sync/engine/backoff_delay_provider.h

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