Add in-memory caching of network quality estimates across network changes.

net/base/network_quality_estimator_unittest.cc

Index: net/base/network_quality_estimator_unittest.cc
diff --git a/net/base/network_quality_estimator_unittest.cc b/net/base/network_quality_estimator_unittest.cc
index 82e1bbaf3d23e58ce960121170ad5d917e83e6f9..8c198d7abe0c7e8c475ed879b5125dd62b19afe8 100644
--- a/net/base/network_quality_estimator_unittest.cc
+++ b/net/base/network_quality_estimator_unittest.cc
@@ -8,6 +8,7 @@
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/run_loop.h"
+#include "base/strings/safe_sprintf.h"
 #include "base/test/histogram_tester.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
@@ -19,6 +20,39 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"
 
+namespace {
+
+// Helps in setting the current network type and id.
+class TestNetworkQualityEstimator : public net::NetworkQualityEstimator {
+ public:
+  TestNetworkQualityEstimator() {}
+
+  ~TestNetworkQualityEstimator() override {}
+
+  // Overrides the current network type and id.
+  // Notifies network quality estimator of change in connection.
+  void SimulateNetworkChangeTo(net::NetworkChangeNotifier::ConnectionType type,
+                               std::string network_id) {
+    current_network_id_ = network_id;
+    OnConnectionTypeChanged(type);
+  }
+
+  using NetworkQualityEstimator::GetCacheSizeForTests;
+  using NetworkQualityEstimator::OnConnectionTypeChanged;
+  using NetworkQualityEstimator::ReadCachedNetworkQualityEstimate;
+
+ private:
+  // NetworkQualityEstimator implementation that returns the overridden network
+  // id (instead of invoking platform APIs).
+  std::string GetCurrentNetworkName() const override {
+    return current_network_id_;
+  }
+
+  std::string current_network_id_;
+};
+
+}  // namespace
+
 namespace net {
 
 // SpawnedTestServer not supported on iOS (see http://crbug.com/148666).
@@ -71,7 +105,7 @@ TEST(NetworkQualityEstimatorTest, TestPeakKbpsFastestRTTUpdates) {
     EXPECT_GT(network_quality.fastest_rtt_confidence, 0);
     EXPECT_GT(network_quality.peak_throughput_kbps_confidence, 0);
     EXPECT_GE(network_quality.fastest_rtt, request_duration);
-    EXPECT_GT(network_quality.peak_throughput_kbps, uint32_t(0));
+    EXPECT_GT(network_quality.peak_throughput_kbps, 0U);
     EXPECT_LE(
         network_quality.peak_throughput_kbps,
         min_transfer_size_in_bytes * 8.0 / request_duration.InMilliseconds());
@@ -89,7 +123,7 @@ TEST(NetworkQualityEstimatorTest, TestPeakKbpsFastestRTTUpdates) {
   histogram_tester.ExpectTotalCount("NQE.FastestRTT.Unknown", 1);
   {
     NetworkQuality network_quality = estimator.GetEstimate();
-    EXPECT_EQ(estimator.current_connection_type_,
+    EXPECT_EQ(estimator.current_network_id_.type,
               NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI);
     EXPECT_EQ(network_quality.fastest_rtt_confidence, 0);
     EXPECT_EQ(network_quality.peak_throughput_kbps_confidence, 0);
@@ -97,4 +131,118 @@ TEST(NetworkQualityEstimatorTest, TestPeakKbpsFastestRTTUpdates) {
 }
 #endif  // !defined(OS_IOS)
 
