| {
+        TimingDistributionMetric::new(12.into(), CommonMetricData {
+            name: "timing_distribution_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, TimeUnit::Nanosecond)
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.memory_distribution_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static memory_distribution_metric: Lazy<MemoryDistributionMetric> = Lazy::new(|| {
+        MemoryDistributionMetric::new(13.into(), CommonMetricData {
+            name: "memory_distribution_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, MemoryUnit::Kilobyte)
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.custom_distribution_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static custom_distribution_metric: Lazy<CustomDistributionMetric> = Lazy::new(|| {
+        CustomDistributionMetric::new(14.into(), CommonMetricData {
+            name: "custom_distribution_metric".into(),
+            category: "test".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, 0, 100, 100, HistogramType::Linear)
+    });
+
+}
+pub mod test_nested {
+    use crate::private::*;
+    use glean::CommonMetricData;
+    #[allow(unused_imports)] // HistogramType might be unusued, let's avoid warnings
+    use glean::HistogramType;
+    use once_cell::sync::Lazy;
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.nested.uuid_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static uuid_metric: Lazy<UuidMetric> = Lazy::new(|| {
+        UuidMetric::new(15.into(), CommonMetricData {
+            name: "uuid_metric".into(),
+            category: "test.nested".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        })
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.nested.datetime_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static datetime_metric: Lazy<DatetimeMetric> = Lazy::new(|| {
+        DatetimeMetric::new(16.into(), CommonMetricData {
+            name: "datetime_metric".into(),
+            category: "test.nested".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Application,
+            disabled: false,
+            ..Default::default()
+        }, TimeUnit::Millisecond)
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.nested.event_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static event_metric: Lazy<EventMetric<NoExtraKeys>> = Lazy::new(|| {
+        EventMetric::new(17.into(), CommonMetricData {
+            name: "event_metric".into(),
+            category: "test.nested".into(),
+            send_in_pings: vec!["events".into()],
+            lifetime: Lifetime::Ping,
+            disabled: false,
+            ..Default::default()
+        })
+    });
+
+    #[derive(Default, Debug, Clone, Hash, Eq, PartialEq)]
+    pub struct EventMetricWithExtraExtra {
+        pub an_extra_key: Option<String>,
+        pub another_extra_key: Option<String>,
+    }
+
+    impl ExtraKeys for EventMetricWithExtraExtra {
+        const ALLOWED_KEYS: &'static [&'static str] = &["an_extra_key", "another_extra_key"];
+
+        fn into_ffi_extra(self) -> ::std::collections::HashMap<String, String> {
+          let mut map = ::std::collections::HashMap::new();
+          self.an_extra_key.and_then(|val| map.insert("an_extra_key".into(), val.to_string()));
+          self.another_extra_key.and_then(|val| map.insert("another_extra_key".into(), val.to_string()));
+          map
+        }
+    }
+    #[allow(non_upper_case_globals)]
+    /// generated from test.nested.event_metric_with_extra
+    ///
+    /// A multi-line
+    /// description
+    pub static event_metric_with_extra: Lazy<EventMetric<EventMetricWithExtraExtra>> = Lazy::new(|| {
+        EventMetric::new(18.into(), CommonMetricData {
+            name: "event_metric_with_extra".into(),
+            category: "test.nested".into(),
+            send_in_pings: vec!["events".into()],
+            lifetime: Lifetime::Ping,
+            disabled: false,
+            ..Default::default()
+        })
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.nested.quantity_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static quantity_metric: Lazy<QuantityMetric> = Lazy::new(|| {
+        QuantityMetric::new(19.into(), CommonMetricData {
+            name: "quantity_metric".into(),
+            category: "test.nested".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Ping,
+            disabled: false,
+            ..Default::default()
+        })
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.nested.rate_metric
+    ///
+    /// A multi-line
+    /// description
+    pub static rate_metric: Lazy<RateMetric> = Lazy::new(|| {
+        RateMetric::new(20.into(), CommonMetricData {
+            name: "rate_metric".into(),
+            category: "test.nested".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Ping,
+            disabled: false,
+            ..Default::default()
+        })
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.nested.rate_with_external_denominator
+    ///
+    /// A multi-line
+    /// description
+    pub static rate_with_external_denominator: Lazy<NumeratorMetric> = Lazy::new(|| {
+        NumeratorMetric::new(21.into(), CommonMetricData {
+            name: "rate_with_external_denominator".into(),
+            category: "test.nested".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Ping,
+            disabled: false,
+            ..Default::default()
+        })
+    });
+
+    #[allow(non_upper_case_globals)]
+    /// generated from test.nested.external_denominator
+    ///
+    /// A multi-line
+    /// description
+    pub static external_denominator: Lazy<DenominatorMetric> = Lazy::new(|| {
+        DenominatorMetric::new(22.into(), CommonMetricData {
+            name: "external_denominator".into(),
+            category: "test.nested".into(),
+            send_in_pings: vec!["metrics".into()],
+            lifetime: Lifetime::Ping,
+            disabled: false,
+            ..Default::default()
+        }, vec![CommonMetricData {name: "rate_with_external_denominator".into(), category: "test.nested".into(), send_in_pings: vec!["metrics".into()], lifetime: Lifetime::Ping, disabled: false,  ..Default::default()}])
+    });
+
+}
+
+#[allow(dead_code)]
+pub(crate) mod __glean_metric_maps {
+    use std::collections::HashMap;
+
+    use crate::metrics::extra_keys_len;
+    use crate::private::*;
+    use once_cell::sync::Lazy;
+
+    pub static BOOLEAN_MAP: Lazy<HashMap<MetricId, &Lazy<BooleanMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(1.into(), &super::test::boolean_metric);
+        map
+    });
+
+    pub static LABELED_BOOLEAN_MAP: Lazy<HashMap<MetricId, &Lazy<LabeledMetric<LabeledBooleanMetric>>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(2);
+        map.insert(2.into(), &super::test::labeled_boolean_metric);
+        map.insert(3.into(), &super::test::labeled_boolean_metric_labels);
+        map
+    });
+
+    pub static COUNTER_MAP: Lazy<HashMap<MetricId, &Lazy<CounterMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(4.into(), &super::test::counter_metric);
+        map
+    });
+
+    pub static LABELED_COUNTER_MAP: Lazy<HashMap<MetricId, &Lazy<LabeledMetric<LabeledCounterMetric>>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(2);
+        map.insert(5.into(), &super::test::labeled_counter_metric);
+        map.insert(6.into(), &super::test::labeled_counter_metric_labels);
+        map
+    });
+
+    pub static STRING_MAP: Lazy<HashMap<MetricId, &Lazy<StringMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(7.into(), &super::test::string_metric);
+        map
+    });
+
+    pub static LABELED_STRING_MAP: Lazy<HashMap<MetricId, &Lazy<LabeledMetric<LabeledStringMetric>>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(2);
+        map.insert(8.into(), &super::test::labeled_string_metric);
+        map.insert(9.into(), &super::test::labeled_string_metric_labels);
+        map
+    });
+
+    pub static STRING_LIST_MAP: Lazy<HashMap<MetricId, &Lazy<StringListMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(10.into(), &super::test::string_list_metric);
+        map
+    });
+
+    pub static TIMESPAN_MAP: Lazy<HashMap<MetricId, &Lazy<TimespanMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(11.into(), &super::test::timespan_metric);
+        map
+    });
+
+    pub static TIMING_DISTRIBUTION_MAP: Lazy<HashMap<MetricId, &Lazy<TimingDistributionMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(12.into(), &super::test::timing_distribution_metric);
+        map
+    });
+
+    pub static MEMORY_DISTRIBUTION_MAP: Lazy<HashMap<MetricId, &Lazy<MemoryDistributionMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(13.into(), &super::test::memory_distribution_metric);
+        map
+    });
+
+    pub static CUSTOM_DISTRIBUTION_MAP: Lazy<HashMap<MetricId, &Lazy<CustomDistributionMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(14.into(), &super::test::custom_distribution_metric);
+        map
+    });
+
+    pub static UUID_MAP: Lazy<HashMap<MetricId, &Lazy<UuidMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(15.into(), &super::test_nested::uuid_metric);
+        map
+    });
+
+    pub static DATETIME_MAP: Lazy<HashMap<MetricId, &Lazy<DatetimeMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(16.into(), &super::test_nested::datetime_metric);
+        map
+    });
+
+    pub static QUANTITY_MAP: Lazy<HashMap<MetricId, &Lazy<QuantityMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(19.into(), &super::test_nested::quantity_metric);
+        map
+    });
+
+    pub static RATE_MAP: Lazy<HashMap<MetricId, &Lazy<RateMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(20.into(), &super::test_nested::rate_metric);
+        map
+    });
+
+    pub static NUMERATOR_MAP: Lazy<HashMap<MetricId, &Lazy<NumeratorMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(21.into(), &super::test_nested::rate_with_external_denominator);
+        map
+    });
+
+    pub static DENOMINATOR_MAP: Lazy<HashMap<MetricId, &Lazy<DenominatorMetric>>> = Lazy::new(|| {
+        let mut map = HashMap::with_capacity(1);
+        map.insert(22.into(), &super::test_nested::external_denominator);
+        map
+    });
+
+
+    /// Wrapper to record an event based on its metric ID.
+    ///
+    /// # Arguments
+    ///
+    /// * `metric_id` - The metric's ID to look up
+    /// * `extra`     - An map of (extra key id, string) pairs.
+    ///                 The map will be decoded into the appropriate `ExtraKeys` type.
+    /// # Returns
+    ///
+    /// Returns `Ok(())` if the event was found and `record` was called with the given `extra`,
+    /// or an `EventRecordingError::InvalidId` if no event by that ID exists
+    /// or an `EventRecordingError::InvalidExtraKey` if the `extra` map could not be deserialized.
+    pub(crate) fn record_event_by_id(metric_id: u32, extra: HashMap<String, String>) -> Result<(), EventRecordingError> {
+        match metric_id {
+          17 => {
+              assert!(
+                  extra_keys_len(&super::test_nested::event_metric) != 0 || extra.is_empty(),
+                  "No extra keys allowed, but some were passed"
+              );
+
+              super::test_nested::event_metric.record_raw(extra);
+              Ok(())
+          }
+          18 => {
+              assert!(
+                  extra_keys_len(&super::test_nested::event_metric_with_extra) != 0 || extra.is_empty(),
+                  "No extra keys allowed, but some were passed"
+              );
+
+              super::test_nested::event_metric_with_extra.record_raw(extra);
+              Ok(())
+          }
+           _ => Err(EventRecordingError::InvalidId),
+        }
+    }
+
+    /// Wrapper to record an event based on its metric ID, with a provided timestamp.
+    ///
+    /// # Arguments
+    ///
+    /// * `metric_id` - The metric's ID to look up
+    /// * `timestamp` - The time at which this event was recorded.
+    /// * `extra`     - An map of (extra key id, string) pairs.
+    ///                 The map will be decoded into the appropriate `ExtraKeys` type.
+    /// # Returns
+    ///
+    /// Returns `Ok(())` if the event was found and `record` was called with the given `extra`,
+    /// or an `EventRecordingError::InvalidId` if no event by that ID exists
+    /// or an `EventRecordingError::InvalidExtraKey` if the event doesn't take extra pairs,
+    /// but some are passed in.
+    pub(crate) fn record_event_by_id_with_time(metric_id: MetricId, timestamp: u64, extra: HashMap<String, String>) -> Result<(), EventRecordingError> {
+        match metric_id {
+          MetricId(17) => {
+              if extra_keys_len(&super::test_nested::event_metric) == 0 && !extra.is_empty() {
+                return Err(EventRecordingError::InvalidExtraKey);
+              }
+
+              super::test_nested::event_metric.record_with_time(timestamp, extra);
+              Ok(())
+          }
+          MetricId(18) => {
+              if extra_keys_len(&super::test_nested::event_metric_with_extra) == 0 && !extra.is_empty() {
+                return Err(EventRecordingError::InvalidExtraKey);
+              }
+
+              super::test_nested::event_metric_with_extra.record_with_time(timestamp, extra);
+              Ok(())
+          }
+           _ => Err(EventRecordingError::InvalidId),
+        }
+    }
+
+    /// Wrapper to record an event based on its metric ID.
+    ///
+    /// # Arguments
+    ///
+    /// * `metric_id` - The metric's ID to look up
+    /// * `extra`     - An map of (string, string) pairs.
+    ///                 The map will be decoded into the appropriate `ExtraKeys` types.
+    /// # Returns
+    ///
+    /// Returns `Ok(())` if the event was found and `record` was called with the given `extra`,
+    /// or an `EventRecordingError::InvalidId` if no event by that ID exists
+    /// or an `EventRecordingError::InvalidExtraKey` if the `extra` map could not be deserialized.
+    pub(crate) fn record_event_by_id_with_strings(metric_id: u32, extra: HashMap<String, String>) -> Result<(), EventRecordingError> {
+        match metric_id {
+          17 => {
+              assert!(
+                  extra_keys_len(&super::test_nested::event_metric) != 0 || extra.is_empty(),
+                  "No extra keys allowed, but some were passed"
+              );
+
+              super::test_nested::event_metric.record_raw(extra);
+              Ok(())
+          }
+          18 => {
+              assert!(
+                  extra_keys_len(&super::test_nested::event_metric_with_extra) != 0 || extra.is_empty(),
+                  "No extra keys allowed, but some were passed"
+              );
+
+              super::test_nested::event_metric_with_extra.record_raw(extra);
+              Ok(())
+          }
+           _ => Err(EventRecordingError::InvalidId),
+        }
+    }
+
+    /// Wrapper to get the currently stored events for event metric.
+    ///
+    /// # Arguments
+    ///
+    /// * `metric_id` - The metric's ID to look up
+    /// * `ping_name` - (Optional) The ping name to look into.
+    ///                 Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// Returns the recorded events or `None` if nothing stored.
+    ///
+    /// # Panics
+    ///
+    /// Panics if no event by the given metric ID could be found.
+    pub(crate) fn event_test_get_value_wrapper(metric_id: u32, ping_name: Option<String>) -> Option<Vec<RecordedEvent>> {
+        match metric_id {
+           17 => super::test_nested::event_metric.test_get_value(ping_name.as_deref()),
+           18 => super::test_nested::event_metric_with_extra.test_get_value(ping_name.as_deref()),
+           _ => panic!("No event for metric id {}", metric_id),
+        }
+    }
+
+    /// Check the provided event for errors.
+    ///
+    /// # Arguments
+    ///
+    /// * `metric_id` - The metric's ID to look up
+    /// * `ping_name` - (Optional) The ping name to look into.
+    ///                 Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// Returns a string for the recorded error or `None`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if no event by the given metric ID could be found.
+    #[allow(unused_variables)]
+    pub(crate) fn event_test_get_error(metric_id: u32) -> Option<String> {
+        #[cfg(feature = "with_gecko")]
+        match metric_id {
+           17 => test_get_errors!(super::test_nested::event_metric),
+           18 => test_get_errors!(super::test_nested::event_metric_with_extra),
+           _ => panic!("No event for metric id {}", metric_id),
+        }
+
+        #[cfg(not(feature = "with_gecko"))]
+        {
+            return None;
+        }
+    }
+
+    pub(crate) mod submetric_maps {
+        use std::sync::{
+          atomic::AtomicU32,
+          RwLock,
+        };
+        use super::*;
+
+        pub(crate) const SUBMETRIC_BIT: u32 = 25;
+        pub(crate) static NEXT_LABELED_SUBMETRIC_ID: AtomicU32 = AtomicU32::new((1 << SUBMETRIC_BIT) + 1);
+        pub(crate) static LABELED_METRICS_TO_IDS: Lazy<RwLock<HashMap<(u32, String), u32>>> = Lazy::new(||
+            RwLock::new(HashMap::new())
+        );
+
+        pub static BOOLEAN_MAP: Lazy<RwLock<HashMap<MetricId, LabeledBooleanMetric>>> = Lazy::new(||
+            RwLock::new(HashMap::new())
+        );
+        pub static COUNTER_MAP: Lazy<RwLock<HashMap<MetricId, LabeledCounterMetric>>> = Lazy::new(||
+            RwLock::new(HashMap::new())
+        );
+        pub static STRING_MAP: Lazy<RwLock<HashMap<MetricId, LabeledStringMetric>>> = Lazy::new(||
+            RwLock::new(HashMap::new())
+        );
+    }
+}
+
diff --git a/toolkit/components/glean/tests/pytest/metrics_test_output_cpp b/toolkit/components/glean/tests/pytest/metrics_test_output_cpp
new file mode 100644
index 0000000000..c9a9cbc619
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/metrics_test_output_cpp
@@ -0,0 +1,244 @@
+// -*- mode: C++ -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_Metrics_h
+#define mozilla_Metrics_h
+
+#include "mozilla/glean/bindings/MetricTypes.h"
+#include "mozilla/Tuple.h"
+#include "mozilla/Maybe.h"
+#include "nsTArray.h"
+#include "nsPrintfCString.h"
+
+namespace mozilla::glean {
+struct NoExtraKeys;
+
+namespace test {
+    /**
+     * generated from test.boolean_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::BooleanMetric boolean_metric(1);
+
+    /**
+     * generated from test.labeled_boolean_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::Labeled<impl::BooleanMetric> labeled_boolean_metric(2);
+
+    /**
+     * generated from test.labeled_boolean_metric_labels
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::Labeled<impl::BooleanMetric> labeled_boolean_metric_labels(3);
+
+    /**
+     * generated from test.counter_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::CounterMetric counter_metric(4);
+
+    /**
+     * generated from test.labeled_counter_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::Labeled<impl::CounterMetric> labeled_counter_metric(5);
+
+    /**
+     * generated from test.labeled_counter_metric_labels
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::Labeled<impl::CounterMetric> labeled_counter_metric_labels(6);
+
+    /**
+     * generated from test.string_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::StringMetric string_metric(7);
+
+    /**
+     * generated from test.labeled_string_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::Labeled<impl::StringMetric> labeled_string_metric(8);
+
+    /**
+     * generated from test.labeled_string_metric_labels
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::Labeled<impl::StringMetric> labeled_string_metric_labels(9);
+
+    /**
+     * generated from test.string_list_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::StringListMetric string_list_metric(10);
+
+    /**
+     * generated from test.timespan_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::TimespanMetric timespan_metric(11);
+
+    /**
+     * generated from test.timing_distribution_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::TimingDistributionMetric timing_distribution_metric(12);
+
+    /**
+     * generated from test.memory_distribution_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::MemoryDistributionMetric memory_distribution_metric(13);
+
+    /**
+     * generated from test.custom_distribution_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::CustomDistributionMetric custom_distribution_metric(14);
+
+}
+namespace test_nested {
+    /**
+     * generated from test.nested.uuid_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::UuidMetric uuid_metric(15);
+
+    /**
+     * generated from test.nested.datetime_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::DatetimeMetric datetime_metric(16);
+
+    /**
+     * generated from test.nested.event_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::EventMetric<NoExtraKeys> event_metric(17);
+
+    /**
+     * generated from test.nested.event_metric_with_extra
+     */
+    struct EventMetricWithExtraExtra {
+      mozilla::Maybe<nsCString> anExtraKey;
+      mozilla::Maybe<nsCString> anotherExtraKey;
+
+      Tuple<nsTArray<nsCString>, nsTArray<nsCString>> ToFfiExtra() const {
+        nsTArray<nsCString> extraKeys;
+        nsTArray<nsCString> extraValues;
+        if (anExtraKey) {
+          extraKeys.AppendElement()->AssignASCII("an_extra_key");
+          extraValues.EmplaceBack(anExtraKey.value());
+        }
+        if (anotherExtraKey) {
+          extraKeys.AppendElement()->AssignASCII("another_extra_key");
+          extraValues.EmplaceBack(anotherExtraKey.value());
+        }
+        return MakeTuple(std::move(extraKeys), std::move(extraValues));
+      }
+    };
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::EventMetric<EventMetricWithExtraExtra> event_metric_with_extra(18);
+
+    /**
+     * generated from test.nested.quantity_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::QuantityMetric quantity_metric(19);
+
+    /**
+     * generated from test.nested.rate_metric
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::RateMetric rate_metric(20);
+
+    /**
+     * generated from test.nested.rate_with_external_denominator
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::NumeratorMetric rate_with_external_denominator(21);
+
+    /**
+     * generated from test.nested.external_denominator
+     */
+    /**
+     * A multi-line
+     * description
+     */
+    constexpr impl::DenominatorMetric external_denominator(22);
+
+}
+
+} // namespace mozilla::glean
+
+#endif // mozilla_Metrics_h
diff --git a/toolkit/components/glean/tests/pytest/metrics_test_output_js b/toolkit/components/glean/tests/pytest/metrics_test_output_js
new file mode 100644
index 0000000000..3c682d5ee7
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/metrics_test_output_js
@@ -0,0 +1,342 @@
+// -*- mode: C++ -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_GleanJSMetricsLookup_h
+#define mozilla_GleanJSMetricsLookup_h
+
+#include "mozilla/PerfectHash.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/glean/bindings/MetricTypes.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+
+#define GLEAN_INDEX_BITS (32)
+#define GLEAN_TYPE_BITS (5)
+#define GLEAN_ID_BITS (27)
+#define GLEAN_TYPE_ID(id) ((id) >> GLEAN_ID_BITS)
+#define GLEAN_METRIC_ID(id) ((id) & ((1ULL << GLEAN_ID_BITS) - 1))
+#define GLEAN_OFFSET(entry) (entry & ((1ULL << GLEAN_INDEX_BITS) - 1))
+
+namespace mozilla::glean {
+
+// The category lookup table's entry type
+using category_entry_t = uint32_t;
+// The metric lookup table's entry type
+// This is a bitpacked type with 32 bits available to index into
+// the string table, 5 bits available to signify the metric type,
+// and the remaining 27 bits devoted to 2 "signal"
+// bits to signify important characteristics (metric's a labeled metric's
+// submetric, metric's been registered at runtime) and 25 bits
+// for built-in metric ids.
+// Gives room for 33554432 of each combination of
+// characteristics (which hopefully will prove to be enough).
+using metric_entry_t = uint64_t;
+
+static_assert(GLEAN_INDEX_BITS + GLEAN_TYPE_BITS + GLEAN_ID_BITS == sizeof(metric_entry_t) * 8, "Index, Type, and ID bits need to fit into a metric_entry_t");
+static_assert(GLEAN_TYPE_BITS + GLEAN_ID_BITS <= sizeof(uint32_t) * 8, "Metric Types and IDs need to fit into at most 32 bits");
+static_assert(2 < UINT32_MAX, "Too many metric categories generated.");
+static_assert(22 < 33554432, "Too many metrics generated. Need room for 2 signal bits.");
+static_assert(18 < 32, "Too many different metric types.");
+
+static already_AddRefed<nsISupports> NewMetricFromId(uint32_t id) {
+  uint32_t typeId = GLEAN_TYPE_ID(id);
+  uint32_t metricId = GLEAN_METRIC_ID(id);
+
+  switch (typeId) {
+    case 1: /* boolean */
+    {
+      return MakeAndAddRef<GleanBoolean>(metricId);
+    }
+    case 2: /* labeled_boolean */
+    {
+      return MakeAndAddRef<GleanLabeled>(metricId, 2);
+    }
+    case 3: /* counter */
+    {
+      return MakeAndAddRef<GleanCounter>(metricId);
+    }
+    case 4: /* labeled_counter */
+    {
+      return MakeAndAddRef<GleanLabeled>(metricId, 4);
+    }
+    case 5: /* string */
+    {
+      return MakeAndAddRef<GleanString>(metricId);
+    }
+    case 6: /* labeled_string */
+    {
+      return MakeAndAddRef<GleanLabeled>(metricId, 6);
+    }
+    case 7: /* string_list */
+    {
+      return MakeAndAddRef<GleanStringList>(metricId);
+    }
+    case 8: /* timespan */
+    {
+      return MakeAndAddRef<GleanTimespan>(metricId);
+    }
+    case 9: /* timing_distribution */
+    {
+      return MakeAndAddRef<GleanTimingDistribution>(metricId);
+    }
+    case 10: /* memory_distribution */
+    {
+      return MakeAndAddRef<GleanMemoryDistribution>(metricId);
+    }
+    case 11: /* custom_distribution */
+    {
+      return MakeAndAddRef<GleanCustomDistribution>(metricId);
+    }
+    case 12: /* uuid */
+    {
+      return MakeAndAddRef<GleanUuid>(metricId);
+    }
+    case 13: /* datetime */
+    {
+      return MakeAndAddRef<GleanDatetime>(metricId);
+    }
+    case 14: /* event */
+    {
+      return MakeAndAddRef<GleanEvent>(metricId);
+    }
+    case 15: /* quantity */
+    {
+      return MakeAndAddRef<GleanQuantity>(metricId);
+    }
+    case 16: /* rate */
+    {
+      return MakeAndAddRef<GleanRate>(metricId);
+    }
+    case 17: /* numerator */
+    {
+      return MakeAndAddRef<GleanNumerator>(metricId);
+    }
+    case 18: /* denominator */
+    {
+      return MakeAndAddRef<GleanDenominator>(metricId);
+    }
+    default:
+    MOZ_ASSERT_UNREACHABLE("Invalid type ID reached when trying to instantiate a new metric");
+    return nullptr;
+  }
+}
+
+/**
+ * Create a submetric instance for a labeled metric of the provided type and id for the given label.
+ * Assigns or retrieves an id for the submetric from the SDK.
+ *
+ * @param aParentTypeId - The type of the parent labeled metric identified as a number generated during codegen.
+ *                        Only used to identify which X of LabeledX you are so that X can be created here.
+ * @param aParentMetricId - The metric id for the parent labeled metric.
+ * @param aLabel - The label for the submetric. Might not adhere to the SDK label format.
+ * @param aSubmetricId - an outparam which is assigned the submetric's SDK-generated submetric id.
+ *                       Used only by GIFFT.
