NQE: Allow algorithm to be set using variation params

net/nqe/network_quality_estimator.cc

 // 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.
 
 #include "net/nqe/network_quality_estimator.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 #include <utility>
@@ skipping 17 matching lines @@
 #include "net/socket/socket_performance_watcher.h"
 #include "net/url_request/url_request.h"
 #include "url/gurl.h"
 
 #if defined(OS_ANDROID)
 #include "net/android/network_library.h"
 #endif  // OS_ANDROID
 
 namespace {
 
+// The algorithm that uses HTTP RTT and downstream throughput to determine the

[bengr, 2016/06/06 20:14:54]

Hmm. This will be hard to extend. I think instead you should do something like
this:

enum class Algorithm {
  UNKNOWN = 0,
  HTTP_RTT_AND_DOWNSTREAM_THROUGHOUT = 1
};

// If needed for UMA:
std::unordered_map<Algorithm, std::string> algorithm_name(
  { { HTTP_RTT_AND_DOWNSTREAM_THROUGHPUT,
      "HttpRTTAndDownstreamThroughput" } });

EffectiveConnectionType
GetRecentEffectiveConnectionType(
  EffectiveConnectionTypeAlgorithm algorithm) {
  EffectiveConnectionType ect = UNKNOWN; // ?
  switch (algorithm) {
    case HTTP_RTT_AND_DOWNSTREAM_THROUGHOUT:
    // fall-through:
    default:
      RunHttpRttAndDownstreamThroughputAlgorithm(&ect);
      break:
  }
  return ect;
}

[tbansal1, 2016/06/08 01:30:53]

I wanted to keep |algorithm_| as a const variable. So, I did something similar.

+// effective connection type.
+const char kHttpRTTDownstreamThroughputAlgorithm[] =
+    "HttpRTTAndDownstreamThroughput";
+
+// The default algorithm to be used if the algorithm value is not available
+// through field trial parameters.
+const char kDefaultEffectiveConnectionTypeAlgorithm[] =
+    "HttpRTTAndDownstreamThroughput";
+
 // Default value of the half life (in seconds) for computing time weighted
 // percentiles. Every half life, the weight of all observations reduces by
 // half. Lowering the half life would reduce the weight of older values faster.
 const int kDefaultHalfLifeSeconds = 60;
 
 // Name of the variation parameter that holds the value of the half life (in
 // seconds) of the observations.
 const char kHalfLifeSecondsParamName[] = "HalfLifeSeconds";
 
 // Returns a descriptive name corresponding to |connection_type|.
@@ skipping 80 matching lines @@
   const char prefix[] = "NQE.";
   return base::Histogram::FactoryGet(
       prefix + statistic_name + GetNameForConnectionType(type), kLowerLimit,
       max_limit, kBucketCount, base::HistogramBase::kUmaTargetedHistogramFlag);
 }
 
 bool GetValueForVariationParam(
     const std::map<std::string, std::string>& variation_params,
     const std::string& parameter_name,
     int32_t* variations_value) {
-  auto it = variation_params.find(parameter_name);
+  const auto it = variation_params.find(parameter_name);
   return it != variation_params.end() &&
          base::StringToInt(it->second, variations_value);
 }
 
+// Returns the value of the |parameter_name| in |variation_params|. If
+// |parameter_name| is not set in |variation_params|, then |default_value| is
+// returned.
+std::string GetValueForVariationParamWithDefaultValue(
+    const std::map<std::string, std::string>& variation_params,
+    const std::string& parameter_name,
+    const std::string& default_value) {
+  const auto it = variation_params.find(parameter_name);
+  return it != variation_params.end() && !it->second.empty() ? it->second
+                                                             : default_value;
+}
+
 net::NetworkQualityObservationSource ProtocolSourceToObservationSource(
     net::SocketPerformanceWatcherFactory::Protocol protocol) {
   switch (protocol) {
     case net::SocketPerformanceWatcherFactory::PROTOCOL_TCP:
       return net::NETWORK_QUALITY_OBSERVATION_SOURCE_TCP;
     case net::SocketPerformanceWatcherFactory::PROTOCOL_QUIC:
       return net::NETWORK_QUALITY_OBSERVATION_SOURCE_QUIC;
   }
   NOTREACHED();
   return net::NETWORK_QUALITY_OBSERVATION_SOURCE_TCP;
@@ skipping 93 matching lines @@
 
