1// Copyright 2012 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef SYNC_ENGINE_BACKOFF_DELAY_PROVIDER_H_
6#define SYNC_ENGINE_BACKOFF_DELAY_PROVIDER_H_
7
8#include "base/time/time.h"
9#include "sync/base/sync_export.h"
10
11namespace syncer {
12
13namespace sessions {
14struct ModelNeutralState;
15}
16
17// A component used to get time delays associated with exponential backoff.
18class SYNC_EXPORT_PRIVATE BackoffDelayProvider {
19 public:
20  // Factory function to create a standard BackoffDelayProvider.
21  static BackoffDelayProvider* FromDefaults();
22
23  // Similar to above, but causes sync to retry very quickly (see
24  // polling_constants.h) when it encounters an error before exponential
25  // backoff.
26  //
27  // *** NOTE *** This should only be used if kSyncShortInitialRetryOverride
28  // was passed to command line.
29  static BackoffDelayProvider* WithShortInitialRetryOverride();
30
31  virtual ~BackoffDelayProvider();
32
33  // DDOS avoidance function.  Calculates how long we should wait before trying
34  // again after a failed sync attempt, where the last delay was |base_delay|.
35  // TODO(tim): Look at URLRequestThrottlerEntryInterface.
36  virtual base::TimeDelta GetDelay(const base::TimeDelta& last_delay);
37
38  // Helper to calculate the initial value for exponential backoff.
39  // See possible values and comments in polling_constants.h.
40  virtual base::TimeDelta GetInitialDelay(
41      const sessions::ModelNeutralState& state) const;
42
43 protected:
44  BackoffDelayProvider(const base::TimeDelta& default_initial_backoff,
45                       const base::TimeDelta& short_initial_backoff);
46
47 private:
48  const base::TimeDelta default_initial_backoff_;
49  const base::TimeDelta short_initial_backoff_;
50
51  DISALLOW_COPY_AND_ASSIGN(BackoffDelayProvider);
52};
53
54}  // namespace syncer
55
56#endif  // SYNC_ENGINE_BACKOFF_DELAY_PROVIDER_H_
57