+ */
+static already_AddRefed<nsISupports> NewSubMetricFromIds(uint32_t aParentTypeId, uint32_t aParentMetricId, const nsACString& aLabel, uint32_t* aSubmetricId) {
+  switch (aParentTypeId) {
+    case 2: { /* labeled_boolean */
+      auto id = impl::fog_labeled_boolean_get(aParentMetricId, &aLabel);
+      *aSubmetricId = id;
+      return MakeAndAddRef<GleanBoolean>(id);
+    }
+    case 4: { /* labeled_counter */
+      auto id = impl::fog_labeled_counter_get(aParentMetricId, &aLabel);
+      *aSubmetricId = id;
+      return MakeAndAddRef<GleanCounter>(id);
+    }
+    case 6: { /* labeled_string */
+      auto id = impl::fog_labeled_string_get(aParentMetricId, &aLabel);
+      *aSubmetricId = id;
+      return MakeAndAddRef<GleanString>(id);
+    }
+    default: {
+      MOZ_ASSERT_UNREACHABLE("Invalid type ID for submetric.");
+      return nullptr;
+    }
+  }
+}
+
+static Maybe<uint32_t> category_result_check(const nsACString& aKey, category_entry_t entry);
+static Maybe<uint32_t> metric_result_check(const nsACString& aKey, metric_entry_t entry);
+
+#if defined(_MSC_VER) && !defined(__clang__)
+const char gCategoryStringTable[] = {
+#else
+constexpr char gCategoryStringTable[] = {
+#endif
+  /*     0 - "test" */ 't', 'e', 's', 't', '\0',
+  /*     5 - "testNested" */ 't', 'e', 's', 't', 'N', 'e', 's', 't', 'e', 'd', '\0',
+};
+
+
+static_assert(sizeof(gCategoryStringTable) < UINT32_MAX, "Category string table is too large.");
+
+const category_entry_t sCategoryByNameLookupEntries[] = {
+  5ul,
+  0ul
+};
+
+
+
+static Maybe<uint32_t>
+CategoryByNameLookup(const nsACString& aKey)
+{
+  static const uint8_t BASES[] = {
+       0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   1,   0,   0,   0,   0,   0,
+       0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+       0,   0,   0,   0,   0,   1,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+       0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+  };
+  
+
+  const char* bytes = aKey.BeginReading();
+  size_t length = aKey.Length();
+  auto& entry = mozilla::perfecthash::Lookup(bytes, length, BASES,
+                                             sCategoryByNameLookupEntries);
+  return category_result_check(aKey, entry);
+}
+
+
+#if defined(_MSC_VER) && !defined(__clang__)
+const char gMetricStringTable[] = {
+#else
+constexpr char gMetricStringTable[] = {
+#endif
+  /*     0 - "test.booleanMetric" */ 't', 'e', 's', 't', '.', 'b', 'o', 'o', 'l', 'e', 'a', 'n', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*    19 - "test.labeledBooleanMetric" */ 't', 'e', 's', 't', '.', 'l', 'a', 'b', 'e', 'l', 'e', 'd', 'B', 'o', 'o', 'l', 'e', 'a', 'n', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*    45 - "test.labeledBooleanMetricLabels" */ 't', 'e', 's', 't', '.', 'l', 'a', 'b', 'e', 'l', 'e', 'd', 'B', 'o', 'o', 'l', 'e', 'a', 'n', 'M', 'e', 't', 'r', 'i', 'c', 'L', 'a', 'b', 'e', 'l', 's', '\0',
+  /*    77 - "test.counterMetric" */ 't', 'e', 's', 't', '.', 'c', 'o', 'u', 'n', 't', 'e', 'r', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*    96 - "test.labeledCounterMetric" */ 't', 'e', 's', 't', '.', 'l', 'a', 'b', 'e', 'l', 'e', 'd', 'C', 'o', 'u', 'n', 't', 'e', 'r', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   122 - "test.labeledCounterMetricLabels" */ 't', 'e', 's', 't', '.', 'l', 'a', 'b', 'e', 'l', 'e', 'd', 'C', 'o', 'u', 'n', 't', 'e', 'r', 'M', 'e', 't', 'r', 'i', 'c', 'L', 'a', 'b', 'e', 'l', 's', '\0',
+  /*   154 - "test.stringMetric" */ 't', 'e', 's', 't', '.', 's', 't', 'r', 'i', 'n', 'g', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   172 - "test.labeledStringMetric" */ 't', 'e', 's', 't', '.', 'l', 'a', 'b', 'e', 'l', 'e', 'd', 'S', 't', 'r', 'i', 'n', 'g', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   197 - "test.labeledStringMetricLabels" */ 't', 'e', 's', 't', '.', 'l', 'a', 'b', 'e', 'l', 'e', 'd', 'S', 't', 'r', 'i', 'n', 'g', 'M', 'e', 't', 'r', 'i', 'c', 'L', 'a', 'b', 'e', 'l', 's', '\0',
+  /*   228 - "test.stringListMetric" */ 't', 'e', 's', 't', '.', 's', 't', 'r', 'i', 'n', 'g', 'L', 'i', 's', 't', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   250 - "test.timespanMetric" */ 't', 'e', 's', 't', '.', 't', 'i', 'm', 'e', 's', 'p', 'a', 'n', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   270 - "test.timingDistributionMetric" */ 't', 'e', 's', 't', '.', 't', 'i', 'm', 'i', 'n', 'g', 'D', 'i', 's', 't', 'r', 'i', 'b', 'u', 't', 'i', 'o', 'n', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   300 - "test.memoryDistributionMetric" */ 't', 'e', 's', 't', '.', 'm', 'e', 'm', 'o', 'r', 'y', 'D', 'i', 's', 't', 'r', 'i', 'b', 'u', 't', 'i', 'o', 'n', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   330 - "test.customDistributionMetric" */ 't', 'e', 's', 't', '.', 'c', 'u', 's', 't', 'o', 'm', 'D', 'i', 's', 't', 'r', 'i', 'b', 'u', 't', 'i', 'o', 'n', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   360 - "testNested.uuidMetric" */ 't', 'e', 's', 't', 'N', 'e', 's', 't', 'e', 'd', '.', 'u', 'u', 'i', 'd', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   382 - "testNested.datetimeMetric" */ 't', 'e', 's', 't', 'N', 'e', 's', 't', 'e', 'd', '.', 'd', 'a', 't', 'e', 't', 'i', 'm', 'e', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   408 - "testNested.eventMetric" */ 't', 'e', 's', 't', 'N', 'e', 's', 't', 'e', 'd', '.', 'e', 'v', 'e', 'n', 't', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   431 - "testNested.eventMetricWithExtra" */ 't', 'e', 's', 't', 'N', 'e', 's', 't', 'e', 'd', '.', 'e', 'v', 'e', 'n', 't', 'M', 'e', 't', 'r', 'i', 'c', 'W', 'i', 't', 'h', 'E', 'x', 't', 'r', 'a', '\0',
+  /*   463 - "testNested.quantityMetric" */ 't', 'e', 's', 't', 'N', 'e', 's', 't', 'e', 'd', '.', 'q', 'u', 'a', 'n', 't', 'i', 't', 'y', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   489 - "testNested.rateMetric" */ 't', 'e', 's', 't', 'N', 'e', 's', 't', 'e', 'd', '.', 'r', 'a', 't', 'e', 'M', 'e', 't', 'r', 'i', 'c', '\0',
+  /*   511 - "testNested.rateWithExternalDenominator" */ 't', 'e', 's', 't', 'N', 'e', 's', 't', 'e', 'd', '.', 'r', 'a', 't', 'e', 'W', 'i', 't', 'h', 'E', 'x', 't', 'e', 'r', 'n', 'a', 'l', 'D', 'e', 'n', 'o', 'm', 'i', 'n', 'a', 't', 'o', 'r', '\0',
+  /*   550 - "testNested.externalDenominator" */ 't', 'e', 's', 't', 'N', 'e', 's', 't', 'e', 'd', '.', 'e', 'x', 't', 'e', 'r', 'n', 'a', 'l', 'D', 'e', 'n', 'o', 'm', 'i', 'n', 'a', 't', 'o', 'r', '\0',
+};
+
+
+static_assert(sizeof(gMetricStringTable) < 4294967296, "Metric string table is too large.");
+
+const metric_entry_t sMetricByNameLookupEntries[] = {
+  6341068335467200842ull,
+  1729382274090139725ull,
+  1152921513196781587ull,
+  2305843034983497850ull,
+  5764607578868810028ull,
+  8070450605262373272ull,
+  3458764548180279468ull,
+  10376293635950903846ull,
+  8646911366155731407ull,
+  9799832879352513023ull,
+  2882303791581888666ull,
+  1152921517491748909ull,
+  4035225309073637604ull,
+  6917529092065591656ull,
+  4611686065672028410ull,
+  7493989848663982462ull,
+  8070450609557340591ull,
+  3458764552475246789ull,
+  5188146822270419214ull,
+  576460756598390784ull,
+  2305843030688530528ull,
+  9223372122754122217ull
+};
+
+
+
+static Maybe<uint32_t>
+MetricByNameLookup(const nsACString& aKey)
+{
+  static const uint8_t BASES[] = {
+       0,   0,   0,   1,   0,   2,   0,   1,   1,   0,   0,   0,   0,   0,   0,   0,
+       1,   1,   0,   0,   1,   0,   0,   1,   0,   4,   0,   0,   1,   0,   1,   0,
+       2,   0,   0,   0,   0,   0,   0,   0,   1,   0,   0,   3,   0,   6,   0,   0,
+       0,   0,  10,   0,   0,   1,   0,   0,   0,   0,   4,   0,   0,   0,   0,  17,
+  };
+  
+
+  const char* bytes = aKey.BeginReading();
+  size_t length = aKey.Length();
+  auto& entry = mozilla::perfecthash::Lookup(bytes, length, BASES,
+                                             sMetricByNameLookupEntries);
+  return metric_result_check(aKey, entry);
+}
+
+
+/**
+ * Get a category's name from the string table.
+ */
+static const char* GetCategoryName(category_entry_t entry) {
+  MOZ_ASSERT(entry < sizeof(gCategoryStringTable), "Entry identifier offset larger than string table");
+  return &gCategoryStringTable[entry];
+}
+
+/**
+ * Get a metric's identifier from the string table.
+ */
+static const char* GetMetricIdentifier(metric_entry_t entry) {
+  uint32_t offset = GLEAN_OFFSET(entry);
+  MOZ_ASSERT(offset < sizeof(gMetricStringTable), "Entry identifier offset larger than string table");
+  return &gMetricStringTable[offset];
+}
+
+/**
+ * Check that the found entry is pointing to the right key
+ * and return it.
+ * Or return `Nothing()` if the entry was not found.
+ */
+static Maybe<uint32_t> category_result_check(const nsACString& aKey, category_entry_t entry) {
+  if (MOZ_UNLIKELY(entry > sizeof(gCategoryStringTable))) {
+    return Nothing();
+  }
+  if (aKey.EqualsASCII(gCategoryStringTable + entry)) {
+    return Some(entry);
+  }
+  return Nothing();
+}
+
+/**
+ * Check if the found entry index is pointing to the right key
+ * and return the corresponding metric ID.
+ * Or return `Nothing()` if the entry was not found.
+ */
+static Maybe<uint32_t> metric_result_check(const nsACString& aKey, uint64_t entry) {
+  uint32_t metricId = entry >> GLEAN_INDEX_BITS;
+  uint32_t offset = GLEAN_OFFSET(entry);
+
+  if (offset > sizeof(gMetricStringTable)) {
+    return Nothing();
+  }
+
+  if (aKey.EqualsASCII(gMetricStringTable + offset)) {
+    return Some(metricId);
+  }
+
+  return Nothing();
+}
+
+
+#undef GLEAN_INDEX_BITS
+#undef GLEAN_ID_BITS
+#undef GLEAN_TYPE_ID
+#undef GLEAN_METRIC_ID
+#undef GLEAN_OFFSET
+
+} // namespace mozilla::glean
+#endif // mozilla_GleanJSMetricsLookup_h
diff --git a/toolkit/components/glean/tests/pytest/pings_test.yaml b/toolkit/components/glean/tests/pytest/pings_test.yaml
new file mode 100644
index 0000000000..efa6ba9e0a
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/pings_test.yaml
@@ -0,0 +1,116 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file defines the built-in pings that are recorded by the Glean SDK. They
+# are automatically converted to Kotlin code at build time using the
+# `glean_parser` PyPI package.
+
+---
+$schema: moz://mozilla.org/schemas/glean/pings/1-0-0
+
+not-baseline:
+  description: >
+    This ping is intended to provide metrics that are managed by the library
+    itself, and not explicitly set by the application or included in the
+    application's `metrics.yaml` file.
+    The `baseline` ping is automatically sent when the application is moved to
+    the background.
+  include_client_id: true
+  bugs:
+    - https://bugzilla.mozilla.org/1512938
+    - https://bugzilla.mozilla.org/1599877
+  data_reviews:
+    - https://bugzilla.mozilla.org/show_bug.cgi?id=1512938#c3
+    - https://bugzilla.mozilla.org/show_bug.cgi?id=1599877#c25
+  notification_emails:
+    - glean-team@mozilla.com
+  reasons:
+    dirty_startup: |
+      The ping was submitted at startup, because the application process was
+      killed before the Glean SDK had the chance to generate this ping, when
+      going to background, in the last session.
+
+      *Note*: this ping will not contain the `glean.baseline.duration` metric.
+    background: |
+      The ping was submitted before going to background.
+    foreground: |
+      The ping was submitted when the application went to foreground, which
+      includes when the application starts.
+
+      *Note*: this ping will not contain the `glean.baseline.duration` metric.
+
+not-metrics:
+  description: >
+    The `metrics` ping is intended for all of the metrics that are explicitly
+    set by the application or are included in the application's `metrics.yaml`
+    file (except events).
+    The reported data is tied to the ping's *measurement window*, which is the
+    time between the collection of two `metrics` ping. Ideally, this window is
+    expected to be about 24 hours, given that the collection is scheduled daily
+    at 4AM. Data in the `ping_info` section of the ping can be used to infer the
+    length of this window.
+  include_client_id: true
+  bugs:
+    - https://bugzilla.mozilla.org/1512938
+  data_reviews:
+    - https://bugzilla.mozilla.org/show_bug.cgi?id=1512938#c3
+    - https://bugzilla.mozilla.org/show_bug.cgi?id=1557048#c13
+  notification_emails:
+    - glean-team@mozilla.com
+  reasons:
+    overdue: |
+      The last ping wasn't submitted on the current calendar day, but it's after
+      4am, so this ping submitted immediately
+    today: |
+      The last ping wasn't submitted on the current calendar day, but it is
+      still before 4am, so schedule to send this ping on the current calendar
+      day at 4am.
+    tomorrow: |
+      The last ping was already submitted on the current calendar day, so
+      schedule this ping for the next calendar day at 4am.
+    upgrade: |
+      This ping was submitted at startup because the application was just
+      upgraded.
+    reschedule: |
+      A ping was just submitted. This ping was rescheduled for the next calendar
+      day at 4am.
+
+not-events:
+  description: >
+    The events ping's purpose is to transport all of the event metric
+    information. The `events` ping is automatically sent when the application is
+    moved to the background.
+  include_client_id: true
+  bugs:
+    - https://bugzilla.mozilla.org/1512938
+  data_reviews:
+    - https://bugzilla.mozilla.org/show_bug.cgi?id=1512938#c3
+  notification_emails:
+    - glean-team@mozilla.com
+  reasons:
+    startup: |
+      The ping was submitted at startup. The events ping is always sent if there
+      are any pending events at startup, because event timestamps can not be
+      mixed across runs of the application.
+    background: |
+      The ping was submitted before going to background.
+    max_capacity: |
+      The maximum number of events was reached (default 500 events).
+
+not-deletion-request:
+  description: >
+    This ping is submitted when a user opts out of
+    sending technical and interaction data to Mozilla.
+    This ping is intended to communicate to the Data Pipeline
+    that the user wishes to have their reported Telemetry data deleted.
+    As such it attempts to send itself at the moment the user
+    opts out of data collection.
+  include_client_id: true
+  send_if_empty: true
+  bugs:
+    - https://bugzilla.mozilla.org/1587095
+  data_reviews:
+    - https://bugzilla.mozilla.org/show_bug.cgi?id=1587095#c6
+  notification_emails:
+    - glean-team@mozilla.com
diff --git a/toolkit/components/glean/tests/pytest/pings_test_output b/toolkit/components/glean/tests/pytest/pings_test_output
new file mode 100644
index 0000000000..a6e32ddadf
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/pings_test_output
@@ -0,0 +1,105 @@
+// -*- mode: Rust -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::private::Ping;
+use once_cell::sync::Lazy;
+
+#[allow(non_upper_case_globals)]
+/// This ping is intended to provide metrics that are managed by the library
+/// itself, and not explicitly set by the application or included in the
+/// application's `metrics.yaml` file. The `baseline` ping is automatically sent
+/// when the application is moved to the background.
+pub static not_baseline: Lazy<Ping> = Lazy::new(|| {
+    Ping::new(
+        "not-baseline",
+        true,
+        false,
+        vec!["background".into(), "dirty_startup".into(), "foreground".into()],
+    )
+});
+
+#[allow(non_upper_case_globals)]
+/// The `metrics` ping is intended for all of the metrics that are explicitly set
+/// by the application or are included in the application's `metrics.yaml` file
+/// (except events). The reported data is tied to the ping's *measurement window*,
+/// which is the time between the collection of two `metrics` ping. Ideally, this
+/// window is expected to be about 24 hours, given that the collection is scheduled
+/// daily at 4AM. Data in the `ping_info` section of the ping can be used to infer
+/// the length of this window.
+pub static not_metrics: Lazy<Ping> = Lazy::new(|| {
+    Ping::new(
+        "not-metrics",
+        true,
+        false,
+        vec!["overdue".into(), "reschedule".into(), "today".into(), "tomorrow".into(), "upgrade".into()],
+    )
+});
+
+#[allow(non_upper_case_globals)]
+/// The events ping's purpose is to transport all of the event metric information.
+/// The `events` ping is automatically sent when the application is moved to the
+/// background.
+pub static not_events: Lazy<Ping> = Lazy::new(|| {
+    Ping::new(
+        "not-events",
+        true,
+        false,
+        vec!["background".into(), "max_capacity".into(), "startup".into()],
+    )
+});
+
+#[allow(non_upper_case_globals)]
+/// This ping is submitted when a user opts out of sending technical and
+/// interaction data to Mozilla. This ping is intended to communicate to the Data
+/// Pipeline that the user wishes to have their reported Telemetry data deleted. As
+/// such it attempts to send itself at the moment the user opts out of data
+/// collection.
+pub static not_deletion_request: Lazy<Ping> = Lazy::new(|| {
+    Ping::new(
+        "not-deletion-request",
+        true,
+        true,
+        vec![],
+    )
+});
+
+
+/// Instantiate each custom ping once to trigger registration.
+#[doc(hidden)]
+pub fn register_pings() {
+    let _ = &*not_baseline;
+    let _ = &*not_metrics;
+    let _ = &*not_events;
+    let _ = &*not_deletion_request;
+}
+
+#[cfg(feature = "with_gecko")]
+pub(crate) fn submit_ping_by_id(id: u32, reason: Option<&str>) {
+    if id & (1 << crate::factory::DYNAMIC_PING_BIT) > 0 {
+        let map = crate::factory::__jog_metric_maps::PING_MAP
+            .read()
+            .expect("Read lock for dynamic ping map was poisoned!");
+        if let Some(ping) = map.get(&id) {
+            ping.submit(reason);
+        } else {
+            // TODO: instrument this error.
+            log::error!("Cannot submit unknown dynamic ping {} by id.", id);
+        }
+        return;
+    }
+    match id {
+        1 => not_baseline.submit(reason),
+        2 => not_metrics.submit(reason),
+        3 => not_events.submit(reason),
+        4 => not_deletion_request.submit(reason),
+        _ => {
+            // TODO: instrument this error.
+            log::error!("Cannot submit unknown ping {} by id.", id);
+        }
+    }
+}
diff --git a/toolkit/components/glean/tests/pytest/pings_test_output_cpp b/toolkit/components/glean/tests/pytest/pings_test_output_cpp
new file mode 100644
index 0000000000..7f9cc03947
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/pings_test_output_cpp
@@ -0,0 +1,62 @@
+// -*- mode: C++ -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_Pings_h
+#define mozilla_glean_Pings_h
+
+#include "mozilla/glean/bindings/Ping.h"
+
+namespace mozilla::glean_pings {
+
+/*
+ * Generated from not-baseline.
+ *
+ * This ping is intended to provide metrics that are managed by the library
+ * itself, and not explicitly set by the application or included in the
+ * application's `metrics.yaml` file. The `baseline` ping is automatically sent
+ * when the application is moved to the background.
+ */
+constexpr glean::impl::Ping NotBaseline(1);
+
+/*
+ * Generated from not-metrics.
+ *
+ * The `metrics` ping is intended for all of the metrics that are explicitly set
+ * by the application or are included in the application's `metrics.yaml` file
+ * (except events). The reported data is tied to the ping's *measurement window*,
+ * which is the time between the collection of two `metrics` ping. Ideally, this
+ * window is expected to be about 24 hours, given that the collection is scheduled
+ * daily at 4AM. Data in the `ping_info` section of the ping can be used to infer
+ * the length of this window.
+ */
+constexpr glean::impl::Ping NotMetrics(2);
+
+/*
+ * Generated from not-events.
+ *
+ * The events ping's purpose is to transport all of the event metric information.
+ * The `events` ping is automatically sent when the application is moved to the
+ * background.
+ */
+constexpr glean::impl::Ping NotEvents(3);
+
+/*
+ * Generated from not-deletion-request.
+ *
+ * This ping is submitted when a user opts out of sending technical and
+ * interaction data to Mozilla. This ping is intended to communicate to the Data
+ * Pipeline that the user wishes to have their reported Telemetry data deleted. As
+ * such it attempts to send itself at the moment the user opts out of data
+ * collection.
+ */
+constexpr glean::impl::Ping NotDeletionRequest(4);
+
+
+}  // namespace mozilla::glean_pings
+
+#endif  // mozilla_glean_Pings_h
diff --git a/toolkit/components/glean/tests/pytest/pings_test_output_js b/toolkit/components/glean/tests/pytest/pings_test_output_js
new file mode 100644
index 0000000000..ecbc6ccf7c
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/pings_test_output_js
@@ -0,0 +1,99 @@
+// -*- mode: C++ -*-
+
+// AUTOGENERATED BY glean_parser.  DO NOT EDIT.
+
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_GleanJSPingsLookup_h
+#define mozilla_GleanJSPingsLookup_h
+
+#define GLEAN_PING_INDEX_BITS (16)
+#define GLEAN_PING_ID(entry) ((entry) >> GLEAN_PING_INDEX_BITS)
+#define GLEAN_PING_INDEX(entry) ((entry) & ((1UL << GLEAN_PING_INDEX_BITS) - 1))
+
+namespace mozilla::glean {
+
+// Contains the ping id and the index into the ping string table.
+using ping_entry_t = uint32_t;
+
+static Maybe<uint32_t> ping_result_check(const nsACString& aKey, ping_entry_t aEntry);
+
+#if defined(_MSC_VER) && !defined(__clang__)
+const char gPingStringTable[] = {
+#else
+constexpr char gPingStringTable[] = {
+#endif
+  /*     0 - "notBaseline" */ 'n', 'o', 't', 'B', 'a', 's', 'e', 'l', 'i', 'n', 'e', '\0',
+  /*    12 - "notMetrics" */ 'n', 'o', 't', 'M', 'e', 't', 'r', 'i', 'c', 's', '\0',
+  /*    23 - "notEvents" */ 'n', 'o', 't', 'E', 'v', 'e', 'n', 't', 's', '\0',
+  /*    33 - "notDeletionRequest" */ 'n', 'o', 't', 'D', 'e', 'l', 'e', 't', 'i', 'o', 'n', 'R', 'e', 'q', 'u', 'e', 's', 't', '\0',
+};
+
+
+
+const ping_entry_t sPingByNameLookupEntries[] = {
+  65536,
+  196631,
+  262177,
+  131084
+};
+
+
+
+static Maybe<uint32_t>
+PingByNameLookup(const nsACString& aKey)
+{
+  static const uint8_t BASES[] = {
+       0,   0,   0,   0,   0,   0,   0,   1,   0,   0,   0,   0,   0,   0,   0,   0,
+       0,   0,   0,   0,   0,   2,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+       0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   3,
+       0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,
+  };
+  
+
+  const char* bytes = aKey.BeginReading();
+  size_t length = aKey.Length();
+  auto& entry = mozilla::perfecthash::Lookup(bytes, length, BASES,
+                                             sPingByNameLookupEntries);
+  return ping_result_check(aKey, entry);
+}
+
+
+/**
+ * Get a ping's name given its entry from the PHF.
+ */
+static const char* GetPingName(ping_entry_t aEntry) {
+  uint32_t idx = GLEAN_PING_INDEX(aEntry);
+  MOZ_ASSERT(idx < sizeof(gPingStringTable), "Ping index larger than string table");
+  return &gPingStringTable[idx];
+}
+
+/**
+ * Check if the found entry is pointing at the correct ping.
+ * PHF can false-positive a result when the key isn't present, so we check
+ * for a string match. If it fails, return Nothing(). If we found it,
+ * return the ping's id.
