Add MediaServiceThrottler

media/base/android/media_service_throttler_unittest.cc

+// Copyright 2016 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 "media/base/android/media_service_throttler.h"
+
+#include "base/message_loop/message_loop.h"
+#include "base/test/simple_test_tick_clock.h"
+#include "media/base/android/media_server_crash_listener.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+
+// From base/media/android/media_service_throttler.cc
+const int kMaxBurstClients = 10;
+
+class MediaServiceThrottlerTest : public testing::Test {
+ public:
+  MediaServiceThrottlerTest() : clock_(new base::SimpleTestTickClock()) {
+    throttler_ = MediaServiceThrottler::GetInstance();
+    clock_->SetNowTicks(base::TimeTicks());
+    throttler_->SetTickClockForTesting(clock_);
+    MediaServerCrashListener::GetInstance()
+        ->ClearOnServerCrashCallbackForTesting();
+    throttler_->ResetInternalStateForTesting();
+    base_delay_ = throttler_->GetBaseThrottlingRateForTesting();
+  }
+
+  void SimulateCrashes(int number_of_crashes) {
+    for (int i = 0; i < number_of_crashes; ++i)
+      throttler_->OnMediaServerCrash();
+  }
+
+  // Simulates the scheduling of |number_of_clients| and returns the last
+  // scheduling delay.
+  base::TimeDelta BatchScheduleClientCreations(int number_of_clients) {
+    for (int i = 0; i < number_of_clients - 1; ++i)
+      throttler_->ScheduleClientCreation();
+
+    return throttler_->ScheduleClientCreation();
+  }
+
+  base::TimeDelta GetCurrentDelayBetweenClients() {
+    // Schedule two clients and return the difference between their scheduling
+    // slots.
+    return -(throttler_->ScheduleClientCreation() -
+             throttler_->ScheduleClientCreation());
+  }
+
+  base::TimeTicks TestNow() { return clock_->NowTicks(); }
+
+  MediaServiceThrottler* throttler_;
+  base::SimpleTestTickClock* clock_;
+
+  base::TimeDelta base_delay_;
+
+  // Necessary, or else base::ThreadTaskRunnerHandle::Get() fails.
+  base::MessageLoop message_loop_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MediaServiceThrottlerTest);
+};
+
+// Canary test case.
+TEST_F(MediaServiceThrottlerTest, BaseCase) {
+  EXPECT_EQ(base::TimeDelta(), throttler_->ScheduleClientCreation());
+}
+
+// Makes sure we can "burst" schedule clients.
+TEST_F(MediaServiceThrottlerTest, NoCrash_UnderBurstThreshold_ShouldNotDelay) {
+  int number_burst_client_scheduled = 0;
+
+  while (base::TimeDelta() == throttler_->ScheduleClientCreation())
+    number_burst_client_scheduled++;
+
+  EXPECT_EQ(kMaxBurstClients, number_burst_client_scheduled);
+}
+
+// Makes sure that, when burst scheduling a client, we schedule it from
+// last scheduled burst client (vs scheduling it |base_delay_| from now).
+TEST_F(MediaServiceThrottlerTest, NoCrash_OverBurstThreshold_ShouldDelay) {
+  // Schedule clients until the next one would be over burst threshold.
+  BatchScheduleClientCreations(kMaxBurstClients);
+
+  // Make sure the next client that is scheduled is scheduled in its normal time
+  // slot.
+  EXPECT_EQ(base_delay_ * (kMaxBurstClients + 1),
+            throttler_->ScheduleClientCreation());
+}
+
+// Makes sure that clients are scheduled |base_delay| apart.
+TEST_F(MediaServiceThrottlerTest,
+       NoCrash_OverBurstThreshold_ShouldDelayLinearly) {
+  // Schedule clients until the next one would be over burst threshold.
+  BatchScheduleClientCreations(kMaxBurstClients);
+
+  // Delays between two clients should be |base_delay_| appart.
+  EXPECT_EQ(base_delay_, GetCurrentDelayBetweenClients());
+
+  // Delays should remain constant (GetCurrentDelayBetweenClients() is not
+  // idempotent and actually schedules new clients).
+  EXPECT_EQ(GetCurrentDelayBetweenClients(), GetCurrentDelayBetweenClients());
+}
+
+// Makes sure that for every |base_delay_| that has elapsed, we can burst
+// schedule an extra client.
+TEST_F(MediaServiceThrottlerTest,
+       NoCrash_BurstThreshold_ShouldBeSlidingWindow) {
+  // Schedule some clients below the burst threshold.
+  BatchScheduleClientCreations(7);
+
+  clock_->Advance(base_delay_ * 5);
+
+  // Make sure the passage of allows for more clients to be scheduled, since
+  // 7 + 8 > kMaxBurstClients.
+  EXPECT_EQ(base::TimeDelta(), BatchScheduleClientCreations(8));
+}
+
+// Makes sure that, if not enough time has elapsed, we do not burst schedule
+// new clients.
+TEST_F(MediaServiceThrottlerTest,
+       NoCrash_OverBurstThresholdWithTimeLapse_ShouldDelay) {
+  // Schedule some clients way above the burst threshold.
+  BatchScheduleClientCreations(3 * kMaxBurstClients);
+
+  // Advance the time so there are still 2 * kMaxBurstClients pending clients.
+  clock_->Advance(base_delay_ * kMaxBurstClients);
+
+  // Make sure delay we do not burst schedule new clients.
