Expose packet loss counts from QUIC to NetworkQualityEstimator

net/base/network_quality_estimator.h

Index: net/base/network_quality_estimator.h
diff --git a/net/base/network_quality_estimator.h b/net/base/network_quality_estimator.h
index 9fa0ad1817604c0472f8e5bafb9f78b619cfe477..796409d1b1ae8e6043ba85d6b2a95284f8bb8a54 100644
--- a/net/base/network_quality_estimator.h
+++ b/net/base/network_quality_estimator.h
@@ -101,6 +101,37 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
     DISALLOW_COPY_AND_ASSIGN(ThroughputObserver);
   };
 
+  // Observes measurements of packet loss.
+  class NET_EXPORT_PRIVATE PacketLossObserver {
+   public:
+    // Will be called when a new packet loss observation is available.

[bengr, 2016/02/16 17:02:02]

Use complete sentences. "This method will.."

[tbansal1, 2016/02/17 18:35:10]

Done.

+    // |num_packets_lost| is the number of packets lost.
+    // |num_packets_received_in_order| is the number of packets received in
+    // order. |num_packets_received_not_in_order| is the number of packets
+    // received out of order. See
+    // SocketPerformanceWatcherFactory::OnUpdatedPacketCountAvailable for more
+    // details on how these values are populated.
+    //
+    // Providing counts of lost, in-order and out-of-order packets provides
+    // consumers with more information. From the perspective of network quality,

[bengr, 2016/02/16 17:02:01]

More information than what?
How does network quality have perspective? :)

[tbansal1, 2016/02/17 18:35:10]

Done.

+    // loss of a packet indicates worse network quality than receival of an

[bengr, 2016/02/16 17:02:02]

receival -> reception

[tbansal1, 2016/02/17 18:35:10]

Removed that comment, it was confusing. Also, how to interpret the 3 counts
depends on the consumers. So, that comment was unnecessary.

+    // out-of-order packet. The latter in turns indicates worse network

[bengr, 2016/02/16 17:02:02]

 turns -> turn

[tbansal1, 2016/02/17 18:35:11]

Done.

+    // quality than receival of an in-order packet.

[bengr, 2016/02/16 17:02:02]

receival -> reception

[tbansal1, 2016/02/17 18:35:10]

Done.

+    virtual void OnPacketLossObservation(
+        uint64_t num_packets_lost,
+        uint64_t num_packets_received_in_order,
+        uint64_t num_packets_received_not_in_order,
+        const base::TimeTicks& timestamp,
+        ObservationSource source) = 0;
+
+   protected:
+    PacketLossObserver() {}
+    virtual ~PacketLossObserver() {}
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(PacketLossObserver);
+  };
+
   // Creates a new NetworkQualityEstimator.
   // |variation_params| is the map containing all field trial parameters
   // related to NetworkQualityEstimator field trial.
@@ -139,6 +170,12 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   // Virtualized for testing. |kbps| should not be null.
   virtual bool GetDownlinkThroughputKbpsEstimate(int32_t* kbps) const;
 
+  // Returns true if the estimated packet loss rate is available and sets
+  // |packet_loss| to the estimated packet loss rate. Virtualized for testing.
+  // |packet_loss| should not be NULL. |packet_loss| is always between 0.0
+  // and 1.0 with a higher value indicating higher packet loss rate.

[bengr, 2016/02/16 17:02:02]

inclusive?

[tbansal1, 2016/02/17 18:35:10]

Done.

+  virtual bool GetPacketLossRateEstimate(float* packet_loss) const;
+
   // Notifies NetworkQualityEstimator that the response header of |request| has
   // been received.
   void NotifyHeadersReceived(const URLRequest& request);
@@ -166,6 +203,11 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
       const Protocol protocol) override;
   void OnUpdatedRTTAvailable(const Protocol protocol,
                              const base::TimeDelta& rtt) override;
+  void OnUpdatedPacketCountAvailable(
+      const Protocol protocol,
+      uint64_t num_packets_lost,
+      uint64_t num_packets_received_in_order,
+      uint64_t num_packets_received_not_in_order) override;
 
   // Adds |rtt_observer| to the list of round trip time observers. Must be
   // called on the IO thread.
@@ -183,6 +225,14 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   // is on the list of observers. Must be called on the IO thread.
   void RemoveThroughputObserver(ThroughputObserver* throughput_observer);
 
+  // Adds |packet_loss_observer| to the list of packet loss observers. Must be
+  // called on the IO thread.
+  void AddPacketLossObserver(PacketLossObserver* packet_loss_observer);
+
+  // Removes |packet_loss_observer| from the list of packet loss observers if it
+  // is on the list of observers. Must be called on the IO thread.
+  void RemovePacketLossObserver(PacketLossObserver* packet_loss_observer);
+
  protected:
   // NetworkID is used to uniquely identify a network.
   // For the purpose of network quality estimation and caching, a network is
@@ -234,6 +284,8 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
  private:
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, StoreObservations);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, TestKbpsRTTUpdates);
+  FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest,
+                           TestPacketLossRateUpdates);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, TestAddObservation);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, ObtainOperatingParams);
   FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, HalfLifeParam);
@@ -398,6 +450,15 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
                        ValueType* result,
                        int percentile) const;
 
+    // Returns true iff the weighted average value of the observations in this
+    // buffer is available. Sets |result| to the computed average
+    // value among all observations since |begin_timestamp|. If the value is
+    // unavailable, false is returned and |result| is not modified. Average

[bengr, 2016/02/16 17:02:02]

Average -> The average

[tbansal1, 2016/02/17 18:35:11]

Done.

