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 320 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 145 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;
+
   // 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 55 matching lines @@
   // fitting) may be used.
   nqe::internal::NetworkQuality
       connection_thresholds_[EFFECTIVE_CONNECTION_TYPE_LAST];
 
   // Latest time when the headers for a main frame request were received.
   base::TimeTicks last_main_frame_request_;
 
   // Estimated network quality when the response headers for the last mainframe
   // request were received.
   nqe::internal::NetworkQuality estimated_quality_at_last_main_frame_;
   EffectiveConnectionType effective_connection_type_at_last_main_frame_;

[bengr, 2016/07/19 00:32:31]

This seems like a bit of a layering violation for net/ to know about main frames
or their timings.

[tbansal1, 2016/07/20 00:28:02]

ack'ed. I can move it to Chrome but it is not clear how important that is.

 
   // ExternalEstimateProvider that provides network quality using operating
   // system APIs. May be NULL.
   const std::unique_ptr<ExternalEstimateProvider> external_estimate_provider_;
 
   // Observer list for changes in effective connection type.
   base::ObserverList<EffectiveConnectionTypeObserver>
       effective_connection_type_observer_list_;
 
   // Observer lists for round trip times and throughput measurements.
   base::ObserverList<RTTObserver> rtt_observer_list_;
   base::ObserverList<ThroughputObserver> throughput_observer_list_;
 
   std::unique_ptr<SocketPerformanceWatcherFactory> watcher_factory_;
 
   // Takes throughput measurements, and passes them back to |this| through the
   // provided callback. |this| stores the throughput observations in
   // |downstream_throughput_kbps_observations_|, which are later used for
   // estimating the throughput.
   std::unique_ptr<nqe::internal::ThroughputAnalyzer> throughput_analyzer_;
 
   // Current effective connection type. It is updated on connection change
   // 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_;
 
+  // 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_