NQE: Record correlation metric in UMA

net/nqe/network_quality_estimator_unittest.cc

Index: net/nqe/network_quality_estimator_unittest.cc
diff --git a/net/nqe/network_quality_estimator_unittest.cc b/net/nqe/network_quality_estimator_unittest.cc
index 87de5f174485ae3b7c27a8ca8be57e374dd8a9de..06e45e7a9d59b2c66408ed88c82e271e1e7cfe06 100644
--- a/net/nqe/network_quality_estimator_unittest.cc
+++ b/net/nqe/network_quality_estimator_unittest.cc
@@ -1728,4 +1728,101 @@ TEST(NetworkQualityEstimatorTest, NameConnectionTypeConversion) {
   }
 }
 
+// Tests that the correlation histogram is recorded correctly based on
+// correlation logging probability set in the variation params.
+TEST(NetworkQualityEstimatorTest, CorrelationHistogram) {
+  // Match the values set in network_quality_estimator.cc.
+  static const int32_t kTrimBits = 5;
+  static const int32_t kBitsPerMetric = 7;
+
+  const struct {
+    double correlation_logging_probability;
+    base::TimeDelta transport_rtt;
+    int32_t expected_transport_rtt_milliseconds;
+    base::TimeDelta http_rtt;
+    int32_t expected_http_rtt_milliseconds;
+    int32_t downstream_throughput_kbps;
+    int32_t expected_downstream_throughput_kbps;
+
+  } tests[] = {
+      {
+          // Verify that the metric is not recorded if the logging probability
+          // is set to 0.0.
+          0.0, base::TimeDelta::FromSeconds(1), 1000 >> kTrimBits,
+          base::TimeDelta::FromSeconds(2), 2000 >> kTrimBits, 3000,
+          3000 >> kTrimBits,
+      },
+      {
+          1.0, base::TimeDelta::FromSeconds(1), 1000 >> kTrimBits,
+          base::TimeDelta::FromSeconds(2), 2000 >> kTrimBits, 3000,
+          3000 >> kTrimBits,
+      },
+      {
+          // Verify that if the metric is larger 2^(kBitsPerMetric + kTrimBits),
+          // it is rounded down to
+          // (2^(kBitsPerMetric + kTrimBits) - 1) >> kTrimBits.
+          1.0, base::TimeDelta::FromSeconds(10), 4095 >> kTrimBits,
+          base::TimeDelta::FromSeconds(20), 4095 >> kTrimBits, 30000,
+          4095 >> kTrimBits,
+      },
+  };
+
+  for (const auto& test : tests) {
+    base::HistogramTester histogram_tester;
+
+    std::map<std::string, std::string> variation_params;
+    variation_params["correlation_logging_probability"] =
+        base::DoubleToString(test.correlation_logging_probability);
+    TestNetworkQualityEstimator estimator(variation_params);
+
+    estimator.set_transport_rtt(test.transport_rtt);
+    estimator.set_recent_transport_rtt(test.transport_rtt);
+    estimator.set_http_rtt(test.http_rtt);
+    estimator.set_recent_http_rtt(test.http_rtt);
+    estimator.set_downlink_throughput_kbps(test.downstream_throughput_kbps);
+
+    TestDelegate test_delegate;
+    TestURLRequestContext context(true);
+    context.set_network_quality_estimator(&estimator);
+    context.Init();
+
+    // Start a main-frame request which should cause network quality estimator
+    // to record the network quality at the last main frame request.
+    std::unique_ptr<URLRequest> request_1(context.CreateRequest(
+        estimator.GetEchoURL(), DEFAULT_PRIORITY, &test_delegate));
+    request_1->SetLoadFlags(request_1->load_flags() | LOAD_MAIN_FRAME);
+    request_1->Start();
+    base::RunLoop().Run();
+    histogram_tester.ExpectTotalCount("NQE.Correlation.ResourceLoadTime", 0);
+
+    // Start another main-frame request which should cause network quality
+    // estimator to record the correlation UMA.
+    std::unique_ptr<URLRequest> request_2(context.CreateRequest(
+        estimator.GetEchoURL(), DEFAULT_PRIORITY, &test_delegate));
+    request_2->Start();
+    base::RunLoop().Run();
+
+    if (test.correlation_logging_probability == 0.0) {
+      histogram_tester.ExpectTotalCount("NQE.Correlation.ResourceLoadTime", 0);
+      continue;
+    }
+    histogram_tester.ExpectTotalCount("NQE.Correlation.ResourceLoadTime", 1);
+    std::vector<base::Bucket> buckets =
+        histogram_tester.GetAllSamples("NQE.Correlation.ResourceLoadTime");
+    // Get the bits at index 0-10 which contain the transport RTT.
+    // 128 is 2^kBitsPerMetric.
+    EXPECT_EQ(test.expected_transport_rtt_milliseconds,
+              buckets.at(0).min >> kBitsPerMetric >> kBitsPerMetric >>
+                  kBitsPerMetric);
+    // Get the bits at index 11-17 which contain the HTTP RTT.
+    EXPECT_EQ(test.expected_http_rtt_milliseconds,
+              (buckets.at(0).min >> kBitsPerMetric >> kBitsPerMetric) % 128);
+    // Get the bits at index 18-24 which contain the downstream throughput.
+    EXPECT_EQ(test.expected_downstream_throughput_kbps,
+              (buckets.at(0).min >> kBitsPerMetric) % 128);
+    // Get the bits at index 25-31 which contain the resource fetch time.
+    EXPECT_LE(0, buckets.at(0).min % 128);
+  }
+}
+
 }  // namespace net