Linux网络编程（六）-高并发服务器04：线程池【1个锁（用于锁住队列）、2个条件变量（一个用于阻塞“取任务线程”，一个用于阻塞“任务添加者线程（主线程）”）、1个任务循环队列（用于存放任务）】

一、线程池概述

1、什么是线程池？

线程池是一个抽象概念，可以简单的认为若干线程在一起运行，线程不退出，等待有任务处理。

2、为什么要有线程池？

以网络编程服务器端为例,作为服务器端支持高并发,可以有多个客户端连接,发出请求,对于多个请求我们每次都去建立线程,这样线程会创建很多,而且线程执行完销毁也会有很大的系统开销,使用上效率很低。

之前在线程篇章中，我们也知道创建线程并非多多益善，所以我们的思路是提前创建好若干个线程，不退出，等待任务的产生，去接收任务处理后等待下一个任务。

3、线程池如何实现？

需要思考2个问题？

1. 假设线程池创建了，线程们如何去协调接收任务并且处理？
2. 线程池上的线程如何能够执行不同的请求任务？

上述问题1就很像我们之前学过的生产者和消费者模型，客户端对应生产者，服务器端这边的线程池对应消费者，需要借助互斥锁和条件变量来搞定。

问题2解决思路就是利用回调机制，我们同样可以借助结构体的方式，对任务进行封装，比如任务的数据和任务处理回调都封装在结构体上，这样线程池的工作线程拿到任务的同时，也知道该如何执行了。

二、线程池代码【简易版】

threadpoolsimple.h

#ifndef _THREADPOOL_H
#define _THREADPOOL_H#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>typedef struct _PoolTask
{int tasknum;//模拟任务编号void *arg;//回调函数参数void (*task_func)(void *arg);//任务的回调函数
}PoolTask ;typedef struct _ThreadPool
{int max_job_num;//最大任务个数int job_num;//实际任务个数PoolTask *tasks;//任务队列数组int job_push;//入队位置int job_pop;// 出队位置int thr_num;//线程池内线程个数pthread_t *threads;//线程池内线程数组int shutdown;//是否关闭线程池pthread_mutex_t pool_lock;//线程池的锁pthread_cond_t empty_task;//任务队列为空的条件pthread_cond_t not_empty_task;//任务队列不为空的条件}ThreadPool;void create_threadpool(int thrnum,int maxtasknum);//创建线程池--thrnum  代表线程个数，maxtasknum 最大任务个数
void destroy_threadpool(ThreadPool *pool);//摧毁线程池
void addtask(ThreadPool *pool);//添加任务到线程池
void taskRun(void *arg);//任务回调函数#endif

