Chromecast: adds class to help record complex histograms.

chromecast/base/metrics/cast_metrics_helper.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 CHROMECAST_BASE_METRICS_CAST_METRICS_HELPER_H_
+#define CHROMECAST_BASE_METRICS_CAST_METRICS_HELPER_H_
+
+#include <string>
+
+#include "base/memory/ref_counted.h"
+#include "base/time/time.h"
+
+namespace base {
+class MessageLoopProxy;
+}
+
+namespace chromecast {
+namespace metrics {
+
+// Helper class for tracking complex metrics. This particularly includes
+// playback metrics that span events across time, such as "time from app launch
+// to video being rendered."
+class CastMetricsHelper {
+ public:
+  enum BufferingType {
+    kInitialBuffering,
+    kBufferingAfterUnderrun,
+    kAbortedBuffering,
+  };
+
+  class MetricsSink {
+   public:
+    virtual ~MetricsSink() {}
+
+    virtual void OnEnumerationEvent(const std::string& name,
+                                    int value, int num_buckets) = 0;
+    virtual void OnTimeEvent(const std::string& name,
+                             const base::TimeDelta& value,
+                             const base::TimeDelta& min,
+                             const base::TimeDelta& max,
+                             int num_buckets) = 0;
+  };
+
+  static CastMetricsHelper* GetInstance();
+
+  explicit CastMetricsHelper(
+      scoped_refptr<base::MessageLoopProxy> message_loop_proxy);
+  virtual ~CastMetricsHelper();
+
+  // This function stores the name and startup time of the active application.
+  virtual void TagAppStart(const std::string& app_name);
+
+  // Logs UMA record for media play/pause user actions.
+  virtual void LogMediaPlay();
+  virtual void LogMediaPause();
+
+  // Logs UMA record of the elapsed time from the app launch
+  // to the time first video frame is displayed.
+  virtual void LogTimeToDisplayVideo();
+
+  // Logs UMA record of the time needed to re-buffer A/V.
+  virtual void LogTimeToBufferAv(BufferingType buffering_type,
+                                 base::TimeDelta time);
+
+  virtual void ResetVideoFrameSampling();
+
+  // Logs UMA statistics for video decoder and rendering data.
+  // Negative values are considered invalid and will not be logged.
+  virtual void LogFramesPer5Seconds(int displayed_frames, int dropped_frames,
+                                    int delayed_frames, int error_frames);
+
+  // Returns metrics name with app name between prefix and suffix.
+  virtual std::string GetMetricsNameWithAppName(
+      const std::string& prefix,
+      const std::string& suffix) const;
+
+  // Provides a MetricsSink instance to delegate UMA event logging.
+  // Once the delegate interface is set, CastMetricsHelper will not log UMA
+  // events internally unless SetMetricsSink(NULL) is called.
+  // CastMetricsHelper can only hold one MetricsSink instance.
+  // Caller retains ownership of MetricsSink.
+  virtual void SetMetricsSink(MetricsSink* delegate);
+
+ protected:
+  // Creates a CastMetricsHelper instance with no MessageLoopProxy. This should
+  // only be used by tests, since invoking any non-overridden methods on this
+  // instance will cause a failure.
+  CastMetricsHelper();
+
+ private:
+  void LogEnumerationHistogramEvent(const std::string& name,
+                                    int value, int num_buckets);
+  void LogTimeHistogramEvent(const std::string& name,
+                             const base::TimeDelta& value,
+                             const base::TimeDelta& min,
+                             const base::TimeDelta& max,
+                             int num_buckets);
+  void LogMediumTimeHistogramEvent(const std::string& name,
+                                   const base::TimeDelta& value);
+
+  scoped_refptr<base::MessageLoopProxy> message_loop_proxy_;
+
+  // Start time of the most recent app.
+  base::TimeTicks app_start_time_;
+
+  // Currently running app name. Used to construct histogram name.
+  std::string app_name_;
+
+  // Whether a new app start time has been stored but not recorded.
+  // After the startup time has been used to generate an UMA event,
+  // this is set to false.
+  bool new_startup_time_;
+
+  base::TimeTicks previous_video_stat_sample_time_;
+
+  MetricsSink* metrics_sink_;
+
+  DISALLOW_COPY_AND_ASSIGN(CastMetricsHelper);
+};
+
+}  // namespace metrics
+}  // namespace chromecast
+
+#endif  // CHROMECAST_BASE_METRICS_CAST_METRICS_HELPER_H_