1 files changed, 186 insertions, 0 deletions
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"
+        );
+    }
+}