threadpoolsimple.c

//简易版线程池
#include "threadpoolsimple.h"ThreadPool *thrPool = NULL;int beginnum = 1000;void *thrRun(void *arg)
{//printf("begin call %s-----\n",__FUNCTION__);ThreadPool *pool = (ThreadPool*)arg;int taskpos = 0;//任务位置PoolTask *task = (PoolTask *)malloc(sizeof(PoolTask));while(1){//获取任务，先要尝试加锁pthread_mutex_lock(&thrPool->pool_lock);//无任务并且线程池不是要摧毁while(thrPool->job_num <= 0 && !thrPool->shutdown ){//如果没有任务，线程会阻塞pthread_cond_wait(&thrPool->not_empty_task,&thrPool->pool_lock);}if(thrPool->job_num){//有任务需要处理taskpos = (thrPool->job_pop++)%thrPool->max_job_num;//printf("task out %d...tasknum===%d tid=%lu\n",taskpos,thrPool->tasks[taskpos].tasknum,pthread_self());//为什么要拷贝？避免任务被修改，生产者会添加任务memcpy(task,&thrPool->tasks[taskpos],sizeof(PoolTask));task->arg = task;thrPool->job_num--;//task = &thrPool->tasks[taskpos];pthread_cond_signal(&thrPool->empty_task);//通知生产者}if(thrPool->shutdown){//代表要摧毁线程池，此时线程退出即可//pthread_detach(pthread_self());//临死前分家pthread_mutex_unlock(&thrPool->pool_lock);free(task);pthread_exit(NULL);}//释放锁pthread_mutex_unlock(&thrPool->pool_lock);task->task_func(task->arg);//执行回调函数}//printf("end call %s-----\n",__FUNCTION__);
}//创建线程池
void create_threadpool(int thrnum,int maxtasknum)
{printf("begin call %s-----\n",__FUNCTION__);thrPool = (ThreadPool*)malloc(sizeof(ThreadPool));thrPool->thr_num = thrnum;thrPool->max_job_num = maxtasknum;thrPool->shutdown = 0;//是否摧毁线程池，1代表摧毁thrPool->job_push = 0;//任务队列添加的位置thrPool->job_pop = 0;//任务队列出队的位置thrPool->job_num = 0;//初始化的任务个数为0thrPool->tasks = (PoolTask*)malloc((sizeof(PoolTask)*maxtasknum));//申请最大的任务队列//初始化锁和条件变量pthread_mutex_init(&thrPool->pool_lock,NULL);pthread_cond_init(&thrPool->empty_task,NULL);pthread_cond_init(&thrPool->not_empty_task,NULL);int i = 0;thrPool->threads = (pthread_t *)malloc(sizeof(pthread_t)*thrnum);//申请n个线程id的空间pthread_attr_t attr;pthread_attr_init(&attr);pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);for(i = 0;i < thrnum;i++){pthread_create(&thrPool->threads[i],&attr,thrRun,(void*)thrPool);//创建多个线程}//printf("end call %s-----\n",__FUNCTION__);
}
//摧毁线程池
void destroy_threadpool(ThreadPool *pool)
{pool->shutdown = 1;//开始自爆pthread_cond_broadcast(&pool->not_empty_task);//诱杀 int i = 0;for(i = 0; i < pool->thr_num ; i++){pthread_join(pool->threads[i],NULL);}pthread_cond_destroy(&pool->not_empty_task);pthread_cond_destroy(&pool->empty_task);pthread_mutex_destroy(&pool->pool_lock);free(pool->tasks);free(pool->threads);free(pool);
}//添加任务到线程池
void addtask(ThreadPool *pool)
{//printf("begin call %s-----\n",__FUNCTION__);pthread_mutex_lock(&pool->pool_lock);//实际任务总数大于最大任务个数则阻塞等待(等待任务被处理)while(pool->max_job_num <= pool->job_num){pthread_cond_wait(&pool->empty_task,&pool->pool_lock);}int taskpos = (pool->job_push++)%pool->max_job_num;//printf("add task %d  tasknum===%d\n",taskpos,beginnum);pool->tasks[taskpos].tasknum = beginnum++;pool->tasks[taskpos].arg = (void*)&pool->tasks[taskpos];pool->tasks[taskpos].task_func = taskRun;pool->job_num++;pthread_mutex_unlock(&pool->pool_lock);pthread_cond_signal(&pool->not_empty_task);//通知包身工//printf("end call %s-----\n",__FUNCTION__);
}//任务回调函数
void taskRun(void *arg)
{PoolTask *task = (PoolTask*)arg;int num = task->tasknum;printf("task %d is runing %lu\n",num,pthread_self());sleep(1);printf("task %d is done %lu\n",num,pthread_self());
}int main()
{create_threadpool(3,20);int i = 0;for(i = 0;i < 50 ; i++){addtask(thrPool);//模拟添加任务}sleep(20);destroy_threadpool(thrPool);return 0;
}

三、线程池代码【复杂版】

pthreadpool.h

#ifndef __THREADPOOL_H_
#define __THREADPOOL_H_typedef struct threadpool_t threadpool_t;/*** @function threadpool_create* @descCreates a threadpool_t object.* @param thr_num  thread num* @param max_thr_num  max thread size* @param queue_max_size   size of the queue.* @return a newly created thread pool or NULL*/
threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size);/*** @function threadpool_add* @desc add a new task in the queue of a thread pool* @param pool     Thread pool to which add the task.* @param function Pointer to the function that will perform the task.* @param argument Argument to be passed to the function.* @return 0 if all goes well,else -1*/
int threadpool_add(threadpool_t *pool, void*(*function)(void *arg), void *arg);/*** @function threadpool_destroy* @desc Stops and destroys a thread pool.* @param pool  Thread pool to destroy.* @return 0 if destory success else -1*/
int threadpool_destroy(threadpool_t *pool);/*** @desc get the thread num* @pool pool threadpool* @return # of the thread*/
int threadpool_all_threadnum(threadpool_t *pool);/*** desc get the busy thread num* @param pool threadpool* return # of the busy thread*/
int threadpool_busy_threadnum(threadpool_t *pool);#endif

