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/**
* Copyright (C) 2015 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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 "mongo/base/disallow_copying.h"
#include "mongo/stdx/functional.h"
namespace mongo {
class Status;
/**
* Interface for a thread pool.
*/
class ThreadPoolInterface {
MONGO_DISALLOW_COPYING(ThreadPoolInterface);
public:
using Task = stdx::function<void()>;
/**
* Destroys a thread pool.
*
* The destructor may block if join() has not previously been called and returned.
* It is fatal to destroy the pool while another thread is blocked on join().
*/
virtual ~ThreadPoolInterface() = default;
/**
* Starts the thread pool. May be called at most once.
*/
virtual void startup() = 0;
/**
* Signals the thread pool to shut down. Returns promptly.
*
* After this call, the thread will return an error for subsequent calls to schedule().
*
* May be called by a task executing in the thread pool. Call join() after calling shutdown()
* to block until all tasks scheduled on the pool complete.
*/
virtual void shutdown() = 0;
/**
* Blocks until the thread pool has fully shut down. Call at most once, and never from a task
* inside the pool.
*/
virtual void join() = 0;
/**
* Schedules "task" to run in the thread pool.
*
* Returns OK on success, ShutdownInProgress if shutdown() has already executed.
*
* It is safe to call this before startup(), but the scheduled task will not execute
* until after startup() is called.
*/
virtual Status schedule(Task task) = 0;
protected:
ThreadPoolInterface() = default;
};
} // namespace mongo
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