+ */
+static Maybe<uint32_t> ping_result_check(const nsACString& aKey, ping_entry_t aEntry) {
+  uint32_t idx = GLEAN_PING_INDEX(aEntry);
+  uint32_t id = GLEAN_PING_ID(aEntry);
+
+  if (MOZ_UNLIKELY(idx > sizeof(gPingStringTable))) {
+    return Nothing();
+  }
+
+  if (aKey.EqualsASCII(&gPingStringTable[idx])) {
+    return Some(id);
+  }
+
+  return Nothing();
+}
+
+#undef GLEAN_PING_INDEX_BITS
+#undef GLEAN_PING_ID
+#undef GLEAN_PING_INDEX
+
+}  // namespace mozilla::glean
+#endif  // mozilla_GleanJSPingsLookup_h
diff --git a/toolkit/components/glean/tests/pytest/python.ini b/toolkit/components/glean/tests/pytest/python.ini
new file mode 100644
index 0000000000..87573cf519
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/python.ini
@@ -0,0 +1,10 @@
+[DEFAULT]
+subsuite = fog
+
+[test_gifft.py]
+[test_glean_parser_rust.py]
+[test_glean_parser_cpp.py]
+[test_glean_parser_js.py]
+[test_jogfile_output.py]
+[test_no_expired_metrics.py]
+[test_yaml_indices.py]
diff --git a/toolkit/components/glean/tests/pytest/test_gifft.py b/toolkit/components/glean/tests/pytest/test_gifft.py
new file mode 100644
index 0000000000..5de0640bca
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/test_gifft.py
@@ -0,0 +1,49 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import io
+import sys
+from os import path
+from pathlib import Path
+
+import mozunit
+from expect_helper import expect
+
+# Shenanigans to import the FOG glean_parser runner
+FOG_ROOT_PATH = path.abspath(
+    path.join(path.dirname(__file__), path.pardir, path.pardir)
+)
+sys.path.append(path.join(FOG_ROOT_PATH, "build_scripts", "glean_parser_ext"))
+import run_glean_parser
+
+
+def test_gifft_codegen():
+    """
+    A regression test. Very fragile.
+    It generates C++ for GIFFT for metrics_test.yaml and compares it
+    byte-for-byte with expected output C++ files.
+    To generate new expected output files, set `UPDATE_EXPECT=1` when running the test suite:
+
+    UPDATE_EXPECT=1 mach test toolkit/components/glean/pytest
+    """
+
+    options = {"allow_reserved": False}
+    here_path = Path(path.dirname(__file__))
+    input_files = [here_path / "metrics_test.yaml"]
+
+    all_objs, options = run_glean_parser.parse_with_options(input_files, options)
+
+    for probe_type in ("Event", "Histogram", "Scalar"):
+        output_fd = io.StringIO()
+        cpp_fd = io.StringIO()
+        run_glean_parser.output_gifft_map(output_fd, probe_type, all_objs, cpp_fd)
+
+        expect(here_path / f"gifft_output_{probe_type}", output_fd.getvalue())
+
+        if probe_type == "Event":
+            expect(here_path / "gifft_output_EventExtra", cpp_fd.getvalue())
+
+
+if __name__ == "__main__":
+    mozunit.main()
diff --git a/toolkit/components/glean/tests/pytest/test_glean_parser_cpp.py b/toolkit/components/glean/tests/pytest/test_glean_parser_cpp.py
new file mode 100644
index 0000000000..05fd691782
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/test_glean_parser_cpp.py
@@ -0,0 +1,70 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import io
+import sys
+from os import path
+from pathlib import Path
+
+import mozunit
+from expect_helper import expect
+
+# Shenanigans to import the cpp outputter extension
+FOG_ROOT_PATH = path.abspath(
+    path.join(path.dirname(__file__), path.pardir, path.pardir)
+)
+sys.path.append(path.join(FOG_ROOT_PATH, "build_scripts", "glean_parser_ext"))
+import cpp
+import run_glean_parser
+
+
+def test_all_metric_types():
+    """Honestly, this is a pretty bad test.
+    It generates C++ for a given test metrics.yaml and compares it byte-for-byte
+    with an expected output C++ file.
+    Expect it to be fragile.
+    To generate new expected output files, set `UPDATE_EXPECT=1` when running the test suite:
+
+    UPDATE_EXPECT=1 mach test toolkit/components/glean/pytest
+    """
+
+    options = {"allow_reserved": False}
+    input_files = [Path(path.join(path.dirname(__file__), "metrics_test.yaml"))]
+
+    all_objs, options = run_glean_parser.parse_with_options(input_files, options)
+
+    output_fd = io.StringIO()
+    cpp.output_cpp(all_objs, output_fd, options)
+
+    expect(
+        path.join(path.dirname(__file__), "metrics_test_output_cpp"),
+        output_fd.getvalue(),
+    )
+
+
+def test_fake_pings():
+    """Another similarly-fragile test.
+    It generates C++ for pings_test.yaml, comparing it byte-for-byte
+    with an expected output C++ file `pings_test_output_cpp`.
+    Expect it to be fragile.
+    To generate new expected output files, set `UPDATE_EXPECT=1` when running the test suite:
+
+    UPDATE_EXPECT=1 mach test toolkit/components/glean/pytest
+    """
+
+    options = {"allow_reserved": False}
+    input_files = [Path(path.join(path.dirname(__file__), "pings_test.yaml"))]
+
+    all_objs, options = run_glean_parser.parse_with_options(input_files, options)
+
+    output_fd = io.StringIO()
+    cpp.output_cpp(all_objs, output_fd, options)
+
+    expect(
+        path.join(path.dirname(__file__), "pings_test_output_cpp"), output_fd.getvalue()
+    )
+
+
+if __name__ == "__main__":
+    mozunit.main()
diff --git a/toolkit/components/glean/tests/pytest/test_glean_parser_js.py b/toolkit/components/glean/tests/pytest/test_glean_parser_js.py
new file mode 100644
index 0000000000..81026231a6
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/test_glean_parser_js.py
@@ -0,0 +1,71 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import io
+import sys
+from os import path
+from pathlib import Path
+
+import mozunit
+from expect_helper import expect
+
+# Shenanigans to import the js outputter extension
+FOG_ROOT_PATH = path.abspath(
+    path.join(path.dirname(__file__), path.pardir, path.pardir)
+)
+sys.path.append(path.join(FOG_ROOT_PATH, "build_scripts", "glean_parser_ext"))
+import run_glean_parser
+
+import js
+
+
+def test_all_metric_types():
+    """Honestly, this is a pretty bad test.
+    It generates C++ for a given test metrics.yaml and compares it byte-for-byte
+    with an expected output C++ file.
+    Expect it to be fragile.
+    To generate new expected output files, set `UPDATE_EXPECT=1` when running the test suite:
+
+    UPDATE_EXPECT=1 mach test toolkit/components/glean/tests/pytest
+    """
+
+    options = {"allow_reserved": False}
+    input_files = [Path(path.join(path.dirname(__file__), "metrics_test.yaml"))]
+
+    all_objs, options = run_glean_parser.parse_with_options(input_files, options)
+
+    output_fd = io.StringIO()
+    js.output_js(all_objs, output_fd, options)
+
+    expect(
+        path.join(path.dirname(__file__), "metrics_test_output_js"),
+        output_fd.getvalue(),
+    )
+
+
+def test_fake_pings():
+    """Another similarly-fragile test.
+    It generates C++ for pings_test.yaml, comparing it byte-for-byte
+    with an expected output C++ file `pings_test_output_js`.
+    Expect it to be fragile.
+    To generate new expected output files, set `UPDATE_EXPECT=1` when running the test suite:
+
+    UPDATE_EXPECT=1 mach test toolkit/components/glean/tests/pytest
+    """
+
+    options = {"allow_reserved": False}
+    input_files = [Path(path.join(path.dirname(__file__), "pings_test.yaml"))]
+
+    all_objs, options = run_glean_parser.parse_with_options(input_files, options)
+
+    output_fd = io.StringIO()
+    js.output_js(all_objs, output_fd, options)
+
+    expect(
+        path.join(path.dirname(__file__), "pings_test_output_js"), output_fd.getvalue()
+    )
+
+
+if __name__ == "__main__":
+    mozunit.main()
diff --git a/toolkit/components/glean/tests/pytest/test_glean_parser_rust.py b/toolkit/components/glean/tests/pytest/test_glean_parser_rust.py
new file mode 100644
index 0000000000..a586b0419b
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/test_glean_parser_rust.py
@@ -0,0 +1,89 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import io
+import sys
+from os import path
+from pathlib import Path
+
+import mozunit
+from expect_helper import expect
+
+# Shenanigans to import the rust outputter extension
+FOG_ROOT_PATH = path.abspath(
+    path.join(path.dirname(__file__), path.pardir, path.pardir)
+)
+sys.path.append(path.join(FOG_ROOT_PATH, "build_scripts", "glean_parser_ext"))
+import run_glean_parser
+import rust
+
+# Shenanigans to import the in-tree glean_parser
+GECKO_PATH = path.join(FOG_ROOT_PATH, path.pardir, path.pardir, path.pardir)
+sys.path.append(path.join(GECKO_PATH, "third_party", "python", "glean_parser"))
+
+
+def test_all_metric_types():
+    """Honestly, this is a pretty bad test.
+    It generates Rust for a given test metrics.yaml and compares it byte-for-byte
+    with an expected output Rust file.
+    Expect it to be fragile.
+    To generate new expected output files, set `UPDATE_EXPECT=1` when running the test suite:
+
+    UPDATE_EXPECT=1 mach test toolkit/components/glean/pytest
+    """
+
+    options = {"allow_reserved": False}
+    input_files = [Path(path.join(path.dirname(__file__), "metrics_test.yaml"))]
+
+    all_objs, options = run_glean_parser.parse_with_options(input_files, options)
+
+    output_fd = io.StringIO()
+    rust.output_rust(all_objs, output_fd, options)
+
+    expect(
+        path.join(path.dirname(__file__), "metrics_test_output"), output_fd.getvalue()
+    )
+
+
+def test_fake_pings():
+    """Another similarly-bad test.
+    It generates Rust for pings_test.yaml, comparing it byte-for-byte
+    with an expected output Rust file.
+    Expect it to be fragile.
+    To generate new expected output files, set `UPDATE_EXPECT=1` when running the test suite:
+
+    UPDATE_EXPECT=1 mach test toolkit/components/glean/pytest
+    """
+
+    options = {"allow_reserved": False}
+    input_files = [Path(path.join(path.dirname(__file__), "pings_test.yaml"))]
+
+    all_objs, options = run_glean_parser.parse_with_options(input_files, options)
+
+    output_fd = io.StringIO()
+    rust.output_rust(all_objs, output_fd, options)
+
+    expect(path.join(path.dirname(__file__), "pings_test_output"), output_fd.getvalue())
+
+
+def test_expires_version():
+    """This test relies on the intermediary object format output by glean_parser.
+    Expect it to be fragile on glean_parser updates that change that format.
+    """
+
+    # The test file has 41, 42, 100. Use 42.0a1 here to ensure "expires == version" means expired.
+    options = run_glean_parser.get_parser_options("42.0a1")
+    input_files = [
+        Path(path.join(path.dirname(__file__), "metrics_expires_versions_test.yaml"))
+    ]
+
+    all_objs, options = run_glean_parser.parse_with_options(input_files, options)
+
+    assert all_objs["test"]["expired1"].disabled is True
+    assert all_objs["test"]["expired2"].disabled is True
+    assert all_objs["test"]["unexpired"].disabled is False
+
+
+if __name__ == "__main__":
+    mozunit.main()
diff --git a/toolkit/components/glean/tests/pytest/test_jogfile_output.py b/toolkit/components/glean/tests/pytest/test_jogfile_output.py
new file mode 100644
index 0000000000..801c0967ff
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/test_jogfile_output.py
@@ -0,0 +1,50 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import io
+import sys
+from os import path
+from pathlib import Path
+
+import mozunit
+from expect_helper import expect
+
+# Shenanigans to import the FOG glean_parser runner
+FOG_ROOT_PATH = path.abspath(
+    path.join(path.dirname(__file__), path.pardir, path.pardir)
+)
+sys.path.append(path.join(FOG_ROOT_PATH, "build_scripts", "glean_parser_ext"))
+import jog
+import run_glean_parser
+
+
+def test_jogfile_output():
+    """
+    A regression test. Very fragile.
+    It generates a jogfile for metrics_test.yaml and compares it
+    byte-for-byte with an expected output file.
+
+    Also, part one of a two-part test.
+    The generated jogfile is consumed in Rust_TestJogfile in t/c/g/tests/gtest/test.rs
+    This is to ensure that the jogfile we generate in Python can be consumed in Rust.
+
+    To generate new expected output files, set `UPDATE_EXPECT=1` when running the test suite:
+
+    UPDATE_EXPECT=1 mach test toolkit/components/glean/pytest
+    """
+
+    options = {"allow_reserved": False}
+    here_path = Path(path.dirname(__file__))
+    input_files = [here_path / "metrics_test.yaml", here_path / "pings_test.yaml"]
+
+    all_objs, options = run_glean_parser.parse_with_options(input_files, options)
+
+    output_fd = io.StringIO()
+    jog.output_file(all_objs, output_fd, options)
+
+    expect(here_path / "jogfile_output", output_fd.getvalue())
+
+
+if __name__ == "__main__":
+    mozunit.main()
diff --git a/toolkit/components/glean/tests/pytest/test_no_expired_metrics.py b/toolkit/components/glean/tests/pytest/test_no_expired_metrics.py
new file mode 100644
index 0000000000..9783acaf0a
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/test_no_expired_metrics.py
@@ -0,0 +1,46 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import sys
+from os import path
+from pathlib import Path
+
+import mozunit
+
+# Shenanigans to import the metrics index's list of metrics.yamls
+FOG_ROOT_PATH = path.abspath(
+    path.join(path.dirname(__file__), path.pardir, path.pardir)
+)
+sys.path.append(FOG_ROOT_PATH)
+from metrics_index import metrics_yamls, tags_yamls
+
+# Shenanigans to import run_glean_parser
+sys.path.append(path.join(FOG_ROOT_PATH, "build_scripts", "glean_parser_ext"))
+import run_glean_parser
+
+# Shenanigans to import the in-tree glean_parser
+GECKO_PATH = path.join(FOG_ROOT_PATH, path.pardir, path.pardir, path.pardir)
+sys.path.append(path.join(GECKO_PATH, "third_party", "python", "glean_parser"))
+from glean_parser import lint, parser, util
+
+
+def test_no_metrics_expired():
+    """
+    Of all the metrics included in this build, are any expired?
+    If so, they must be removed or renewed.
+
+    (This also checks other lints, as a treat.)
+    """
+    with open("browser/config/version.txt", "r") as version_file:
+        app_version = version_file.read().strip()
+
+    options = run_glean_parser.get_parser_options(app_version)
+    paths = [Path(x) for x in metrics_yamls] + [Path(x) for x in tags_yamls]
+    all_objs = parser.parse_objects(paths, options)
+    assert not util.report_validation_errors(all_objs)
+    assert not lint.lint_metrics(all_objs.value, options)
+
+
+if __name__ == "__main__":
+    mozunit.main()
diff --git a/toolkit/components/glean/tests/pytest/test_yaml_indices.py b/toolkit/components/glean/tests/pytest/test_yaml_indices.py
new file mode 100644
index 0000000000..a8d185e59f
--- /dev/null
+++ b/toolkit/components/glean/tests/pytest/test_yaml_indices.py
@@ -0,0 +1,38 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import sys
+from os import path
+
+import mozunit
+
+# Shenanigans to import the metrics index's lists of yamls
+FOG_ROOT_PATH = path.abspath(
+    path.join(path.dirname(__file__), path.pardir, path.pardir)
+)
+sys.path.append(FOG_ROOT_PATH)
+import metrics_index
+
+
+def test_yamls_sorted():
+    """
+    Ensure the yamls indices are sorted lexicographically.
+    """
+    # Ignore lists that are the concatenation of others.
+    to_ignore = ["metrics_yamls", "pings_yamls"]
+
+    # Fetch names of all variables defined in the `metrics_index` module.
+    yaml_lists = [item for item in dir(metrics_index) if not item.startswith("__")]
+    for name in yaml_lists:
+        if name in to_ignore:
+            continue
+
+        yamls_to_test = metrics_index.__dict__[name]
+        assert (
+            sorted(yamls_to_test) == yamls_to_test
+        ), f"{name} must be be lexicographically sorted."
+
+
+if __name__ == "__main__":
+    mozunit.main()
diff --git a/toolkit/components/glean/tests/test_metrics.yaml b/toolkit/components/glean/tests/test_metrics.yaml
new file mode 100644
index 0000000000..9ff471fd6b
--- /dev/null
+++ b/toolkit/components/glean/tests/test_metrics.yaml
@@ -0,0 +1,780 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is for Internal FOG Test Use Only.
+
+---
+$schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
+
+test_only:
+  bad_code:
+    type: counter
+    description: |
+      Number of times we encountered bad code.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - test-ping
+
+  can_we_time_it:
+    type: timespan
+    time_unit: nanosecond
+    description: |
+      Test metric for a timespan.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - test-ping
+
+  cheesy_string:
+    type: string
+    description: |
+      Only the cheesiest of strings.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1673662
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1673662#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - test-ping
+
+  cheesy_string_list:
+    type: string_list
+    description: |
+      Only the cheesiest of strings. In list form!
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1682960
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1682960#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - test-ping
+
+  what_a_date:
+    type: datetime
+    time_unit: second
+    description: >
+      ...To be writing FOG code.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - test-ping
+
+  what_id_it:  # Using a different metrics yaml style for fun.
+    type: uuid
+    description: |
+      Just a UUID.
+      This is a test-only metric.
+    bugs: ["https://bugzilla.mozilla.org/show_bug.cgi?id=1673664"]
+    data_reviews: ["https://bugzilla.mozilla.org/show_bug.cgi?id=1673664#c1"]
+    data_sensitivity: ["technical"]
+    notification_emails: ["glean-team@mozilla.com"]
+    expires: never
+    send_in_pings: ["test-ping"]
+
+  can_we_flag_it:
+    type: boolean
+    description: |
+      Test metric for a boolean.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - test-ping
+
+  do_you_remember:
+    type: memory_distribution
+    memory_unit: megabyte
+    description: |
+      They say it's the second thing to go.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1673648
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1673648#c1
+    data_sensitivity:
+      - technical
+    expires: never
+    notification_emails:
+      - glean-team@mozilla.com
+    send_in_pings:
+      - test-ping
+
+  what_time_is_it:
+    type: timing_distribution
+    time_unit: microsecond
+    description: |
+      Adheres to at least two of the top ten fallacies programmers believe
+      about time.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1673663
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1673663#c1
+    data_sensitivity:
+      - technical
+    expires: never
+    notification_emails:
+      - glean-team@mozilla.com
+    send_in_pings:
+      - test-ping
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_TIMING
+
+  mabels_kitchen_counters:
+    type: labeled_counter
+    description: |
+      Counts Mabels labeled by their kitchen counters.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1675277
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1675277#c1
+    data_sensitivity:
+      - technical
+    expires: never
+    notification_emails:
+      - glean-team@mozilla.com
+    send_in_pings:
+      - test-ping
+
+  mabels_bathroom_counters:
+    type: labeled_counter
+    description: |
+      Counts Mabels labeled by their bathroom counters.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1683171
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1683171#c1
+    data_sensitivity:
+      - technical
+    expires: never
+    notification_emails:
+      - glean-team@mozilla.com
+    send_in_pings:
+      - test-ping
+
+  mabels_like_balloons:
+    type: labeled_boolean
+    description: |
+      Does the labeled Mabel like balloons?
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1675277
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1675277#c1
+    data_sensitivity:
+      - technical
+    expires: never
+    notification_emails:
+      - glean-team@mozilla.com
+    send_in_pings:
+      - test-ping
+
+  mabels_balloon_strings:
+    type: labeled_string
+    description: |
+      What do the labeled Mabel's liked balloons' strings say?
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1675277
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1675277#c1
+    data_sensitivity:
+      - technical
+    expires: never
+    notification_emails:
+      - glean-team@mozilla.com
+    send_in_pings:
+      - test-ping
+
+  mabels_label_maker:
+    type: labeled_string
+    description: |
+      Mabel just got a label maker and wants to party like it's
+      1999.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1696388
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1696388
+    data_sensitivity:
+      - technical
+    expires: never
+    notification_emails:
+      - glean-team@mozilla.com
+    send_in_pings:
+      - test-ping
+
+  mirror_time:
+    type: timespan
+    time_unit: nanosecond
+    description: |
+      Mirrored metric for a timespan.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - test-ping
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_TIMESPAN
+
+  mirror_time_nanos:
+    type: timespan
+    time_unit: nanosecond
+    description: |
+      Mirrored metric for a timespan.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1704106
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1704106#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - test-ping
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_TIMESPAN_NANOS
+
+  mirrors_for_labeled_bools:
+    type: labeled_boolean
+    description: |
+      Mirrored metric.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1675277
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1675277#c1
+    data_sensitivity:
+      - technical
+    expires: never
+    notification_emails:
+      - glean-team@mozilla.com
+    send_in_pings:
+      - test-ping
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_LABELED_BOOL
+
+  one_ping_one_bool:
+    type: boolean
+    description: |
+      One bool for one ping only.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685402
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685402#c1
+    data_sensitivity:
+      - technical
+    expires: never
+    notification_emails:
+      - glean-team@mozilla.com
+    send_in_pings:
+      - one-ping-only
+
+  meaning_of_life:
+    type: quantity
+    unit: unfathomable
+    description: |
+      Measures the one true answer to the Ultimate Question of Life,
+      the Universe, and Everything.
+      Approximately.
+      This is a test-only metric.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1704846
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1704846#c1
+    data_sensitivity:
+      - technical
+    expires: never
+    notification_emails:
+      - glean-team@mozilla.com
+    send_in_pings:
+      - test-ping
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_QUANTITY
+
+
+test_only.ipc:
+  a_counter:
+    type: counter
+    description: |
+      This is a test-only metric.
+      Just counting things.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_COUNTER
+  a_bool:
+    type: boolean
+    description: |
+      This is a test-only metric.
+      Just flagging things.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_BOOLEAN_KIND
+  a_date:
+    type: datetime
+    time_unit: second
+    description: |
+      This is a test-only metric.
+      Just putting things on the calendar.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_DATE
+  a_string:
+    type: string
+    description: |
+      This is a test-only metric.
+      Just setting some strings.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_MULTIPLE_STORES_STRING
+  a_memory_dist:
+    type: memory_distribution
+    memory_unit: kilobyte
+    description: |
+      This is a test-only metric.
+      Just measuring memory.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_LINEAR
+  a_timing_dist:
+    type: timing_distribution
+    description: |
+      This is a test-only metric.
+      Just measuring time.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_EXPONENTIAL
+  a_custom_dist:
+    type: custom_distribution
+    description: |
+      This is a test-only metric.
+      Just measuring samples.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1713398
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1713398#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    range_min: 1
+    range_max: 2147483646
+    bucket_count: 10
+    histogram_type: linear
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_CUSTOM
+  a_string_list:
+    type: string_list
+    description: |
+      This is a test-only metric.
+      Just appending some strings.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_KEYED_BOOLEAN_KIND
+  an_event:
+    type: event
+    extra_keys:
+      extra1:
+        type: string
+        description: "Some extra data"
+      extra2:
+        type: string
+        description: "Some extra data again"
+    description: |
+      This is a test-only metric.
+      Just recording some events.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TelemetryTest_MirrorWithExtra_Object1
+  event_with_extra:
+    type: event
+    extra_keys:
+      extra1:
+        type: string
+        description: "Some extra data"
+      extra2:
+        type: quantity
+        description: "Some extra data again"
+      extra3_longer_name:
+        type: boolean
+        description: "Some extra data again. Also tests extras with underscores"
+    description: |
+      This is a test-only metric.
+      Just recording some events.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+  no_extra_event:
+    type: event
+    description: |
+      This is a test-only metric.
+      Just recording some events without the extra fuss.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    telemetry_mirror: TelemetryTest_NotExpiredOptout_Object1
+  a_uuid:
+    type: uuid
+    description: |
+      This is a test-only metric.
+      Just recording some unique identifiers.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_STRING_KIND
+  a_labeled_counter:
+    type: labeled_counter
+    description: |
+      This is a test-only metric.
+      Just counting labeled things.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1688281
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1688281#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_ANOTHER_MIRROR_FOR_LABELED_COUNTER
+  another_labeled_counter:
+    type: labeled_counter
+    description: |
+      This is a test-only metric.
+      Just another metric counting labeled things.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1688281
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1685406
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1758795
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1688281#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_LABELED_COUNTER
+  a_quantity:
+    type: quantity
+    unit: squad
+    description: |
+      This is a test-only metric.
+      Just quantifying things.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1704846
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1704846#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+  irate:
+    type: rate
+    description: |
+      This is a test-only metric.
+      A rate that isn't happy about it.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694496
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694496#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_RATE
+  rate_with_external_denominator:
+    type: rate
+    denominator_metric: test_only.ipc.an_external_denominator
+    description: |
+      This is a test-only metric.
+      A rate with a denominator that is Out There.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694496
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694496#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+  an_external_denominator:
+    type: counter
+    description: |
+      This is a test-only metric.
+      A denominator not from around here.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694496
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1694496#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+  a_url:
+    type: url
+    description: |
+      This is a test-only metric.
+      Just setting some Urls.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1766980
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1646165#c1
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+    no_lint:
+      - COMMON_PREFIX
+    telemetry_mirror: TELEMETRY_TEST_MIRROR_FOR_URL
+
+test_only.jog:
+  a_counter:
+    type: counter
+    description: |
+      This is a test-only metric.
+      Just counting things.
+      Tied closely to test_jog_name_collision.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1767039
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1767039
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
+
+  an_event:
+    type: event
+    extra_keys:
+      extra1:
+        type: string
+        description: "Some extra data"
+      extra2:
+        type: string
+        description: "Some extra data again"
+    description: |
+      This is a test-only metric.
+      Just recording some events.
+      Tied closely to test_jog_name_collision.
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1767039
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1767039
+    data_sensitivity:
+      - technical
+    notification_emails:
+      - glean-team@mozilla.com
+    expires: never
+    send_in_pings:
+      - store1
diff --git a/toolkit/components/glean/tests/test_pings.yaml b/toolkit/components/glean/tests/test_pings.yaml
new file mode 100644
index 0000000000..d62f682109
--- /dev/null
+++ b/toolkit/components/glean/tests/test_pings.yaml
@@ -0,0 +1,42 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file defines the pings that are recorded by the Glean SDK. They are
+# automatically converted to platform-specific code at build time using the
+# `glean_parser` PyPI package.
