Add DataReductionProxyExperimentsStats and UMA for measuring potentially non-compressed bytes.

components/data_reduction_proxy/core/browser/data_reduction_proxy_experiments_stats.h

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_experiments_stats.h
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_experiments_stats.h b/components/data_reduction_proxy/core/browser/data_reduction_proxy_experiments_stats.h
new file mode 100644
index 0000000000000000000000000000000000000000..5aeb3e960d26f0ac2a5976beac0f6cb6f09ecd24
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+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_experiments_stats.h
@@ -0,0 +1,194 @@
+// Copyright 2015 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 COMPONENTS_DATA_REDUCTION_PROXY_CORE_BROWSER_DATA_REDUCTION_PROXY_EXPERIMENTS_STATS_H_
+#define COMPONENTS_DATA_REDUCTION_PROXY_CORE_BROWSER_DATA_REDUCTION_PROXY_EXPERIMENTS_STATS_H_
+
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "base/time/time.h"
+#include "base/timer/timer.h"
+#include "components/data_reduction_proxy/core/browser/data_reduction_proxy_metrics.h"
+
+class PrefService;
+
+namespace base {
+class HistogramBase;
+class Value;
+}
+
+namespace net {
+class URLRequest;
+}
+
+namespace data_reduction_proxy {
+
+namespace experiments {
+
+// The name of the trial group for measuring lost bytes during fetching the
+// configuration.
+extern const char kConfigFetchTrialGroup[];
+
+// The config retrieval round trip time is calculated as:
+// (previous base) * (multiplier) + increment.
+// Multipler is >= 1. Increment is >= 0.
+// The name of the param prefix for determining the base round trip time in
+// milliseconds for simulating a configuration fetch.
+extern const char kConfigRoundtripMillisecondsBaseParam[];
+
+// The name of the param prefix for determining the base round trip time in
+// milliseconds for simulating a configuration fetch.
+extern const char kConfigRoundtripMultiplierParam[];
+
+// The name of the param prefix for determining the base round trip time in
+// milliseconds for simulating a configuration fetch.
+extern const char kConfigRoundtripMillisecondsIncrementParam[];
+
+// The name of the param for determining the expiration interval of the
+// configuration in seconds.
+extern const char kConfigExpirationSecondsParam[];
+
+// The name of the param for determining if the config should be
+// considered

[sclittle, 2015/05/12 19:32:25]

nit: line wrapping

[jeremyim, 2015/05/12 20:38:29]

Done.

+// stale on startup (regardless of whether it is stale or not).
+extern const char kConfigAlwaysStaleParam[];
+
+// The number of seconds by which the expiration interval exceeds the refresh
+// interval so that we maintain a valid configuration.
+extern const int kConfigFetchBufferSeconds;
+
+}  // namespace experiments
+
+typedef base::Callback<void(const std::string&, int64)> Int64ValueSetter;
+
+// Collects statistics specific to experiments of which a client may be part.
+// Any calls into this class should be as lightweight as possible such that if
+// no experiments are being performed, there should be minimal code being
+// executed.
+// Currently supported experiments are:
+// - Measuring potentially uncompressed bytes during simulated config retrieval.
+class DataReductionProxyExperimentsStats {
+ public:
+  enum ConfigState {
+    VALID = 0,
+    RETRIEVING = 1,
+    EXPIRED = 2,
+  };
+
+  // Parameters for setting up an experiment to measure potentially uncompressed
+  // bytes during the retrieval of the Data Reduction Proxy configuration.
+  class ConfigRetrievalParams {
+   public:
+    class Variation {

[sclittle, 2015/05/12 19:32:25]

Could you add a comment describing what this class is for?

[jeremyim, 2015/05/12 20:38:29]

Done.

+     public:
+      Variation(int index, const base::Time& simulated_config_retrieved);

[sclittle, 2015/05/12 19:32:25]

optional nit: This is three levels deep of classes - have you considered moving
ConfigRetrievalParams to its own file or something like that?

I'm not sure what it would be called -
DataReductionProxySimulatedConfigRetrievalParams or something doesn't exactly
roll off the tongue - but it might help clear up this file and the .cc, as well
as the tests (instead of needing to friend
DataReductionProxyExperimentsStatsTest from ConfigRetrievalParams).

