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/* Copyright 2009 10gen 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 <list>
#include <string>
#include "mongo/base/disallow_copying.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/functional.h"
#include "mongo/stdx/mutex.h"
namespace mongo {
/**
* Implementation of a fixed-size pool of threads that can perform scheduled
* tasks.
*/
class OldThreadPool {
MONGO_DISALLOW_COPYING(OldThreadPool);
public:
typedef stdx::function<void(void)> Task; //nullary function or functor
struct DoNotStartThreadsTag {};
explicit OldThreadPool(int nThreads=8, const std::string& threadNamePrefix="");
explicit OldThreadPool(const DoNotStartThreadsTag&,
int nThreads=8,
const std::string& threadNamePrefix="");
// blocks until all tasks are complete (tasks_remaining() == 0)
// You should not call schedule while in the destructor
~OldThreadPool();
// Launches the worker threads; call exactly once, if and only if
// you used the DoNotStartThreadsTag form of the constructor.
void startThreads();
// blocks until all tasks are complete (tasks_remaining() == 0)
// does not prevent new tasks from being scheduled so could wait forever.
// Also, new tasks could be scheduled after this returns.
void join();
// task will be copied a few times so make sure it's relatively cheap
void schedule(Task task);
// Helpers that wrap schedule and stdx::bind.
// Functor and args will be copied a few times so make sure it's relatively cheap
template<typename F, typename A>
void schedule(F f, A a) { schedule(stdx::bind(f,a)); }
template<typename F, typename A, typename B>
void schedule(F f, A a, B b) { schedule(stdx::bind(f,a,b)); }
template<typename F, typename A, typename B, typename C>
void schedule(F f, A a, B b, C c) { schedule(stdx::bind(f,a,b,c)); }
template<typename F, typename A, typename B, typename C, typename D>
void schedule(F f, A a, B b, C c, D d) { schedule(stdx::bind(f,a,b,c,d)); }
template<typename F, typename A, typename B, typename C, typename D, typename E>
void schedule(F f, A a, B b, C c, D d, E e) { schedule(stdx::bind(f,a,b,c,d,e)); }
int tasks_remaining() { return _tasksRemaining; }
private:
class Worker;
stdx::mutex _mutex;
stdx::condition_variable _condition;
std::list<Worker*> _freeWorkers; //used as LIFO stack (always front)
std::list<Task> _tasks; //used as FIFO queue (push_back, pop_front)
int _tasksRemaining; // in queue + currently processing
int _nThreads; // only used for sanity checking. could be removed in the future.
const std::string _threadNamePrefix; // used for logging/diagnostics
// should only be called by a worker from the worker's thread
void task_done(Worker* worker);
friend class Worker;
};
} //namespace mongo
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