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_ 57