+
+# This file is presently for Internal FOG Test Use Only.
+
+---
+$schema: moz://mozilla.org/schemas/glean/pings/2-0-0
+
+one-ping-only:
+  description: |
+    This ping is for tests only.
+  include_client_id: false
+  send_if_empty: true
+  bugs:
+    - https://bugzilla.mozilla.org/1673660
+  data_reviews:
+    - https://bugzilla.mozilla.org/show_bug.cgi?id=1673660#c1
+  notification_emails:
+    - chutten@mozilla.com
+    - glean-team@mozilla.com
+  no_lint:
+    - REDUNDANT_PING
+
+test-ping:
+  description: |
+    This ping is for tests only.
+  include_client_id: false
+  send_if_empty: true
+  bugs:
+    - https://bugzilla.mozilla.org/show_bug.cgi?id=1737157
+  data_reviews:
+    - https://bugzilla.mozilla.org/show_bug.cgi?id=1737157#c1
+  notification_emails:
+    - chutten@mozilla.com
+    - glean-team@mozilla.com
+  no_lint:
+    - REDUNDANT_PING
diff --git a/toolkit/components/glean/tests/xpcshell/head.js b/toolkit/components/glean/tests/xpcshell/head.js
new file mode 100644
index 0000000000..f42bd02822
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/head.js
@@ -0,0 +1,6 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const { XPCOMUtils } = ChromeUtils.importESModule(
+  "resource://gre/modules/XPCOMUtils.sys.mjs"
+);
diff --git a/toolkit/components/glean/tests/xpcshell/test_FOGIPCLimit.js b/toolkit/components/glean/tests/xpcshell/test_FOGIPCLimit.js
new file mode 100644
index 0000000000..10ab9f5bc3
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_FOGIPCLimit.js
@@ -0,0 +1,51 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+const { ContentTaskUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/ContentTaskUtils.sys.mjs"
+);
+
+add_setup(
+  /* on Android FOG is set up through head.js */
+  { skip_if: () => !runningInParent || AppConstants.platform == "android" },
+  function test_setup() {
+    // Give FOG a temp profile to init within.
+    do_get_profile();
+
+    // We need to initialize it once, otherwise operations will be stuck in the pre-init queue.
+    Services.fog.initializeFOG();
+  }
+);
+
+// Keep in sync with ipc.rs.
+// "Why no -1?" Because the limit's 100k. The -1 is because of atomic ops.
+const FOG_IPC_PAYLOAD_ACCESS_LIMIT = 100000;
+
+add_task({ skip_if: () => runningInParent }, async function run_child_stuff() {
+  for (let i = 0; i < FOG_IPC_PAYLOAD_ACCESS_LIMIT + 1; i++) {
+    Glean.testOnly.badCode.add(1);
+  }
+});
+
+add_task(
+  { skip_if: () => !runningInParent },
+  async function test_fog_ipc_limit() {
+    await run_test_in_child("test_FOGIPCLimit.js");
+
+    await ContentTaskUtils.waitForCondition(() => {
+      return !!Glean.testOnly.badCode.testGetValue();
+    }, "Waiting for IPC.");
+
+    // The child exceeded the number of accesses to trigger an IPC flush.
+    Assert.greater(
+      Glean.testOnly.badCode.testGetValue(),
+      FOG_IPC_PAYLOAD_ACCESS_LIMIT
+    );
+  }
+);
diff --git a/toolkit/components/glean/tests/xpcshell/test_FOGInit.js b/toolkit/components/glean/tests/xpcshell/test_FOGInit.js
new file mode 100644
index 0000000000..f8c4a410ad
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_FOGInit.js
@@ -0,0 +1,41 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+add_setup(
+  /* on Android FOG is set up through head.js */
+  { skip_if: () => AppConstants.platform == "android" },
+  function test_setup() {
+    // FOG needs a profile directory to put its data in.
+    do_get_profile();
+
+    // Glean init (via `chrono`) gets the timezone via unprotected write.
+    // This is being worked around:
+    // https://github.com/chronotope/chrono/pull/677
+    // Until that reaches a release and we update to it (bug 1780401), ensure
+    // local time has been loaded by JS before we kick of Glean init.
+    new Date().getHours(); // used for its side effect.
+
+    // We need to initialize it once, otherwise operations will be stuck in the pre-init queue.
+    Services.fog.initializeFOG();
+  }
+);
+
+add_task(function test_fog_init_works() {
+  if (new Date().getHours() >= 3 && new Date().getHours() <= 4) {
+    // We skip this test if it's too close to 4AM, when we might send a
+    // "metrics" ping between init and this test being run.
+    Assert.ok(true, "Too close to 'metrics' ping send window. Skipping test.");
+    return;
+  }
+  Assert.greater(
+    Glean.fog.initialization.testGetValue(),
+    0,
+    "FOG init happened, and its time was measured."
+  );
+});
diff --git a/toolkit/components/glean/tests/xpcshell/test_FOGPrefs.js b/toolkit/components/glean/tests/xpcshell/test_FOGPrefs.js
new file mode 100644
index 0000000000..943ffb3186
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_FOGPrefs.js
@@ -0,0 +1,47 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const TELEMETRY_SERVER_PREF = "toolkit.telemetry.server";
+const UPLOAD_PREF = "datareporting.healthreport.uploadEnabled";
+const LOCALHOST_PREF = "telemetry.fog.test.localhost_port";
+
+// FOG needs a profile directory to put its data in.
+do_get_profile();
+
+// We want Glean to use a localhost server so we can be SURE not to send data to the outside world.
+// Yes, the port spells GLEAN on a T9 keyboard, why do you ask?
+Services.prefs.setIntPref(LOCALHOST_PREF, 45326);
+// We need to initialize it once, otherwise operations will be stuck in the pre-init queue.
+Services.fog.initializeFOG();
+
+add_task(function test_fog_upload_only() {
+  // Don't forget to point the telemetry server to localhost, or Telemetry
+  // might make a non-local connection during the test run.
+  Services.prefs.setStringPref(
+    TELEMETRY_SERVER_PREF,
+    "http://localhost/telemetry-fake/"
+  );
+  // Be sure to set port=-1 for faking success _before_ enabling upload.
+  // Or else there's a short window where we might send something.
+  Services.prefs.setIntPref(LOCALHOST_PREF, -1);
+  Services.prefs.setBoolPref(UPLOAD_PREF, true);
+
+  const value = 42;
+  Glean.testOnly.meaningOfLife.set(value);
+  // We specifically look at the custom ping's value because we know it
+  // won't be reset by being sent.
+  Assert.equal(value, Glean.testOnly.meaningOfLife.testGetValue("test-ping"));
+
+  // Despite upload being disabled, we keep the old values around.
+  Services.prefs.setBoolPref(UPLOAD_PREF, false);
+  Assert.equal(value, Glean.testOnly.meaningOfLife.testGetValue("test-ping"));
+
+  // Now, when we turn the fake upload off, we clear the stores
+  Services.prefs.setIntPref(LOCALHOST_PREF, 0);
+  Assert.equal(
+    undefined,
+    Glean.testOnly.meaningOfLife.testGetValue("test-ping")
+  );
+});
diff --git a/toolkit/components/glean/tests/xpcshell/test_GIFFT.js b/toolkit/components/glean/tests/xpcshell/test_GIFFT.js
new file mode 100644
index 0000000000..20923d057e
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_GIFFT.js
@@ -0,0 +1,538 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+const { setTimeout } = ChromeUtils.importESModule(
+  "resource://gre/modules/Timer.sys.mjs"
+);
+const { TelemetryTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TelemetryTestUtils.sys.mjs"
+);
+
+const Telemetry = Services.telemetry;
+
+function sleep(ms) {
+  /* eslint-disable mozilla/no-arbitrary-setTimeout */
+  return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+function scalarValue(aScalarName) {
+  let snapshot = Telemetry.getSnapshotForScalars();
+  return "parent" in snapshot ? snapshot.parent[aScalarName] : undefined;
+}
+
+function keyedScalarValue(aScalarName) {
+  let snapshot = Telemetry.getSnapshotForKeyedScalars();
+  return "parent" in snapshot ? snapshot.parent[aScalarName] : undefined;
+}
+
+add_setup(function test_setup() {
+  // FOG needs a profile directory to put its data in.
+  do_get_profile();
+
+  Services.prefs.setBoolPref(
+    "toolkit.telemetry.testing.overrideProductsCheck",
+    true
+  );
+
+  // We need to initialize it once, otherwise operations will be stuck in the pre-init queue.
+  // On Android FOG is set up through head.js.
+  if (AppConstants.platform != "android") {
+    Services.fog.initializeFOG();
+  }
+});
+
+add_task(function test_gifft_counter() {
+  Glean.testOnlyIpc.aCounter.add(20);
+  Assert.equal(20, Glean.testOnlyIpc.aCounter.testGetValue());
+  Assert.equal(20, scalarValue("telemetry.test.mirror_for_counter"));
+});
+
+add_task(function test_gifft_boolean() {
+  Glean.testOnlyIpc.aBool.set(false);
+  Assert.equal(false, Glean.testOnlyIpc.aBool.testGetValue());
+  Assert.equal(false, scalarValue("telemetry.test.boolean_kind"));
+});
+
+add_task(function test_gifft_datetime() {
+  const dateStr = "2021-03-22T16:06:00";
+  const value = new Date(dateStr);
+  Glean.testOnlyIpc.aDate.set(value.getTime() * 1000);
+
+  let received = Glean.testOnlyIpc.aDate.testGetValue();
+  Assert.equal(value.getTime(), received.getTime());
+  Assert.ok(scalarValue("telemetry.test.mirror_for_date").startsWith(dateStr));
+});
+
+add_task(function test_gifft_string() {
+  const value = "a string!";
+  Glean.testOnlyIpc.aString.set(value);
+
+  Assert.equal(value, Glean.testOnlyIpc.aString.testGetValue());
+  Assert.equal(value, scalarValue("telemetry.test.multiple_stores_string"));
+});
+
+add_task(function test_gifft_memory_dist() {
+  Glean.testOnlyIpc.aMemoryDist.accumulate(7);
+  Glean.testOnlyIpc.aMemoryDist.accumulate(17);
+
+  let data = Glean.testOnlyIpc.aMemoryDist.testGetValue();
+  // `data.sum` is in bytes, but the metric is in KB.
+  Assert.equal(24 * 1024, data.sum, "Sum's correct");
+  for (let [bucket, count] of Object.entries(data.values)) {
+    Assert.ok(
+      count == 0 || (count == 1 && (bucket == 6888 || bucket == 17109)),
+      `Only two buckets have a sample ${bucket} ${count}`
+    );
+  }
+
+  data = Telemetry.getHistogramById("TELEMETRY_TEST_LINEAR").snapshot();
+  Telemetry.getHistogramById("TELEMETRY_TEST_LINEAR").clear();
+  Assert.equal(24, data.sum, "Histogram's in `memory_unit` units");
+  Assert.equal(2, data.values["1"], "Both samples in a low bucket");
+
+  // MemoryDistribution's Accumulate method to takes
+  // a platform specific type (size_t).
+  // Glean's, however, is i64, and, glean_memory_dist is uint64_t
+  // What happens when we give accumulate dubious values?
+  // This may occur on some uncommon platforms.
+  // Note: there are issues in JS with numbers above 2**53
+  Glean.testOnlyIpc.aMemoryDist.accumulate(36893488147419103232);
+  let dubiousValue = Object.entries(
+    Glean.testOnlyIpc.aMemoryDist.testGetValue().values
+  )[0][1];
+  Assert.equal(
+    dubiousValue,
+    1,
+    "Greater than 64-Byte number did not accumulate correctly"
+  );
+
+  // Values lower than the out-of-range value are not clamped
+  // resulting in an exception being thrown from the glean side
+  // when the value exceeds the glean maximum allowed value
+  Glean.testOnlyIpc.aMemoryDist.accumulate(Math.pow(2, 31));
+  Assert.throws(
+    () => Glean.testOnlyIpc.aMemoryDist.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Did not accumulate correctly"
+  );
+});
+
+add_task(function test_gifft_custom_dist() {
+  Glean.testOnlyIpc.aCustomDist.accumulateSamples([7, 268435458]);
+
+  let data = Glean.testOnlyIpc.aCustomDist.testGetValue();
+  Assert.equal(7 + 268435458, data.sum, "Sum's correct");
+  for (let [bucket, count] of Object.entries(data.values)) {
+    Assert.ok(
+      count == 0 || (count == 1 && (bucket == 1 || bucket == 268435456)),
+      `Only two buckets have a sample ${bucket} ${count}`
+    );
+  }
+
+  data = Telemetry.getHistogramById(
+    "TELEMETRY_TEST_MIRROR_FOR_CUSTOM"
+  ).snapshot();
+  Telemetry.getHistogramById("TELEMETRY_TEST_MIRROR_FOR_CUSTOM").clear();
+  Assert.equal(7 + 268435458, data.sum, "Sum in histogram is correct");
+  Assert.equal(1, data.values["1"], "One sample in the low bucket");
+  // Yes, the bucket is off-by-one compared to Glean.
+  Assert.equal(1, data.values["268435457"], "One sample in the next bucket");
+});
+
+add_task(async function test_gifft_timing_dist() {
+  let t1 = Glean.testOnlyIpc.aTimingDist.start();
+  // Interleave some other metric's samples. bug 1768636.
+  let ot1 = Glean.testOnly.whatTimeIsIt.start();
+  let t2 = Glean.testOnlyIpc.aTimingDist.start();
+  let ot2 = Glean.testOnly.whatTimeIsIt.start();
+  Glean.testOnly.whatTimeIsIt.cancel(ot1);
+  Glean.testOnly.whatTimeIsIt.cancel(ot2);
+
+  await sleep(5);
+
+  let t3 = Glean.testOnlyIpc.aTimingDist.start();
+  Glean.testOnlyIpc.aTimingDist.cancel(t1);
+
+  await sleep(5);
+
+  Glean.testOnlyIpc.aTimingDist.stopAndAccumulate(t2); // 10ms
+  Glean.testOnlyIpc.aTimingDist.stopAndAccumulate(t3); // 5ms
+
+  let data = Glean.testOnlyIpc.aTimingDist.testGetValue();
+  const NANOS_IN_MILLIS = 1e6;
+  // bug 1701949 - Sleep gets close, but sometimes doesn't wait long enough.
+  const EPSILON = 40000;
+
+  // Variance in timing makes getting the sum impossible to know.
+  // 10 and 5 input value can be trunacted to 4. + 9. >= 13. from cast
+  Assert.greater(data.sum, 13 * NANOS_IN_MILLIS - EPSILON);
+
+  // No guarantees from timers means no guarantees on buckets.
+  // But we can guarantee it's only two samples.
+  Assert.equal(
+    2,
+    Object.entries(data.values).reduce(
+      (acc, [bucket, count]) => acc + count,
+      0
+    ),
+    "Only two buckets with samples"
+  );
+
+  data = Telemetry.getHistogramById("TELEMETRY_TEST_EXPONENTIAL").snapshot();
+  // Suffers from same cast truncation issue of 9.... and 4.... values
+  Assert.greaterOrEqual(data.sum, 13, "Histogram's in milliseconds");
+  Assert.equal(
+    2,
+    Object.entries(data.values).reduce(
+      (acc, [bucket, count]) => acc + count,
+      0
+    ),
+    "Only two samples"
+  );
+});
+
+add_task(function test_gifft_string_list_works() {
+  const value = "a string!";
+  const value2 = "another string!";
+  const value3 = "yet another string.";
+
+  // `set` doesn't work in the mirror, so use `add`
+  Glean.testOnlyIpc.aStringList.add(value);
+  Glean.testOnlyIpc.aStringList.add(value2);
+  Glean.testOnlyIpc.aStringList.add(value3);
+
+  let val = Glean.testOnlyIpc.aStringList.testGetValue();
+  // Note: This is incredibly fragile and will break if we ever rearrange items
+  // in the string list.
+  Assert.deepEqual([value, value2, value3], val);
+
+  val = keyedScalarValue("telemetry.test.keyed_boolean_kind");
+  // This too may be fragile.
+  Assert.deepEqual(
+    {
+      [value]: true,
+      [value2]: true,
+      [value3]: true,
+    },
+    val
+  );
+});
+
+add_task(function test_gifft_events() {
+  Telemetry.setEventRecordingEnabled("telemetry.test", true);
+
+  Glean.testOnlyIpc.noExtraEvent.record();
+  var events = Glean.testOnlyIpc.noExtraEvent.testGetValue();
+  Assert.equal(1, events.length);
+  Assert.equal("test_only.ipc", events[0].category);
+  Assert.equal("no_extra_event", events[0].name);
+
+  let extra = { extra1: "can set extras", extra2: "passing more data" };
+  Glean.testOnlyIpc.anEvent.record(extra);
+  events = Glean.testOnlyIpc.anEvent.testGetValue();
+  Assert.equal(1, events.length);
+  Assert.equal("test_only.ipc", events[0].category);
+  Assert.equal("an_event", events[0].name);
+  Assert.deepEqual(extra, events[0].extra);
+
+  TelemetryTestUtils.assertEvents(
+    [
+      ["telemetry.test", "not_expired_optout", "object1", undefined, undefined],
+      ["telemetry.test", "mirror_with_extra", "object1", null, extra],
+    ],
+    { category: "telemetry.test" }
+  );
+});
+
+add_task(function test_gifft_uuid() {
+  const kTestUuid = "decafdec-afde-cafd-ecaf-decafdecafde";
+  Glean.testOnlyIpc.aUuid.set(kTestUuid);
+  Assert.equal(kTestUuid, Glean.testOnlyIpc.aUuid.testGetValue());
+  Assert.equal(kTestUuid, scalarValue("telemetry.test.string_kind"));
+});
+
+add_task(function test_gifft_labeled_counter() {
+  Assert.equal(
+    undefined,
+    Glean.testOnlyIpc.aLabeledCounter.a_label.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.testOnlyIpc.aLabeledCounter.a_label.add(1);
+  Glean.testOnlyIpc.aLabeledCounter.another_label.add(2);
+  Glean.testOnlyIpc.aLabeledCounter.a_label.add(3);
+  Assert.equal(4, Glean.testOnlyIpc.aLabeledCounter.a_label.testGetValue());
+  Assert.equal(
+    2,
+    Glean.testOnlyIpc.aLabeledCounter.another_label.testGetValue()
+  );
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.testOnlyIpc.aLabeledCounter.__other__.testGetValue()
+  );
+  Glean.testOnlyIpc.aLabeledCounter.InvalidLabel.add(3);
+  Assert.throws(
+    () => Glean.testOnlyIpc.aLabeledCounter.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Can't get the value when you're error'd"
+  );
+
+  let value = keyedScalarValue(
+    "telemetry.test.another_mirror_for_labeled_counter"
+  );
+  Assert.deepEqual(
+    {
+      a_label: 4,
+      another_label: 2,
+      InvalidLabel: 3,
+    },
+    value
+  );
+});
+
+add_task(async function test_gifft_timespan() {
+  // We start, briefly sleep and then stop.
+  // That guarantees some time to measure.
+  Glean.testOnly.mirrorTime.start();
+  await sleep(10);
+  Glean.testOnly.mirrorTime.stop();
+
+  const NANOS_IN_MILLIS = 1e6;
+  // bug 1701949 - Sleep gets close, but sometimes doesn't wait long enough.
+  const EPSILON = 40000;
+  Assert.greater(
+    Glean.testOnly.mirrorTime.testGetValue(),
+    10 * NANOS_IN_MILLIS - EPSILON
+  );
+  // Mirrored to milliseconds.
+  Assert.greaterOrEqual(scalarValue("telemetry.test.mirror_for_timespan"), 9);
+});
+
+add_task(async function test_gifft_timespan_raw() {
+  Glean.testOnly.mirrorTimeNanos.setRaw(15 /*ns*/);
+
+  Assert.equal(15, Glean.testOnly.mirrorTimeNanos.testGetValue());
+  // setRaw, unlike start/stop, mirrors the raw value directly.
+  Assert.equal(scalarValue("telemetry.test.mirror_for_timespan_nanos"), 15);
+});
+
+add_task(async function test_gifft_labeled_boolean() {
+  Assert.equal(
+    undefined,
+    Glean.testOnly.mirrorsForLabeledBools.a_label.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.testOnly.mirrorsForLabeledBools.a_label.set(true);
+  Glean.testOnly.mirrorsForLabeledBools.another_label.set(false);
+  Assert.equal(
+    true,
+    Glean.testOnly.mirrorsForLabeledBools.a_label.testGetValue()
+  );
+  Assert.equal(
+    false,
+    Glean.testOnly.mirrorsForLabeledBools.another_label.testGetValue()
+  );
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.testOnly.mirrorsForLabeledBools.__other__.testGetValue()
+  );
+  Glean.testOnly.mirrorsForLabeledBools.InvalidLabel.set(true);
+  Assert.throws(
+    () => Glean.testOnly.mirrorsForLabeledBools.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because of a recording error."
+  );
+
+  // In Telemetry there is no invalid label
+  let value = keyedScalarValue("telemetry.test.mirror_for_labeled_bool");
+  Assert.deepEqual(
+    {
+      a_label: true,
+      another_label: false,
+      InvalidLabel: true,
+    },
+    value
+  );
+});
+
+add_task(function test_gifft_boolean() {
+  Glean.testOnly.meaningOfLife.set(42);
+  Assert.equal(42, Glean.testOnly.meaningOfLife.testGetValue());
+  Assert.equal(42, scalarValue("telemetry.test.mirror_for_quantity"));
+});
+
+add_task(function test_gifft_rate() {
+  Glean.testOnlyIpc.irate.addToNumerator(22);
+  Glean.testOnlyIpc.irate.addToDenominator(7);
+  Assert.deepEqual(
+    { numerator: 22, denominator: 7 },
+    Glean.testOnlyIpc.irate.testGetValue()
+  );
+  Assert.deepEqual(
+    { numerator: 22, denominator: 7 },
+    keyedScalarValue("telemetry.test.mirror_for_rate")
+  );
+});
+
+add_task(
+  {
+    // bug 1670259 to see if we can implement `testResetFOG` on Android.
+    skip_if: () => AppConstants.platform == "android",
+  },
+  function test_gifft_numeric_limits() {
+    // Glean and Telemetry don't share the same storage sizes or signedness.
+    // Check the edges.
+
+    // 0) Reset everything
+    Services.fog.testResetFOG();
+    Services.telemetry.getSnapshotForHistograms("main", true /* aClearStore */);
+    Services.telemetry.getSnapshotForScalars("main", true /* aClearStore */);
+    Services.telemetry.getSnapshotForKeyedScalars(
+      "main",
+      true /* aClearStore */
+    );
+
+    // 1) Counter: i32 (saturates), mirrored to uint Scalar: u32 (overflows)
+    // 1.1) Negative parameters refused.
+    Glean.testOnlyIpc.aCounter.add(-20);
+    // Unfortunately we can't check what the error was, due to API design.
+    // (chutten blames chutten for his shortsightedness)
+    Assert.throws(
+      () => Glean.testOnlyIpc.aCounter.testGetValue(),
+      /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+      "Can't get the value when you're error'd"
+    );
+    Assert.equal(undefined, scalarValue("telemetry.test.mirror_for_counter"));
+    // Clear the error state
+    Services.fog.testResetFOG();
+
+    // 1.2) Values that sum larger than u32::max saturate (counter) and overflow (Scalar)
+    // Sums to 2^32 + 1
+    Glean.testOnlyIpc.aCounter.add(Math.pow(2, 31) - 1);
+    Glean.testOnlyIpc.aCounter.add(1);
+    Glean.testOnlyIpc.aCounter.add(Math.pow(2, 31) - 1);
+    Glean.testOnlyIpc.aCounter.add(2);
+    // Glean doesn't actually throw on saturation (bug 1751469),
+    // so we can just check the saturation value.
+    Assert.equal(
+      Math.pow(2, 31) - 1,
+      Glean.testOnlyIpc.aCounter.testGetValue()
+    );
+    // Telemetry will have wrapped around to 1
+    Assert.equal(1, scalarValue("telemetry.test.mirror_for_counter"));
+
+    // 2) Quantity: i64 (saturates), mirrored to uint Scalar: u32 (overflows)
+    // 2.1) Negative parameters refused.
+    Glean.testOnly.meaningOfLife.set(-42);
+    // Glean will error on this.
+    Assert.throws(
+      () => Glean.testOnly.meaningOfLife.testGetValue(),
+      /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+      "Can't get the value when you're error'd"
+    );
+    // GIFFT doesn't tell Telemetry about the weird value at all.
+    Assert.equal(undefined, scalarValue("telemetry.test.mirror_for_quantity"));
+    // Clear the error state
+    Services.fog.testResetFOG();
+
+    // 2.2) A parameter larger than u32::max is passed to Glean unchanged,
+    //      but is clamped to u32::max before being passed to Telemetry.
+    Glean.testOnly.meaningOfLife.set(Math.pow(2, 32));
+    Assert.equal(Math.pow(2, 32), Glean.testOnly.meaningOfLife.testGetValue());
+    Assert.equal(
+      Math.pow(2, 32) - 1,
+      scalarValue("telemetry.test.mirror_for_quantity")
+    );
+
+    // 3) Rate: two i32 (saturates), mirrored to keyed uint Scalar: u32s (overflow)
+    // 3.1) Negative parameters refused.