threadpool.c

#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <errno.h>
#include "threadpool.h"#define DEFAULT_TIME 10                 /*10s检测一次*/
#define MIN_WAIT_TASK_NUM 10            /*如果queue_size > MIN_WAIT_TASK_NUM 添加新的线程到线程池*/ 
#define DEFAULT_THREAD_VARY 10          /*每次创建和销毁线程的个数*/
#define true 1
#define false 0typedef struct 
{void *(*function)(void *);          /* 函数指针，回调函数 */void *arg;                          /* 上面函数的参数 */
} threadpool_task_t;                    /* 各子线程任务结构体 *//* 描述线程池相关信息 */
struct threadpool_t 
{pthread_mutex_t lock;               /* 用于锁住本结构体 */    pthread_mutex_t thread_counter;     /* 记录忙状态线程个数de琐 -- busy_thr_num */pthread_cond_t queue_not_full;      /* 当任务队列满时，添加任务的线程阻塞，等待此条件变量 */pthread_cond_t queue_not_empty;     /* 任务队列里不为空时，通知等待任务的线程 */pthread_t *threads;                 /* 存放线程池中每个线程的tid。数组 */pthread_t adjust_tid;               /* 存管理线程tid */threadpool_task_t *task_queue;      /* 任务队列(数组首地址) */int min_thr_num;                    /* 线程池最小线程数 */int max_thr_num;                    /* 线程池最大线程数 */int live_thr_num;                   /* 当前存活线程个数 */int busy_thr_num;                   /* 忙状态线程个数 */int wait_exit_thr_num;              /* 要销毁的线程个数 */int queue_front;                    /* task_queue队头下标 */int queue_rear;                     /* task_queue队尾下标 */int queue_size;                     /* task_queue队中实际任务数 */int queue_max_size;                 /* task_queue队列可容纳任务数上限 */int shutdown;                       /* 标志位，线程池使用状态，true或false */
};void *threadpool_thread(void *threadpool);void *adjust_thread(void *threadpool);int is_thread_alive(pthread_t tid);
int threadpool_free(threadpool_t *pool);//threadpool_create(3,100,100);  
threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size)
{int i;threadpool_t *pool = NULL;do {if((pool = (threadpool_t *)malloc(sizeof(threadpool_t))) == NULL) {  printf("malloc threadpool fail");break;                                      /*跳出do while*/}pool->min_thr_num = min_thr_num;pool->max_thr_num = max_thr_num;pool->busy_thr_num = 0;pool->live_thr_num = min_thr_num;               /* 活着的线程数 初值=最小线程数 */pool->wait_exit_thr_num = 0;pool->queue_size = 0;                           /* 有0个产品 */pool->queue_max_size = queue_max_size;pool->queue_front = 0;pool->queue_rear = 0;pool->shutdown = false;                         /* 不关闭线程池 *//* 根据最大线程上限数， 给工作线程数组开辟空间, 并清零 */pool->threads = (pthread_t *)malloc(sizeof(pthread_t)*max_thr_num); if (pool->threads == NULL) {printf("malloc threads fail");break;}memset(pool->threads, 0, sizeof(pthread_t)*max_thr_num);/* 队列开辟空间 */pool->task_queue = (threadpool_task_t *)malloc(sizeof(threadpool_task_t)*queue_max_size);if (pool->task_queue == NULL) {printf("malloc task_queue fail\n");break;}/* 初始化互斥琐、条件变量 */if (pthread_mutex_init(&(pool->lock), NULL) != 0|| pthread_mutex_init(&(pool->thread_counter), NULL) != 0|| pthread_cond_init(&(pool->queue_not_empty), NULL) != 0|| pthread_cond_init(&(pool->queue_not_full), NULL) != 0){printf("init the lock or cond fail\n");break;}//启动工作线程pthread_attr_t attr;pthread_attr_init(&attr);pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);for (i = 0; i < min_thr_num; i++) {pthread_create(&(pool->threads[i]), &attr, threadpool_thread, (void *)pool);/*pool指向当前线程池*/printf("start thread 0x%x...\n", (unsigned int)pool->threads[i]);}//创建管理者线程pthread_create(&(pool->adjust_tid), &attr, adjust_thread, (void *)pool);return pool;} while (0);/* 前面代码调用失败时,释放poll存储空间 */threadpool_free(pool);return NULL;
