sync/engine/backoff_delay_provider.h

   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
  11 namespace syncer {
  12
  13 namespace sessions {
  14 struct ModelNeutralState;
  15 }
  16
  17 // A component used to get time delays associated with exponential backoff.
  18 class 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_