1 files changed, 70 insertions, 0 deletions
diff --git a/toolkit/components/glean/bindings/GleanMetric.cpp b/toolkit/components/glean/bindings/GleanMetric.cpp
new file mode 100644
index 0000000000..cb15432913
--- /dev/null
+++ b/toolkit/components/glean/bindings/GleanMetric.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/GleanMetric.h"
+
+#include "nsThreadUtils.h"
+#include "nsWrapperCache.h"
+#include "mozilla/AppShutdown.h"
+#include "mozilla/ClearOnShutdown.h"
+
+namespace mozilla::glean {
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(GleanMetric, mParent)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(GleanMetric)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(GleanMetric)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(GleanMetric)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+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 mozilla::glean