+  EXPECT_NE(base::TimeDelta(), throttler_->ScheduleClientCreation());
+}
+
+// Makes sure that after a certain amount of inactivity, the scheduling clock is
+// reset.
+TEST_F(MediaServiceThrottlerTest, NoCrash_LongInactivity_ShouldReset) {
+  // Schedule two minute's worth of clients
+  BatchScheduleClientCreations(base::TimeDelta::FromMinutes(2) / base_delay_);
+
+  // Advance the time so the scheduler perceived a full minute of inactivity.
+  clock_->Advance(base::TimeDelta::FromSeconds(61));
+
+  // Make sure new clients are burst scheduled.
+  EXPECT_EQ(base::TimeDelta(), throttler_->ScheduleClientCreation());
+}
+
+// Makes sure that crashes increase the scheduling delay.
+TEST_F(MediaServiceThrottlerTest, WithCrash_BaseCase_DelayShouldIncrease) {
+  // Schedule clients until the next one would be over burst threshold.
+  BatchScheduleClientCreations(kMaxBurstClients);
+
+  base::TimeDelta no_crash_delay = GetCurrentDelayBetweenClients();
+
+  SimulateCrashes(1);
+
+  base::TimeDelta crash_delay = GetCurrentDelayBetweenClients();
+
+  EXPECT_NE(base_delay_, crash_delay);
+  EXPECT_GT(crash_delay, no_crash_delay);
+}
+
+// Makes sure that we tolerate 1 crash per minute.
+TEST_F(MediaServiceThrottlerTest,
+       WithCrash_SingleCrash_DelayShouldNotIncrease) {
+  // Schedule clients until the next one would be over burst threshold.
+  BatchScheduleClientCreations(kMaxBurstClients);
+
+  SimulateCrashes(1);
+  clock_->Advance(base::TimeDelta::FromMilliseconds(1));
+
+  // Because we use the floor function when calculating crashes, a small time
+  // advance should nullify a single crash.
+  EXPECT_EQ(base_delay_, GetCurrentDelayBetweenClients());
+}
+
+// Makes sure that more than 1 crash per minute causes increased delays.
+TEST_F(MediaServiceThrottlerTest, WithCrash_ManyCrashes_DelayShouldIncrease) {
+  // Schedule clients until the next one would be over burst threshold.
+  BatchScheduleClientCreations(kMaxBurstClients);
+
+  SimulateCrashes(2);
+  clock_->Advance(base::TimeDelta::FromMilliseconds(1));
+
+  // The delay after crashes should be greater than the base delay.
+  EXPECT_LT(base_delay_, GetCurrentDelayBetweenClients());
+}
+
+// Makes sure that an increase in server crashes leads to delay increases.
+TEST_F(MediaServiceThrottlerTest,
+       WithCrash_ConsecutiveCrashes_DelayShouldIncreaseWithNumberOfCrashes) {
+  // Schedule clients until the next one would be over burst threshold.
+  BatchScheduleClientCreations(kMaxBurstClients);
+
+  base::TimeDelta last_delay = base_delay_;
+
+  for (int i = 0; i < 5; ++i) {
+    SimulateCrashes(1);
+    base::TimeDelta current_delay = GetCurrentDelayBetweenClients();
+    EXPECT_LT(last_delay, current_delay);
+    last_delay = current_delay;
+  }
+}
+
+// Makes sure that crashes affect the number of burst clients we can schedule.
+TEST_F(MediaServiceThrottlerTest, WithCrash_ShouldAllowFewerBurstClients) {
+  int number_burst_client_scheduled = 0;
+
+  SimulateCrashes(1);
+
+  while (base::TimeDelta() == throttler_->ScheduleClientCreation())
+    number_burst_client_scheduled++;
+
+  EXPECT_GT(kMaxBurstClients, number_burst_client_scheduled);
+}
+
+// Makes sure delays are capped to a certain maximal value.
+TEST_F(MediaServiceThrottlerTest, WithCrash_ManyCrashes_DelayShouldMaxOut) {
+  // Schedule clients until the next one would be over burst threshold.
+  BatchScheduleClientCreations(kMaxBurstClients);
+
+  SimulateCrashes(10);
+  base::TimeDelta capped_delay = GetCurrentDelayBetweenClients();
+
+  SimulateCrashes(10);
+
+  EXPECT_EQ(capped_delay, GetCurrentDelayBetweenClients());
+}
+
+// Makes sure a minute without crashes resets the crash counter.
+TEST_F(MediaServiceThrottlerTest, WithCrash_NoCrashesForAMinute_ShouldReset) {
+  SimulateCrashes(10);
+
+  // The effective server crash count should be reset because it has been over
+  // a minute since the last crash.
+  clock_->Advance(base::TimeDelta::FromSeconds(61));
+
+  BatchScheduleClientCreations(kMaxBurstClients);
+
+  EXPECT_EQ(base_delay_, GetCurrentDelayBetweenClients());
+}
+
+// Makes sure a steady crashes do not resets the crash counter.
+TEST_F(MediaServiceThrottlerTest, WithCrash_ConstantCrashes_ShouldNotReset) {
+  SimulateCrashes(9);
+
+  // The effective server crash count should not be reset.
+  clock_->Advance(base::TimeDelta::FromSeconds(59));
+  SimulateCrashes(1);
+  clock_->Advance(base::TimeDelta::FromSeconds(2));
+
+  BatchScheduleClientCreations(kMaxBurstClients);
+
+  EXPECT_LT(base_delay_, GetCurrentDelayBetweenClients());
+}
+
+}  // namespace media