Add a feature to control if we drop records due to excess events. Enabled by default as this is cur…

components/metrics/metrics_service.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 //------------------------------------------------------------------------------
 // Description of the life cycle of a instance of MetricsService.
 //
 //  OVERVIEW
 //
 // A MetricsService instance is typically created at application startup.  It is
@@ skipping 160 matching lines @@
 
 namespace {
 
 // This feature moves the upload schedule to a seperate schedule from the
 // log rotation schedule.  This may change upload timing slightly, but
 // would allow some compartmentalization of uploader logic to allow more
 // code reuse between different metrics services.
 const base::Feature kUploadSchedulerFeature{"UMAUploadScheduler",
                                             base::FEATURE_DISABLED_BY_DEFAULT};
 
+// This drops records if the number of events (user action and omnibox) exceeds
+// the kEventLimit.
+const base::Feature kUMAThrottleEvents{"UMAThrottleEvents",
+                                       base::FEATURE_ENABLED_BY_DEFAULT};
+
 bool HasUploadScheduler() {
   return base::FeatureList::IsEnabled(kUploadSchedulerFeature);
 }
 
 // Check to see that we're being called on only one thread.
 bool IsSingleThreaded() {
   static base::PlatformThreadId thread_id = 0;
   if (!thread_id)
     thread_id = base::PlatformThread::CurrentId();
   return base::PlatformThread::CurrentId() == thread_id;
@@ skipping 605 matching lines @@
 void MetricsService::StartInitTask() {
   client_->InitializeSystemProfileMetrics(
       base::Bind(&MetricsService::FinishedInitTask,
                  self_ptr_factory_.GetWeakPtr()));
 }
 
 void MetricsService::CloseCurrentLog() {
   if (!log_manager_.current_log())
     return;
 
-  // TODO(jar): Integrate bounds on log recording more consistently, so that we
-  // can stop recording logs that are too big much sooner.
+  // TODO(rkaplow): Evaluate if this is needed.
   if (log_manager_.current_log()->num_events() > kEventLimit) {
     UMA_HISTOGRAM_COUNTS("UMA.Discarded Log Events",
                          log_manager_.current_log()->num_events());
-    log_manager_.DiscardCurrentLog();
-    OpenNewLog();  // Start trivial log to hold our histograms.
+    if (base::FeatureList::IsEnabled(kUMAThrottleEvents)) {
+      log_manager_.DiscardCurrentLog();
+      OpenNewLog();  // Start trivial log to hold our histograms.
+    }
   }
 
   // If a persistent allocator is in use, update its internal histograms (such
   // as how much memory is being used) before reporting.
   base::PersistentHistogramAllocator* allocator =
       base::GlobalHistogramAllocator::Get();
   if (allocator)
     allocator->UpdateTrackingHistograms();
 
   // Put incremental data (histogram deltas, and realtime stats deltas) at the
@@ skipping 483 matching lines @@
   local_state_->SetBoolean(prefs::kStabilitySessionEndCompleted, end_completed);
   RecordCurrentState(local_state_);
 }
 
 void MetricsService::RecordCurrentState(PrefService* pref) {
   pref->SetInt64(prefs::kStabilityLastTimestampSec,
                  base::Time::Now().ToTimeT());
 }
 
 }  // namespace metrics