1 files changed, 134 insertions, 0 deletions
diff --git a/toolkit/components/glean/api/src/private/timespan.rs b/toolkit/components/glean/api/src/private/timespan.rs
new file mode 100644
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+++ b/toolkit/components/glean/api/src/private/timespan.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 super::{CommonMetricData, MetricId, TimeUnit};
+
+use glean_core::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),
+    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))
+        }
+    }
+}
+
+#[inherent(pub)]
+impl Timespan for TimespanMetric {
+    fn start(&self) {
+        match self {
+            TimespanMetric::Parent(p) => Timespan::start(p),
+            TimespanMetric::Child => {
+                log::error!("Unable to start timespan metric in non-main process. Ignoring.");
+                // TODO: Record an error.
+            }
+        }
+    }
+
+    fn stop(&self) {
+        match self {
+            TimespanMetric::Parent(p) => Timespan::stop(p),
+            TimespanMetric::Child => {
+                log::error!("Unable to stop timespan metric in non-main process. Ignoring.");
+                // TODO: Record an error.
+            }
+        }
+    }
+
+    fn cancel(&self) {
+        match self {
+            TimespanMetric::Parent(p) => Timespan::cancel(p),
+            TimespanMetric::Child => {
+                log::error!("Unable to cancel timespan metric in non-main process. Ignoring.");
+                // TODO: Record an error.
+            }
+        }
+    }
+
+    fn test_get_value<'a, S: Into<Option<&'a str>>>(&self, ping_name: S) -> Option<u64> {
+        match self {
+            TimespanMetric::Parent(p) => p.test_get_value(ping_name),
+            TimespanMetric::Child => {
+                panic!("Cannot get test value for in non-parent process!");
+            }
+        }
+    }
+
+    fn test_get_num_recorded_errors<'a, S: Into<Option<&'a str>>>(
+        &self,
+        error: glean::ErrorType,
+        ping_name: S,
+    ) -> i32 {
+        match self {
+            TimespanMetric::Parent(p) => p.test_get_num_recorded_errors(error, ping_name),
+            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)
+    }
+}