Expose changes in the network quality to the renderers

content/browser/net/network_quality_observer_impl.cc

+// Copyright 2017 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 "content/browser/net/network_quality_observer_impl.h"
+
+#include "base/memory/ptr_util.h"
+#include "content/browser/renderer_host/render_process_host_impl.h"
+#include "content/common/view_messages.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+#include "content/public/browser/notification_service.h"
+#include "content/public/browser/notification_types.h"
+#include "content/public/browser/render_process_host.h"
+
+namespace {
+
+// Returns true if the |current_value| is meaningfully different from the
+// |past_value|.
+bool MetricChangedMeaningfully(int32_t past_value, int32_t current_value) {
+  if ((past_value == net::nqe::internal::INVALID_RTT_THROUGHPUT) !=
+      (current_value == net::nqe::internal::INVALID_RTT_THROUGHPUT)) {
+    return true;
+  }
+
+  if (past_value == net::nqe::internal::INVALID_RTT_THROUGHPUT &&
+      current_value == net::nqe::internal::INVALID_RTT_THROUGHPUT) {
+    return false;
+  }
+
+  // Metric has changed meaningfully only if (i) the difference between the two
+  // values exceed the threshold; and, (ii) the ratio of the values also exceeds
+  // the threshold.
+  static const int kMinDifferenceInMetrics = 100;
+  static const float kMinRatio = 1.2f;
+
+  if (std::abs(past_value - current_value) < kMinDifferenceInMetrics) {
+    // The absolute change in the value is not sufficient enough.
+    return false;
+  }
+
+  if (past_value < (kMinRatio * current_value) &&
+      current_value < (kMinRatio * past_value)) {
+    // The relative change in the value is not sufficient enough.
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace
+
+namespace content {
+
+// UiThreadObserver observes the changes to the network quality on the UI
+// thread, and notifies the renderers of the change in the network quality.
+class NetworkQualityObserverImpl::UiThreadObserver
+    : public content::NotificationObserver {
+ public:
+  UiThreadObserver() {}
+
+  ~UiThreadObserver() override {
+    registrar_.Remove(this, NOTIFICATION_RENDERER_PROCESS_CREATED,
+                      NotificationService::AllSources());
+  }
+
+  void InitOnUIThread() {
+    DCHECK_CURRENTLY_ON(BrowserThread::UI);
+    registrar_.Add(this, NOTIFICATION_RENDERER_PROCESS_CREATED,
+                   NotificationService::AllSources());
+  }
+
+  void OnRTTOrThroughputEstimatesComputed(
+      const net::nqe::internal::NetworkQuality& network_quality) {
+    DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+    last_notified_network_quality_ = network_quality;
+
+    // Notify all the existing renderers of the change in the network quality.
+    for (RenderProcessHost::iterator it(RenderProcessHost::AllHostsIterator());
+         !it.IsAtEnd(); it.Advance()) {
+      it.GetCurrentValue()->GetRendererInterface()->OnNetworkQualityChanged(
+          last_notified_network_quality_.http_rtt().InMilliseconds(),
+          last_notified_network_quality_.transport_rtt().InMilliseconds(),
+          last_notified_network_quality_.downstream_throughput_kbps());
+    }
+  }
+
+ private:
+  // NotificationObserver implementation:
+  void Observe(int type,
+               const NotificationSource& source,
+               const NotificationDetails& details) override {
+    DCHECK_CURRENTLY_ON(BrowserThread::UI);
+    DCHECK_EQ(NOTIFICATION_RENDERER_PROCESS_CREATED, type);
+
+    RenderProcessHost* rph = Source<RenderProcessHost>(source).ptr();
+
+    // Notify the newly created renderer of the current network quality.
+    rph->GetRendererInterface()->OnNetworkQualityChanged(
+        last_notified_network_quality_.http_rtt().InMilliseconds(),
+        last_notified_network_quality_.transport_rtt().InMilliseconds(),
+        last_notified_network_quality_.downstream_throughput_kbps());
+  }
+
+  content::NotificationRegistrar registrar_;
+
+  // The network quality that was last sent to the renderers.
+  net::nqe::internal::NetworkQuality last_notified_network_quality_;
+
+  DISALLOW_COPY_AND_ASSIGN(UiThreadObserver);
+};
+
+NetworkQualityObserverImpl::NetworkQualityObserverImpl(
+    net::NetworkQualityEstimator* network_quality_estimator)
+    : network_quality_estimator_(network_quality_estimator) {
+  network_quality_estimator_->AddRTTAndThroughputEstimatesObserver(this);
+
+  ui_thread_observer_ = base::MakeUnique<UiThreadObserver>();
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::BindOnce(&UiThreadObserver::InitOnUIThread,
+                     base::Unretained(ui_thread_observer_.get())));
+}
+
+NetworkQualityObserverImpl::~NetworkQualityObserverImpl() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  network_quality_estimator_->RemoveRTTAndThroughputEstimatesObserver(this);
+
+  DCHECK(ui_thread_observer_);
+
+  // If possible, delete |ui_thread_observer_| on UI thread.
+  UiThreadObserver* ui_thread_observer_ptr = ui_thread_observer_.release();
+  bool posted = BrowserThread::DeleteSoon(BrowserThread::UI, FROM_HERE,
+                                          ui_thread_observer_ptr);
+
+  if (!posted)
+    delete ui_thread_observer_ptr;
+}
+
+void NetworkQualityObserverImpl::OnRTTOrThroughputEstimatesComputed(
+    base::TimeDelta http_rtt,
+    base::TimeDelta transport_rtt,
+    int32_t downstream_throughput_kbps) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  // Check if any of the network quality metrics changed meaningfully.
+  bool http_rtt_changed = MetricChangedMeaningfully(
+      last_notified_network_quality_.http_rtt().InMilliseconds(),
+      http_rtt.InMilliseconds());
+
+  bool transport_rtt_changed = MetricChangedMeaningfully(
+      last_notified_network_quality_.transport_rtt().InMilliseconds(),
+      transport_rtt.InMilliseconds());
+  bool kbps_changed = MetricChangedMeaningfully(
+      last_notified_network_quality_.downstream_throughput_kbps(),
+      downstream_throughput_kbps);
+
+  if (!http_rtt_changed && !transport_rtt_changed && !kbps_changed) {
+    // Return since none of the metrics changed meaningfully. This reduces
+    // the number of notifications to the different renderers every time
+    // the network quality is recomputed.
+    return;
+  }
+
+  last_notified_network_quality_ = net::nqe::internal::NetworkQuality(
+      http_rtt, transport_rtt, downstream_throughput_kbps);
+
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::BindOnce(&UiThreadObserver::OnRTTOrThroughputEstimatesComputed,
+                     base::Unretained(ui_thread_observer_.get()),
+                     last_notified_network_quality_));
+}
+
+std::unique_ptr<net::NetworkQualityEstimator::RTTAndThroughputEstimatesObserver>
+CreateNetworkQualityObserver(
+    net::NetworkQualityEstimator* network_quality_estimator) {
+  return base::MakeUnique<NetworkQualityObserverImpl>(
+      network_quality_estimator);
+}
+
+}  // namespace content