+    Glean.testOnlyIpc.irate.addToNumerator(-22);
+    Glean.testOnlyIpc.irate.addToDenominator(7);
+    Assert.throws(
+      () => Glean.testOnlyIpc.irate.testGetValue(),
+      /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+      "Can't get the value when you're error'd"
+    );
+    Assert.deepEqual(
+      { denominator: 7 },
+      keyedScalarValue("telemetry.test.mirror_for_rate")
+    );
+    // Clear the error state
+    Services.fog.testResetFOG();
+    // Clear the partial Telemetry value
+    Services.telemetry.getSnapshotForKeyedScalars(
+      "main",
+      true /* aClearStore */
+    );
+
+    // Now the denominator:
+    Glean.testOnlyIpc.irate.addToNumerator(22);
+    Glean.testOnlyIpc.irate.addToDenominator(-7);
+    Assert.throws(
+      () => Glean.testOnlyIpc.irate.testGetValue(),
+      /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+      "Can't get the value when you're error'd"
+    );
+    Assert.deepEqual(
+      { numerator: 22 },
+      keyedScalarValue("telemetry.test.mirror_for_rate")
+    );
+
+    // 4) Timespan
+    // ( Can't overflow time without finding a way to get TimeStamp to think
+    // we're 2^32 milliseconds later without waiting a month )
+
+    // 5) TimingDistribution
+    // ( Can't overflow time with start() and stopAndAccumulate() without
+    // waiting for ages. But we _do_ have a test-only raw API...)
+    // The max sample for timing_distribution is 600000000000.
+    // The type for timing_distribution samples is i64.
+    // This means when we explore the edges of GIFFT's limits, we're well past
+    // Glean's limits. All we can get out of Glean is errors.
+    // (Which is good for data, difficult for tests.)
+    // But GIFFT should properly saturate in Telemetry at i32::max,
+    // so we shall test that.
+    Glean.testOnlyIpc.aTimingDist.testAccumulateRawMillis(Math.pow(2, 31) + 1);
+    Glean.testOnlyIpc.aTimingDist.testAccumulateRawMillis(Math.pow(2, 32) + 1);
+    Assert.throws(
+      () => Glean.testOnlyIpc.aTimingDist.testGetValue(),
+      /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+      "Can't get the value when you're error'd"
+    );
+    let snapshot = Telemetry.getHistogramById(
+      "TELEMETRY_TEST_EXPONENTIAL"
+    ).snapshot();
+    Assert.equal(
+      snapshot.values["2147483646"],
+      2,
+      "samples > i32::max should end up in the top bucket"
+    );
+  }
+);
+
+add_task(function test_gifft_url() {
+  const value = "https://www.example.com";
+  Glean.testOnlyIpc.aUrl.set(value);
+
+  Assert.equal(value, Glean.testOnlyIpc.aUrl.testGetValue());
+  Assert.equal(value, scalarValue("telemetry.test.mirror_for_url"));
+});
+
+add_task(function test_gifft_url_cropped() {
+  const value = `https://example.com${"/test".repeat(47)}`;
+  Glean.testOnlyIpc.aUrl.set(value);
+
+  Assert.equal(value, Glean.testOnlyIpc.aUrl.testGetValue());
+  // We expect the mirrored URL to be truncated at the maximum
+  // length supported by string scalars.
+  Assert.equal(
+    value.substring(0, 50),
+    scalarValue("telemetry.test.mirror_for_url")
+  );
+});
diff --git a/toolkit/components/glean/tests/xpcshell/test_GIFFTIPC.js b/toolkit/components/glean/tests/xpcshell/test_GIFFTIPC.js
new file mode 100644
index 0000000000..73a9da9be2
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_GIFFTIPC.js
@@ -0,0 +1,315 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+const { ContentTaskUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/ContentTaskUtils.sys.mjs"
+);
+const { setTimeout } = ChromeUtils.importESModule(
+  "resource://gre/modules/Timer.sys.mjs"
+);
+const Telemetry = Services.telemetry;
+const { TelemetryTestUtils } = ChromeUtils.importESModule(
+  "resource://testing-common/TelemetryTestUtils.sys.mjs"
+);
+
+function sleep(ms) {
+  /* eslint-disable mozilla/no-arbitrary-setTimeout */
+  return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+function scalarValue(aScalarName, aProcessName) {
+  let snapshot = Telemetry.getSnapshotForScalars();
+  return aProcessName in snapshot
+    ? snapshot[aProcessName][aScalarName]
+    : undefined;
+}
+
+function keyedScalarValue(aScalarName, aProcessName) {
+  let snapshot = Telemetry.getSnapshotForKeyedScalars();
+  return aProcessName in snapshot
+    ? snapshot[aProcessName][aScalarName]
+    : undefined;
+}
+
+add_setup({ skip_if: () => !runningInParent }, function test_setup() {
+  // Give FOG a temp profile to init within.
+  do_get_profile();
+
+  // Allows these tests to properly run on e.g. Thunderbird
+  Services.prefs.setBoolPref(
+    "toolkit.telemetry.testing.overrideProductsCheck",
+    true
+  );
+
+  // We need to initialize it once, otherwise operations will be stuck in the pre-init queue.
+  // on Android FOG is set up through head.js
+  if (AppConstants.platform != "android") {
+    Services.fog.initializeFOG();
+  }
+});
+
+const COUNT = 42;
+const CHEESY_STRING = "a very cheesy string!";
+const CHEESIER_STRING = "a much cheesier string!";
+const CUSTOM_SAMPLES = [3, 4];
+const EVENT_EXTRA = { extra1: "so very extra" };
+const MEMORIES = [13, 31];
+const MEMORY_BUCKETS = ["13193", "31378"]; // buckets are strings : |
+const A_LABEL_COUNT = 3;
+const ANOTHER_LABEL_COUNT = 5;
+const INVALID_COUNTERS = 7;
+const IRATE_NUMERATOR = 44;
+const IRATE_DENOMINATOR = 14;
+
+add_task({ skip_if: () => runningInParent }, async function run_child_stuff() {
+  let oldCanRecordBase = Telemetry.canRecordBase;
+  Telemetry.canRecordBase = true; // Ensure we're able to record things.
+
+  Glean.testOnlyIpc.aCounter.add(COUNT);
+  Glean.testOnlyIpc.aStringList.add(CHEESY_STRING);
+  Glean.testOnlyIpc.aStringList.add(CHEESIER_STRING);
+
+  Glean.testOnlyIpc.noExtraEvent.record();
+  Glean.testOnlyIpc.anEvent.record(EVENT_EXTRA);
+
+  for (let memory of MEMORIES) {
+    Glean.testOnlyIpc.aMemoryDist.accumulate(memory);
+  }
+
+  let t1 = Glean.testOnlyIpc.aTimingDist.start();
+  let t2 = Glean.testOnlyIpc.aTimingDist.start();
+
+  await sleep(5);
+
+  let t3 = Glean.testOnlyIpc.aTimingDist.start();
+  Glean.testOnlyIpc.aTimingDist.cancel(t1);
+
+  await sleep(5);
+
+  Glean.testOnlyIpc.aTimingDist.stopAndAccumulate(t2); // 10ms
+  Glean.testOnlyIpc.aTimingDist.stopAndAccumulate(t3); // 5ms
+
+  Glean.testOnlyIpc.aCustomDist.accumulateSamples(CUSTOM_SAMPLES);
+
+  Glean.testOnlyIpc.aLabeledCounter.a_label.add(A_LABEL_COUNT);
+  Glean.testOnlyIpc.aLabeledCounter.another_label.add(ANOTHER_LABEL_COUNT);
+
+  // Has to be different from aLabeledCounter so the error we record doesn't
+  // get in the way.
+  Glean.testOnlyIpc.anotherLabeledCounter.InvalidLabel.add(INVALID_COUNTERS);
+
+  Glean.testOnlyIpc.irate.addToNumerator(IRATE_NUMERATOR);
+  Glean.testOnlyIpc.irate.addToDenominator(IRATE_DENOMINATOR);
+  Telemetry.canRecordBase = oldCanRecordBase;
+});
+
+add_task(
+  { skip_if: () => !runningInParent },
+  async function test_child_metrics() {
+    Telemetry.setEventRecordingEnabled("telemetry.test", true);
+
+    // Clear any stray Telemetry data
+    Telemetry.clearScalars();
+    Telemetry.getSnapshotForHistograms("main", true);
+    Telemetry.clearEvents();
+
+    await run_test_in_child("test_GIFFTIPC.js");
+
+    // Wait for both IPC mechanisms to flush.
+    await Services.fog.testFlushAllChildren();
+    await ContentTaskUtils.waitForCondition(() => {
+      let snapshot = Telemetry.getSnapshotForKeyedScalars();
+      return (
+        "content" in snapshot &&
+        "telemetry.test.mirror_for_rate" in snapshot.content
+      );
+    }, "failed to find content telemetry in parent");
+
+    // boolean
+    // Doesn't work over IPC
+
+    // counter
+    Assert.equal(Glean.testOnlyIpc.aCounter.testGetValue(), COUNT);
+    Assert.equal(
+      scalarValue("telemetry.test.mirror_for_counter", "content"),
+      COUNT,
+      "content-process Scalar has expected count"
+    );
+
+    // custom_distribution
+    const customSampleSum = CUSTOM_SAMPLES.reduce((acc, a) => acc + a, 0);
+    const customData = Glean.testOnlyIpc.aCustomDist.testGetValue("store1");
+    Assert.equal(customSampleSum, customData.sum, "Sum's correct");
+    for (let [bucket, count] of Object.entries(customData.values)) {
+      Assert.ok(
+        count == 0 || (count == CUSTOM_SAMPLES.length && bucket == 1), // both values in the low bucket
+        `Only two buckets have a sample ${bucket} ${count}`
+      );
+    }
+    const histSnapshot = Telemetry.getSnapshotForHistograms(
+      "main",
+      false,
+      false
+    );
+    const histData = histSnapshot.content.TELEMETRY_TEST_MIRROR_FOR_CUSTOM;
+    Assert.equal(customSampleSum, histData.sum, "Sum in histogram's correct");
+    Assert.equal(2, histData.values["1"], "Two samples in the first bucket");
+
+    // datetime
+    // Doesn't work over IPC
+
+    // event
+    var events = Glean.testOnlyIpc.noExtraEvent.testGetValue();
+    Assert.equal(1, events.length);
+    Assert.equal("test_only.ipc", events[0].category);
+    Assert.equal("no_extra_event", events[0].name);
+
+    events = Glean.testOnlyIpc.anEvent.testGetValue();
+    Assert.equal(1, events.length);
+    Assert.equal("test_only.ipc", events[0].category);
+    Assert.equal("an_event", events[0].name);
+    Assert.deepEqual(EVENT_EXTRA, events[0].extra);
+
+    TelemetryTestUtils.assertEvents(
+      [
+        [
+          "telemetry.test",
+          "not_expired_optout",
+          "object1",
+          undefined,
+          undefined,
+        ],
+        ["telemetry.test", "mirror_with_extra", "object1", null, EVENT_EXTRA],
+      ],
+      { category: "telemetry.test" },
+      { process: "content" }
+    );
+
+    // labeled_boolean
+    // Doesn't work over IPC
+
+    // labeled_counter
+    const counters = Glean.testOnlyIpc.aLabeledCounter;
+    Assert.equal(counters.a_label.testGetValue(), A_LABEL_COUNT);
+    Assert.equal(counters.another_label.testGetValue(), ANOTHER_LABEL_COUNT);
+
+    Assert.throws(
+      () => Glean.testOnlyIpc.anotherLabeledCounter.__other__.testGetValue(),
+      /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+      "Invalid labels record errors, which throw"
+    );
+
+    let value = keyedScalarValue(
+      "telemetry.test.another_mirror_for_labeled_counter",
+      "content"
+    );
+    Assert.deepEqual(
+      {
+        a_label: A_LABEL_COUNT,
+        another_label: ANOTHER_LABEL_COUNT,
+      },
+      value
+    );
+    value = keyedScalarValue(
+      "telemetry.test.mirror_for_labeled_counter",
+      "content"
+    );
+    Assert.deepEqual(
+      {
+        InvalidLabel: INVALID_COUNTERS,
+      },
+      value
+    );
+
+    // labeled_string
+    // Doesn't work over IPC
+
+    // memory_distribution
+    const memoryData = Glean.testOnlyIpc.aMemoryDist.testGetValue();
+    const memorySum = MEMORIES.reduce((acc, a) => acc + a, 0);
+    // The sum's in bytes, but the metric's in KB
+    Assert.equal(memorySum * 1024, memoryData.sum);
+    for (let [bucket, count] of Object.entries(memoryData.values)) {
+      // We could assert instead, but let's skip to save the logspam.
+      if (count == 0) {
+        continue;
+      }
+      Assert.ok(count == 1 && MEMORY_BUCKETS.includes(bucket));
+    }
+
+    const memoryHist = histSnapshot.content.TELEMETRY_TEST_LINEAR;
+    Assert.equal(
+      memorySum,
+      memoryHist.sum,
+      "Histogram's in `memory_unit` units"
+    );
+    Assert.equal(2, memoryHist.values["1"], "Samples are in the right bucket");
+
+    // quantity
+    // Doesn't work over IPC
+
+    // rate
+    Assert.deepEqual(
+      { numerator: IRATE_NUMERATOR, denominator: IRATE_DENOMINATOR },
+      Glean.testOnlyIpc.irate.testGetValue()
+    );
+    Assert.deepEqual(
+      { numerator: IRATE_NUMERATOR, denominator: IRATE_DENOMINATOR },
+      keyedScalarValue("telemetry.test.mirror_for_rate", "content")
+    );
+
+    // string
+    // Doesn't work over IPC
+
+    // string_list
+    // Note: this will break if string list ever rearranges its items.
+    const cheesyStrings = Glean.testOnlyIpc.aStringList.testGetValue();
+    Assert.deepEqual(cheesyStrings, [CHEESY_STRING, CHEESIER_STRING]);
+    // Note: this will break if keyed scalars rearrange their items.
+    Assert.deepEqual(
+      {
+        [CHEESY_STRING]: true,
+        [CHEESIER_STRING]: true,
+      },
+      keyedScalarValue("telemetry.test.keyed_boolean_kind", "content")
+    );
+
+    // timespan
+    // Doesn't work over IPC
+
+    // timing_distribution
+    const NANOS_IN_MILLIS = 1e6;
+    const EPSILON = 40000; // bug 1701949
+    const times = Glean.testOnlyIpc.aTimingDist.testGetValue();
+    Assert.greater(times.sum, 15 * NANOS_IN_MILLIS - EPSILON);
+    // We can't guarantee any specific time values (thank you clocks),
+    // but we can assert there are only two samples.
+    Assert.equal(
+      2,
+      Object.entries(times.values).reduce(
+        (acc, [bucket, count]) => acc + count,
+        0
+      )
+    );
+    const timingHist = histSnapshot.content.TELEMETRY_TEST_EXPONENTIAL;
+    Assert.greaterOrEqual(timingHist.sum, 13, "Histogram's in milliseconds.");
+    // Both values, 10 and 5, are truncated by a cast in AccumulateTimeDelta
+    // Minimally downcast 9. + 4. could realistically result in 13.
+    Assert.equal(
+      2,
+      Object.entries(timingHist.values).reduce(
+        (acc, [bucket, count]) => acc + count,
+        0
+      ),
+      "Only two samples"
+    );
+
+    // uuid
+    // Doesn't work over IPC
+  }
+);
diff --git a/toolkit/components/glean/tests/xpcshell/test_Glean.js b/toolkit/components/glean/tests/xpcshell/test_Glean.js
new file mode 100644
index 0000000000..cfab9d77ff
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_Glean.js
@@ -0,0 +1,405 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+const { setTimeout } = ChromeUtils.importESModule(
+  "resource://gre/modules/Timer.sys.mjs"
+);
+
+function sleep(ms) {
+  /* eslint-disable mozilla/no-arbitrary-setTimeout */
+  return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+add_setup(
+  /* on Android FOG is set up through head.js */
+  { skip_if: () => AppConstants.platform == "android" },
+  function test_setup() {
+    // FOG needs a profile directory to put its data in.
+    do_get_profile();
+
+    // We need to initialize it once, otherwise operations will be stuck in the pre-init queue.
+    Services.fog.initializeFOG();
+  }
+);
+
+add_task(function test_fog_counter_works() {
+  Glean.testOnly.badCode.add(31);
+  Assert.equal(31, Glean.testOnly.badCode.testGetValue("test-ping"));
+});
+
+add_task(async function test_fog_string_works() {
+  const value = "a cheesy string!";
+  Glean.testOnly.cheesyString.set(value);
+
+  Assert.equal(value, Glean.testOnly.cheesyString.testGetValue("test-ping"));
+});
+
+add_task(async function test_fog_string_list_works() {
+  const value = "a cheesy string!";
+  const value2 = "a cheesier string!";
+  const value3 = "the cheeziest of strings.";
+
+  const cheeseList = [value, value2];
+  Glean.testOnly.cheesyStringList.set(cheeseList);
+
+  let val = Glean.testOnly.cheesyStringList.testGetValue();
+  // Note: This is incredibly fragile and will break if we ever rearrange items
+  // in the string list.
+  Assert.deepEqual(cheeseList, val);
+
+  Glean.testOnly.cheesyStringList.add(value3);
+  Assert.ok(Glean.testOnly.cheesyStringList.testGetValue().includes(value3));
+});
+
+add_task(async function test_fog_timespan_works() {
+  Glean.testOnly.canWeTimeIt.start();
+  Glean.testOnly.canWeTimeIt.cancel();
+  Assert.equal(undefined, Glean.testOnly.canWeTimeIt.testGetValue());
+
+  // We start, briefly sleep and then stop.
+  // That guarantees some time to measure.
+  Glean.testOnly.canWeTimeIt.start();
+  await sleep(10);
+  Glean.testOnly.canWeTimeIt.stop();
+
+  Assert.ok(Glean.testOnly.canWeTimeIt.testGetValue("test-ping") > 0);
+});
+
+add_task(async function test_fog_timespan_throws_on_stop_wout_start() {
+  Glean.testOnly.canWeTimeIt.stop();
+  Assert.throws(
+    () => Glean.testOnly.canWeTimeIt.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because stop was called without start."
+  );
+});
+
+add_task(async function test_fog_uuid_works() {
+  const kTestUuid = "decafdec-afde-cafd-ecaf-decafdecafde";
+  Glean.testOnly.whatIdIt.set(kTestUuid);
+  Assert.equal(kTestUuid, Glean.testOnly.whatIdIt.testGetValue("test-ping"));
+
+  Glean.testOnly.whatIdIt.generateAndSet();
+  // Since we generate v4 UUIDs, and the first character of the third group
+  // isn't 4, this won't ever collide with kTestUuid.
+  Assert.notEqual(kTestUuid, Glean.testOnly.whatIdIt.testGetValue("test-ping"));
+});
+
+add_task(function test_fog_datetime_works() {
+  const value = new Date("2020-06-11T12:00:00");
+
+  Glean.testOnly.whatADate.set(value.getTime() * 1000);
+
+  const received = Glean.testOnly.whatADate.testGetValue("test-ping");
+  Assert.equal(received.getTime(), value.getTime());
+});
+
+add_task(function test_fog_boolean_works() {
+  Glean.testOnly.canWeFlagIt.set(false);
+  Assert.equal(false, Glean.testOnly.canWeFlagIt.testGetValue("test-ping"));
+  // While you're here, might as well test that the ping name's optional.
+  Assert.equal(false, Glean.testOnly.canWeFlagIt.testGetValue());
+});
+
+add_task(async function test_fog_event_works() {
+  Glean.testOnlyIpc.noExtraEvent.record();
+  var events = Glean.testOnlyIpc.noExtraEvent.testGetValue();
+  Assert.equal(1, events.length);
+  Assert.equal("test_only.ipc", events[0].category);
+  Assert.equal("no_extra_event", events[0].name);
+
+  let extra = { extra1: "can set extras", extra2: "passing more data" };
+  Glean.testOnlyIpc.anEvent.record(extra);
+  events = Glean.testOnlyIpc.anEvent.testGetValue();
+  Assert.equal(1, events.length);
+  Assert.equal("test_only.ipc", events[0].category);
+  Assert.equal("an_event", events[0].name);
+  Assert.deepEqual(extra, events[0].extra);
+
+  let extra2 = {
+    extra1: "can set extras",
+    extra2: 37,
+    extra3_longer_name: false,
+  };
+  Glean.testOnlyIpc.eventWithExtra.record(extra2);
+  events = Glean.testOnlyIpc.eventWithExtra.testGetValue();
+  Assert.equal(1, events.length);
+  Assert.equal("test_only.ipc", events[0].category);
+  Assert.equal("event_with_extra", events[0].name);
+  let expectedExtra = {
+    extra1: "can set extras",
+    extra2: "37",
+    extra3_longer_name: "false",
+  };
+  Assert.deepEqual(expectedExtra, events[0].extra);
+
+  // Quantities need to be non-negative.
+  // This does not record a Glean error.
+  let extra4 = {
+    extra2: -1,
+  };
+  Glean.testOnlyIpc.eventWithExtra.record(extra4);
+  events = Glean.testOnlyIpc.eventWithExtra.testGetValue();
+  // Unchanged number of events
+  Assert.equal(1, events.length, "Recorded one event too many.");
+
+  // Invalid extra keys don't crash, the event is not recorded,
+  // but an error is recorded.
+  let extra3 = {
+    extra1_nonexistent_extra: "this does not crash",
+  };
+  Glean.testOnlyIpc.eventWithExtra.record(extra3);
+  Assert.throws(
+    () => Glean.testOnlyIpc.eventWithExtra.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because of a recording error."
+  );
+});
+
+add_task(async function test_fog_memory_distribution_works() {
+  Glean.testOnly.doYouRemember.accumulate(7);
+  Glean.testOnly.doYouRemember.accumulate(17);
+
+  let data = Glean.testOnly.doYouRemember.testGetValue("test-ping");
+  // `data.sum` is in bytes, but the metric is in MB.
+  Assert.equal(24 * 1024 * 1024, data.sum, "Sum's correct");
+  for (let [bucket, count] of Object.entries(data.values)) {
+    Assert.ok(
+      count == 0 || (count == 1 && (bucket == 17520006 || bucket == 7053950)),
+      "Only two buckets have a sample"
+    );
+  }
+});
+
+add_task(async function test_fog_custom_distribution_works() {
+  Glean.testOnlyIpc.aCustomDist.accumulateSamples([7, 268435458]);
+
+  let data = Glean.testOnlyIpc.aCustomDist.testGetValue("store1");
+  Assert.equal(7 + 268435458, data.sum, "Sum's correct");
+  for (let [bucket, count] of Object.entries(data.values)) {
+    Assert.ok(
+      count == 0 || (count == 1 && (bucket == 1 || bucket == 268435456)),
+      `Only two buckets have a sample ${bucket} ${count}`
+    );
+  }
+
+  // Negative values will not be recorded, instead an error is recorded.
+  Glean.testOnlyIpc.aCustomDist.accumulateSamples([-7]);
+  Assert.throws(
+    () => Glean.testOnlyIpc.aCustomDist.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/
+  );
+});
+
+add_task(
+  /* TODO(bug 1737520): Enable custom ping support on Android */
+  { skip_if: () => AppConstants.platform == "android" },
+  function test_fog_custom_pings() {
+    Assert.ok("onePingOnly" in GleanPings);
+    let submitted = false;
+    Glean.testOnly.onePingOneBool.set(false);
+    GleanPings.onePingOnly.testBeforeNextSubmit(reason => {
+      submitted = true;
+      Assert.equal(false, Glean.testOnly.onePingOneBool.testGetValue());
+    });
+    GleanPings.onePingOnly.submit();
+    Assert.ok(submitted, "Ping was submitted, callback was called.");
+  }
+);
+
+add_task(async function test_fog_timing_distribution_works() {
+  let t1 = Glean.testOnly.whatTimeIsIt.start();
+  let t2 = Glean.testOnly.whatTimeIsIt.start();
+
+  await sleep(5);
+
+  let t3 = Glean.testOnly.whatTimeIsIt.start();
+  Glean.testOnly.whatTimeIsIt.cancel(t1);
+
+  await sleep(5);
+
+  Glean.testOnly.whatTimeIsIt.stopAndAccumulate(t2); // 10ms
+  Glean.testOnly.whatTimeIsIt.stopAndAccumulate(t3); // 5ms
+
+  let data = Glean.testOnly.whatTimeIsIt.testGetValue();
+  const NANOS_IN_MILLIS = 1e6;
+  // bug 1701949 - Sleep gets close, but sometimes doesn't wait long enough.
+  const EPSILON = 40000;
+
+  // Variance in timing makes getting the sum impossible to know.
+  Assert.greater(data.sum, 15 * NANOS_IN_MILLIS - EPSILON);
+
+  // No guarantees from timers means no guarantees on buckets.
+  // But we can guarantee it's only two samples.
+  Assert.equal(
+    2,
+    Object.entries(data.values).reduce(
+      (acc, [bucket, count]) => acc + count,
+      0
+    ),
+    "Only two buckets with samples"
+  );
+});
+
+add_task(async function test_fog_labels_conform() {
+  Glean.testOnly.mabelsLabelMaker.singleword.set("portmanteau");
+  Assert.equal(
+    "portmanteau",
+    Glean.testOnly.mabelsLabelMaker.singleword.testGetValue()
+  );
+  Glean.testOnly.mabelsLabelMaker.snake_case.set("snek");
+  Assert.equal(
+    "snek",
+    Glean.testOnly.mabelsLabelMaker.snake_case.testGetValue()
+  );
+  Glean.testOnly.mabelsLabelMaker["dash-character"].set("Dash Rendar");
+  Assert.equal(
+    "Dash Rendar",
+    Glean.testOnly.mabelsLabelMaker["dash-character"].testGetValue()
+  );
+  Glean.testOnly.mabelsLabelMaker["dot.separated"].set("dot product");
+  Assert.equal(
+    "dot product",
+    Glean.testOnly.mabelsLabelMaker["dot.separated"].testGetValue()
+  );
+  Glean.testOnly.mabelsLabelMaker.camelCase.set("wednesday");
+  Assert.throws(
+    () => Glean.testOnly.mabelsLabelMaker.camelCase.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because of an invalid label."
+  );
+  Assert.throws(
+    () => Glean.testOnly.mabelsLabelMaker.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because of an invalid label."
