NQE: Record correlation metric in UMA

net/nqe/network_quality_estimator.h

 // 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 NET_NQE_NETWORK_QUALITY_ESTIMATOR_H_
 #define NET_NQE_NETWORK_QUALITY_ESTIMATOR_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 331 matching lines @@
       int32_t* kbps) const WARN_UNUSED_RESULT;
 
   // Returns the list of intervals at which the accuracy of network quality
   // prediction should be recorded. Virtualized for testing.
   virtual const std::vector<base::TimeDelta>& GetAccuracyRecordingIntervals()
       const;
 
   // Overrides the tick clock used by |this| for testing.
   void SetTickClockForTesting(std::unique_ptr<base::TickClock> tick_clock);
 
+  // Returns a random double in the range [0.0, 1.0). Virtualized for testing.
+  virtual double RandDouble() const;
+
  private:
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, StoreObservations);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, TestAddObservation);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, ObtainOperatingParams);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest,
                            ObtainAlgorithmToUseFromParams);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, HalfLifeParam);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, ComputedPercentiles);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, TestCaching);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest,
@@ skipping 174 matching lines @@
     EXTERNAL_ESTIMATE_PROVIDER_STATUS_CALLBACK,
     EXTERNAL_ESTIMATE_PROVIDER_STATUS_RTT_AVAILABLE,
     EXTERNAL_ESTIMATE_PROVIDER_STATUS_DOWNLINK_BANDWIDTH_AVAILABLE,
     EXTERNAL_ESTIMATE_PROVIDER_STATUS_BOUNDARY
   };
 
   // Records the metrics related to external estimate provider.
   void RecordExternalEstimateProviderMetrics(
       NQEExternalEstimateProviderStatus status) const;
 
+  // Records a correlation metric that can be used for computing the correlation
+  // between HTTP-layer RTT, transport-layer RTT, throughput and the time
+  // taken to complete |request|.
+  void RecordCorrelationMetric(const URLRequest& request) const;
+
+  // Returns true if transport RTT should be used for computing the effective
+  // connection type.
+  bool UseTransportRTT() const;
+
   // Determines if the requests to local host can be used in estimating the
   // network quality. Set to true only for tests.
   bool use_localhost_requests_;
 
   // Determines if the responses smaller than |kMinTransferSizeInBytes|
   // or shorter than |kMinTransferSizeInBytes| can be used in estimating the
   // network quality. Set to true only for tests.
   bool use_small_responses_;
 
   // The factor by which the weight of an observation reduces every second.
@@ skipping 88 matching lines @@
   // events. It is also updated every time there is network traffic (provided
   // the last computation was more than
   // |effective_connection_type_recomputation_interval_| ago).
   EffectiveConnectionType effective_connection_type_;
 
   // Minimum and Maximum signal strength (in dbM) observed since last connection
   // change. Updated on connection change and main frame requests.
   int32_t min_signal_strength_since_connection_change_;
   int32_t max_signal_strength_since_connection_change_;
 
+  // It is costlier to add values to a sparse histogram. So, the correlation UMA
+  // is recorded with |correlation_uma_logging_probability_| since recording it
+  // in a sparse histogram for each request is unnecessary and cost-prohibitive.
+  // e.g., if it is 0.0, then the UMA will never be recorded. On the other hand,
+  // if it is 1.0, then it will be recorded for all valid HTTP requests.
+  const double correlation_uma_logging_probability_;
+
   base::ThreadChecker thread_checker_;
 
   base::WeakPtrFactory<NetworkQualityEstimator> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkQualityEstimator);
 };
 
 }  // namespace net
 
 #endif  // NET_NQE_NETWORK_QUALITY_ESTIMATOR_H_