}/* 向线程池中 添加一个任务 */
//threadpool_add(thp, process, (void*)&num[i]);   /* 向线程池中添加任务 process: 小写---->大写*/int threadpool_add(threadpool_t *pool, void*(*function)(void *arg), void *arg)
{pthread_mutex_lock(&(pool->lock));/* ==为真，队列已经满， 调wait阻塞 */while ((pool->queue_size == pool->queue_max_size) && (!pool->shutdown)) {pthread_cond_wait(&(pool->queue_not_full), &(pool->lock));}if (pool->shutdown) {pthread_cond_broadcast(&(pool->queue_not_empty));pthread_mutex_unlock(&(pool->lock));return 0;}/* 清空 工作线程 调用的回调函数 的参数arg */if (pool->task_queue[pool->queue_rear].arg != NULL) {pool->task_queue[pool->queue_rear].arg = NULL;}/*添加任务到任务队列里*/pool->task_queue[pool->queue_rear].function = function;pool->task_queue[pool->queue_rear].arg = arg;pool->queue_rear = (pool->queue_rear + 1) % pool->queue_max_size;       /* 队尾指针移动, 模拟环形 */pool->queue_size++;/*添加完任务后，队列不为空，唤醒线程池中 等待处理任务的线程*/pthread_cond_signal(&(pool->queue_not_empty));pthread_mutex_unlock(&(pool->lock));return 0;
}/* 线程池中各个工作线程 */
void *threadpool_thread(void *threadpool)
{threadpool_t *pool = (threadpool_t *)threadpool;threadpool_task_t task;while (true) {/* Lock must be taken to wait on conditional variable *//*刚创建出线程，等待任务队列里有任务，否则阻塞等待任务队列里有任务后再唤醒接收任务*/pthread_mutex_lock(&(pool->lock));/*queue_size == 0 说明没有任务，调 wait 阻塞在条件变量上, 若有任务，跳过该while*/while ((pool->queue_size == 0) && (!pool->shutdown)) {  printf("thread 0x%x is waiting\n", (unsigned int)pthread_self());pthread_cond_wait(&(pool->queue_not_empty), &(pool->lock));//暂停到这/*清除指定数目的空闲线程，如果要结束的线程个数大于0，结束线程*/if (pool->wait_exit_thr_num > 0) {pool->wait_exit_thr_num--;/*如果线程池里线程个数大于最小值时可以结束当前线程*/if (pool->live_thr_num > pool->min_thr_num) {printf("thread 0x%x is exiting\n", (unsigned int)pthread_self());pool->live_thr_num--;pthread_mutex_unlock(&(pool->lock));//pthread_detach(pthread_self());pthread_exit(NULL);}}}/*如果指定了true，要关闭线程池里的每个线程，自行退出处理---销毁线程池*/if (pool->shutdown) {pthread_mutex_unlock(&(pool->lock));printf("thread 0x%x is exiting\n", (unsigned int)pthread_self());//pthread_detach(pthread_self());pthread_exit(NULL);     /* 线程自行结束 */}/*从任务队列里获取任务, 是一个出队操作*/task.function = pool->task_queue[pool->queue_front].function;task.arg = pool->task_queue[pool->queue_front].arg;pool->queue_front = (pool->queue_front + 1) % pool->queue_max_size;       /* 出队，模拟环形队列 */pool->queue_size--;/*通知可以有新的任务添加进来*/pthread_cond_broadcast(&(pool->queue_not_full));/*任务取出后，立即将 线程池琐 释放*/pthread_mutex_unlock(&(pool->lock));/*执行任务*/ printf("thread 0x%x start working\n", (unsigned int)pthread_self());pthread_mutex_lock(&(pool->thread_counter));                            /*忙状态线程数变量琐*/pool->busy_thr_num++;                                                   /*忙状态线程数+1*/pthread_mutex_unlock(&(pool->thread_counter));(*(task.function))(task.arg);                                           /*执行回调函数任务*///task.function(task.arg);                                              /*执行回调函数任务*//*任务结束处理*/ printf("thread 0x%x end working\n", (unsigned int)pthread_self());pthread_mutex_lock(&(pool->thread_counter));pool->busy_thr_num--;                                       /*处理掉一个任务，忙状态数线程数-1*/pthread_mutex_unlock(&(pool->thread_counter));}pthread_exit(NULL);
}/* 管理线程 */
void *adjust_thread(void *threadpool)
