[metrics] Add on-demand metrics flush with notify

Allows clients to flush the buffer for metrics data on-demand, e.g.
just before program termination.

bug: b/159458935
Test: Added unit test
Change-Id: I6bd287eb99fba4c153a96a22881efc4353264664
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2478202
Commit-Queue: Hai Bi <bihai@google.com>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818698}

fuchsia/base/legacymetrics_client.cc

@@ -123,6 +123,7 @@ void LegacyMetricsClient::DrainBuffer() {
 
     if (is_flushing_) {
       metrics_recorder_.Unbind();
+      std::move(on_flush_complete_).Run();
     } else {
       ScheduleNextReport();
     }
@@ -154,9 +155,14 @@ void LegacyMetricsClient::OnMetricsRecorderDisconnected(zx_status_t status) {
   timer_.AbandonAndStop();
 }
 
-void LegacyMetricsClient::OnCloseSoon() {
+void LegacyMetricsClient::FlushAndDisconnect(
+    base::OnceClosure on_flush_complete) {
   DVLOG(1) << __func__ << " called.";
+  DCHECK(on_flush_complete);
+  if (is_flushing_)
+    return;
 
+  on_flush_complete_ = std::move(on_flush_complete);
   timer_.AbandonAndStop();
 
   is_flushing_ = true;
@@ -170,4 +176,8 @@ void LegacyMetricsClient::OnCloseSoon() {
   }
 }
 
+void LegacyMetricsClient::OnCloseSoon() {
+  FlushAndDisconnect(base::DoNothing::Once());
+}
+
 }  // namespace cr_fuchsia

fuchsia/base/legacymetrics_client.h

@@ -57,6 +57,11 @@ class LegacyMetricsClient {
   // |callback| should be invoked to signal flush completion.
   void SetNotifyFlushCallback(NotifyFlushCallback callback);
 
+  // Use when caller needs an explicit flush and then disconnect, such as before
+  // termination. Caller will be notified when all events in the buffer are
+  // sent.
+  void FlushAndDisconnect(base::OnceClosure on_flush_complete);
+
  private:
   void ScheduleNextReport();
   void StartReport();
@@ -79,6 +84,8 @@ class LegacyMetricsClient {
   base::RetainingOneShotTimer timer_;
   SEQUENCE_CHECKER(sequence_checker_);
 
+  base::OnceClosure on_flush_complete_;
+
   // Prevents use-after-free if |report_additional_callback_| is invoked after
   // |this| is destroyed.
   base::WeakPtrFactory<LegacyMetricsClient> weak_factory_{this};

fuchsia/base/legacymetrics_client_unittest.cc

@@ -10,6 +10,7 @@
 #include "base/fuchsia/scoped_service_binding.h"
 #include "base/fuchsia/test_component_context_for_process.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/test/bind_test_util.h"
 #include "base/test/task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "fuchsia/base/legacymetrics_client.h"
@@ -317,5 +318,46 @@ TEST_F(LegacyMetricsClientTest, ExternalFlushSignal) {
   EXPECT_TRUE(test_recorder_.IsRecordInFlight());
 }
 
+TEST_F(LegacyMetricsClientTest, ExplicitFlush) {
+  client_.Start(kReportInterval);
+
+  base::RecordComputedAction("bar");
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(test_recorder_.IsRecordInFlight());
+
+  bool called = false;
+  client_.FlushAndDisconnect(
+      base::BindLambdaForTesting([&called] { called = true; }));
+  base::RunLoop().RunUntilIdle();
+  EXPECT_TRUE(test_recorder_.IsRecordInFlight());
+  EXPECT_FALSE(called);
+
+  auto events = test_recorder_.WaitForEvents();
+  EXPECT_EQ(1u, events.size());
+  EXPECT_EQ("bar", events[0].user_action_event().name());
+
+  test_recorder_.SendAck();
+  base::RunLoop().RunUntilIdle();
+  EXPECT_TRUE(called);
+}
+
+TEST_F(LegacyMetricsClientTest, ExplicitFlushMultipleBatches) {
+  const size_t kSizeForMultipleBatches = LegacyMetricsClient::kMaxBatchSize * 2;
+  client_.Start(kReportInterval);
+
+  for (size_t i = 0; i < kSizeForMultipleBatches; ++i)
+    base::RecordComputedAction("bar");
+
+  client_.FlushAndDisconnect(base::DoNothing::Once());
+  base::RunLoop().RunUntilIdle();
+  test_recorder_.SendAck();
+  base::RunLoop().RunUntilIdle();
+
+  auto events = test_recorder_.WaitForEvents();
+  EXPECT_EQ(kSizeForMultipleBatches, events.size());
+  for (size_t i = 0; i < kSizeForMultipleBatches; ++i)
+    EXPECT_EQ("bar", events[i].user_action_event().name());
+}
+
 }  // namespace
 }  // namespace cr_fuchsia