Expose packet loss counts from QUIC to NetworkQualityEstimator

net/base/network_quality_estimator.cc

Index: net/base/network_quality_estimator.cc
diff --git a/net/base/network_quality_estimator.cc b/net/base/network_quality_estimator.cc
index e0a10cfc44ba75d8b21ee95d0a5cb6fa7f4a27bc..128074ad9e9e5e57625884027c17e81449549fbe 100644
--- a/net/base/network_quality_estimator.cc
+++ b/net/base/network_quality_estimator.cc
@@ -141,6 +141,8 @@ NetworkQualityEstimator::NetworkQualityEstimator(
       downstream_throughput_kbps_observations_(
           GetWeightMultiplierPerSecond(variation_params)),
       rtt_msec_observations_(GetWeightMultiplierPerSecond(variation_params)),
+      packet_loss_rate_observations_(
+          GetWeightMultiplierPerSecond(variation_params)),
       external_estimate_provider_(std::move(external_estimates_provider)) {
   static_assert(kMinRequestDurationMicroseconds > 0,
                 "Minimum request duration must be > 0");
@@ -250,6 +252,17 @@ void NetworkQualityEstimator::NotifyHeadersReceived(const URLRequest& request) {
     estimated_median_network_quality_ = NetworkQuality(
         GetRTTEstimateInternal(base::TimeTicks(), 50),
         GetDownlinkThroughputKbpsEstimateInternal(base::TimeTicks(), 50));
+
+    float packet_loss_rate;
+    if (GetPacketLossRateEstimate(&packet_loss_rate)) {
+      DCHECK_LE(0.0f, packet_loss_rate);
+      DCHECK_GE(1.0f, packet_loss_rate);
+
+      // Largest bucket is 101.
+      base::HistogramBase* packet_loss_histogram =
+          GetHistogram("PacketLossRate.", current_network_id_.type, 101);
+      packet_loss_histogram->Add(packet_loss_rate * 100.0f);
+    }
   }
 
   base::TimeTicks now = base::TimeTicks::Now();
@@ -376,6 +389,18 @@ void NetworkQualityEstimator::RemoveThroughputObserver(
   throughput_observer_list_.RemoveObserver(throughput_observer);
 }
 
+void NetworkQualityEstimator::AddPacketLossObserver(
+    PacketLossObserver* packet_loss_observer) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  packet_loss_observer_list_.AddObserver(packet_loss_observer);
+}
+
+void NetworkQualityEstimator::RemovePacketLossObserver(
+    PacketLossObserver* packet_loss_observer) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  packet_loss_observer_list_.RemoveObserver(packet_loss_observer);
+}
+
 void NetworkQualityEstimator::RecordRTTUMA(int32_t estimated_value_msec,
                                            int32_t actual_value_msec) const {
   DCHECK(thread_checker_.CalledOnValidThread());
@@ -429,6 +454,22 @@ void NetworkQualityEstimator::RecordExternalEstimateProviderMetrics(
                             EXTERNAL_ESTIMATE_PROVIDER_STATUS_BOUNDARY);
 }
 
+bool NetworkQualityEstimator::GetObservationSourceForProtocol(
+    Protocol protocol,
+    NetworkQualityEstimator::ObservationSource* observation_source) const {
+  switch (protocol) {
+    case PROTOCOL_TCP:
+      *observation_source = TCP;
+      return true;
+    case PROTOCOL_QUIC:
+      *observation_source = QUIC;
+      return true;
+    default:
+      NOTREACHED();
+      return false;
+  }
+}
+
 void NetworkQualityEstimator::OnConnectionTypeChanged(
     NetworkChangeNotifier::ConnectionType type) {
   DCHECK(thread_checker_.CalledOnValidThread());
@@ -546,6 +587,7 @@ void NetworkQualityEstimator::OnConnectionTypeChanged(
   peak_network_quality_ = NetworkQuality();
   downstream_throughput_kbps_observations_.Clear();
   rtt_msec_observations_.Clear();
+  packet_loss_rate_observations_.Clear();
   current_network_id_ = GetCurrentNetworkID();
 
   QueryExternalEstimateProvider();
@@ -580,6 +622,17 @@ bool NetworkQualityEstimator::GetDownlinkThroughputKbpsEstimate(
   return (*kbps != kInvalidThroughput);
 }
 
+bool NetworkQualityEstimator::GetPacketLossRateEstimate(
+    float* packet_loss_rate_estimate) const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  float estimate = GetPacketLossRateEstimateInternal(base::TimeTicks());
+  if (estimate < 0.0f || estimate > 1.0f)
+    return false;
+  *packet_loss_rate_estimate = estimate;
+  return true;
+}
+
 bool NetworkQualityEstimator::GetRecentMedianRTT(
     const base::TimeTicks& begin_timestamp,
     base::TimeDelta* rtt) const {
@@ -644,6 +697,23 @@ int32_t NetworkQualityEstimator::GetDownlinkThroughputKbpsEstimateInternal(
   return kbps;
 }
 
+float NetworkQualityEstimator::GetPacketLossRateEstimateInternal(
+    const base::TimeTicks& begin_timestamp) const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  if (packet_loss_rate_observations_.Size() == 0)
+    return -1.0f;
+
+  float packet_loss_rate;
+  if (!packet_loss_rate_observations_.GetWeightedAverage(begin_timestamp,
+                                                         &packet_loss_rate)) {
+    return -1.0f;
+  }
+  DCHECK_LE(0.0f, packet_loss_rate);
+  DCHECK_GE(1.0f, packet_loss_rate);
+  return packet_loss_rate;
+}
+
 template <typename ValueType>
 void NetworkQualityEstimator::ObservationBuffer<ValueType>::
     ComputeWeightedObservations(
@@ -717,6 +787,39 @@ bool NetworkQualityEstimator::ObservationBuffer<ValueType>::GetPercentile(
   return true;
 }
 
