Allow BackoffEntry to be serialized and deserialized.

net/base/backoff_entry_serializer_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/backoff_entry.h"
+
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/time/tick_clock.h"
+#include "base/values.h"
+#include "net/base/backoff_entry_serializer.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace net {
+
+namespace {
+
+using base::Time;
+using base::TimeDelta;
+using base::TimeTicks;
+
+BackoffEntry::Policy base_policy = {
+  0 /* num_errors_to_ignore */,
+  1000 /* initial_delay_ms */,
+  2.0 /* multiply_factor */,
+  0.0 /* jitter_factor */,
+  20000 /* maximum_backoff_ms */,
+  2000 /* entry_lifetime_ms */,
+  false /* always_use_initial_delay */
+};
+
+class TestTickClock : public base::TickClock {
+ public:
+  TestTickClock() {}
+  ~TestTickClock() override {}
+
+  TimeTicks NowTicks() override { return now_ticks_; }
+  void set_now(TimeTicks now) { now_ticks_ = now; }
+
+ private:
+  TimeTicks now_ticks_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestTickClock);
+};
+
+TEST(BackoffEntrySerializerTest, SerializeNoFailures) {
+  Time original_time = Time::Now();
+  TestTickClock original_ticks;
+  original_ticks.set_now(TimeTicks::Now());
+  BackoffEntry original(&base_policy, &original_ticks);
+  scoped_ptr<base::Value> serialized =
+      BackoffEntrySerializer::SerializeToValue(original, original_time);
+
+  scoped_ptr<BackoffEntry> deserialized =
+      BackoffEntrySerializer::DeserializeFromValue(*serialized, &base_policy,
+                                                   &original_ticks,
+                                                   original_time);
+  ASSERT_TRUE(deserialized.get());
+  EXPECT_EQ(original.failure_count(), deserialized->failure_count());
+  EXPECT_EQ(original.GetReleaseTime(), deserialized->GetReleaseTime());
+}
+
+TEST(BackoffEntrySerializerTest, SerializeTimeOffsets) {
+  Time original_time = Time::FromJsTime(1430907555111);  // May 2015 for realism
+  TestTickClock original_ticks;
+  BackoffEntry original(&base_policy, &original_ticks);
+  // 2 errors.
+  original.InformOfRequest(false);
+  original.InformOfRequest(false);
+  scoped_ptr<base::Value> serialized =
+      BackoffEntrySerializer::SerializeToValue(original, original_time);
+
+  {
+    // Test that immediate deserialization round-trips.
+    scoped_ptr<BackoffEntry> deserialized =
+        BackoffEntrySerializer::DeserializeFromValue(*serialized, &base_policy,
+                                                     &original_ticks,
+                                                     original_time);
+    ASSERT_TRUE(deserialized.get());
+    EXPECT_EQ(original.failure_count(), deserialized->failure_count());
+    EXPECT_EQ(original.GetReleaseTime(), deserialized->GetReleaseTime());
+  }
+
+  {
+    // Test deserialization when wall clock has advanced but TimeTicks::Now()
+    // hasn't (e.g. device was rebooted).
+    Time later_time = original_time + TimeDelta::FromDays(1);
+    scoped_ptr<BackoffEntry> deserialized =
+        BackoffEntrySerializer::DeserializeFromValue(*serialized, &base_policy,
+                                                     &original_ticks,
+                                                     later_time);
+    ASSERT_TRUE(deserialized.get());
+    EXPECT_EQ(original.failure_count(), deserialized->failure_count());
+    // Remaining backoff duration continues decreasing while device is off.
+    // Since TimeTicks::Now() has not advanced, the absolute release time ticks
+    // will decrease accordingly.
+    EXPECT_GT(original.GetTimeUntilRelease(),
+              deserialized->GetTimeUntilRelease());
+    EXPECT_EQ(original.GetReleaseTime() - TimeDelta::FromDays(1),
+              deserialized->GetReleaseTime());
+  }
+
+  {
+    // Test deserialization when TimeTicks::Now() has advanced but wall clock
+    // hasn't (e.g. it's an hour later, but a DST change cancelled that out).
