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diff --git a/toolkit/components/glean/api/src/private/string.rs b/toolkit/components/glean/api/src/private/string.rs
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+++ b/toolkit/components/glean/api/src/private/string.rs
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+// 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"
+        );
+    }
+}