69 lines
2.1 KiB
C++
69 lines
2.1 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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#pragma once
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#include <atomic>
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#include <chrono>
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#include <cstdint>
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#include <folly/Chrono.h>
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namespace folly {
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namespace logging {
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/**
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* A rate limiter that can rate limit events to N events per M milliseconds.
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*
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* It is intended to be fast to check when messages are not being rate limited.
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* When messages are being rate limited it is slightly slower, as it has to
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* check the clock each time check() is called in this case.
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*/
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class IntervalRateLimiter {
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public:
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using clock = chrono::coarse_steady_clock;
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constexpr IntervalRateLimiter(
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uint64_t maxPerInterval, clock::duration interval)
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: maxPerInterval_{maxPerInterval}, interval_{interval} {}
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bool check() {
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auto origCount = count_.fetch_add(1, std::memory_order_acq_rel);
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if (origCount < maxPerInterval_) {
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return true;
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}
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return checkSlow();
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}
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private:
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bool checkSlow();
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const uint64_t maxPerInterval_;
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const clock::time_point::duration interval_;
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// Initialize count_ to the maximum possible value so that the first
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// call to check() will call checkSlow() to initialize timestamp_,
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// but subsequent calls will hit the fast-path and avoid checkSlow()
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std::atomic<uint64_t> count_{std::numeric_limits<uint64_t>::max()};
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// Ideally timestamp_ would be a
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// std::atomic<clock::time_point>, but this does not
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// work since time_point's constructor is not noexcept
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std::atomic<clock::rep> timestamp_{0};
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};
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} // namespace logging
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} // namespace folly
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