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

net/base/network_quality_estimator_unittest.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/base/network_quality_estimator.h"
 
 #include <limits>
 
 #include "base/basictypes.h"
 #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/time/time.h"
 #include "build/build_config.h"
 #include "net/base/network_change_notifier.h"
 #include "net/base/network_quality.h"
 #include "net/test/embedded_test_server/embedded_test_server.h"
 #include "net/url_request/url_request_test_util.h"
 #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() : NetworkQualityEstimator(true, true) {}
+
+  ~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_type_ = type;
+    current_network_id_ = network_id;
+    OnConnectionTypeChanged(type);
+  }
+
+  using NetworkQualityEstimator::GetNetworkQualityCacheSizeForTests;
+  using NetworkQualityEstimator::ReadCachedNetworkQualityEstimate;
+  using NetworkQualityEstimator::OnConnectionTypeChanged;
+
+ private:
+  // NetworkQualityEstimator implementation that returns the overridden network
+  // id (instead of invoking platform APIs).
+  NetworkQualityEstimator::NetworkID GetCurrentNetworkID() const override {
+    return NetworkQualityEstimator::NetworkID(current_network_type_,
+                                              current_network_id_);
+  }
+
+  net::NetworkChangeNotifier::ConnectionType current_network_type_;
+  std::string current_network_id_;
+};
+
+}  // namespace
+
 namespace net {
 
 // http://crbug.com/492410
 TEST(NetworkQualityEstimatorTest, DISABLED_TestPeakKbpsFastestRTTUpdates) {
   net::test_server::EmbeddedTestServer embedded_test_server;
   embedded_test_server.ServeFilesFromDirectory(
       base::FilePath(FILE_PATH_LITERAL("net/data/url_request_unittest")));
   ASSERT_TRUE(embedded_test_server.InitializeAndWaitUntilReady());
 
   // Enable requests to local host to be used for network quality estimation.
-  NetworkQualityEstimator estimator(true, true);
+  TestNetworkQualityEstimator estimator;
   {
     NetworkQuality network_quality = estimator.GetPeakEstimate();
     EXPECT_EQ(network_quality.rtt(), base::TimeDelta::Max());
     EXPECT_EQ(network_quality.downstream_throughput_kbps(), 0);
   }
 
   TestDelegate test_delegate;
   TestURLRequestContext context(false);
 
   scoped_ptr<URLRequest> request(
       context.CreateRequest(embedded_test_server.GetURL("/echo.html"),
                             DEFAULT_PRIORITY, &test_delegate));
   request->Start();
 
   base::RunLoop().Run();
 
   // Both RTT and downstream throughput should be updated.
   estimator.NotifyDataReceived(*request, 1000, 1000);
   {
     NetworkQuality network_quality = estimator.GetPeakEstimate();
-    EXPECT_GT(network_quality.rtt(), base::TimeDelta());
     EXPECT_LT(network_quality.rtt(), base::TimeDelta::Max());
     EXPECT_GE(network_quality.downstream_throughput_kbps(), 1);
   }
 
   // Check UMA histograms.
   base::HistogramTester histogram_tester;
   histogram_tester.ExpectTotalCount("NQE.PeakKbps.Unknown", 0);
   histogram_tester.ExpectTotalCount("NQE.FastestRTT.Unknown", 0);
 
-  estimator.OnConnectionTypeChanged(
-      NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI);
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI, std::string());
   histogram_tester.ExpectTotalCount("NQE.PeakKbps.Unknown", 1);
   histogram_tester.ExpectTotalCount("NQE.FastestRTT.Unknown", 1);
   {
     NetworkQuality network_quality = estimator.GetPeakEstimate();
-    EXPECT_EQ(estimator.current_connection_type_,
-              NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI);
     EXPECT_EQ(network_quality.rtt(), base::TimeDelta::Max());
     EXPECT_EQ(network_quality.downstream_throughput_kbps(), 0);
   }
 }
 
 TEST(NetworkQualityEstimatorTest, StoreObservations) {
   net::test_server::EmbeddedTestServer embedded_test_server;
   embedded_test_server.ServeFilesFromDirectory(
       base::FilePath(FILE_PATH_LITERAL("net/data/url_request_unittest")));
   ASSERT_TRUE(embedded_test_server.InitializeAndWaitUntilReady());
 
   NetworkQualityEstimator estimator(true, true);
   TestDelegate test_delegate;
   TestURLRequestContext context(false);
 
