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Diffstat (limited to 'Firestore/core/src/firebase/firestore/remote/exponential_backoff.cc')
-rw-r--r-- | Firestore/core/src/firebase/firestore/remote/exponential_backoff.cc | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/Firestore/core/src/firebase/firestore/remote/exponential_backoff.cc b/Firestore/core/src/firebase/firestore/remote/exponential_backoff.cc new file mode 100644 index 0000000..a880c45 --- /dev/null +++ b/Firestore/core/src/firebase/firestore/remote/exponential_backoff.cc @@ -0,0 +1,93 @@ +/* + * Copyright 2018 Google + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#include "Firestore/core/src/firebase/firestore/remote/exponential_backoff.h" + +#include <random> +#include <utility> + +#include "Firestore/core/src/firebase/firestore/util/hard_assert.h" +#include "Firestore/core/src/firebase/firestore/util/log.h" + +namespace firebase { +namespace firestore { +namespace remote { + +using firebase::firestore::util::AsyncQueue; +using firebase::firestore::util::TimerId; +namespace chr = std::chrono; + +ExponentialBackoff::ExponentialBackoff(AsyncQueue* queue, + TimerId timer_id, + double backoff_factor, + Milliseconds initial_delay, + Milliseconds max_delay) + : queue_{queue}, + timer_id_{timer_id}, + backoff_factor_{backoff_factor}, + initial_delay_{initial_delay}, + max_delay_{max_delay} { + HARD_ASSERT(queue, "Queue can't be null"); + + HARD_ASSERT(backoff_factor >= 1.0, "Backoff factor must be at least 1"); + + HARD_ASSERT(initial_delay.count() >= 0, "Delays must be non-negative"); + HARD_ASSERT(max_delay.count() >= 0, "Delays must be non-negative"); + HARD_ASSERT(initial_delay <= max_delay, + "Initial delay can't be greater than max delay"); +} + +void ExponentialBackoff::BackoffAndRun(AsyncQueue::Operation&& operation) { + Cancel(); + + // First schedule the block using the current base (which may be 0 and should + // be honored as such). + Milliseconds delay_with_jitter = current_base_ + GetDelayWithJitter(); + if (delay_with_jitter.count() > 0) { + LOG_DEBUG("Backing off for %s milliseconds (base delay: %s milliseconds)", + delay_with_jitter.count(), current_base_.count()); + } + + delayed_operation_ = queue_->EnqueueAfterDelay(delay_with_jitter, timer_id_, + std::move(operation)); + + // Apply backoff factor to determine next delay, but ensure it is within + // bounds. + current_base_ = ClampDelay( + chr::duration_cast<Milliseconds>(current_base_ * backoff_factor_)); +} + +ExponentialBackoff::Milliseconds ExponentialBackoff::GetDelayWithJitter() { + std::uniform_real_distribution<double> distribution; + double random_double = distribution(secure_random_); + return chr::duration_cast<Milliseconds>((random_double - 0.5) * + current_base_); +} + +ExponentialBackoff::Milliseconds ExponentialBackoff::ClampDelay( + Milliseconds delay) const { + if (delay < initial_delay_) { + return initial_delay_; + } + if (delay > max_delay_) { + return max_delay_; + } + return delay; +} + +} // namespace remote +} // namespace firestore +} // namespace firebase |