C++封装POSIX 线程库（六）线程池

线程池有两个主要组件:

1.threads
2.blocking queue

解决的问题是线程创建与销毁带来的开销和通过线程池实现伪异步
过程类似于简单的生产者消费者问题(详见wiki)

Blocking Queue

对应用户添加任务CallBack和线程拿任务执行两个操作,因此需要两个条件变量和一个互斥锁

如果把用户添加任务比做生产者,线程拿任务比做消费者..那么需要两个条件变量就解决了

1.生产者>消费者(防止”撑爆”任务队列)
2.生产者<消费者(没有任务可执行时线程会挂起)

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Threads

线程池由一组线程组成,构造阶段创建一组线程并挂起,每当添加一个任务的时候就notify一个线程执行…
当线程池析构的时候,将这些线程回收….这里有个很大的坑…

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代码

完整代码:https://github.com/NearXdu/ThreadPool

#ifndef __THREADPOLL_H__#define __THREADPOLL_H__#include "MutexLock.h"#include "Condition.h"#include "Thread.h"#include <boost/noncopyable.hpp>#include <boost/function.hpp>#include <boost/bind.hpp>#include <boost/ptr_container/ptr_vector.hpp>#include <queue>class ThreadPool : boost::noncopyable{    public:    typedef boost::function<void()>Task;    ThreadPool(size_t qsize,size_t nthreads);    ~ThreadPool();    void start();    void stop();    void addTask(Task t);    Task getTask();    bool isStarted()const{return isStarted_;}    void runInThread();    private:    mutable MutexLock mutex_;    Condition notEmpty_;//blocking queue  full条件变量    Condition notFull_;//blocking queue empty 条件变量    size_t queueSize_;//任务队列大小    std::queue<Task> queue_;//任务队列    size_t threadsNum_;//线程数目    boost::ptr_vector<Thread> threads_;//线程池中的线程    volatile bool isStarted_;};#endif///////////////////////////////////#include "ThreadPool.h"ThreadPool::ThreadPool(size_t q,size_t n)    :mutex_(),     notEmpty_(mutex_),     notFull_(mutex_),     queueSize_(q),     threadsNum_(n),     isStarted_(false){}ThreadPool::~ThreadPool(){    if(isStarted_)    {    stop();    }}void ThreadPool::stop(){       {    MutexLockGuard lock(mutex_);    isStarted_ = false;    notEmpty_.notifyAll(); //激活所有的线程    }    for_each(threads_.begin(),        threads_.end(),        boost::bind(&Thread::join, _1));}void ThreadPool::addTask(Task t){    if(threads_.empty())    {    t();    }    else    {    MutexLockGuard lock(mutex_);    while(queue_.size()>=queueSize_&&isStarted_)        notFull_.wait();    if(!isStarted_)        return ;    queue_.push(std::move(t));    notEmpty_.notify();    }}ThreadPool::Task ThreadPool::getTask(){    MutexLockGuard lock(mutex_);    while(queue_.empty()&&isStarted_)    {    notEmpty_.wait();    }    Task t;    if(!queue_.empty())    {    assert(!queue_.empty());    t=queue_.front();    queue_.pop();    notFull_.notify();    }    return t;}void ThreadPool::runInThread(){    while(isStarted_)    {    //  std::cout<<"hello runinThread"<<std::endl;    Task t(getTask());//will blocked until "add" ops    //assert(t!=NULL);    if(t)    {        t();//run    }    }}void ThreadPool::start(){    isStarted_=true;    threads_.reserve(threadsNum_);    for(size_t i=0;i<threadsNum_;++i)    {    threads_.push_back(        new Thread(boost::bind(            &ThreadPool::runInThread,this)));    threads_[i].start();    }}