+    TestTickClock later_ticks;
+    later_ticks.set_now(TimeTicks() + TimeDelta::FromDays(1));
+    scoped_ptr<BackoffEntry> deserialized =
+        BackoffEntrySerializer::DeserializeFromValue(*serialized, &base_policy,
+                                                     &later_ticks,
+                                                     original_time);
+    ASSERT_TRUE(deserialized.get());
+    EXPECT_EQ(original.failure_count(), deserialized->failure_count());
+    // According to the wall clock, no time has passed. So remaining backoff
+    // duration is preserved, hence the absolute release time ticks increases.
+    // This isn't ideal - by also serializing the current time and time ticks,
+    // it would be possible to detect that time has passed but the wall clock
+    // went backwards, and reduce the remaining backoff duration accordingly,
+    // however the current implementation does not do this as the benefit would
+    // be somewhat marginal.
+    EXPECT_EQ(original.GetTimeUntilRelease(),
+              deserialized->GetTimeUntilRelease());
+    EXPECT_EQ(original.GetReleaseTime() + TimeDelta::FromDays(1),
+              deserialized->GetReleaseTime());
+  }
+
+  {
+    // Test deserialization when both wall clock and TimeTicks::Now() have
+    // advanced (e.g. it's just later than it used to be).
+    TestTickClock later_ticks;
+    later_ticks.set_now(TimeTicks() + TimeDelta::FromDays(1));
+    Time later_time = original_time + TimeDelta::FromDays(1);
+    scoped_ptr<BackoffEntry> deserialized =
+        BackoffEntrySerializer::DeserializeFromValue(*serialized, &base_policy,
+                                                     &later_ticks, later_time);
+    ASSERT_TRUE(deserialized.get());
+    EXPECT_EQ(original.failure_count(), deserialized->failure_count());
+    // Since both have advanced by the same amount, the absolute release time
+    // ticks should be preserved; the remaining backoff duration will have
+    // decreased of course, since time has passed.
+    EXPECT_GT(original.GetTimeUntilRelease(),
+              deserialized->GetTimeUntilRelease());
+    EXPECT_EQ(original.GetReleaseTime(), deserialized->GetReleaseTime());
+  }
+
+  {
+    // Test deserialization when wall clock has gone backwards but TimeTicks
+    // haven't (e.g. the system clock was fast but they fixed it).
+    EXPECT_LT(TimeDelta::FromSeconds(1), original.GetTimeUntilRelease());
+    Time earlier_time = original_time - TimeDelta::FromSeconds(1);
+    scoped_ptr<BackoffEntry> deserialized =
+        BackoffEntrySerializer::DeserializeFromValue(*serialized, &base_policy,
+                                                     &original_ticks,
+                                                     earlier_time);
+    ASSERT_TRUE(deserialized.get());
+    EXPECT_EQ(original.failure_count(), deserialized->failure_count());
+    // If only the absolute wall clock time was serialized, subtracting the
+    // (decreased) current wall clock time from the serialized wall clock time
+    // could give very large (incorrect) values for remaining backoff duration.
+    // But instead the implementation also serializes the remaining backoff
+    // duration, and doesn't allow the duration to increase beyond it's previous
+    // value during deserialization. Hence when the wall clock goes backwards
+    // the remaining backoff duration will be preserved.
+    EXPECT_EQ(original.GetTimeUntilRelease(),
+              deserialized->GetTimeUntilRelease());
+    // Since TimeTicks::Now() hasn't changed, the absolute release time ticks
+    // will be equal too in this particular case.
+    EXPECT_EQ(original.GetReleaseTime(), deserialized->GetReleaseTime());
+  }
+}
+
+}  // namespace
+
+}  // namespace net