+  );
+  // This test _should_ throw because we are calling data after an invalid label
+  // has been set.
+  Assert.throws(
+    () => Glean.testOnly.mabelsLabelMaker["dot.separated"].testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because of an invalid label."
+  );
+});
+
+add_task(async function test_fog_labeled_boolean_works() {
+  Assert.equal(
+    undefined,
+    Glean.testOnly.mabelsLikeBalloons.at_parties.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.testOnly.mabelsLikeBalloons.at_parties.set(true);
+  Glean.testOnly.mabelsLikeBalloons.at_funerals.set(false);
+  Assert.equal(
+    true,
+    Glean.testOnly.mabelsLikeBalloons.at_parties.testGetValue()
+  );
+  Assert.equal(
+    false,
+    Glean.testOnly.mabelsLikeBalloons.at_funerals.testGetValue()
+  );
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.testOnly.mabelsLikeBalloons.__other__.testGetValue()
+  );
+  Glean.testOnly.mabelsLikeBalloons.InvalidLabel.set(true);
+  Assert.throws(
+    () => Glean.testOnly.mabelsLikeBalloons.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because of a recording error."
+  );
+});
+
+add_task(async function test_fog_labeled_counter_works() {
+  Assert.equal(
+    undefined,
+    Glean.testOnly.mabelsKitchenCounters.near_the_sink.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.testOnly.mabelsKitchenCounters.near_the_sink.add(1);
+  Glean.testOnly.mabelsKitchenCounters.with_junk_on_them.add(2);
+  Assert.equal(
+    1,
+    Glean.testOnly.mabelsKitchenCounters.near_the_sink.testGetValue()
+  );
+  Assert.equal(
+    2,
+    Glean.testOnly.mabelsKitchenCounters.with_junk_on_them.testGetValue()
+  );
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.testOnly.mabelsKitchenCounters.__other__.testGetValue()
+  );
+  Glean.testOnly.mabelsKitchenCounters.InvalidLabel.add(1);
+  Assert.throws(
+    () => Glean.testOnly.mabelsKitchenCounters.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because of a recording error."
+  );
+});
+
+add_task(async function test_fog_labeled_string_works() {
+  Assert.equal(
+    undefined,
+    Glean.testOnly.mabelsBalloonStrings.colour_of_99.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.testOnly.mabelsBalloonStrings.colour_of_99.set("crimson");
+  Glean.testOnly.mabelsBalloonStrings.string_lengths.set("various");
+  Assert.equal(
+    "crimson",
+    Glean.testOnly.mabelsBalloonStrings.colour_of_99.testGetValue()
+  );
+  Assert.equal(
+    "various",
+    Glean.testOnly.mabelsBalloonStrings.string_lengths.testGetValue()
+  );
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.testOnly.mabelsBalloonStrings.__other__.testGetValue()
+  );
+  Glean.testOnly.mabelsBalloonStrings.InvalidLabel.set("valid");
+  Assert.throws(
+    () => Glean.testOnly.mabelsBalloonStrings.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/
+  );
+});
+
+add_task(function test_fog_quantity_works() {
+  Glean.testOnly.meaningOfLife.set(42);
+  Assert.equal(42, Glean.testOnly.meaningOfLife.testGetValue());
+});
+
+add_task(function test_fog_rate_works() {
+  // 1) Standard rate with internal denominator
+  Glean.testOnlyIpc.irate.addToNumerator(22);
+  Glean.testOnlyIpc.irate.addToDenominator(7);
+  Assert.deepEqual(
+    { numerator: 22, denominator: 7 },
+    Glean.testOnlyIpc.irate.testGetValue()
+  );
+
+  // 2) Rate with external denominator
+  Glean.testOnlyIpc.anExternalDenominator.add(11);
+  Glean.testOnlyIpc.rateWithExternalDenominator.addToNumerator(121);
+  Assert.equal(11, Glean.testOnlyIpc.anExternalDenominator.testGetValue());
+  Assert.deepEqual(
+    { numerator: 121, denominator: 11 },
+    Glean.testOnlyIpc.rateWithExternalDenominator.testGetValue()
+  );
+});
+
+add_task(async function test_fog_url_works() {
+  const value = "https://www.example.com/fog";
+  Glean.testOnlyIpc.aUrl.set(value);
+
+  Assert.equal(value, Glean.testOnlyIpc.aUrl.testGetValue("store1"));
+});
diff --git a/toolkit/components/glean/tests/xpcshell/test_GleanExperiments.js b/toolkit/components/glean/tests/xpcshell/test_GleanExperiments.js
new file mode 100644
index 0000000000..cf8871e9d1
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_GleanExperiments.js
@@ -0,0 +1,28 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// FOG needs a profile directory to put its data in.
+do_get_profile();
+
+// We need to initialize it once, otherwise operations will be stuck in the pre-init queue.
+Services.fog.initializeFOG();
+
+add_task(function test_fog_experiment_annotations() {
+  const id = "my-experiment-id";
+  const branch = "my-branch";
+  const extra = { extra_key: "extra_value" };
+  Services.fog.setExperimentActive(id, branch, extra);
+
+  let data = Services.fog.testGetExperimentData(id);
+  Assert.equal(data.branch, branch);
+  Assert.deepEqual(data.extra, extra);
+
+  // Unknown id gets nothing.
+  Assert.equal(undefined, Services.fog.testGetExperimentData(id + id));
+
+  // Inactive id gets nothing.
+  Services.fog.setExperimentInactive(id);
+  Assert.equal(undefined, Services.fog.testGetExperimentData(id));
+});
diff --git a/toolkit/components/glean/tests/xpcshell/test_GleanIPC.js b/toolkit/components/glean/tests/xpcshell/test_GleanIPC.js
new file mode 100644
index 0000000000..182a584841
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_GleanIPC.js
@@ -0,0 +1,157 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+const { setTimeout } = ChromeUtils.importESModule(
+  "resource://gre/modules/Timer.sys.mjs"
+);
+
+function sleep(ms) {
+  /* eslint-disable mozilla/no-arbitrary-setTimeout */
+  return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+add_setup(
+  /* on Android FOG is set up through head.js */
+  { skip_if: () => !runningInParent || AppConstants.platform == "android" },
+  function test_setup() {
+    // Give FOG a temp profile to init within.
+    do_get_profile();
+
+    // We need to initialize it once, otherwise operations will be stuck in the pre-init queue.
+    Services.fog.initializeFOG();
+  }
+);
+
+const BAD_CODE_COUNT = 42;
+const CHEESY_STRING = "a very cheesy string!";
+const CHEESIER_STRING = "a much cheesier string!";
+const EVENT_EXTRA = { extra1: "so very extra" };
+const MEMORIES = [13, 31];
+const MEMORY_BUCKETS = ["13509772", "32131834"]; // buckets are strings : |
+const COUNTERS_NEAR_THE_SINK = 3;
+const COUNTERS_WITH_JUNK_ON_THEM = 5;
+const INVALID_COUNTERS = 7;
+
+add_task({ skip_if: () => runningInParent }, async function run_child_stuff() {
+  Glean.testOnly.badCode.add(BAD_CODE_COUNT);
+  Glean.testOnly.cheesyStringList.add(CHEESY_STRING);
+  Glean.testOnly.cheesyStringList.add(CHEESIER_STRING);
+
+  Glean.testOnlyIpc.noExtraEvent.record();
+  Glean.testOnlyIpc.anEvent.record(EVENT_EXTRA);
+
+  for (let memory of MEMORIES) {
+    Glean.testOnly.doYouRemember.accumulate(memory);
+  }
+
+  let t1 = Glean.testOnly.whatTimeIsIt.start();
+  let t2 = Glean.testOnly.whatTimeIsIt.start();
+
+  await sleep(5);
+
+  let t3 = Glean.testOnly.whatTimeIsIt.start();
+  Glean.testOnly.whatTimeIsIt.cancel(t1);
+
+  await sleep(5);
+
+  Glean.testOnly.whatTimeIsIt.stopAndAccumulate(t2); // 10ms
+  Glean.testOnly.whatTimeIsIt.stopAndAccumulate(t3); // 5ms
+
+  Glean.testOnlyIpc.aCustomDist.accumulateSamples([3, 4]);
+
+  Glean.testOnly.mabelsKitchenCounters.near_the_sink.add(
+    COUNTERS_NEAR_THE_SINK
+  );
+  Glean.testOnly.mabelsKitchenCounters.with_junk_on_them.add(
+    COUNTERS_WITH_JUNK_ON_THEM
+  );
+
+  Glean.testOnly.mabelsBathroomCounters.InvalidLabel.add(INVALID_COUNTERS);
+
+  Glean.testOnlyIpc.irate.addToNumerator(44);
+  Glean.testOnlyIpc.irate.addToDenominator(14);
+});
+
+add_task(
+  { skip_if: () => !runningInParent },
+  async function test_child_metrics() {
+    await run_test_in_child("test_GleanIPC.js");
+    await Services.fog.testFlushAllChildren();
+
+    Assert.equal(Glean.testOnly.badCode.testGetValue(), BAD_CODE_COUNT);
+
+    // Note: this will break if string list ever rearranges its items.
+    const cheesyStrings = Glean.testOnly.cheesyStringList.testGetValue();
+    Assert.deepEqual(cheesyStrings, [CHEESY_STRING, CHEESIER_STRING]);
+
+    const data = Glean.testOnly.doYouRemember.testGetValue();
+    Assert.equal(MEMORIES.reduce((a, b) => a + b, 0) * 1024 * 1024, data.sum);
+    for (let [bucket, count] of Object.entries(data.values)) {
+      // We could assert instead, but let's skip to save the logspam.
+      if (count == 0) {
+        continue;
+      }
+      Assert.ok(count == 1 && MEMORY_BUCKETS.includes(bucket));
+    }
+
+    const customData = Glean.testOnlyIpc.aCustomDist.testGetValue("store1");
+    Assert.equal(3 + 4, customData.sum, "Sum's correct");
+    for (let [bucket, count] of Object.entries(customData.values)) {
+      Assert.ok(
+        count == 0 || (count == 2 && bucket == 1), // both values in the low bucket
+        `Only two buckets have a sample ${bucket} ${count}`
+      );
+    }
+
+    var events = Glean.testOnlyIpc.noExtraEvent.testGetValue();
+    Assert.equal(1, events.length);
+    Assert.equal("test_only.ipc", events[0].category);
+    Assert.equal("no_extra_event", events[0].name);
+
+    events = Glean.testOnlyIpc.anEvent.testGetValue();
+    Assert.equal(1, events.length);
+    Assert.equal("test_only.ipc", events[0].category);
+    Assert.equal("an_event", events[0].name);
+    Assert.deepEqual(EVENT_EXTRA, events[0].extra);
+
+    const NANOS_IN_MILLIS = 1e6;
+    const EPSILON = 40000; // bug 1701949
+    const times = Glean.testOnly.whatTimeIsIt.testGetValue();
+    Assert.greater(times.sum, 15 * NANOS_IN_MILLIS - EPSILON);
+    // We can't guarantee any specific time values (thank you clocks),
+    // but we can assert there are only two samples.
+    Assert.equal(
+      2,
+      Object.entries(times.values).reduce(
+        (acc, [bucket, count]) => acc + count,
+        0
+      )
+    );
+
+    const mabelsCounters = Glean.testOnly.mabelsKitchenCounters;
+    Assert.equal(
+      mabelsCounters.near_the_sink.testGetValue(),
+      COUNTERS_NEAR_THE_SINK
+    );
+    Assert.equal(
+      mabelsCounters.with_junk_on_them.testGetValue(),
+      COUNTERS_WITH_JUNK_ON_THEM
+    );
+
+    Assert.throws(
+      () => Glean.testOnly.mabelsBathroomCounters.__other__.testGetValue(),
+      /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+      "Invalid labels record errors, which throw"
+    );
+
+    Assert.deepEqual(
+      { numerator: 44, denominator: 14 },
+      Glean.testOnlyIpc.irate.testGetValue()
+    );
+  }
+);
diff --git a/toolkit/components/glean/tests/xpcshell/test_JOG.js b/toolkit/components/glean/tests/xpcshell/test_JOG.js
new file mode 100644
index 0000000000..c18ce8cb74
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_JOG.js
@@ -0,0 +1,723 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+const { setTimeout } = ChromeUtils.importESModule(
+  "resource://gre/modules/Timer.sys.mjs"
+);
+
+function sleep(ms) {
+  /* eslint-disable mozilla/no-arbitrary-setTimeout */
+  return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+add_task(
+  /* on Android FOG is set up through head.js */
+  { skip_if: () => AppConstants.platform == "android" },
+  function test_setup() {
+    // FOG needs a profile directory to put its data in.
+    do_get_profile();
+
+    // We need to initialize it once, otherwise operations will be stuck in the pre-init queue.
+    Services.fog.initializeFOG();
+  }
+);
+
+add_task(function test_jog_counter_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "counter",
+    "jog_cat",
+    "jog_counter",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  Glean.jogCat.jogCounter.add(53);
+  Assert.equal(53, Glean.jogCat.jogCounter.testGetValue());
+});
+
+add_task(async function test_jog_string_works() {
+  const value = "an active string!";
+  Services.fog.testRegisterRuntimeMetric(
+    "string",
+    "jog_cat",
+    "jog_string",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  Glean.jogCat.jogString.set(value);
+
+  Assert.equal(value, Glean.jogCat.jogString.testGetValue());
+});
+
+add_task(async function test_jog_string_list_works() {
+  const value = "an active string!";
+  const value2 = "a more active string!";
+  const value3 = "the most active of strings.";
+  Services.fog.testRegisterRuntimeMetric(
+    "string_list",
+    "jog_cat",
+    "jog_string_list",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+
+  const jogList = [value, value2];
+  Glean.jogCat.jogStringList.set(jogList);
+
+  let val = Glean.jogCat.jogStringList.testGetValue();
+  // Note: This is incredibly fragile and will break if we ever rearrange items
+  // in the string list.
+  Assert.deepEqual(jogList, val);
+
+  Glean.jogCat.jogStringList.add(value3);
+  Assert.ok(Glean.jogCat.jogStringList.testGetValue().includes(value3));
+});
+
+add_task(async function test_jog_timespan_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "timespan",
+    "jog_cat",
+    "jog_timespan",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ time_unit: "millisecond" })
+  );
+  Glean.jogCat.jogTimespan.start();
+  Glean.jogCat.jogTimespan.cancel();
+  Assert.equal(undefined, Glean.jogCat.jogTimespan.testGetValue());
+
+  // We start, briefly sleep and then stop.
+  // That guarantees some time to measure.
+  Glean.jogCat.jogTimespan.start();
+  await sleep(10);
+  Glean.jogCat.jogTimespan.stop();
+
+  Assert.ok(Glean.jogCat.jogTimespan.testGetValue() > 0);
+});
+
+add_task(async function test_jog_uuid_works() {
+  const kTestUuid = "decafdec-afde-cafd-ecaf-decafdecafde";
+  Services.fog.testRegisterRuntimeMetric(
+    "uuid",
+    "jog_cat",
+    "jog_uuid",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  Glean.jogCat.jogUuid.set(kTestUuid);
+  Assert.equal(kTestUuid, Glean.jogCat.jogUuid.testGetValue());
+
+  Glean.jogCat.jogUuid.generateAndSet();
+  // Since we generate v4 UUIDs, and the first character of the third group
+  // isn't 4, this won't ever collide with kTestUuid.
+  Assert.notEqual(kTestUuid, Glean.jogCat.jogUuid.testGetValue());
+});
+
+add_task(function test_jog_datetime_works() {
+  const value = new Date("2020-06-11T12:00:00");
+  Services.fog.testRegisterRuntimeMetric(
+    "datetime",
+    "jog_cat",
+    "jog_datetime",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ time_unit: "nanosecond" })
+  );
+
+  Glean.jogCat.jogDatetime.set(value.getTime() * 1000);
+
+  const received = Glean.jogCat.jogDatetime.testGetValue();
+  Assert.equal(received.getTime(), value.getTime());
+});
+
+add_task(function test_jog_boolean_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "boolean",
+    "jog_cat",
+    "jog_bool",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  Glean.jogCat.jogBool.set(false);
+  Assert.equal(false, Glean.jogCat.jogBool.testGetValue());
+});
+
+add_task(async function test_jog_event_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "event",
+    "jog_cat",
+    "jog_event_no_extra",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  Glean.jogCat.jogEventNoExtra.record();
+  var events = Glean.jogCat.jogEventNoExtra.testGetValue();
+  Assert.equal(1, events.length);
+  Assert.equal("jog_cat", events[0].category);
+  Assert.equal("jog_event_no_extra", events[0].name);
+
+  Services.fog.testRegisterRuntimeMetric(
+    "event",
+    "jog_cat",
+    "jog_event",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ allowed_extra_keys: ["extra1", "extra2"] })
+  );
+  let extra = { extra1: "can set extras", extra2: "passing more data" };
+  Glean.jogCat.jogEvent.record(extra);
+  events = Glean.jogCat.jogEvent.testGetValue();
+  Assert.equal(1, events.length);
+  Assert.equal("jog_cat", events[0].category);
+  Assert.equal("jog_event", events[0].name);
+  Assert.deepEqual(extra, events[0].extra);
+
+  Services.fog.testRegisterRuntimeMetric(
+    "event",
+    "jog_cat",
+    "jog_event_with_extra",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({
+      allowed_extra_keys: ["extra1", "extra2", "extra3_longer_name"],
+    })
+  );
+  let extra2 = {
+    extra1: "can set extras",
+    extra2: 37,
+    extra3_longer_name: false,
+  };
+  Glean.jogCat.jogEventWithExtra.record(extra2);
+  events = Glean.jogCat.jogEventWithExtra.testGetValue();
+  Assert.equal(1, events.length);
+  Assert.equal("jog_cat", events[0].category);
+  Assert.equal("jog_event_with_extra", events[0].name);
+  let expectedExtra = {
+    extra1: "can set extras",
+    extra2: "37",
+    extra3_longer_name: "false",
+  };
+  Assert.deepEqual(expectedExtra, events[0].extra);
+
+  // Quantities need to be non-negative.
+  let extra4 = {
+    extra2: -1,
+  };
+  Glean.jogCat.jogEventWithExtra.record(extra4);
+  events = Glean.jogCat.jogEventWithExtra.testGetValue();
+  Assert.equal(1, events.length, "Recorded one event too many.");
+
+  // Invalid extra keys don't crash, the event is not recorded.
+  let extra3 = {
+    extra1_nonexistent_extra: "this does not crash",
+  };
+  Glean.jogCat.jogEventWithExtra.record(extra3);
+  // And test methods throw appropriately
+  Assert.throws(
+    () => Glean.jogCat.jogEventWithExtra.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/
+  );
+});
+
+add_task(async function test_jog_memory_distribution_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "memory_distribution",
+    "jog_cat",
+    "jog_memory_dist",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ memory_unit: "megabyte" })
+  );
+  Glean.jogCat.jogMemoryDist.accumulate(7);
+  Glean.jogCat.jogMemoryDist.accumulate(17);
+
+  let data = Glean.jogCat.jogMemoryDist.testGetValue();
+  // `data.sum` is in bytes, but the metric is in MB.
+  Assert.equal(24 * 1024 * 1024, data.sum, "Sum's correct");
+  for (let [bucket, count] of Object.entries(data.values)) {
+    Assert.ok(
+      count == 0 || (count == 1 && (bucket == 17520006 || bucket == 7053950)),
+      "Only two buckets have a sample"
+    );
+  }
+});
+
+add_task(async function test_jog_custom_distribution_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "custom_distribution",
+    "jog_cat",
+    "jog_custom_dist",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({
+      range_min: 1,
+      range_max: 2147483646,
+      bucket_count: 10,
+      histogram_type: "linear",
+    })
+  );
+  Glean.jogCat.jogCustomDist.accumulateSamples([7, 268435458]);
+
+  let data = Glean.jogCat.jogCustomDist.testGetValue();
+  Assert.equal(7 + 268435458, data.sum, "Sum's correct");
+  for (let [bucket, count] of Object.entries(data.values)) {
+    Assert.ok(
+      count == 0 || (count == 1 && (bucket == 1 || bucket == 268435456)),
+      `Only two buckets have a sample ${bucket} ${count}`
+    );
+  }
+
+  // Negative values will not be recorded, instead an error is recorded.
+  Glean.jogCat.jogCustomDist.accumulateSamples([-7]);
+  Assert.throws(
+    () => Glean.jogCat.jogCustomDist.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/
+  );
+});
+
+add_task(
+  /* TODO: Enable custom ping support on Android */
+  { skip_if: () => AppConstants.platform == "android" },
+  async function test_jog_custom_pings() {
+    Services.fog.testRegisterRuntimeMetric(
+      "boolean",
+      "jog_cat",
+      "jog_ping_bool",
+      ["jog-ping"],
+      `"ping"`,
+      false
+    );
+    Services.fog.testRegisterRuntimePing("jog-ping", true, true, []);
+    Assert.ok("jogPing" in GleanPings);
+    let submitted = false;
+    Glean.jogCat.jogPingBool.set(false);
+    GleanPings.jogPing.testBeforeNextSubmit(reason => {
+      submitted = true;
+      Assert.equal(false, Glean.jogCat.jogPingBool.testGetValue());
+    });
+    GleanPings.jogPing.submit();
+    Assert.ok(submitted, "Ping was submitted, callback was called.");
+    // ping-lifetime value was cleared.
+    Assert.equal(undefined, Glean.jogCat.jogPingBool.testGetValue());
+  }
+);
+
+add_task(async function test_jog_timing_distribution_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "timing_distribution",
+    "jog_cat",
+    "jog_timing_dist",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ time_unit: "microsecond" })
+  );
+  let t1 = Glean.jogCat.jogTimingDist.start();
+  let t2 = Glean.jogCat.jogTimingDist.start();
+
+  await sleep(5);
+
+  let t3 = Glean.jogCat.jogTimingDist.start();
+  Glean.jogCat.jogTimingDist.cancel(t1);
+
+  await sleep(5);
+
+  Glean.jogCat.jogTimingDist.stopAndAccumulate(t2); // 10ms
+  Glean.jogCat.jogTimingDist.stopAndAccumulate(t3); // 5ms
+
+  let data = Glean.jogCat.jogTimingDist.testGetValue();
+  const NANOS_IN_MILLIS = 1e6;
+  // bug 1701949 - Sleep gets close, but sometimes doesn't wait long enough.
+  const EPSILON = 40000;
+
+  // Variance in timing makes getting the sum impossible to know.
+  Assert.greater(data.sum, 15 * NANOS_IN_MILLIS - EPSILON);
+
+  // No guarantees from timers means no guarantees on buckets.
+  // But we can guarantee it's only two samples.
+  Assert.equal(
+    2,
+    Object.entries(data.values).reduce(
+      (acc, [bucket, count]) => acc + count,
+      0
+    ),
+    "Only two buckets with samples"
+  );
+});
+
+add_task(async function test_jog_labeled_boolean_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "labeled_boolean",
+    "jog_cat",
+    "jog_labeled_bool",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledBool.label_1.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.jogCat.jogLabeledBool.label_1.set(true);
+  Glean.jogCat.jogLabeledBool.label_2.set(false);
+  Assert.equal(true, Glean.jogCat.jogLabeledBool.label_1.testGetValue());
+  Assert.equal(false, Glean.jogCat.jogLabeledBool.label_2.testGetValue());
+  // What about invalid/__other__?
+  Assert.equal(undefined, Glean.jogCat.jogLabeledBool.__other__.testGetValue());
+  Glean.jogCat.jogLabeledBool.InvalidLabel.set(true);
+  Assert.throws(
+    () => Glean.jogCat.jogLabeledBool.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because of a recording error."
+  );
+});
+
+add_task(async function test_jog_labeled_boolean_with_static_labels_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "labeled_boolean",
+    "jog_cat",
+    "jog_labeled_bool_with_labels",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ labels: ["label_1", "label_2"] })
+  );
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledBoolWithLabels.label_1.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.jogCat.jogLabeledBoolWithLabels.label_1.set(true);
+  Glean.jogCat.jogLabeledBoolWithLabels.label_2.set(false);
+  Assert.equal(
+    true,
+    Glean.jogCat.jogLabeledBoolWithLabels.label_1.testGetValue()
+  );
+  Assert.equal(
+    false,
+    Glean.jogCat.jogLabeledBoolWithLabels.label_2.testGetValue()
+  );
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledBoolWithLabels.__other__.testGetValue()
+  );
+  Glean.jogCat.jogLabeledBoolWithLabels.label_3.set(true);
+  Assert.equal(
+    true,
+    Glean.jogCat.jogLabeledBoolWithLabels.__other__.testGetValue()
+  );
+  // TODO: Test that we have the right number and type of errors (bug 1683171)
+});
+
+add_task(async function test_jog_labeled_counter_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "labeled_counter",
+    "jog_cat",
+    "jog_labeled_counter",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledCounter.label_1.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.jogCat.jogLabeledCounter.label_1.add(1);
+  Glean.jogCat.jogLabeledCounter.label_2.add(2);
+  Assert.equal(1, Glean.jogCat.jogLabeledCounter.label_1.testGetValue());
+  Assert.equal(2, Glean.jogCat.jogLabeledCounter.label_2.testGetValue());
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledCounter.__other__.testGetValue()
+  );
+  Glean.jogCat.jogLabeledCounter.InvalidLabel.add(1);
+  Assert.throws(
+    () => Glean.jogCat.jogLabeledCounter.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because of a recording error."
+  );
+});
+
+add_task(async function test_jog_labeled_counter_with_static_labels_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "labeled_counter",
+    "jog_cat",
+    "jog_labeled_counter_with_labels",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ labels: ["label_1", "label_2"] })
+  );
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledCounterWithLabels.label_1.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.jogCat.jogLabeledCounterWithLabels.label_1.add(1);
+  Glean.jogCat.jogLabeledCounterWithLabels.label_2.add(2);
+  Assert.equal(
+    1,
+    Glean.jogCat.jogLabeledCounterWithLabels.label_1.testGetValue()
+  );
+  Assert.equal(
+    2,
+    Glean.jogCat.jogLabeledCounterWithLabels.label_2.testGetValue()
+  );
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledCounterWithLabels.__other__.testGetValue()
+  );
+  Glean.jogCat.jogLabeledCounterWithLabels.InvalidLabel.add(1);
+  // TODO:(bug 1766515) - This should throw.