{int i;threadpool_t *pool = (threadpool_t *)threadpool;while (!pool->shutdown) {sleep(DEFAULT_TIME);                                    /*定时 对线程池管理*/pthread_mutex_lock(&(pool->lock));int queue_size = pool->queue_size;                      /* 关注 任务数 */int live_thr_num = pool->live_thr_num;                  /* 存活 线程数 */pthread_mutex_unlock(&(pool->lock));pthread_mutex_lock(&(pool->thread_counter));int busy_thr_num = pool->busy_thr_num;                  /* 忙着的线程数 */pthread_mutex_unlock(&(pool->thread_counter));/* 创建新线程 算法： 任务数大于最小线程池个数, 且存活的线程数少于最大线程个数时 如：30>=10 && 40<100*/if (queue_size >= MIN_WAIT_TASK_NUM && live_thr_num < pool->max_thr_num) {pthread_mutex_lock(&(pool->lock));  int add = 0;/*一次增加 DEFAULT_THREAD 个线程*/for (i = 0; i < pool->max_thr_num && add < DEFAULT_THREAD_VARY&& pool->live_thr_num < pool->max_thr_num; i++) {if (pool->threads[i] == 0 || !is_thread_alive(pool->threads[i])) {pthread_create(&(pool->threads[i]), NULL, threadpool_thread, (void *)pool);add++;pool->live_thr_num++;}}pthread_mutex_unlock(&(pool->lock));}/* 销毁多余的空闲线程 算法：忙线程X2 小于 存活的线程数 且 存活的线程数 大于 最小线程数时*/if ((busy_thr_num * 2) < live_thr_num  &&  live_thr_num > pool->min_thr_num) {/* 一次销毁DEFAULT_THREAD个线程, 隨機10個即可 */pthread_mutex_lock(&(pool->lock));pool->wait_exit_thr_num = DEFAULT_THREAD_VARY;      /* 要销毁的线程数 设置为10 */pthread_mutex_unlock(&(pool->lock));for (i = 0; i < DEFAULT_THREAD_VARY; i++) {/* 通知处在空闲状态的线程, 他们会自行终止*/pthread_cond_signal(&(pool->queue_not_empty));}}}return NULL;
}int threadpool_destroy(threadpool_t *pool)
{int i;if (pool == NULL) {return -1;}pool->shutdown = true;/*先销毁管理线程*///pthread_join(pool->adjust_tid, NULL);for (i = 0; i < pool->live_thr_num; i++) {/*通知所有的空闲线程*/pthread_cond_broadcast(&(pool->queue_not_empty));}/*for (i = 0; i < pool->live_thr_num; i++) {pthread_join(pool->threads[i], NULL);}*/threadpool_free(pool);return 0;
}int threadpool_free(threadpool_t *pool)
{if (pool == NULL) {return -1;}if (pool->task_queue) {free(pool->task_queue);}if (pool->threads) {free(pool->threads);pthread_mutex_lock(&(pool->lock));pthread_mutex_destroy(&(pool->lock));pthread_mutex_lock(&(pool->thread_counter));pthread_mutex_destroy(&(pool->thread_counter));pthread_cond_destroy(&(pool->queue_not_empty));pthread_cond_destroy(&(pool->queue_not_full));}free(pool);pool = NULL;return 0;
}int threadpool_all_threadnum(threadpool_t *pool)
{int all_threadnum = -1;pthread_mutex_lock(&(pool->lock));all_threadnum = pool->live_thr_num;pthread_mutex_unlock(&(pool->lock));return all_threadnum;
}int threadpool_busy_threadnum(threadpool_t *pool)
{int busy_threadnum = -1;pthread_mutex_lock(&(pool->thread_counter));busy_threadnum = pool->busy_thr_num;pthread_mutex_unlock(&(pool->thread_counter));return busy_threadnum;
}int is_thread_alive(pthread_t tid)
{int kill_rc = pthread_kill(tid, 0);     //发0号信号，测试线程是否存活if (kill_rc == ESRCH) {return false;}return true;
}/*测试*/ #if 1
/* 线程池中的线程，模拟处理业务 */
void *process(void *arg)
{printf("thread 0x%x working on task %d\n ",(unsigned int)pthread_self(),*(int *)arg);sleep(1);printf("task %d is end\n", *(int *)arg);return NULL;
}int main(void)
{/*threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size);*/threadpool_t *thp = threadpool_create(3,100,100);   /*创建线程池，池里最小3个线程，最大100，队列最大100*/printf("pool inited");//int *num = (int *)malloc(sizeof(int)*20);int num[20], i;for (i = 0; i < 20; i++) {num[i]=i;printf("add task %d\n",i);threadpool_add(thp, process, (void*)&num[i]);   /* 向线程池中添加任务 */}sleep(10);                                          /* 等子线程完成任务 */threadpool_destroy(thp);return 0;
}#endif