105 lines
3.2 KiB
C++
105 lines
3.2 KiB
C++
/*
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* IRateControl.h
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*
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* This source file is part of the FoundationDB open source project
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*
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* Copyright 2013-2022 Apple Inc. and the FoundationDB project authors
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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 "flow/flow.h"
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class IRateControl {
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public:
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virtual ~IRateControl() {}
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// Future is Ready once you can use n units;
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virtual Future<Void> getAllowance(unsigned int n) = 0;
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// If all of the allowance is not used the unused units can be given back.
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// For convenience, n can safely be negative.
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virtual void returnUnused(int n) = 0;
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virtual void killWaiters(const Error& e) = 0;
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virtual void wakeWaiters() = 0;
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virtual void addref() = 0;
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virtual void delref() = 0;
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};
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// An IRateControl implementation that allows at most hands out at most windowLimit units of 'credit' in windowSeconds
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// seconds
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class SpeedLimit final : public IRateControl, ReferenceCounted<SpeedLimit> {
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public:
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SpeedLimit(int windowLimit, double windowSeconds)
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: m_limit(windowLimit), m_seconds(windowSeconds), m_last_update(0), m_budget(0) {
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m_last_update = now();
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}
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~SpeedLimit() override { m_stop.send(Never()); }
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void addref() override { ReferenceCounted<SpeedLimit>::addref(); }
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void delref() override { ReferenceCounted<SpeedLimit>::delref(); }
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Future<Void> getAllowance(unsigned int n) override {
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// Replenish budget based on time since last update
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double ts = now();
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// returnUnused happens to do exactly what we want here
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returnUnused((ts - m_last_update) / m_seconds * m_limit);
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m_last_update = ts;
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m_budget -= n;
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// If budget is still >= 0 then it's safe to use the allowance right now.
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if (m_budget >= 0)
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return Void();
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// Otherise return the amount of time it will take for the budget to rise to 0.
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return m_stop.getFuture() || delay(m_seconds * -m_budget / m_limit);
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}
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void returnUnused(int n) override {
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if (n < 0)
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return;
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m_budget = std::min<int64_t>(m_budget + n, m_limit);
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}
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void wakeWaiters() override {
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Promise<Void> p;
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p.swap(m_stop);
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p.send(Void());
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}
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void killWaiters(const Error& e) override {
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Promise<Void> p;
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p.swap(m_stop);
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p.sendError(e);
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}
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private:
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int m_limit;
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double m_seconds;
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double m_last_update;
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int64_t m_budget;
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Promise<Void> m_stop;
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};
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// An IRateControl implementation that enforces no limit
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class Unlimited final : public IRateControl, ReferenceCounted<Unlimited> {
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public:
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Unlimited() {}
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~Unlimited() override = default;
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void addref() override { ReferenceCounted<Unlimited>::addref(); }
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void delref() override { ReferenceCounted<Unlimited>::delref(); }
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Future<Void> getAllowance(unsigned int n) override { return Void(); }
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void returnUnused(int n) override {}
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void wakeWaiters() override {}
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void killWaiters(const Error& e) override {}
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};
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