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Summary: This is a very simple rate limiter that allows us to very cheaply limit things like Initials per server per window. See the comment in SlidingWindowRateLimiter.h for a description of how it functions. Reviewed By: sharmafb Differential Revision: D20311019 fbshipit-source-id: e0b4fddd467252c43b63ae21dfd3d0284b7926e7
39 lines
1.4 KiB
C++
39 lines
1.4 KiB
C++
// Copyright 2004-present Facebook. All Rights Reserved.
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#include "SlidingWindowRateLimiter.h"
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namespace quic {
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bool SlidingWindowRateLimiter::check(TimePoint time) {
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// This is the first time point.
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if (!currentWindowStartPoint_) {
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currentWindowStartPoint_ = time;
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}
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auto timeElapsedSinceCurWindow =
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std::chrono::duration_cast<std::chrono::seconds>(
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time - currentWindowStartPoint_.value());
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// A full window has elapsed.
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if (timeElapsedSinceCurWindow > window_) {
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int windowsElapsed = timeElapsedSinceCurWindow.count() / window_.count();
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currentWindowStartPoint_.value() +=
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std::chrono::seconds(window_.count() * windowsElapsed);
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// If more than one window has elapsed, there were zero in the previous
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// window.
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countInPrevWindow_ = windowsElapsed == 1 ? countInCurWindow_ : 0;
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countInCurWindow_ = 0;
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timeElapsedSinceCurWindow %= window_.count();
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}
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// The weighted count accounts for the "sliding" window by using the
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// previous windows average rate over the time that has elapsed in the
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// current window.
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double weightedCount = countInPrevWindow_ *
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(static_cast<double>((window_ - timeElapsedSinceCurWindow).count()) /
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window_.count()) +
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countInCurWindow_ + 1;
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bool limited = weightedCount > count_;
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countInCurWindow_ = limited ? countInCurWindow_ : countInCurWindow_ + 1;
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return limited;
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}
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} // namespace quic
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