[Muduo网络库源码分析] (10) base/ThreadPoll_cc_h_线程池

线程池

实现：ThreadPool类

---

功能：实现固定大小的线程池，用来高效的处理大量任务

---

知识点：

• 回调函数
  通俗的讲，回调函数就是在放在另一个函数中执行的函数，在回调中，我们利用某种方式，把回调函数像参数一样传入中间函数。
• boost::ptr_vector
  Boost中的指针容器
  threads_.reserve 设置指针容器的大小
• for_each
  for_each 算法范围 [first, last) 中的每个元素调用函数 F，并返回输入的参数 f。此函数不会修改序列中的任何元素。

---

用途：

可用于创建线程，创建多线程程序，可用于创建线程池。

---

模块拆分与封装：

已把其线程池对象模块单独分离出来，并利用Makefile统一编译，模块代码地址如下：https://github.com/chudongfang/Learn_From_Muduo/tree/master/ThreadPoll

---

代码及分析：

ThreadPoll.h

// Use of this source code is governed by a BSD-style license// that can be found in the License file.//// Author: Shuo Chen (chenshuo at chenshuo dot com)#ifndef MUDUO_BASE_THREADPOOL_H#define MUDUO_BASE_THREADPOOL_H#include <muduo/base/Condition.h>#include <muduo/base/Mutex.h>#include <muduo/base/Thread.h>#include <muduo/base/Types.h>#include <boost/function.hpp>#include <boost/noncopyable.hpp>#include <boost/ptr_container/ptr_vector.hpp>#include <deque>namespace muduo{class ThreadPool : boost::noncopyable{ public:  typedef boost::function<void ()> Task;  //构造函数，设置默认线程池名  explicit ThreadPool(const string& nameArg = string("ThreadPool"));  ~ThreadPool();  // Must be called before start().  //设置线程池最大线程数量  void setMaxQueueSize(int maxSize) { maxQueueSize_ = maxSize; }  //设置线程初始化回调函数  void setThreadInitCallback(const Task& cb)  { threadInitCallback_ = cb; }  //开启线程池  void start(int numThreads);  //停止线程池  void stop();  //返回线程池名  const string& name() const  { return name_; }  //返回队列大小  size_t queueSize() const;  // Could block if maxQueueSize > 0  //向任务队列放入任务  void run(const Task& f);#ifdef __GXX_EXPERIMENTAL_CXX0X__  void run(Task&& f);#endif private:  bool isFull() const;//判断线程池是否满  void runInThread(); //子进程函数，在子进程中执行任务  Task take();        //从任务队列中取任务  mutable MutexLock mutex_;//互斥锁，保证数据互斥访问  Condition notEmpty_;     //条件变量，是否为空  Condition notFull_;      //条件变量，是否满  string name_;            //线程名字  Task threadInitCallback_;//线程初始化化回调函数  boost::ptr_vector<muduo::Thread> threads_;//线程队列，利用指针容器实现  std::deque<Task> queue_;    //双向队列  size_t maxQueueSize_;       //最大队列容量  bool running_;              //线程池是否运行};}#endif

---

ThreadPoll.cc

// Use of this source code is governed by a BSD-style license// that can be found in the License file.//// Author: Shuo Chen (chenshuo at chenshuo dot com)#include <muduo/base/ThreadPool.h>#include <muduo/base/Exception.h>#include <boost/bind.hpp>#include <assert.h>#include <stdio.h>using namespace muduo;//构造函数ThreadPool::ThreadPool(const string& nameArg)  : mutex_(),//初始化锁    notEmpty_(mutex_),//初始化条件变量    notFull_(mutex_),    name_(nameArg),  //初始化线程池名    maxQueueSize_(0),     running_(false){}//析构函数，停止线程池ThreadPool::~ThreadPool(){  if (running_)  {    stop();  }}void ThreadPool::start(int numThreads){  assert(threads_.empty());  running_ = true;  //设置指针容器大小  threads_.reserve(numThreads);  for (int i = 0; i < numThreads; ++i)  {    char id[32];    snprintf(id, sizeof id, "%d", i+1);    //新建立进程，并用bind绑定函数进行传参    threads_.push_back(new muduo::Thread(          boost::bind(&ThreadPool::runInThread, this), name_+id));    //运行线程    threads_[i].start();  }  //初始化回调函数  if (numThreads == 0 && threadInitCallback_)  {    threadInitCallback_();  }}void ThreadPool::stop(){  {  //加互斥锁，当其出当前{}后会自动析构，并解锁  MutexLockGuard lock(mutex_);  running_ = false;  //以广播的形式唤醒等待notEmpty条件变量的线程  notEmpty_.notifyAll();  }  //遍历这个容器，并在每个线程中执行join函数，对线程进程阻塞  for_each(threads_.begin(),           threads_.end(),           boost::bind(&muduo::Thread::join, _1));}//返回队列长度size_t ThreadPool::queueSize() const{  //MutexLockGuard类对mutex_加锁，当函数结束时，其会自动利用析构函数解锁  MutexLockGuard lock(mutex_);  return queue_.size();}//主线程函数//不断添加task到task队列void ThreadPool::run(const Task& task){  //如果线程池中没有线程，由主线程执行task  if (threads_.empty())  {    task();  }  else  {    MutexLockGuard lock(mutex_);    //如果线程池满，则阻塞等待子线程对task进行处理    while (isFull())    {      notFull_.wait();    }    assert(!isFull());    //向线程队列中添加task    queue_.push_back(task);    //唤醒子线程处理task    notEmpty_.notify();  }}#ifdef __GXX_EXPERIMENTAL_CXX0X__void ThreadPool::run(Task&& task){  if (threads_.empty())  {    task();  }  else  {    MutexLockGuard lock(mutex_);    while (isFull())    {      notFull_.wait();    }    assert(!isFull());    queue_.push_back(std::move(task));    notEmpty_.notify();  }}#endif//子线程函数//从任务队列（queue）中取taskThreadPool::Task ThreadPool::take(){  MutexLockGuard lock(mutex_);  // always use a while-loop, due to spurious wakeup  //子进程等待任务队列中的task  while (queue_.empty() && running_)  {    notEmpty_.wait();  }  Task task;  //从任务队列中取task  if (!queue_.empty())  {    task = queue_.front();    queue_.pop_front();    //唤醒其他子线程来取task，保证了task被挨个取走    if (maxQueueSize_ > 0)    {      notFull_.notify();    }  }  return task;}//判断队列是否满bool ThreadPool::isFull() const{  mutex_.assertLocked();  return maxQueueSize_ > 0 && queue_.size() >= maxQueueSize_;}//子线程函数//利用回调函数初始化线程//从任务队列中取task并执行//抛出异常void ThreadPool::runInThread(){  try  {    if (threadInitCallback_)    {      threadInitCallback_();    }    while (running_)    {      Task task(take());      if (task)      {        task();      }    }  }  catch (const Exception& ex)  {    fprintf(stderr, "exception caught in ThreadPool %s\n", name_.c_str());    fprintf(stderr, "reason: %s\n", ex.what());    fprintf(stderr, "stack trace: %s\n", ex.stackTrace());    abort();  }  catch (const std::exception& ex)  {    fprintf(stderr, "exception caught in ThreadPool %s\n", name_.c_str());    fprintf(stderr, "reason: %s\n", ex.what());    abort();  }  catch (...)  {    fprintf(stderr, "unknown exception caught in ThreadPool %s\n", name_.c_str());    throw; // rethrow  }}