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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_SYNC_ENGINE_BACKOFF_DELAY_PROVIDER_H_
#define COMPONENTS_SYNC_ENGINE_BACKOFF_DELAY_PROVIDER_H_
#include <memory>
#include "base/time/time.h"
namespace syncer {
struct ModelNeutralState;
// A component used to get time delays associated with exponential backoff.
class BackoffDelayProvider {
public:
// Factory function to create a standard BackoffDelayProvider.
static std::unique_ptr<BackoffDelayProvider> FromDefaults();
// Similar to above, but causes sync to retry very quickly (see
// polling_constants.h) when it encounters an error before exponential
// backoff.
//
// *** NOTE *** This should only be used if kSyncShortInitialRetryOverride
// was passed to command line.
static std::unique_ptr<BackoffDelayProvider> WithShortInitialRetryOverride();
BackoffDelayProvider(const BackoffDelayProvider&) = delete;
BackoffDelayProvider& operator=(const BackoffDelayProvider&) = delete;
virtual ~BackoffDelayProvider();
// DDOS avoidance function. Calculates how long we should wait before trying
// again after a failed sync attempt, where the last delay was `base_delay`.
// TODO(tim): Look at URLRequestThrottlerEntryInterface.
virtual base::TimeDelta GetDelay(const base::TimeDelta& last_delay);
// Helper to calculate the initial value for exponential backoff.
// See possible values and comments in polling_constants.h.
virtual base::TimeDelta GetInitialDelay(const ModelNeutralState& state) const;
// Test-only variant that avoids randomness in tests. `jitter_sign` must be -1
// or 1 and determines whether the jitter in the delay will be positive or
// negative.
base::TimeDelta GetDelayForTesting(base::TimeDelta last_delay,
int jitter_sign);
protected:
BackoffDelayProvider(const base::TimeDelta& default_initial_backoff,
const base::TimeDelta& short_initial_backoff);
private:
const base::TimeDelta default_initial_backoff_;
const base::TimeDelta short_initial_backoff_;
};
} // namespace syncer
#endif // COMPONENTS_SYNC_ENGINE_BACKOFF_DELAY_PROVIDER_H_
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