+  /*Assert.throws(
+    () => Glean.jogCat.jogLabeledCounterWithLabels.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+    "Should throw because of a recording error."
+  );*/
+  Assert.equal(
+    1,
+    Glean.jogCat.jogLabeledCounterWithLabels.__other__.testGetValue()
+  );
+});
+
+add_task(async function test_jog_labeled_string_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "labeled_string",
+    "jog_cat",
+    "jog_labeled_string",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledString.label_1.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.jogCat.jogLabeledString.label_1.set("crimson");
+  Glean.jogCat.jogLabeledString.label_2.set("various");
+  Assert.equal("crimson", Glean.jogCat.jogLabeledString.label_1.testGetValue());
+  Assert.equal("various", Glean.jogCat.jogLabeledString.label_2.testGetValue());
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledString.__other__.testGetValue()
+  );
+  Glean.jogCat.jogLabeledString.InvalidLabel.set("valid");
+  Assert.throws(
+    () => Glean.jogCat.jogLabeledString.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/
+  );
+});
+
+add_task(async function test_jog_labeled_string_with_labels_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "labeled_string",
+    "jog_cat",
+    "jog_labeled_string_with_labels",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ labels: ["label_1", "label_2"] })
+  );
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledStringWithLabels.label_1.testGetValue(),
+    "New labels with no values should return undefined"
+  );
+  Glean.jogCat.jogLabeledStringWithLabels.label_1.set("crimson");
+  Glean.jogCat.jogLabeledStringWithLabels.label_2.set("various");
+  Assert.equal(
+    "crimson",
+    Glean.jogCat.jogLabeledStringWithLabels.label_1.testGetValue()
+  );
+  Assert.equal(
+    "various",
+    Glean.jogCat.jogLabeledStringWithLabels.label_2.testGetValue()
+  );
+  // What about invalid/__other__?
+  Assert.equal(
+    undefined,
+    Glean.jogCat.jogLabeledStringWithLabels.__other__.testGetValue()
+  );
+  Glean.jogCat.jogLabeledStringWithLabels.InvalidLabel.set("valid");
+  // TODO:(bug 1766515) - This should throw.
+  /*Assert.throws(
+    () => Glean.jogCat.jogLabeledStringWithLabels.__other__.testGetValue(),
+    /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/
+  );*/
+  Assert.equal(
+    "valid",
+    Glean.jogCat.jogLabeledStringWithLabels.__other__.testGetValue()
+  );
+});
+
+add_task(function test_jog_quantity_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "quantity",
+    "jog_cat",
+    "jog_quantity",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  Glean.jogCat.jogQuantity.set(42);
+  Assert.equal(42, Glean.jogCat.jogQuantity.testGetValue());
+});
+
+add_task(function test_jog_rate_works() {
+  Services.fog.testRegisterRuntimeMetric(
+    "rate",
+    "jog_cat",
+    "jog_rate",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  // 1) Standard rate with internal denominator
+  Glean.jogCat.jogRate.addToNumerator(22);
+  Glean.jogCat.jogRate.addToDenominator(7);
+  Assert.deepEqual(
+    { numerator: 22, denominator: 7 },
+    Glean.jogCat.jogRate.testGetValue()
+  );
+
+  Services.fog.testRegisterRuntimeMetric(
+    "denominator",
+    "jog_cat",
+    "jog_denominator",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({
+      numerators: [
+        {
+          name: "jog_rate_ext",
+          category: "jog_cat",
+          send_in_pings: ["test-only"],
+          lifetime: "ping",
+          disabled: false,
+        },
+      ],
+    })
+  );
+  Services.fog.testRegisterRuntimeMetric(
+    "rate",
+    "jog_cat",
+    "jog_rate_ext",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  // 2) Rate with external denominator
+  Glean.jogCat.jogDenominator.add(11);
+  Glean.jogCat.jogRateExt.addToNumerator(121);
+  Assert.equal(11, Glean.jogCat.jogDenominator.testGetValue());
+  Assert.deepEqual(
+    { numerator: 121, denominator: 11 },
+    Glean.jogCat.jogRateExt.testGetValue()
+  );
+});
+
+add_task(function test_jog_dotted_categories_work() {
+  Services.fog.testRegisterRuntimeMetric(
+    "counter",
+    "jog_cat.dotted",
+    "jog_counter",
+    ["test-only"],
+    `"ping"`,
+    false
+  );
+  Glean.jogCatDotted.jogCounter.add(314);
+  Assert.equal(314, Glean.jogCatDotted.jogCounter.testGetValue());
+});
+
+add_task(
+  /* TODO: Enable custom ping support on Android */
+  { skip_if: () => AppConstants.platform == "android" },
+  async function test_jog_ping_works() {
+    const kReason = "reason-1";
+    Services.fog.testRegisterRuntimePing("my-ping", true, true, [kReason]);
+    let submitted = false;
+    GleanPings.myPing.testBeforeNextSubmit(reason => {
+      submitted = true;
+      Assert.equal(kReason, reason);
+    });
+    GleanPings.myPing.submit("reason-1");
+    Assert.ok(submitted, "Ping must have been submitted");
+  }
+);
+
+add_task(function test_jog_name_collision() {
+  Assert.ok("aCounter" in Glean.testOnlyJog);
+  Assert.equal(undefined, Glean.testOnlyJog.aCounter.testGetValue());
+  const kValue = 42;
+  Glean.testOnlyJog.aCounter.add(kValue);
+  Assert.equal(kValue, Glean.testOnlyJog.aCounter.testGetValue());
+
+  // Let's overwrite the test_only.jog.a_counter counter.
+  Services.fog.testRegisterRuntimeMetric(
+    "counter",
+    "test_only.jog",
+    "a_counter",
+    ["store1"],
+    `"ping"`,
+    true // changing the metric to disabled.
+  );
+
+  Assert.ok("aCounter" in Glean.testOnlyJog);
+  Assert.equal(kValue, Glean.testOnlyJog.aCounter.testGetValue());
+  Glean.testOnlyJog.aCounter.add(kValue);
+  Assert.equal(
+    kValue,
+    Glean.testOnlyJog.aCounter.testGetValue(),
+    "value of now-disabled metric remains unchanged."
+  );
+
+  // Now let's mess with events:
+  Assert.ok("anEvent" in Glean.testOnlyJog);
+  Assert.equal(undefined, Glean.testOnlyJog.anEvent.testGetValue());
+  const extra12 = {
+    extra1: "a value",
+    extra2: "another value",
+  };
+  Glean.testOnlyJog.anEvent.record(extra12);
+  Assert.deepEqual(extra12, Glean.testOnlyJog.anEvent.testGetValue()[0].extra);
+  Services.fog.testRegisterRuntimeMetric(
+    "event",
+    "test_only.jog",
+    "an_event",
+    ["store1"],
+    `"ping"`,
+    false,
+    JSON.stringify({ allowed_extra_keys: ["extra1", "extra2", "extra3"] }) // New extra key just dropped
+  );
+  const extra123 = {
+    extra1: "different value",
+    extra2: "another different value",
+    extra3: 42,
+  };
+  Glean.testOnlyJog.anEvent.record(extra123);
+  Assert.deepEqual(extra123, Glean.testOnlyJog.anEvent.testGetValue()[1].extra);
+});
diff --git a/toolkit/components/glean/tests/xpcshell/test_JOGIPC.js b/toolkit/components/glean/tests/xpcshell/test_JOGIPC.js
new file mode 100644
index 0000000000..2df5a934ba
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_JOGIPC.js
@@ -0,0 +1,260 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+const { setTimeout } = ChromeUtils.importESModule(
+  "resource://gre/modules/Timer.sys.mjs"
+);
+
+function sleep(ms) {
+  /* eslint-disable mozilla/no-arbitrary-setTimeout */
+  return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+add_task(
+  /* on Android FOG is set up through head.js */
+  { skip_if: () => !runningInParent || AppConstants.platform == "android" },
+  function test_setup() {
+    // Give FOG a temp profile to init within.
+    do_get_profile();
+
+    // We need to initialize it once, otherwise operations will be stuck in the pre-init queue.
+    Services.fog.initializeFOG();
+  }
+);
+
+const COUNT = 42;
+const STRING = "a string!";
+const ANOTHER_STRING = "another string!";
+const EVENT_EXTRA = { extra1: "so very extra" };
+const MEMORIES = [13, 31];
+const MEMORY_BUCKETS = ["13509772", "32131834"]; // buckets are strings : |
+const COUNTERS_1 = 3;
+const COUNTERS_2 = 5;
+const INVALID_COUNTERS = 7;
+
+// It is CRUCIAL that we register metrics in the same order in the parent and
+// in the child or their metric ids will not line up and ALL WILL EXPLODE.
+const METRICS = [
+  ["counter", "jog_ipc", "jog_counter", ["test-only"], `"ping"`, false],
+  ["string_list", "jog_ipc", "jog_string_list", ["test-only"], `"ping"`, false],
+  ["event", "jog_ipc", "jog_event_no_extra", ["test-only"], `"ping"`, false],
+  [
+    "event",
+    "jog_ipc",
+    "jog_event",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ allowed_extra_keys: ["extra1"] }),
+  ],
+  [
+    "memory_distribution",
+    "jog_ipc",
+    "jog_memory_dist",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ memory_unit: "megabyte" }),
+  ],
+  [
+    "timing_distribution",
+    "jog_ipc",
+    "jog_timing_dist",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ time_unit: "nanosecond" }),
+  ],
+  [
+    "custom_distribution",
+    "jog_ipc",
+    "jog_custom_dist",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({
+      range_min: 1,
+      range_max: 2147483646,
+      bucket_count: 10,
+      histogram_type: "linear",
+    }),
+  ],
+  [
+    "labeled_counter",
+    "jog_ipc",
+    "jog_labeled_counter",
+    ["test-only"],
+    `"ping"`,
+    false,
+  ],
+  [
+    "labeled_counter",
+    "jog_ipc",
+    "jog_labeled_counter_err",
+    ["test-only"],
+    `"ping"`,
+    false,
+  ],
+  [
+    "labeled_counter",
+    "jog_ipc",
+    "jog_labeled_counter_with_labels",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ labels: ["label_1", "label_2"] }),
+  ],
+  [
+    "labeled_counter",
+    "jog_ipc",
+    "jog_labeled_counter_with_labels_err",
+    ["test-only"],
+    `"ping"`,
+    false,
+    JSON.stringify({ labels: ["label_1", "label_2"] }),
+  ],
+  ["rate", "jog_ipc", "jog_rate", ["test-only"], `"ping"`, false],
+];
+
+add_task({ skip_if: () => runningInParent }, async function run_child_stuff() {
+  for (let metric of METRICS) {
+    Services.fog.testRegisterRuntimeMetric(...metric);
+  }
+  Glean.jogIpc.jogCounter.add(COUNT);
+  Glean.jogIpc.jogStringList.add(STRING);
+  Glean.jogIpc.jogStringList.add(ANOTHER_STRING);
+
+  Glean.jogIpc.jogEventNoExtra.record();
+  Glean.jogIpc.jogEvent.record(EVENT_EXTRA);
+
+  for (let memory of MEMORIES) {
+    Glean.jogIpc.jogMemoryDist.accumulate(memory);
+  }
+
+  let t1 = Glean.jogIpc.jogTimingDist.start();
+  let t2 = Glean.jogIpc.jogTimingDist.start();
+
+  await sleep(5);
+
+  let t3 = Glean.jogIpc.jogTimingDist.start();
+  Glean.jogIpc.jogTimingDist.cancel(t1);
+
+  await sleep(5);
+
+  Glean.jogIpc.jogTimingDist.stopAndAccumulate(t2); // 10ms
+  Glean.jogIpc.jogTimingDist.stopAndAccumulate(t3); // 5ms
+
+  Glean.jogIpc.jogCustomDist.accumulateSamples([3, 4]);
+
+  Glean.jogIpc.jogLabeledCounter.label_1.add(COUNTERS_1);
+  Glean.jogIpc.jogLabeledCounter.label_2.add(COUNTERS_2);
+
+  Glean.jogIpc.jogLabeledCounterErr.InvalidLabel.add(INVALID_COUNTERS);
+
+  Glean.jogIpc.jogLabeledCounterWithLabels.label_1.add(COUNTERS_1);
+  Glean.jogIpc.jogLabeledCounterWithLabels.label_2.add(COUNTERS_2);
+
+  Glean.jogIpc.jogLabeledCounterWithLabelsErr.InvalidLabel.add(
+    INVALID_COUNTERS
+  );
+
+  Glean.jogIpc.jogRate.addToNumerator(44);
+  Glean.jogIpc.jogRate.addToDenominator(14);
+});
+
+add_task(
+  { skip_if: () => !runningInParent },
+  async function test_child_metrics() {
+    for (let metric of METRICS) {
+      Services.fog.testRegisterRuntimeMetric(...metric);
+    }
+    await run_test_in_child("test_JOGIPC.js");
+    await Services.fog.testFlushAllChildren();
+
+    Assert.equal(Glean.jogIpc.jogCounter.testGetValue(), COUNT);
+
+    // Note: this will break if string list ever rearranges its items.
+    const strings = Glean.jogIpc.jogStringList.testGetValue();
+    Assert.deepEqual(strings, [STRING, ANOTHER_STRING]);
+
+    const data = Glean.jogIpc.jogMemoryDist.testGetValue();
+    Assert.equal(MEMORIES.reduce((a, b) => a + b, 0) * 1024 * 1024, data.sum);
+    for (let [bucket, count] of Object.entries(data.values)) {
+      // We could assert instead, but let's skip to save the logspam.
+      if (count == 0) {
+        continue;
+      }
+      Assert.ok(count == 1 && MEMORY_BUCKETS.includes(bucket));
+    }
+
+    const customData = Glean.jogIpc.jogCustomDist.testGetValue();
+    Assert.equal(3 + 4, customData.sum, "Sum's correct");
+    for (let [bucket, count] of Object.entries(customData.values)) {
+      Assert.ok(
+        count == 0 || (count == 2 && bucket == 1), // both values in the low bucket
+        `Only two buckets have a sample ${bucket} ${count}`
+      );
+    }
+
+    let events = Glean.jogIpc.jogEventNoExtra.testGetValue();
+    Assert.equal(1, events.length);
+    Assert.equal("jog_ipc", events[0].category);
+    Assert.equal("jog_event_no_extra", events[0].name);
+
+    events = Glean.jogIpc.jogEvent.testGetValue();
+    Assert.equal(1, events.length);
+    Assert.equal("jog_ipc", events[0].category);
+    Assert.equal("jog_event", events[0].name);
+    Assert.deepEqual(EVENT_EXTRA, events[0].extra);
+
+    const NANOS_IN_MILLIS = 1e6;
+    const EPSILON = 40000; // bug 1701949
+    const times = Glean.jogIpc.jogTimingDist.testGetValue();
+    Assert.greater(times.sum, 15 * NANOS_IN_MILLIS - EPSILON);
+    // We can't guarantee any specific time values (thank you clocks),
+    // but we can assert there are only two samples.
+    Assert.equal(
+      2,
+      Object.entries(times.values).reduce(
+        (acc, [bucket, count]) => acc + count,
+        0
+      )
+    );
+
+    const labeledCounter = Glean.jogIpc.jogLabeledCounter;
+    Assert.equal(labeledCounter.label_1.testGetValue(), COUNTERS_1);
+    Assert.equal(labeledCounter.label_2.testGetValue(), COUNTERS_2);
+
+    Assert.throws(
+      () => Glean.jogIpc.jogLabeledCounterErr.__other__.testGetValue(),
+      /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+      "Invalid labels record errors, which throw"
+    );
+
+    const labeledCounterWLabels = Glean.jogIpc.jogLabeledCounterWithLabels;
+    Assert.equal(labeledCounterWLabels.label_1.testGetValue(), COUNTERS_1);
+    Assert.equal(labeledCounterWLabels.label_2.testGetValue(), COUNTERS_2);
+
+    // TODO:(bug 1766515) - This should throw.
+    /*Assert.throws(
+      () =>
+        Glean.jogIpc.jogLabeledCounterWithLabelsErr.__other__.testGetValue(),
+      /NS_ERROR_LOSS_OF_SIGNIFICANT_DATA/,
+      "Invalid labels record errors, which throw"
+    );*/
+    Assert.equal(
+      Glean.jogIpc.jogLabeledCounterWithLabelsErr.__other__.testGetValue(),
+      INVALID_COUNTERS
+    );
+
+    Assert.deepEqual(
+      { numerator: 44, denominator: 14 },
+      Glean.jogIpc.jogRate.testGetValue()
+    );
+  }
+);
diff --git a/toolkit/components/glean/tests/xpcshell/test_MillionQ.js b/toolkit/components/glean/tests/xpcshell/test_MillionQ.js
new file mode 100644
index 0000000000..d98e73b451
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/test_MillionQ.js
@@ -0,0 +1,19 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_task(function test_queue_longer_than_1k() {
+  // FOG needs a profile directory to put its data in.
+  do_get_profile();
+
+  // Before init, try and fill the preinit queue with > 1000 tasks.
+  const kIterations = 2000;
+  for (let _i = 0; _i < kIterations; _i++) {
+    Glean.testOnly.badCode.add(1);
+  }
+
+  Services.fog.initializeFOG();
+
+  Assert.equal(kIterations, Glean.testOnly.badCode.testGetValue());
+});
diff --git a/toolkit/components/glean/tests/xpcshell/xpcshell.ini b/toolkit/components/glean/tests/xpcshell/xpcshell.ini
new file mode 100644
index 0000000000..01c527d865
--- /dev/null
+++ b/toolkit/components/glean/tests/xpcshell/xpcshell.ini
@@ -0,0 +1,30 @@
+# Please keep test files lexicographically sorted, with whitespace between.
+[DEFAULT]
+firefox-appdir = browser
+head = head.js
+
+[test_FOGInit.js]
+
+[test_FOGIPCLimit.js]
+
+[test_FOGPrefs.js]
+skip-if = os == "android" # FOG isn't responsible for monitoring prefs and controlling upload on Android
+
+[test_GIFFT.js]
+run-sequentially = very high failure rate in parallel
+
+[test_GIFFTIPC.js]
+
+[test_Glean.js]
+
+[test_GleanIPC.js]
+
+[test_GleanExperiments.js]
+skip-if = os == "android" # FOG isn't responsible for experiment annotations on Android
+
+[test_JOG.js]
+
+[test_JOGIPC.js]
+
+[test_MillionQ.js]
+skip-if = os == "android" # Android inits its own FOG, so the test won't work.
diff --git a/toolkit/components/glean/xpcom/FOG.cpp b/toolkit/components/glean/xpcom/FOG.cpp
new file mode 100644
index 0000000000..a113ae86d9
--- /dev/null
+++ b/toolkit/components/glean/xpcom/FOG.cpp
@@ -0,0 +1,363 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/FOG.h"
+
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/FOGIPC.h"
+#include "mozilla/glean/bindings/Common.h"
+#include "mozilla/glean/bindings/jog/jog_ffi_generated.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "mozilla/glean/GleanMetrics.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/ShutdownPhase.h"
+#include "mozilla/Unused.h"
+#include "nsContentUtils.h"
+#include "nsIFOG.h"
+#include "nsIUserIdleService.h"
+#include "nsServiceManagerUtils.h"
+
+namespace mozilla {
+
+using glean::LogToBrowserConsole;
+
+#ifdef MOZ_GLEAN_ANDROID
+// Defined by `glean-core`. We reexport it here for later use.
+extern "C" NS_EXPORT void glean_enable_logging(void);
+
+// Workaround to force a re-export of the `no_mangle` symbols from `glean-core`
+//
+// Due to how linking works and hides symbols the symbols from `glean-core`
+// might not be re-exported and thus not usable. By forcing use of _at least
+// one_ symbol in an exported function the functions will also be rexported.
+//
+// See also https://github.com/rust-lang/rust/issues/50007
+extern "C" NS_EXPORT void _fog_force_reexport_donotcall(void) {
+  glean_enable_logging();
+}
+#endif
+
+static StaticRefPtr<FOG> gFOG;
+
+// We wait for 5s of idle before dumping IPC and flushing ping data to disk.
+// This number hasn't been tuned, so if you have a reason to change it,
+// please by all means do.
+const uint32_t kIdleSecs = 5;
+
+// static
+already_AddRefed<FOG> FOG::GetSingleton() {
+  if (gFOG) {
+    return do_AddRef(gFOG);
+  }
+
+  gFOG = new FOG();
+
+  if (XRE_IsParentProcess()) {
+    nsresult rv;
+    nsCOMPtr<nsIUserIdleService> idleService =
+        do_GetService("@mozilla.org/widget/useridleservice;1", &rv);
+    NS_ENSURE_SUCCESS(rv, nullptr);
+    MOZ_ASSERT(idleService);
+    if (NS_WARN_IF(NS_FAILED(idleService->AddIdleObserver(gFOG, kIdleSecs)))) {
+      glean::fog::failed_idle_registration.Set(true);
+    }
+
+    RunOnShutdown(
+        [&] {
+          nsresult rv;
+          nsCOMPtr<nsIUserIdleService> idleService =
+              do_GetService("@mozilla.org/widget/useridleservice;1", &rv);
+          if (NS_SUCCEEDED(rv)) {
+            MOZ_ASSERT(idleService);
+            Unused << idleService->RemoveIdleObserver(gFOG, kIdleSecs);
+          }
+          gFOG->Shutdown();
+          gFOG = nullptr;
+        },
+        ShutdownPhase::XPCOMShutdown);
+  }
+  return do_AddRef(gFOG);
+}
+
+void FOG::Shutdown() {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  glean::impl::fog_shutdown();
+}
+
+NS_IMETHODIMP
+FOG::InitializeFOG(const nsACString& aDataPathOverride,
+                   const nsACString& aAppIdOverride) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  return glean::impl::fog_init(&aDataPathOverride, &aAppIdOverride);
+}
+
+NS_IMETHODIMP
+FOG::RegisterCustomPings() {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  glean::impl::fog_register_pings();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+FOG::SetLogPings(bool aEnableLogPings) {
+#ifdef MOZ_GLEAN_ANDROID
+  return NS_OK;
+#else
+  MOZ_ASSERT(XRE_IsParentProcess());
+  return glean::impl::fog_set_log_pings(aEnableLogPings);
+#endif
+}
+
+NS_IMETHODIMP
+FOG::SetTagPings(const nsACString& aDebugTag) {
+#ifdef MOZ_GLEAN_ANDROID
+  return NS_OK;
+#else
+  MOZ_ASSERT(XRE_IsParentProcess());
+  return glean::impl::fog_set_debug_view_tag(&aDebugTag);
+#endif
+}
+
+NS_IMETHODIMP
+FOG::SendPing(const nsACString& aPingName) {
+#ifdef MOZ_GLEAN_ANDROID
+  return NS_OK;
+#else
+  MOZ_ASSERT(XRE_IsParentProcess());
+  return glean::impl::fog_submit_ping(&aPingName);
+#endif
+}
+
+NS_IMETHODIMP
+FOG::SetExperimentActive(const nsACString& aExperimentId,
+                         const nsACString& aBranch, JS::HandleValue aExtra,
+                         JSContext* aCx) {
+#ifdef MOZ_GLEAN_ANDROID
+  NS_WARNING("Don't set experiments from Gecko in Android. Ignoring.");
+  return NS_OK;
+#else
+  MOZ_ASSERT(XRE_IsParentProcess());
+  nsTArray<nsCString> extraKeys;
+  nsTArray<nsCString> extraValues;
+  if (!aExtra.isNullOrUndefined()) {
+    JS::RootedObject obj(aCx, &aExtra.toObject());
+    JS::Rooted<JS::IdVector> keys(aCx, JS::IdVector(aCx));
+    if (!JS_Enumerate(aCx, obj, &keys)) {
+      LogToBrowserConsole(nsIScriptError::warningFlag,
+                          u"Failed to enumerate experiment extras object."_ns);
+      return NS_OK;
+    }
+
+    for (size_t i = 0, n = keys.length(); i < n; i++) {
+      nsAutoJSCString jsKey;
+      if (!jsKey.init(aCx, keys[i])) {
+        LogToBrowserConsole(
+            nsIScriptError::warningFlag,
+            u"Extra dictionary should only contain string keys."_ns);
+        return NS_OK;
+      }
+
+      JS::Rooted<JS::Value> value(aCx);
+      if (!JS_GetPropertyById(aCx, obj, keys[i], &value)) {
+        LogToBrowserConsole(nsIScriptError::warningFlag,
+                            u"Failed to get experiment extra property."_ns);
+        return NS_OK;
+      }
+
+      nsAutoJSCString jsValue;
+      if (!value.isString()) {
+        LogToBrowserConsole(
+            nsIScriptError::warningFlag,
+            u"Experiment extra properties must have string values."_ns);
+        return NS_OK;
+      }
+
+      if (!jsValue.init(aCx, value)) {
+        LogToBrowserConsole(nsIScriptError::warningFlag,
+                            u"Can't extract experiment extra property"_ns);
+        return NS_OK;
+      }
+
+      extraKeys.AppendElement(jsKey);
+      extraValues.AppendElement(jsValue);
+    }
+  }
+  glean::impl::fog_set_experiment_active(&aExperimentId, &aBranch, &extraKeys,
+                                         &extraValues);
+  return NS_OK;
+#endif
+}
+
+NS_IMETHODIMP
+FOG::SetExperimentInactive(const nsACString& aExperimentId) {
+#ifdef MOZ_GLEAN_ANDROID
+  NS_WARNING("Don't unset experiments from Gecko in Android. Ignoring.");
+  return NS_OK;
+#else
+  MOZ_ASSERT(XRE_IsParentProcess());
+  glean::impl::fog_set_experiment_inactive(&aExperimentId);
+  return NS_OK;
+#endif
+}
+
+NS_IMETHODIMP
+FOG::TestGetExperimentData(const nsACString& aExperimentId, JSContext* aCx,
+                           JS::MutableHandleValue aResult) {
+#ifdef MOZ_GLEAN_ANDROID
+  NS_WARNING("Don't test experiments from Gecko in Android. Throwing.");
+  aResult.set(JS::UndefinedValue());
+  return NS_ERROR_FAILURE;
+#else
+  MOZ_ASSERT(XRE_IsParentProcess());
+  if (!glean::impl::fog_test_is_experiment_active(&aExperimentId)) {
+    aResult.set(JS::UndefinedValue());
+    return NS_OK;
+  }
+
+  // We could struct-up the branch and extras and do what
+  // EventMetric::TestGetValue does... but keeping allocation on this side feels
+  // cleaner to me at the moment.
