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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "sync/engine/backoff_delay_provider.h"
#include <stdint.h>
#include <algorithm>
#include "base/rand_util.h"
#include "sync/internal_api/public/engine/polling_constants.h"
#include "sync/internal_api/public/sessions/model_neutral_state.h"
#include "sync/internal_api/public/util/syncer_error.h"
using base::TimeDelta;
namespace syncer {
// static
BackoffDelayProvider* BackoffDelayProvider::FromDefaults() {
return new BackoffDelayProvider(
TimeDelta::FromSeconds(kInitialBackoffRetrySeconds),
TimeDelta::FromSeconds(kInitialBackoffImmediateRetrySeconds));
}
// static
BackoffDelayProvider* BackoffDelayProvider::WithShortInitialRetryOverride() {
return new BackoffDelayProvider(
TimeDelta::FromSeconds(kInitialBackoffShortRetrySeconds),
TimeDelta::FromSeconds(kInitialBackoffImmediateRetrySeconds));
}
BackoffDelayProvider::BackoffDelayProvider(
const base::TimeDelta& default_initial_backoff,
const base::TimeDelta& short_initial_backoff)
: default_initial_backoff_(default_initial_backoff),
short_initial_backoff_(short_initial_backoff) {
}
BackoffDelayProvider::~BackoffDelayProvider() {}
TimeDelta BackoffDelayProvider::GetDelay(const base::TimeDelta& last_delay) {
if (last_delay.InSeconds() >= kMaxBackoffSeconds)
return TimeDelta::FromSeconds(kMaxBackoffSeconds);
// This calculates approx. base_delay_seconds * 2 +/- base_delay_seconds / 2
int64_t backoff_s =
std::max(static_cast<int64_t>(1),
last_delay.InSeconds() * kBackoffRandomizationFactor);
// Flip a coin to randomize backoff interval by +/- 50%.
int rand_sign = base::RandInt(0, 1) * 2 - 1;
// Truncation is adequate for rounding here.
backoff_s = backoff_s +
(rand_sign * (last_delay.InSeconds() / kBackoffRandomizationFactor));
// Cap the backoff interval.
backoff_s = std::max(static_cast<int64_t>(1),
std::min(backoff_s, kMaxBackoffSeconds));
return TimeDelta::FromSeconds(backoff_s);
}
TimeDelta BackoffDelayProvider::GetInitialDelay(
const sessions::ModelNeutralState& state) const {
// NETWORK_CONNECTION_UNAVAILABLE implies we did not receive HTTP response
// from server because of some network error. If network is unavailable then
// on next connection type or address change scheduler will run canary job.
// Otherwise we'll retry in 30 seconds.
if (state.commit_result == NETWORK_CONNECTION_UNAVAILABLE ||
state.last_download_updates_result == NETWORK_CONNECTION_UNAVAILABLE) {
return default_initial_backoff_;
}
if (SyncerErrorIsError(state.last_get_key_result))
return default_initial_backoff_;
// Note: If we received a MIGRATION_DONE on download updates, then commit
// should not have taken place. Moreover, if we receive a MIGRATION_DONE
// on commit, it means that download updates succeeded. Therefore, we only
// need to check if either code is equal to SERVER_RETURN_MIGRATION_DONE,
// and not if there were any more serious errors requiring the long retry.
if (state.last_download_updates_result == SERVER_RETURN_MIGRATION_DONE ||
state.commit_result == SERVER_RETURN_MIGRATION_DONE) {
return short_initial_backoff_;
}
// If a datatype decides the GetUpdates must be retried (e.g. because the
// context has been updated since the request), use the short delay.
if (state.last_download_updates_result == DATATYPE_TRIGGERED_RETRY)
return short_initial_backoff_;
// When the server tells us we have a conflict, then we should download the
// latest updates so we can see the conflict ourselves, resolve it locally,
// then try again to commit. Running another sync cycle will do all these
// things. There's no need to back off, we can do this immediately.
//
// TODO(sync): We shouldn't need to handle this in BackoffDelayProvider.
// There should be a way to deal with protocol errors before we get to this
// point.
if (state.commit_result == SERVER_RETURN_CONFLICT)
return short_initial_backoff_;
return default_initial_backoff_;
}
} // namespace syncer
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