 NetworkQualityEstimator::NetworkQualityEstimator(
     std::unique_ptr<ExternalEstimateProvider> external_estimates_provider,
     const std::map<std::string, std::string>& variation_params,
     bool use_local_host_requests_for_tests,
     bool use_smaller_responses_for_tests)
     : use_localhost_requests_(use_local_host_requests_for_tests),
       use_small_responses_(use_smaller_responses_for_tests),
       weight_multiplier_per_second_(
           GetWeightMultiplierPerSecond(variation_params)),
+      algorithm_(GetValueForVariationParamWithDefaultValue(
+          variation_params,
+          "algorithm",
+          kDefaultEffectiveConnectionTypeAlgorithm)),
       tick_clock_(new base::DefaultTickClock()),
       effective_connection_type_recomputation_interval_(
           base::TimeDelta::FromSeconds(15)),
       last_connection_change_(tick_clock_->NowTicks()),
       current_network_id_(
           NetworkID(NetworkChangeNotifier::ConnectionType::CONNECTION_UNKNOWN,
                     std::string())),
       downstream_throughput_kbps_observations_(weight_multiplier_per_second_),
       rtt_observations_(weight_multiplier_per_second_),
       external_estimate_provider_(std::move(external_estimates_provider)),
@@ skipping 482 matching lines @@
 NetworkQualityEstimator::GetEffectiveConnectionType() const {
   DCHECK(thread_checker_.CalledOnValidThread());
   return GetRecentEffectiveConnectionType(base::TimeTicks());
 }
 
 NetworkQualityEstimator::EffectiveConnectionType
 NetworkQualityEstimator::GetRecentEffectiveConnectionType(
     const base::TimeTicks& start_time) const {
   DCHECK(thread_checker_.CalledOnValidThread());
 
+  if (algorithm_ == kHttpRTTDownstreamThroughputAlgorithm) {
+    return GetRecentEffectiveConnectionTypeHttpRTTAndDownstreamThroughput(
+        start_time);
+  }
+  // Add additional algorithms here.
+  NOTREACHED();
+  return EFFECTIVE_CONNECTION_TYPE_UNKNOWN;
+}
+
+NetworkQualityEstimator::EffectiveConnectionType NetworkQualityEstimator::
+    GetRecentEffectiveConnectionTypeHttpRTTAndDownstreamThroughput(
+        const base::TimeTicks& start_time) const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
   // If the device is currently offline, then return
   // EFFECTIVE_CONNECTION_TYPE_OFFLINE.
   if (GetCurrentNetworkID().type == NetworkChangeNotifier::CONNECTION_NONE)
     return EFFECTIVE_CONNECTION_TYPE_OFFLINE;
 
   base::TimeDelta http_rtt = nqe::internal::InvalidRTT();
   if (!GetRecentHttpRTTMedian(start_time, &http_rtt))
     http_rtt = nqe::internal::InvalidRTT();
 
   int32_t kbps = nqe::internal::kInvalidThroughput;
   if (!GetRecentMedianDownlinkThroughputKbps(start_time, &kbps))
     kbps = nqe::internal::kInvalidThroughput;
 
-  if (http_rtt == nqe::internal::InvalidRTT() &&
+  if (http_rtt == nqe::internal::InvalidRTT() ||
       kbps == nqe::internal::kInvalidThroughput) {
     // Quality of the current network is unknown.
     return EFFECTIVE_CONNECTION_TYPE_UNKNOWN;
   }
 
   // Search from the slowest connection type to the fastest to find the
   // EffectiveConnectionType that best matches the current connection's
   // performance. The match is done by comparing RTT and throughput.
   for (size_t i = 0; i < EFFECTIVE_CONNECTION_TYPE_LAST; ++i) {
     EffectiveConnectionType type = static_cast<EffectiveConnectionType>(i);
@@ skipping 408 matching lines @@
     NotifyObserversOfEffectiveConnectionTypeChanged() {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   // TODO(tbansal): Add hysteresis in the notification.
   FOR_EACH_OBSERVER(
       EffectiveConnectionTypeObserver, effective_connection_type_observer_list_,
       OnEffectiveConnectionTypeChanged(effective_connection_type_));
 }
 
 }  // namespace net