Battery impact UMA

content/browser/power_usage_monitor_impl.h

+// 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.
+
+#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/gtest_prod_util.h"
+#include "base/memory/singleton.h"
+#include "base/power_monitor/power_monitor.h"
+#include "base/time/time.h"
+#include "content/common/content_export.h"
+#include "content/public/browser/browser_message_filter.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+#include "device/battery/battery_status_service.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:
+// * Data collection starts after system uptime exceeds 30 minutes.
+// * If the machine goes to sleep or all renderers are closed then the current
+//   measurement is cancelled.
+class CONTENT_EXPORT PowerUsageMonitor : public base::PowerObserver,
+                                         public NotificationObserver {
+ public:
+  class SystemInterface {
+   public:
+    virtual ~SystemInterface() {}
+
+    virtual void ScheduleHistogramReport(base::TimeDelta delay) = 0;
+    virtual void CancelPendingHistogramReports() = 0;
+
+    // Record the battery discharge percent per hour over the time the system
+    // is on battery power, legal values [0,100].
+    virtual void RecordDischargePercentPerHour(int percent_per_hour) = 0;
+
+    // Allow tests to override clock.
+    virtual base::Time Now() = 0;
+  };
+
+ public:
+  PowerUsageMonitor();
+  ~PowerUsageMonitor() override;
+
+  double discharge_amount() const {
+    return initial_battery_level_ - current_battery_level_;
+  }
+
+  // Start monitoring power usage.
+  // Note that the actual monitoring will be delayed until 30 minutes after
+  // system boot.
+  void Start();
+
+  void SetSystemInterfaceForTest(scoped_ptr<SystemInterface> interface);
+
+  // Overridden from base::PowerObserver:
+  void OnPowerStateChange(bool on_battery_power) override;
+  void OnResume() override;
+  void OnSuspend() override;
+
+  // Overridden from NotificationObserver:
+  void Observe(int type,
+               const NotificationSource& source,
+               const NotificationDetails& details) override;
+
+ private:
+  friend class PowerUsageMonitorTest;
+  FRIEND_TEST_ALL_PREFIXES(PowerUsageMonitorTest, OnBatteryStatusUpdate);
+  FRIEND_TEST_ALL_PREFIXES(PowerUsageMonitorTest, OnRenderProcessNotification);
+
+  // Start monitoring system power usage.
+  // This function may be called after a delay, see Start() for details.
+  void StartInternal();
+
+  void OnBatteryStatusUpdate(const device::BatteryStatus& status);
+  void OnRenderProcessNotification(int type, int rph_id);
+
+  void DischargeStarted(double battery_level);
+  void WallPowerConnected(double battery_level);
+
+  void CancelPendingHistogramReporting();
+
+  device::BatteryStatusService::BatteryUpdateCallback callback_;
+  scoped_ptr<device::BatteryStatusService::BatteryUpdateSubscription>

[ppi, 2014/11/16 16:03:08]

From the point of view of Mojo-fication of browser services, I'm worried about
hooking this up directly to BatteryStatusService.

BatteryStatusService is an implementation detail of one particular
implementation of the abstract BatteryMonitor service. Right now we have only
one implementation, so hooking this up here would work on all platforms, but
we're working on having entirely independent implementation for Android. Once
this change is done, we would stop recording UMA on Android.

Ideally, instead of talking to BatteryStatusService, PowerUsageMonitor would
connect to the battery monitor Mojo service as a client, just like the renderer
does. This way we'd be isolated from any implementation details of the service.

Could you explore going this way? I'd be happy to help with the Mojo-specific
bits.

[jeremy, 2014/11/17 07:50:48]

Thanks, wasn't aware of that.

Unless you are strongly opposed, I'd like to land this as is and then look into
porting this to use the Mojo service.  The lead time on getting numbers from the
stable channel for these UMAs is quite large so I'd like to get the clock
ticking.
If the underlying Mojo service is ready I can work with you next week to port
the code to use the preferred interface.

[ppi, 2014/11/17 10:51:01]

Porting to Mojo in a separate CL sounds good, thanks.

+      subscription_;
+
+  NotificationRegistrar registrar_;
+
+  scoped_ptr<SystemInterface> system_interface_;
+
+  // True if monitoring was started (Start() called).
+  bool started_;
+
+  // True if collecting metrics for the current discharge cycle e.g. if no
+  // renderers are open we don't keep track of discharge.
+  bool tracking_discharge_;
+
+  // True if the system is running on battery power, false if on wall power.
+  bool on_battery_power_;
+
+  // Battery level when wall power disconnected. [0.0, 1.0] - 0 if on wall
+  // power, 1 means fully charged.
+  double initial_battery_level_;
+
+  // Current battery level. [0.0, 1.0] - 0 if on wall power, 1 means fully
+  // charged.
+  double current_battery_level_;
+
+  // Timestamp when wall power was disconnected, null Time object otherwise.
+  base::Time start_discharge_time_;
+
+  // IDs of live renderer processes.
+  base::hash_set<int> live_renderer_ids_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PowerUsageMonitor);
+};
+
+}  // namespace content
+
+#endif  // CHROME_CONTENT_BROWSER_POWER_USAGE_MONITOR_IMPL_H_