[jeremyim, 2015/05/12 20:38:29]

Done.

+
+      // Returns the current state of the Data Reduction Proxy configuration.
+      // Virtual for testing.
+      virtual ConfigState GetState(const base::Time& request_time,
+                                   const base::Time& config_expiration) const;
+
+      void RecordStats(int64 received_content_length,
+                       int64 original_content_length) const;
+
+     private:
+      // The time at which the simulated Data Reduction Proxy configuration is
+      // considered to have been received.
+      base::Time simulated_config_retrieved_;
+
+      // Histograms for recording stats.
+      base::HistogramBase* lost_bytes_ocl_;
+      base::HistogramBase* lost_bytes_rcl_;
+      base::HistogramBase* lost_bytes_diff_;
+    };
+
+    static scoped_ptr<ConfigRetrievalParams> Create(PrefService* pref_service);
+
+    virtual ~ConfigRetrievalParams();
+
+    void RecordStats(const base::Time& request_time,
+                     int64 received_content_length,
+                     int64 original_content_length) const;
+
+    // Simulates retrieving a new configuration.
+    void RefreshConfig();
+
+    // Returns the expiration time of the current configuration.
+    const base::Time& config_expiration() const { return config_expiration_; }
+
+    // Returns how often the configuration should be retrieved.
+    const base::TimeDelta& refresh_interval() const {
+      return config_refresh_interval_;
+    }
+
+   private:
+    friend class DataReductionProxyExperimentsStatsTest;
+
+    ConfigRetrievalParams(const std::vector<Variation>& variations,
+                          const base::Time& config_expiration,
+                          const base::TimeDelta& config_refresh_interval);
+
+    // The time at which the simulated Data Reduction Proxy configuration
+    // expires.
+    base::Time config_expiration_;
+
+    // The duration for which a Data Reduction Proxy configuration is considered
+    // valid.
+    base::TimeDelta config_expiration_interval_;
+
+    // The duration after which a simulated retrieval of a new Data Reduction
+    // Proxy configuration should be performed.
+    base::TimeDelta config_refresh_interval_;
+
+    // The different variations on roundtrip time that can take place.
+    std::vector<Variation> variations_;
+  };
+
+  DataReductionProxyExperimentsStats(Int64ValueSetter value_setter);

[sclittle, 2015/05/12 19:32:25]

nit: const Int64ValueSetter&

[jeremyim, 2015/05/12 20:38:29]

Done.

+  virtual ~DataReductionProxyExperimentsStats();
+
+  // Initializes |this| on the UI thread.
+  void InitializeOnUIThread(
+      scoped_ptr<ConfigRetrievalParams> config_retrieval_params);
+
+  // Initializes |this| on the IO thread.
+  void InitializeOnIOThread();
+
+  // Collect received bytes for the experiment.
+  void RecordBytes(const base::Time& request_time,
+                   DataReductionProxyRequestType request_type,
+                   int64 received_content_length,
+                   int64 original_content_length);
+
+ private:
+  // Updates the simulated expiration of the Data Reduction Proxy configuration
+  // if |config_retrieval_| is set.
+  void UpdateSimulatedConfig();
+
+  // Allows an experiment to persist data to preferences.
+  Int64ValueSetter value_setter_;
+
+  // Enables measuring of potentially uncompressed bytes during a simulated Data
+  // Reduction Proxy configuration retrieval.
+  scoped_ptr<ConfigRetrievalParams> config_retrieval_params_;
+
+  // If set, periodically updates the simulated expiration of the Data Reduction
+  // Proxy configuration.
+  base::RepeatingTimer<DataReductionProxyExperimentsStats> config_refresh_time_;
+
+  // Enforce usage on the IO thread.
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(DataReductionProxyExperimentsStats);
+};
+
+}  // namespace data_reduction_proxy
+
+#endif  // COMPONENTS_DATA_REDUCTION_PROXY_CORE_BROWSER_DATA_REDUCTION_PROXY_EXPERIMENTS_STATS_H_