   // Push 10 more observations than the maximum buffer size.
-  for (size_t i = 0;
-       i < estimator.GetMaximumObservationBufferSizeForTests() + 10U; ++i) {
+  for (size_t i = 0; i < estimator.kMaximumObservationsBufferSize + 10U; ++i) {
     scoped_ptr<URLRequest> request(
         context.CreateRequest(embedded_test_server.GetURL("/echo.html"),
                               DEFAULT_PRIORITY, &test_delegate));
     request->Start();
     base::RunLoop().Run();
 
     estimator.NotifyDataReceived(*request, 1000, 1000);
   }
 
-  EXPECT_TRUE(estimator.VerifyBufferSizeForTests(
-      estimator.GetMaximumObservationBufferSizeForTests()));
+  EXPECT_EQ(NetworkQualityEstimator::kMaximumObservationsBufferSize,
+            estimator.GetKbpsObservationBufferSizeForTests());
+  EXPECT_EQ(NetworkQualityEstimator::kMaximumObservationsBufferSize,
+            estimator.GetRTTObservationBufferSizeForTests());
 
   // Verify that the stored observations are cleared on network change.
   estimator.OnConnectionTypeChanged(
       NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI);
-  EXPECT_TRUE(estimator.VerifyBufferSizeForTests(0U));
+  EXPECT_EQ(0U, estimator.GetKbpsObservationBufferSizeForTests());
+  EXPECT_EQ(0U, estimator.GetRTTObservationBufferSizeForTests());
 
   scoped_ptr<URLRequest> request(
       context.CreateRequest(embedded_test_server.GetURL("/echo.html"),
                             DEFAULT_PRIORITY, &test_delegate));
 
   // Verify that overflow protection works.
   request->Start();
   base::RunLoop().Run();
   estimator.NotifyDataReceived(*request, std::numeric_limits<int64_t>::max(),
                                std::numeric_limits<int64_t>::max());
   {
     NetworkQuality network_quality = estimator.GetPeakEstimate();
     EXPECT_EQ(std::numeric_limits<int32_t>::max() - 1,
               network_quality.downstream_throughput_kbps());
   }
 }
 
+// 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.GetNetworkQualityCacheSizeForTests());
+
+  // Cache entry will not be added for (NONE, "").
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_2G, "test-1");
+  EXPECT_EQ(expected_cache_size,
+            estimator.GetNetworkQualityCacheSizeForTests());
+
+  // 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.GetNetworkQualityCacheSizeForTests());
+
+  // 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.GetNetworkQualityCacheSizeForTests());
+
+  // Entry will be added for (3G, "test2").
+  estimator.SimulateNetworkChangeTo(
+      NetworkChangeNotifier::ConnectionType::CONNECTION_2G, "test-1");
+  EXPECT_EQ(++expected_cache_size,
+            estimator.GetNetworkQualityCacheSizeForTests());
+
+  // Read the network quality for (2G, "test-1").
+  EXPECT_TRUE(estimator.ReadCachedNetworkQualityEstimate());
+  EXPECT_EQ(1, 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.GetNetworkQualityCacheSizeForTests());
+
+  // Read the network quality for (3G, "test1").
+  EXPECT_TRUE(estimator.ReadCachedNetworkQualityEstimate());
+  EXPECT_EQ(2, 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.GetNetworkQualityCacheSizeForTests());
+
+  // Reading quality of (3G, "test2") should return true.
+  EXPECT_TRUE(estimator.ReadCachedNetworkQualityEstimate());
+  EXPECT_EQ(0, estimator.peak_kbps_since_last_connection_change_);
+  EXPECT_EQ(base::TimeDelta::Max(),
+            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(
+      net::NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI,
+      std::string());
+  EXPECT_EQ(0U, estimator.GetNetworkQualityCacheSizeForTests());
+
+  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 = 0; i < network_count; ++i) {
+    base::strings::SafeSPrintf(network_name, "%d", i);
+    estimator.SimulateNetworkChangeTo(
+        net::NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI,
+        network_name);
+    EXPECT_LE(estimator.GetNetworkQualityCacheSizeForTests(),
+              NetworkQualityEstimator::kMaximumNetworkQualityCacheSize)
+        << i;
+  }
+  // One more call so that the last network is also written to cache.
+  estimator.SimulateNetworkChangeTo(
+      net::NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI,
+      network_name);
+
+  EXPECT_EQ(NetworkQualityEstimator::kMaximumNetworkQualityCacheSize,
+            estimator.GetNetworkQualityCacheSizeForTests());
+
+  // Test that the cache is LRU by examining its contents.
+  for (size_t i = 0; i < network_count; ++i) {
+    // The first 100 networks should not be present in the cache.
+    bool expect_present_in_cache = i >= 100;
+    base::strings::SafeSPrintf(network_name, "%d", i);
+
+    NetworkQualityEstimator::NetworkID network_id(
+        NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI, network_name);
+
+    bool found = estimator.cached_network_qualities_.find(network_id) !=
+                 estimator.cached_network_qualities_.end();
+    EXPECT_EQ(expect_present_in_cache, found) << i;
+  }
+}
+
 }  // namespace net