+// Test if the network estimates are cached when network change notification
+// is invoked.
+TEST(NetworkQualityEstimatorTest, TestCaching) {
+  TestNetworkQualityEstimator estimator;
+  size_t expected_cache_size = 0;
+  EXPECT_EQ(expected_cache_size, estimator.GetCacheSizeForTests());
+
+  // Cache entry will be added for (NONE, "").
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_2G, "test-1");
+  EXPECT_EQ(++expected_cache_size, estimator.GetCacheSizeForTests());
+
+  // Entry will be added for (2G, "test1").
+  // Also, set the network quality for (2G, "test1") so that it is stored in the
+  // cache.
+  estimator.peak_kbps_since_last_connection_change_ = 1;
+  estimator.fastest_RTT_since_last_connection_change_ =
+      base::TimeDelta::FromMilliseconds(1000);
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_3G, "test-1");
+  EXPECT_EQ(++expected_cache_size, estimator.GetCacheSizeForTests());
+
+  // Entry will be added for (3G, "test1").
+  // Also, set the network quality for (3G, "test1") so that it is stored in the
+  // cache.
+  estimator.peak_kbps_since_last_connection_change_ = 2;
+  estimator.fastest_RTT_since_last_connection_change_ =
+      base::TimeDelta::FromMilliseconds(500);
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_3G, "test-2");
+  EXPECT_EQ(++expected_cache_size, estimator.GetCacheSizeForTests());
+
+  // Entry will be added for (3G, "test2").
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_2G, "test-1");
+  EXPECT_EQ(++expected_cache_size, estimator.GetCacheSizeForTests());
+
+  // Read the network quality for (2G, "test-1").
+  EXPECT_TRUE(estimator.ReadCachedNetworkQualityEstimate());
+  EXPECT_EQ(1U, estimator.peak_kbps_since_last_connection_change_);
+  EXPECT_EQ(base::TimeDelta::FromMilliseconds(1000),
+            estimator.fastest_RTT_since_last_connection_change_);
+  // No new entry should be added for (2G, "test1") since it already exists
+  // in the cache.
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_3G, "test-1");
+  EXPECT_EQ(expected_cache_size, estimator.GetCacheSizeForTests());
+
+  // Read the network quality for (3G, "test1").
+  EXPECT_TRUE(estimator.ReadCachedNetworkQualityEstimate());
+  EXPECT_EQ(2U, estimator.peak_kbps_since_last_connection_change_);
+  EXPECT_EQ(base::TimeDelta::FromMilliseconds(500),
+            estimator.fastest_RTT_since_last_connection_change_);
+  // No new entry should be added for (3G, "test1") since it already exists
+  // in the cache.
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_3G, "test-2");
+  EXPECT_EQ(expected_cache_size, estimator.GetCacheSizeForTests());
+
+  // Reading quality of (3G, "test2") should return true.
+  EXPECT_TRUE(estimator.ReadCachedNetworkQualityEstimate());
+  EXPECT_EQ(0U, estimator.peak_kbps_since_last_connection_change_);
+  EXPECT_EQ(base::TimeDelta(),
+            estimator.fastest_RTT_since_last_connection_change_);
+
+  // Reading quality of (2G, "test-3") should return false.
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_2G, "test-3");
+  EXPECT_FALSE(estimator.ReadCachedNetworkQualityEstimate());
+}
+
+// Tests if the cache size remains bounded. Also, ensure that the cache is
+// LRU.
+TEST(NetworkQualityEstimatorTest, TestLRUCacheMaximumSize) {
+  TestNetworkQualityEstimator estimator;
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI, std::string());
+  EXPECT_EQ(1U, estimator.GetCacheSizeForTests());
+
+  char network_name[20];
+  // Add 100 more networks than the maximum size of the cache.
+  size_t network_count =
+      NetworkQualityEstimator::kMaximumNetworkQualityCacheSize + 100;
+
+  for (size_t i = 1; i <= network_count; ++i) {
+    base::strings::SafeSPrintf(network_name, "%d", i);
+    estimator.SimulateNetworkChangeTo(
+        NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI, network_name);
+    EXPECT_LE(estimator.GetCacheSizeForTests(),
+              NetworkQualityEstimator::kMaximumNetworkQualityCacheSize)
+        << i;
+  }
+  // One more call so that the last network is also written to cache.
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI, network_name);
+
+  EXPECT_EQ(NetworkQualityEstimator::kMaximumNetworkQualityCacheSize,
+            estimator.GetCacheSizeForTests());
+
+  // Test that the cache is LRU by examining its contents.
+  for (size_t i = 1; i <= network_count; ++i) {
+    // The first 100 networks should not be present in the cache.
+    bool expect_present_in_cache = i >= 101;
+    base::strings::SafeSPrintf(network_name, "%d", i);
+
+    NetworkQualityEstimator::NetworkID network_id(
+        NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI, network_name);
+
+    bool found = estimator.cached_network_quality_.find(network_id) !=
+                 estimator.cached_network_quality_.end();
+    EXPECT_EQ(expect_present_in_cache, found) << i;
+  }
+}
+
 }  // namespace net