+    // value is unavailable if all the values in observation buffer are older

[bengr, 2016/02/16 17:02:02]

all the -> all of the
in observation -> in the observation

[tbansal1, 2016/02/17 18:35:11]

Done.

+    // than |begin_timestamp|. |result| must not be NULL.
+    bool GetWeightedAverage(const base::TimeTicks& begin_timestamp,
+                            ValueType* result) const;
+
    private:
     FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest, StoreObservations);
     FRIEND_TEST_ALL_PREFIXES(NetworkQualityEstimatorTest,
@@ -441,6 +502,12 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   typedef net::NetworkQualityEstimator::ObservationBuffer<int32_t>
       ThroughputObservationBuffer;
 
+  // Value of a packet loss observation. A value of 0.0 indicates one packet
+  // was received successfully in-order, while a value of 1.0 indicates one
+  // packet was lost.

[bengr, 2016/02/16 17:02:02]

What does a value of 0.5 mean? Why can't this be a bool?

[tbansal1, 2016/02/17 18:35:11]

This is packet loss rate observation from the reception of a single packet.
Using a float makes it easier if in future, we record observation over multiple
packets (say 10 packets). Also, the current implementation of ObservationBuffer
computes the median/average with the same variable type as the observation
itself. So, using bool would make it complicated to compute median/average.

Renamed the variables a  bit to make it clearer.

+  typedef net::NetworkQualityEstimator::Observation<float>
+      PacketLossObservation;
+
   // This does not use a unordered_map or hash_map for code simplicity (key just
   // implements operator<, rather than hash and equality) and because the map is
   // tiny.
@@ -451,6 +518,11 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   // |kInvalidThroughput|.
   static const int32_t kInvalidThroughput;
 
+  // Packet loss rate is set to |kInvalidPacketLossRate| if a valid value is
+  // unavailable. Readers should discard the packet loss rate value if it is
+  // set to |kInvalidPacketLossRate|.
+  static const float kInvalidPacketLossRate;

[bengr, 2016/02/16 17:02:02]

It might be better to provide an is_valid() method.

[tbansal1, 2016/02/17 18:35:11]

Changed to use a min valid value.

+
   // Tiny transfer sizes may give inaccurate throughput results.
   // Minimum size of the transfer over which the throughput is computed.
   static const int kMinTransferSizeInBytes = 10000;
@@ -509,6 +581,11 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
       const base::TimeTicks& begin_timestamp,
       int percentile) const;
 
+  // Returns an estimate of the packet loss rate. Only the observations later
+  // than |begin_timestamp| are taken into account.
+  float GetPacketLossRateEstimateInternal(
+      const base::TimeTicks& begin_timestamp) const;
+
   // Returns the current network ID checking by calling the platform APIs.
   // Virtualized for testing.
   virtual NetworkID GetCurrentNetworkID() const;
@@ -520,6 +597,12 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
 
   void NotifyObserversOfThroughput(const ThroughputObservation& observation);
 
+  void NotifyObserversOfPacketLoss(uint64_t num_packets_lost,
+                                   uint64_t num_packets_received_in_order,
+                                   uint64_t num_packets_received_not_in_order,
+                                   const base::TimeTicks& timestamp,
+                                   ObservationSource source);
+
   // Records the UMA related to RTT.
   void RecordRTTUMA(int32_t estimated_value_msec,
                     int32_t actual_value_msec) const;
@@ -545,6 +628,13 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   void RecordExternalEstimateProviderMetrics(
       NQEExternalEstimateProviderStatus status) const;
 
+  // Sets  |observation_source| that corresponds to the given |protocol|, and

[bengr, 2016/02/16 17:02:02]

Do you mean "Gets the?" The entire comment is awkward, so please rewrite.

[tbansal1, 2016/02/17 18:35:11]

Done.

+  // returns true. If the corresponding ObservationSource is unknown, false is
+  // returned and |observation_source| is not modified.
+  bool GetObservationSourceForProtocol(
+      const Protocol protocol,
+      ObservationSource* observation_source) const;
+
   // Determines if the requests to local host can be used in estimating the
   // network quality. Set to true only for tests.
   const bool allow_localhost_requests_;
@@ -578,6 +668,9 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   // Buffer that holds RTT observations sorted by timestamp.
   RttObservationBuffer rtt_msec_observations_;
 
+  // Buffer that holds packet loss observations sorted by timestamp.
+  ObservationBuffer<float> packet_loss_rate_observations_;
+
   // Default network quality observations obtained from the network quality
   // estimator field trial parameters. The observations are indexed by
   // ConnectionType.
@@ -591,9 +684,11 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   // system APIs. May be NULL.
   const scoped_ptr<ExternalEstimateProvider> external_estimate_provider_;
 
-  // Observer lists for round trip times and throughput measurements.
+  // Observer lists for round trip times, throughput and packet loss
+  // measurements.
   base::ObserverList<RTTObserver> rtt_observer_list_;
   base::ObserverList<ThroughputObserver> throughput_observer_list_;
+  base::ObserverList<PacketLossObserver> packet_loss_observer_list_;
 
   base::ThreadChecker thread_checker_;