+template <typename ValueType>
+bool NetworkQualityEstimator::ObservationBuffer<ValueType>::GetWeightedAverage(
+    const base::TimeTicks& begin_timestamp,
+    ValueType* result) const {
+  DCHECK(result);
+
+  // Stores |weighted_observations| in the increasing order of value with lower
+  // values at the front of the vector.
+  std::vector<WeightedObservation<ValueType>> weighted_observations;
+
+  // The sum of the weights of all observations in |weighted_observations|.
+  double total_weight = 0.0;
+
+  ComputeWeightedObservations(begin_timestamp, weighted_observations,
+                              &total_weight);
+  if (weighted_observations.empty())
+    return false;
+
+  DCHECK_GT(total_weight, 0.0);
+
+  // |weighted_observations| may have a smaller size than |observations_| since
+  // the former only contains the observations later than |begin_timestamp|.
+  DCHECK_GE(observations_.size(), weighted_observations.size());
+
+  double total_weight_times_value = 0.0;
+  for (const auto& weighted_observation : weighted_observations) {
+    total_weight_times_value +=
+        (weighted_observation.weight * weighted_observation.value);
+  }
+  *result = total_weight_times_value / total_weight;
+  return true;
+}
+
 NetworkQualityEstimator::NetworkID
 NetworkQualityEstimator::GetCurrentNetworkID() const {
   DCHECK(thread_checker_.CalledOnValidThread());
@@ -900,20 +1003,53 @@ void NetworkQualityEstimator::OnUpdatedRTTAvailable(
     const base::TimeDelta& rtt) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
-  switch (protocol) {
-    case PROTOCOL_TCP:
-      NotifyObserversOfRTT(RttObservation(rtt, base::TimeTicks::Now(), TCP));
-      return;
-    case PROTOCOL_QUIC:
-      NotifyObserversOfRTT(RttObservation(rtt, base::TimeTicks::Now(), QUIC));
-      return;
-    default:
-      NOTREACHED();
+  ObservationSource observation_source;
+  if (!GetObservationSourceForProtocol(protocol, &observation_source))
+    return;
+
+  NotifyObserversOfRTT(
+      RttObservation(rtt, base::TimeTicks::Now(), observation_source));
+}
+
+void NetworkQualityEstimator::OnUpdatedPacketCountAvailable(
+    Protocol protocol,
+    size_t packets_missing,
+    size_t packets_received_in_order,
+    size_t packets_received_out_of_order) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  const base::TimeTicks now = base::TimeTicks::Now();
+
+  ObservationSource observation_source;
+  if (!GetObservationSourceForProtocol(protocol, &observation_source))
+    return;
+
+  // Consider it as a packet loss only if at least 3 packets are received after
+  // the missing packets.
+  // TODO(tbansal): Maintain a watcher specific state to accurately compute if
+  // more than 3 packets were received after the missing packet.
+  if (packets_received_in_order >= 3) {

[Ryan Hamilton, 2016/03/07 20:02:10]

But this argument is really only going to ever be 0 or 1, right?

[tbansal1, 2016/03/08 02:59:58]

Obsolete.

+    for (size_t i = 0; i < packets_missing; ++i) {
+      packet_loss_rate_observations_.AddObservation(
+          PacketLossRateObservation(1.0, now, observation_source));
+    }
   }
+  for (size_t i = 0; i < packets_received_in_order; ++i) {
+    packet_loss_rate_observations_.AddObservation(
+        PacketLossRateObservation(0.0, now, observation_source));

[Ryan Hamilton, 2016/03/07 20:02:10]

You're computing packet loss rate per-packet? That seems unusual.

[tbansal1, 2016/03/08 02:59:58]

Obsolete.

+  }
+  // For packet loss estimation, we neglect the packets that were previously
+  // marked as lost but are later received out-of-order.
+  NotifyObserversOfPacketCount(packets_missing, packets_received_in_order,
+                               packets_received_out_of_order, now,
+                               observation_source);
 }
 
 void NetworkQualityEstimator::NotifyObserversOfRTT(
     const RttObservation& observation) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK_NE(EXTERNAL_ESTIMATE, observation.source);
+
   FOR_EACH_OBSERVER(
       RTTObserver, rtt_observer_list_,
       OnRTTObservation(observation.value.InMilliseconds(),
@@ -922,12 +1058,30 @@ void NetworkQualityEstimator::NotifyObserversOfRTT(
 
 void NetworkQualityEstimator::NotifyObserversOfThroughput(
     const ThroughputObservation& observation) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK_NE(EXTERNAL_ESTIMATE, observation.source);
+
   FOR_EACH_OBSERVER(
       ThroughputObserver, throughput_observer_list_,
       OnThroughputObservation(observation.value, observation.timestamp,
                               observation.source));
 }
 
+void NetworkQualityEstimator::NotifyObserversOfPacketCount(
+    size_t packets_missing,
+    size_t packets_received_in_order,
+    size_t packets_received_out_of_order,
+    const base::TimeTicks& timestamp,
+    ObservationSource source) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK_NE(EXTERNAL_ESTIMATE, source);
+
+  FOR_EACH_OBSERVER(PacketLossObserver, packet_loss_observer_list_,
+                    OnPacketLossObservation(
+                        packets_missing, packets_received_in_order,
+                        packets_received_out_of_order, timestamp, source));
+}
+
 NetworkQualityEstimator::CachedNetworkQuality::CachedNetworkQuality(
     const NetworkQuality& network_quality)
     : last_update_time_(base::TimeTicks::Now()),