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