sync: add InternalComponentsFactory::Switches to simplify passing switches to internal components.

sync/engine/backoff_delay_provider.cc

+// Copyright (c) 2012 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 "sync/engine/backoff_delay_provider.h"
+
+#include "base/rand_util.h"
+#include "sync/internal_api/public/engine/polling_constants.h"
+#include "sync/internal_api/public/sessions/model_neutral_state.h"
+#include "sync/internal_api/public/util/syncer_error.h"
+
+using base::TimeDelta;
+
+namespace syncer {
+
+// static
+BackoffDelayProvider* BackoffDelayProvider::FromDefaults() {
+  return new BackoffDelayProvider(
+      TimeDelta::FromSeconds(kInitialBackoffRetrySeconds),
+      TimeDelta::FromSeconds(kInitialBackoffShortRetrySeconds));
+}
+
+// static
+BackoffDelayProvider* BackoffDelayProvider::WithShortInitialRetryOverride() {
+  return new BackoffDelayProvider(
+      TimeDelta::FromSeconds(kInitialBackoffShortRetrySeconds),
+      TimeDelta::FromSeconds(kInitialBackoffShortRetrySeconds));
+}
+
+BackoffDelayProvider::BackoffDelayProvider(
+    const base::TimeDelta& default_initial_backoff,
+    const base::TimeDelta& short_initial_backoff)
+    : default_initial_backoff_(default_initial_backoff),
+      short_initial_backoff_(short_initial_backoff) {
+}
+
+BackoffDelayProvider::~BackoffDelayProvider() {}
+
+TimeDelta BackoffDelayProvider::GetDelay(const base::TimeDelta& last_delay) {
+  if (last_delay.InSeconds() >= kMaxBackoffSeconds)
+    return TimeDelta::FromSeconds(kMaxBackoffSeconds);
+
+  // This calculates approx. base_delay_seconds * 2 +/- base_delay_seconds / 2
+  int64 backoff_s =
+      std::max(static_cast<int64>(1),
+               last_delay.InSeconds() * kBackoffRandomizationFactor);
+
+  // Flip a coin to randomize backoff interval by +/- 50%.
+  int rand_sign = base::RandInt(0, 1) * 2 - 1;
+
+  // Truncation is adequate for rounding here.
+  backoff_s = backoff_s +
+      (rand_sign * (last_delay.InSeconds() / kBackoffRandomizationFactor));
+
+  // Cap the backoff interval.
+  backoff_s = std::max(static_cast<int64>(1),
+                       std::min(backoff_s, kMaxBackoffSeconds));
+
+  return TimeDelta::FromSeconds(backoff_s);
+}
+
+TimeDelta BackoffDelayProvider::GetInitialDelay(
+    const sessions::ModelNeutralState& state) const {
+  if (SyncerErrorIsError(state.last_get_key_result))
+    return default_initial_backoff_;
+  // Note: If we received a MIGRATION_DONE on download updates, then commit
+  // should not have taken place.  Moreover, if we receive a MIGRATION_DONE
+  // on commit, it means that download updates succeeded.  Therefore, we only
+  // need to check if either code is equal to SERVER_RETURN_MIGRATION_DONE,
+  // and not if there were any more serious errors requiring the long retry.
+  if (state.last_download_updates_result == SERVER_RETURN_MIGRATION_DONE ||
+      state.commit_result == SERVER_RETURN_MIGRATION_DONE) {
+    return short_initial_backoff_;
+  }
+
+  return default_initial_backoff_;
+}
+
+}  // namespace syncer