54 lines
1.8 KiB
C++
54 lines
1.8 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <folly/logging/RateLimiter.h>
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namespace folly {
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namespace logging {
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bool IntervalRateLimiter::checkSlow() {
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auto ts = timestamp_.load();
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auto now = clock::now().time_since_epoch().count();
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if (now < (ts + interval_.count())) {
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return false;
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}
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if (!timestamp_.compare_exchange_strong(ts, now)) {
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// We raced with another thread that reset the timestamp.
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// We treat this as if we fell into the previous interval, and so we
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// rate-limit ourself.
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return false;
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}
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if (ts == 0) {
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// If we initialized timestamp_ for the very first time increment count_ by
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// one instead of setting it to 0. Our original increment made it roll over
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// to 0, so other threads may have already incremented it again and passed
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// the check.
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auto origCount = count_.fetch_add(1, std::memory_order_acq_rel);
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// Check to see if other threads already hit the rate limit cap before we
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// finished checkSlow().
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return (origCount < maxPerInterval_);
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}
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// In the future, if we wanted to return the number of dropped events we
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// could use (count_.exchange(0) - maxPerInterval_) here.
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count_.store(1, std::memory_order_release);
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return true;
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}
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} // namespace logging
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} // namespace folly
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