+  nsCString branch;
+  nsTArray<nsCString> extraKeys;
+  nsTArray<nsCString> extraValues;
+
+  glean::impl::fog_test_get_experiment_data(&aExperimentId, &branch, &extraKeys,
+                                            &extraValues);
+  MOZ_ASSERT(extraKeys.Length() == extraValues.Length());
+
+  JS::RootedObject jsExperimentDataObj(aCx, JS_NewPlainObject(aCx));
+  if (NS_WARN_IF(!jsExperimentDataObj)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  JS::RootedValue jsBranchStr(aCx);
+  if (!dom::ToJSValue(aCx, branch, &jsBranchStr) ||
+      !JS_DefineProperty(aCx, jsExperimentDataObj, "branch", jsBranchStr,
+                         JSPROP_ENUMERATE)) {
+    NS_WARNING("Failed to define branch for experiment data object.");
+    return NS_ERROR_FAILURE;
+  }
+
+  JS::RootedObject jsExtraObj(aCx, JS_NewPlainObject(aCx));
+  if (!JS_DefineProperty(aCx, jsExperimentDataObj, "extra", jsExtraObj,
+                         JSPROP_ENUMERATE)) {
+    NS_WARNING("Failed to define extra for experiment data object.");
+    return NS_ERROR_FAILURE;
+  }
+
+  for (unsigned int i = 0; i < extraKeys.Length(); i++) {
+    JS::RootedValue jsValueStr(aCx);
+    if (!dom::ToJSValue(aCx, extraValues[i], &jsValueStr) ||
+        !JS_DefineProperty(aCx, jsExtraObj, extraKeys[i].Data(), jsValueStr,
+                           JSPROP_ENUMERATE)) {
+      NS_WARNING("Failed to define extra property for experiment data object.");
+      return NS_ERROR_FAILURE;
+    }
+  }
+  aResult.setObject(*jsExperimentDataObj);
+  return NS_OK;
+#endif
+}
+
+NS_IMETHODIMP
+FOG::TestFlushAllChildren(JSContext* aCx, mozilla::dom::Promise** aOutPromise) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  NS_ENSURE_ARG(aOutPromise);
+  *aOutPromise = nullptr;
+  nsIGlobalObject* global = xpc::CurrentNativeGlobal(aCx);
+  if (NS_WARN_IF(!global)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  ErrorResult erv;
+  RefPtr<dom::Promise> promise = dom::Promise::Create(global, erv);
+  if (NS_WARN_IF(erv.Failed())) {
+    return erv.StealNSResult();
+  }
+
+  glean::FlushAndUseFOGData()->Then(
+      GetCurrentSerialEventTarget(), __func__,
+      [promise]() { promise->MaybeResolveWithUndefined(); });
+
+  promise.forget(aOutPromise);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+FOG::Observe(nsISupports* aSubject, const char* aTopic, const char16_t* aData) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // On idle, opportunistically flush child process data to the parent,
+  // then persist ping-lifetime data to the db.
+  if (!strcmp(aTopic, OBSERVER_TOPIC_IDLE)) {
+    glean::FlushAndUseFOGData();
+#ifndef MOZ_GLEAN_ANDROID
+    Unused << glean::impl::fog_persist_ping_lifetime_data();
+#endif
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+FOG::TestResetFOG(const nsACString& aDataPathOverride,
+                  const nsACString& aAppIdOverride) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  return glean::impl::fog_test_reset(&aDataPathOverride, &aAppIdOverride);
+}
+
+NS_IMETHODIMP
+FOG::TestTriggerMetrics(uint32_t aProcessType, JSContext* aCx,
+                        mozilla::dom::Promise** aOutPromise) {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  NS_ENSURE_ARG(aOutPromise);
+  *aOutPromise = nullptr;
+  nsIGlobalObject* global = xpc::CurrentNativeGlobal(aCx);
+  if (NS_WARN_IF(!global)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  ErrorResult erv;
+  RefPtr<dom::Promise> promise = dom::Promise::Create(global, erv);
+  if (NS_WARN_IF(erv.Failed())) {
+    return erv.StealNSResult();
+  }
+
+  glean::TestTriggerMetrics(aProcessType, promise);
+
+  promise.forget(aOutPromise);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+FOG::TestRegisterRuntimeMetric(
+    const nsACString& aType, const nsACString& aCategory,
+    const nsACString& aName, const nsTArray<nsCString>& aPings,
+    const nsACString& aLifetime, const bool aDisabled,
+    const nsACString& aExtraArgs, uint32_t* aMetricIdOut) {
+  *aMetricIdOut = 0;
+  *aMetricIdOut = glean::jog::jog_test_register_metric(
+      &aType, &aCategory, &aName, &aPings, &aLifetime, aDisabled, &aExtraArgs);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+FOG::TestRegisterRuntimePing(const nsACString& aName,
+                             const bool aIncludeClientId,
+                             const bool aSendIfEmpty,
+                             const nsTArray<nsCString>& aReasonCodes,
+                             uint32_t* aPingIdOut) {
+  *aPingIdOut = 0;
+  *aPingIdOut = glean::jog::jog_test_register_ping(&aName, aIncludeClientId,
+                                                   aSendIfEmpty, &aReasonCodes);
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS(FOG, nsIFOG, nsIObserver)
+
+}  //  namespace mozilla
diff --git a/toolkit/components/glean/xpcom/FOG.h b/toolkit/components/glean/xpcom/FOG.h
new file mode 100644
index 0000000000..55e155052e
--- /dev/null
+++ b/toolkit/components/glean/xpcom/FOG.h
@@ -0,0 +1,29 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_FOG_h
+#define mozilla_FOG_h
+
+#include "nsIFOG.h"
+#include "nsIObserver.h"
+
+namespace mozilla {
+class FOG final : public nsIFOG, public nsIObserver {
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIFOG
+  NS_DECL_NSIOBSERVER
+
+ public:
+  FOG() = default;
+  static already_AddRefed<FOG> GetSingleton();
+
+ private:
+  ~FOG() = default;
+  void Shutdown();
+};
+
+};  // namespace mozilla
+
+#endif  // mozilla_FOG_h
diff --git a/toolkit/components/glean/xpcom/components.conf b/toolkit/components/glean/xpcom/components.conf
new file mode 100644
index 0000000000..b5a86537c0
--- /dev/null
+++ b/toolkit/components/glean/xpcom/components.conf
@@ -0,0 +1,18 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Classes = [
+    {
+        'cid': '{98d0e975-9cad-4ce3-ae2f-f878b8be6307}',
+        'contract_ids': ['@mozilla.org/toolkit/glean;1'],
+        'singleton': True,
+        'type': 'mozilla::FOG',
+        'headers': ['mozilla/FOG.h'],
+        'constructor': 'mozilla::FOG::GetSingleton',
+        'js_name': 'fog',
+        'interfaces': ['nsIFOG'],
+    }
+]
diff --git a/toolkit/components/glean/xpcom/moz.build b/toolkit/components/glean/xpcom/moz.build
new file mode 100644
index 0000000000..3a9ededa44
--- /dev/null
+++ b/toolkit/components/glean/xpcom/moz.build
@@ -0,0 +1,27 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+FINAL_LIBRARY = "xul"
+
+EXPORTS.mozilla += [
+    "FOG.h",
+]
+
+UNIFIED_SOURCES += [
+    "FOG.cpp",
+]
+
+XPCOM_MANIFESTS += ["components.conf"]
+
+XPIDL_MODULE = "fog"
+
+XPIDL_SOURCES += [
+    "nsIFOG.idl",
+    "nsIGleanMetrics.idl",
+]
+
+with Files("**"):
+    BUG_COMPONENT = ("Toolkit", "Telemetry")
diff --git a/toolkit/components/glean/xpcom/nsIFOG.idl b/toolkit/components/glean/xpcom/nsIFOG.idl
new file mode 100644
index 0000000000..3c3829db95
--- /dev/null
+++ b/toolkit/components/glean/xpcom/nsIFOG.idl
@@ -0,0 +1,178 @@
+/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 8 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+[scriptable, uuid(98d0e975-9cad-4ce3-ae2f-f878b8be6307)]
+interface nsIFOG : nsISupports
+{
+
+  /**
+   * Initialize FOG.
+   *
+   * To be scheduled at some opportune time after the bulk of Firefox startup
+   * has completed.
+   *
+   * @param aDataPathOverride - The path of a custom Glean data path to use
+   *        instead of the profile dir.
+   * @param aAppIdOverride - The application_id to use instead of
+   *        "firefox.desktop".
+   */
+  void initializeFOG([optional] in AUTF8String aDataPathOverride, [optional] in AUTF8String aAppIdOverride);
+
+  /**
+   * Register custom pings.
+   *
+   * Ensure all custom pings are registered with Glean.
+   */
+  void registerCustomPings();
+
+  /**
+   * Enable or Disable the logging of pings in the Glean SDK.
+   * See https://firefox-source-docs.mozilla.org/toolkit/components/glean/testing.html
+   * for details.
+   *
+   * @param aEnableLogPings - true to enable logging, false to disable.
+   */
+  void setLogPings(in boolean aEnableLogPings);
+
+  /**
+   * Set the tag to be applied to pings assembled from now on.
+   * See https://firefox-source-docs.mozilla.org/toolkit/components/glean/testing.html
+   * for details.
+   *
+   * @param aDebugTag - The string tag to apply.
+   *                    If it cannot be applied (e.g it contains characters that are
+   *                    forbidden in HTTP headers) the old value will remain.
+   */
+  void setTagPings(in ACString aDebugTag);
+
+  /**
+   * Send the named ping.
+   * See https://firefox-source-docs.mozilla.org/toolkit/components/glean/testing.html
+   * for details.
+   *
+   * @param aPingName - The name of the ping to send. If no ping of that name
+   *                    exists, or the ping is known but cannot be assembled
+   *                    (e.g if it is empty), no ping will be sent.
+   */
+  void sendPing(in ACString aPingName);
+
+  /**
+   * Indicate that an experiment is running.
+   * Glean will add an experiment annotation which is sent with pings.
+   * This information is not persisted between runs.
+   *
+   * See `glean_core::Glean::set_experiment_active`.
+   *
+   * Logs on error, but does not throw.
+   *
+   * @param aExperimentId - The id/slug of the experiment.
+   * @param aBranch - The name of the active branch of the experiment.
+   * @param aExtra - Optional string -> string dictionary of extra information.
+   */
+  [implicit_jscontext]
+  void setExperimentActive(in ACString aExperimentId, in ACString aBranch, [optional] in jsval aExtra);
+
+  /**
+   * Indicate that an experiment is no longer running.
+   *
+   * See `glean_core::Glean::set_experiment_inactive`.
+   *
+   * Logs on error, but does not throw.
+   *
+   * @param aExperimentId - The id/slug of the experiment from setExperimentActive.
+   */
+  void setExperimentInactive(in ACString aExperimentId);
+
+  /**
+   * **Test-only API**
+   *
+   * If the identified experiment was set active and hasn't been set inactive,
+   * this will give you the active branch and extra information.
+   *
+   * @param aExperimentId - The id/slug of the experiment from setExperimentActive.
+   *
+   * @return an object of the form
+   *         {branch: "branch-name", extra: {extra_key1: extra_value1, ...}}
+   *         if there is an active experiment. Undefined, otherwise.
+   */
+  [implicit_jscontext]
+  jsval testGetExperimentData(in ACString aExperimentId);
+
+  /**
+   * ** Test-only Method **
+   *
+   * Flush all data from all child processes.
+   *
+   * @returns A promise that resolves when the data's been stored.
+   */
+  [implicit_jscontext]
+  Promise testFlushAllChildren();
+
+  /**
+   * ** Test-only Method **
+   *
+   * Reset FOG and the Glean SDK, clearing storage.
+   */
+  void testResetFOG([optional] in AUTF8String aDataPathOverride, [optional] in AUTF8String aAppIdOverride);
+
+  /**
+   * ** Test-only Method **
+   *
+   * Trigger test metric instrumentation on the GPU, RDD or Socket process.
+   *
+   * @param aProcessType - A PROCESS_TYPE_* value from the constants defined
+   *                       in the nsIXULRuntime interface.
+   *
+   * @returns A promise that resolves when the test data has been added.
+   *          The promise will be rejected if the process type is not supported
+   *          or if sending the IPC to the child process fails.
+   */
+  [implicit_jscontext]
+  Promise testTriggerMetrics(in unsigned long aProcessType);
+
+  /**
+   * ** Test-only Method **
+   *
+   * Register a metric.
+   *
+   * This function is deliberately not too friendly to use. You probably aren't
+   * supposed to use it unless you're testing metric registration itself.
+   *
+   * @param aType - The metric's type.
+   * @param aCategory - The metric's category.
+   * @param aName - The metric's name.
+   * @param aPings - The pings to send it in.
+   * @param aLifetime - The metric's lifetime.
+   * @param aDisabled - Whether the metric, though existing, isn't enabled.
+   * @param aExtraArgs - Optional JSON string of extra args.
+   */
+  uint32_t testRegisterRuntimeMetric(in ACString aType,
+                                 in ACString aCategory,
+                                 in ACString aName,
+                                 in Array<ACString> aPings,
+                                 in ACString aLifetime,
+                                 in boolean aDisabled,
+                                 [optional] in ACString aExtraArgs);
+
+  /**
+   * ** Test-only Method **
+   *
+   * Register a ping.
+   *
+   * This function is deliberately not too friendly to use. You probably aren't
+   * supposed to use it unless you're testing ping registration itself.
+   *
+   * @param aName - The ping's name.
+   * @param aIncludeClientId - Whether the ping should include the client_id.
+   * @param aSendIfEmpty - Whether the ping should send even if empty.
+   * @param aReasonCodes - The list of valid reasons for ping submission.
+   */
+  uint32_t testRegisterRuntimePing(in ACString aName,
+                                   in boolean aIncludeClientId,
+                                   in boolean aSendIfEmpty,
+                                   in Array<ACString> aReasonCodes);
+};
diff --git a/toolkit/components/glean/xpcom/nsIGleanMetrics.idl b/toolkit/components/glean/xpcom/nsIGleanMetrics.idl
new file mode 100644
index 0000000000..b4faf26be5
--- /dev/null
+++ b/toolkit/components/glean/xpcom/nsIGleanMetrics.idl
@@ -0,0 +1,665 @@
+/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 8 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+[scriptable, uuid(d3180fe0-19fa-11eb-8b6f-0800200c9a66)]
+interface nsIGleanBoolean : nsISupports
+{
+  /**
+   * Set to the specified boolean value.
+   *
+   * @param value the value to set.
+   */
+  void set(in bool value);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a boolean.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(aa15fd20-1e8a-11eb-9bec-0800200c9a66)]
+interface nsIGleanDatetime : nsISupports
+{
+  /**
+   * Set the datetime to the provided value, or the local now.
+   * The internal value will store the local timezone.
+   *
+   * Note: The metric's time_unit affects the resolution of the value, not the
+   *       unit of this function's parameter (which is always PRTime/nanos).
+   *
+   * @param aValue The (optional) time value as PRTime (nanoseconds since epoch).
+   *        Defaults to local now.
+   */
+  [optional_argc]
+  void set([optional] in PRTime aValue);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as an integer.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric as a JS Date with timezone,
+   *         or undefined if there is no value.
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(05b89d2a-d57c-11ea-82da-3f63399a6f5a)]
+interface nsIGleanCounter : nsISupports
+{
+  /*
+  * Increases the counter by `amount`.
+  *
+  * @param amount The amount to increase by. Should be positive.
+  */
+  void add(in int32_t amount);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as an integer.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(92e14730-9b5f-45a1-b018-f588d0b964d8)]
+interface nsIGleanTimingDistribution : nsISupports
+{
+  /**
+   * Starts tracking time for the provided metric.
+   *
+   * @returns A unique timer id for the new timer
+   */
+  [implicit_jscontext]
+  jsval start();
+
+  /**
+   * Stops tracking time for the provided metric and timer id.
+   *
+   * Adds a count to the corresponding bucket in the timing distribution.
+   * This will record an error if no `start` was called for this TimerId or
+   * if this TimerId was used to call `cancel`.
+   *
+   * @param aId The TimerId associated with this timing. This allows for
+   *            concurrent timing of events associated with different ids.
+   */
+  void stopAndAccumulate(in uint64_t aId);
+
+  /**
+   * Aborts a previous `start` call. No error is recorded if no `start` was
+   * called. (But then where did you get that id from?)
+   *
+   * @param aId The TimerID whose `start` you wish to abort.
+   */
+  void cancel(in uint64_t aId);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a DistributionData.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in ACString aPingName);
+
+  /**
+   * **Test-only API**
+   *
+   * Accumulates a raw numeric sample of milliseconds.
+   *
+   * Test-only until we find a use-case and decent JS Time Duration type.
+   *
+   * @param aSample The sample, in milliseconds, to add.
+   */
+  void testAccumulateRawMillis(in uint64_t aSample);
+};
+
+[scriptable, uuid(eea5ed46-16ba-46cd-bb1f-504581987fe1)]
+interface nsIGleanMemoryDistribution : nsISupports
+{
+  /*
+   * Accumulates the provided sample in the metric.
+   *
+   * @param aSample The sample to be recorded by the metric. The sample is
+   *                assumed to be in the confgured memory unit of the metric.
+   *
+   * Notes: Values bigger than 1 Terabyte (2^40 bytes) are truncated and an
+   * InvalidValue error is recorded.
+   */
+  void accumulate(in uint64_t aSample);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a DistributionData.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in ACString aPingName);
+};
+
+[scriptable, uuid(45cc016f-c1d5-4d54-aaa5-a802cf65f23b)]
+interface nsIGleanCustomDistribution : nsISupports
+{
+  /*
+   * Accumulates the provided signed samples in the metric.
+   *
+   * @param aSamples - The vector holding the samples to be recorded by the metric.
+   *
+   * Notes: Discards any negative value in `samples`
+   * and report an `ErrorType::InvalidValue` for each of them.
+   */
+  void accumulateSamples(in Array<int64_t> aSamples);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a DistributionData.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in ACString aPingName);
+};
+
+[scriptable, function, uuid(e5447f62-4b03-497c-81e9-6ab683d20380)]
+interface nsIGleanPingTestCallback : nsISupports
+{
+  void call(in ACString aReason);
+};
+
+[scriptable, uuid(5223a48b-687d-47ff-a629-fd4a72d1ecfa)]
+interface nsIGleanPing : nsISupports
+{
+  /**
+   * Collect and submit the ping for eventual upload.
+   *
+   * This will collect all stored data to be included in the ping.
+   * Data with lifetime `ping` will then be reset.
+   *
+   * If the ping is configured with `send_if_empty = false`
+   * and the ping currently contains no content,
+   * it will not be queued for upload.
+   * If the ping is configured with `send_if_empty = true`
+   * it will be queued for upload even if empty.
+   *
+   * Pings always contain the `ping_info` and `client_info` sections.
+   * See [ping sections](https://mozilla.github.io/glean/book/user/pings/index.html#ping-sections)
+   * for details.
+   *
+   * @param aReason - Optional. The reason the ping is being submitted.
+   *                  Must match one of the configured `reason_codes`.
+   */
+  void submit([optional] in ACString aReason);
+
+  /**
+   * **Test-only API**
+   *
+   * Register a callback to be called right before this ping is next submitted.
+   * The provided function is called exactly once before submitting.
+   *
+   * Note: The callback will be called on any call to submit.
+   * A ping might not be sent afterwards, e.g. if the ping is empty and
+   * `send_if_empty` is `false`.
+   *
+   * @param aCallback - The callback to call on the next submit.
+   */
+  void testBeforeNextSubmit(in nsIGleanPingTestCallback aCallback);
+};
+
+[scriptable, uuid(d84a3555-46f1-48c1-9122-e8e88b069d2b)]
+interface nsIGleanString : nsISupports
+{
+  /*
+  * Set to the specified value.
+  *
+  * @param value The string to set the metric to.
+  */
+  void set(in AUTF8String value);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a string.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(46751205-2ac7-47dc-91d2-ef4a95ef2af9)]
+interface nsIGleanStringList : nsISupports
+{
+  /**
+   * Adds a new string to the list.
+   *
+   * Truncates the value and logs an error if it is longer than 50 bytes.
+   *
+   * @param value The string to add.
+   */
+  void add(in AUTF8String value);
+
+  /**
+   * Sets to a specific list of strings.
+   *
+   * Truncates the list and logs an error if longer than 20 items.
+   * Truncates any item longer than 50 bytes and logs an error.
+   *
+   * @param value The list of strings to set.
+   */
+  void set(in Array<AUTF8String> value);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(2586530c-030f-11eb-93cb-cbf30d25225a)]
+interface nsIGleanTimespan : nsISupports
+{
+  /**
+   * Start tracking time for the provided metric.
+   *
+   * This records an error if it’s already tracking time (i.e. start was already
+   * called with no corresponding [stop]): in that case the original
+   * start time will be preserved.
+   */
+  void start();
+
+  /**
+   * Stop tracking time for the provided metric.
+   *
+   * Sets the metric to the elapsed time, but does not overwrite an already
+   * existing value.
+   * This will record an error if no [start] was called or there is an already
+   * existing value.
+   */
+  void stop();
+
+  /**
+   * Aborts a previous start.
+   *
+   * Does not record an error if there was no previous call to start.
+   */
+  void cancel();
+
+  /**
+   * Explicitly sets the timespan value.
+   *
+   * This API should only be used if you cannot make use of
+   * `start`/`stop`/`cancel`.
+   *
+   * @param aDuration The duration of this timespan, in units matching the
+   *        `time_unit` of this metric's definition.
+   */
+  void setRaw(in uint32_t aDuration);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as an integer.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(395700e7-06f6-46be-adcc-ea58977fda6d)]
+interface nsIGleanUuid : nsISupports
+{
+  /**
+   * Set to the specified value.
+   *
+   * @param aValue The UUID to set the metric to.
+   */
+  void set(in AUTF8String aValue);
+
+  /**
+   * Generate a new random UUID and set the metric to it.
+   */
+  void generateAndSet();
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as an integer.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(1b01424a-1f55-11eb-92a5-0754f6c3f240)]
+interface nsIGleanEvent : nsISupports
+{
+  /*
+   * Record an event.
+   *
+   * @param aExtra An (optional) map of extra values.
+   */
+  [implicit_jscontext]
+  void record([optional] in jsval aExtra);
+
+  /**
+   * **Test-only API**
+   *
+   * Get a list of currently stored events for this event metric.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   *
+   * The data is an array of objects:
+   *
+   * ```
+   * [
+   *    {
+   *        timestamp: Integer,
+   *        category: String,
+   *        name: String,
+   *        extra: {
+   *          String: String
+   *          ...
+   *        }
+   *    },
+   *    ...
+   * ]
+   * ```
+   *
+   * The difference between event timestamps is in milliseconds
+   * See https://mozilla.github.io/glean/book/user/metrics/event.html for further details.
+   * Due to limitations of numbers in JavaScript, the timestamp will only be accurate up until 2^53.
+   * (This is probably not an issue with the current clock implementation. Probably.)
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(0558c1b2-2cb1-4e21-a0a0-6a91a35ef219)]
+interface nsIGleanQuantity : nsISupports
+{
+  /**
+   * Set to the specified value.
+   *
+   * @param value the value to set.
+   */
+  void set(in int64_t value);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(394d9d3b-9e7e-48cc-b76c-a89a51830da3)]
+interface nsIGleanDenominator : nsISupports
+{
+  /*
+  * Increases the counter by `amount`.
+  *
+  * @param amount The amount to increase by. Should be positive.
+  */
+  void add(in int32_t amount);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as an integer.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(153fff71-7edd-49b4-a166-4697aa89c7a1)]
+interface nsIGleanNumerator : nsISupports
+{
+  /*
+  * Increases the numerator by `amount`.
+  *
+  * @param amount The amount to increase by. Should be positive.
+  */
+  void addToNumerator(in int32_t amount);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value in the form {numerator: n, denominator: d}
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(920cf631-2b1e-4efe-ae2e-f03277c3112a)]
+interface nsIGleanRate : nsISupports
+{
+  /*
+  * Increases the numerator by `amount`.
+  *
+  * @param amount The amount to increase by. Should be positive.
+  */
+  void addToNumerator(in int32_t amount);
+
+  /*
+  * Increases the denominator by `amount`.
+  *
+  * @param amount The amount to increase by. Should be positive.
+  */
+  void addToDenominator(in int32_t amount);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value in the form {numerator: n, denominator: d}
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};
+
+[scriptable, uuid(a59672c4-bc48-4bfe-8f9c-6f408a59d819)]
+interface nsIGleanUrl : nsISupports
+{
+  /*
+  * Sets to the specified stringified URL.
+  *
+  * @param value The stringified URL to set the metric to.
+  */
+  void set(in AUTF8String value);
+
+  /**
+   * **Test-only API**
+   *
+   * Gets the currently stored value as a string.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or undefined if there is no value.
+   */
+  [implicit_jscontext]
+  jsval testGetValue([optional] in AUTF8String aPingName);
+};