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fbdb46f5cb
Reviewed By: chadaustin Differential Revision: D17872966 fbshipit-source-id: cd60a364a2146f0dadbeca693b1d4a5d7c97ff63
114 lines
3.0 KiB
C++
114 lines
3.0 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This software may be used and distributed according to the terms of the
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* GNU General Public License version 2.
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*/
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#pragma once
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#include <chrono>
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#include <string>
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#include <folly/Range.h>
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#include <folly/io/async/HHWheelTimer.h>
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namespace facebook {
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namespace eden {
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class EdenServer;
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/**
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* A helper class for implementing periodic tasks that should be run by
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* EdenServer.
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*
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* Tasks will run on the main EventBase thread. As a result tasks should
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* complete relatively quickly. If a task needs to perform an expensive
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* operation it should schedule it in a separate executor.
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*/
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class PeriodicTask : private folly::HHWheelTimer::Callback {
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public:
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// This should match the duration used by folly::HHWheelTimer.
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// Unfortunately HHWheelTimer does not expose this as a class member.
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using Duration = std::chrono::milliseconds;
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PeriodicTask(EdenServer* server, folly::StringPiece name);
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EdenServer* getServer() const {
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return server_;
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}
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const std::string& getName() const {
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return name_;
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}
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/**
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* Get the interval on which this task is scheduled.
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*
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* This function should only be called from the EdenServer's main event base
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* thread.
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*/
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Duration getInterval() const {
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return interval_;
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}
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/**
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* Update the interval at which the PeriodicTask runs.
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*
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* If interval is 0 or negative the task will be stopped, otherwise the task
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* will be scheduled to run at the specified interval.
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*
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* If the task was not previously running and splay is true, a random amount
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* of time between 0 and interval will be added before the task runs for the
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* first time. Therefore the first run won't happen until somewhere between
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* [interval and 2*interval]. If you have multiple tasks running with the
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* same interval this helps distribute tasks out along the interval, rather
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* than having them all try to run at the same time at the start of each
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* interval period. If the task was already running the splay parameter is
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* ignored.
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*/
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void updateInterval(Duration interval, bool splay = true);
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protected:
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/**
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* Subclasses should implement runTask()
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*/
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virtual void runTask() = 0;
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private:
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/**
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* Implementation of the HHWheelTimer::Callback interface.
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*/
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void timeoutExpired() noexcept override final;
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void reschedule();
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EdenServer* const server_;
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std::string const name_;
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/*
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* PeriodicTask objects are only ever used from the EdenServer's main
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* EventBase thread. Therefore we do not need synchronization for accessing
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* the mutable member variables.
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*/
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/**
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* How frequently this PeriodicTask should be scheduled.
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*/
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Duration interval_;
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/**
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* The number of times this task has run slowly.
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* This is tracked purely for reporting purposes.
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*/
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size_t slowCount_{0};
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/**
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* running_ is set to true while runTask() is running.
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*/
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bool running_{false};
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};
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} // namespace eden
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} // namespace facebook
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