Battery impact UMA

content/browser/power_usage_monitor_impl.h

+// Copyright (c) 2014 The Chromium Authors. All rights reserved.

[Daniel Erat, 2014/09/22 16:10:20]

nit: we don't use (c) on new files

[jeremy, 2014/09/29 06:27:15]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_CONTENT_BROWSER_POWER_USAGE_MONITOR_IMPL_H_
+#define CHROME_CONTENT_BROWSER_POWER_USAGE_MONITOR_IMPL_H_
+
+#include "base/basictypes.h"
+#include "base/containers/hash_tables.h"
+#include "base/memory/singleton.h"
+#include "base/power_monitor/power_monitor.h"
+#include "base/time/time.h"
+#include "content/browser/battery_status/battery_status_service.h"
+#include "content/public/browser/browser_message_filter.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+#include "third_party/WebKit/public/platform/WebBatteryStatus.h"
+
+namespace content {
+
+// Record statistics on power usage.
+//
+// Two main statics are recorded by this class:
+// * Power.BatteryDischarge_{5,15,30} - delta between battery level when
+//   unplugged from wallpower, over the specified period - in minutes.
+// * Power.BatteryDischargeRateWhenUnplugged - the rate of battery discharge
+//   from the device being unplugged until it's plugged back in, if said period
+//   was longer than 30 minutes.
+//
+// Heuristics:
+// * Metrics are only collected once per day.
+// * If the machine goes to sleep or all renderers are closed then the current
+//   measurement is cancelled.
+//
+// Threading: Most methods are called on the IO thread.
+class PowerUsageMonitor : base::PowerObserver, NotificationObserver {
+ public:
+  class HistogramRecorder {
+   public:
+    HistogramRecorder();
+    virtual ~HistogramRecorder();
+
+    virtual void ReportBatteryLevelHistogram(base::TimeDelta discharge_time);
+
+    void CancelPendingHistgramReports();
+    base::WeakPtr<HistogramRecorder> GetWeakPtr() {
+        return weak_ptr_factory_.GetWeakPtr();
+    }
+
+    // Used to cancel in progress timers.
+    base::WeakPtrFactory<HistogramRecorder> weak_ptr_factory_;
+  };
+
+ public:
+  // Returns the PowerUsageMonitor singleton.
+  static PowerUsageMonitor* GetInstance();
+
+  // Start monitoring power usage.
+  void Initialize();
+  void StartOnIOThread();
+
+  void OnBatteryStatusUpdate(const blink::WebBatteryStatus& status);
+
+  double DischargeAmount() {
+    return initial_battery_level_ - current_battery_level_;
+  }
+
+  // Called by HistogramRecorder after a histogram was succesfully recorded.
+  void BatteryLevelReported();
+
+  void SetHistogramRecorderForTest(scoped_ptr<HistogramRecorder> recorder);
+
+  // POverridden from basde::PowerObserver:
+  virtual void OnPowerStateChange(bool on_battery_power) OVERRIDE {};
+  virtual void OnResume() OVERRIDE {};
+  virtual void OnSuspend() OVERRIDE;
+
+  // Overridden from NotificationObserver:
+  virtual void Observe(int type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details) OVERRIDE;
+
+
+ private:
+  friend struct DefaultSingletonTraits<PowerUsageMonitor>;
+
+  PowerUsageMonitor();
+  virtual ~PowerUsageMonitor();
+
+  void ReportBatteryLevelHistogram(base::Time discharge_time);
+  void DischargeStarted(double battery_level);
+  void WallPowerConnected(double battery_level);
+
+  void CancelPendingHistogramRecordingOnIOThread();
+
+  BatteryStatusService::BatteryUpdateCallback callback_;
+  scoped_ptr<BatteryStatusService::BatteryUpdateSubscription> subscription_;
+
+  NotificationRegistrar registrar_;
+
+  scoped_ptr<HistogramRecorder> histogram_recorder_;
+
+  bool was_on_battery_power_;
+  double initial_battery_level_;
+  double current_battery_level_;
+  base::Time start_discharge_time_;
+
+  // Timestamp for when the first histogram is reported in a 24 hour period.
+  // Used for rate-limiting.
+  base::Time first_histogram_report_timestamp_;
+
+  base::hash_map<int, int> live_renderers_;

[Daniel Erat, 2014/09/22 16:10:20]

any particular reason to use base::hash_map here instead of std::map? this is
probably small, right?

[jeremy, 2014/09/29 06:27:15]

I've changed this to base::hash_set since that's all I really need. Happy to
change to std::map or whatever you think is best.

+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PowerUsageMonitor);
+};
+
+}  // namespace content
+
+#endif  // CHROME_CONTENT_BROWSER_POWER_USAGE_MONITOR_IMPL_H_