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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <functional>
#include <memory>
#include <string>
#include <boost/optional.hpp>
#include "mongo/platform/mutex.h"
#include "mongo/util/time_support.h"
namespace mongo {
class Client;
class PeriodicJobAnchor;
/**
* An interface for objects that run work items at specified intervals. Each individually scheduled
* job will be called in series.
*
* Implementations may use whatever internal threading and eventing
* model they wish. Implementations may choose when to stop running
* scheduled jobs (for example, some implementations may stop running
* when the server is in global shutdown).
*
* The runner will create client objects that it passes to jobs to use.
*/
class PeriodicRunner {
public:
using Job = std::function<void(Client* client)>;
using JobAnchor = PeriodicJobAnchor;
struct PeriodicJob {
PeriodicJob(std::string name, Job callable, Milliseconds period)
: name(std::move(name)), job(std::move(callable)), interval(period) {}
/**
* name of the job
*/
std::string name;
/**
* A task to be run at regular intervals by the runner.
*/
Job job;
/**
* An interval at which the job should be run.
*/
Milliseconds interval;
};
/**
* A ControllableJob allows a user to reschedule the execution of a Job
*/
class ControllableJob {
public:
virtual ~ControllableJob() = default;
/**
* Starts running the job
*/
virtual void start() = 0;
/**
* Pauses the job temporarily so that it does not execute until
* unpaused
*/
virtual void pause() = 0;
/**
* Resumes a paused job so that it continues executing each interval
*/
virtual void resume() = 0;
/**
* Stops the job, this function blocks until the job is stopped
* Safe to invalidate the job callable after calling this.
*/
virtual void stop() = 0;
/**
* Returns the current period for the job
*/
virtual Milliseconds getPeriod() = 0;
/**
* Updates the period of the job. This takes effect immediately by altering the current
* scheduling of the task. I.e. if more than ms have passed since the last execution of the
* job, it is run immediately. Otherwise the scheduling is adjusted forward or back by
* abs(new - old).
*/
virtual void setPeriod(Milliseconds ms) = 0;
};
virtual ~PeriodicRunner();
/**
* Creates a new job and adds it to the runner, but does not schedule it.
* The caller is responsible for calling 'start' on the resulting handle in
* order to begin the job running. This API should be used when the caller
* is interested in observing and controlling the job execution state.
*/
virtual JobAnchor makeJob(PeriodicJob job) = 0;
};
/**
* A PeriodicJobAnchor allows the holder to control the scheduling of a job for the lifetime of the
* anchor. When an anchor is destructed, it stops its underlying job.
*
* The underlying weak_ptr for this class is not synchronized. In essence, treat use of this class
* as if it were a raw pointer to a ControllableJob.
*
* Each wrapped PeriodicRunner::ControllableJob function on this object throws
* if the underlying job is gone (e.g. in shutdown).
*/
class [[nodiscard]] PeriodicJobAnchor {
public:
using Job = PeriodicRunner::ControllableJob;
public:
// Note that this constructor is only intended for use with PeriodicRunner::makeJob()
explicit PeriodicJobAnchor(std::shared_ptr<Job> handle);
PeriodicJobAnchor() = default;
PeriodicJobAnchor(PeriodicJobAnchor&&) = default;
PeriodicJobAnchor& operator=(PeriodicJobAnchor&&) = default;
PeriodicJobAnchor(const PeriodicJobAnchor&) = delete;
PeriodicJobAnchor& operator=(const PeriodicJobAnchor&) = delete;
~PeriodicJobAnchor();
void start();
void pause();
void resume();
void stop();
void setPeriod(Milliseconds ms);
Milliseconds getPeriod();
/**
* Abandon responsibility for scheduling the execution of this job
*
* This effectively invalidates the anchor.
*/
void detach();
/**
* Returns if this PeriodicJobAnchor is associated with a PeriodicRunner::ControllableJob
*
* This function is useful to see if a PeriodicJobAnchor is initialized. It does not necessarily
* inform whether a PeriodicJobAnchor will throw from a control function above.
*/
bool isValid() const noexcept;
explicit operator bool() const noexcept {
return isValid();
}
private:
std::shared_ptr<Job> _handle;
};
} // namespace mongo
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