nginx源码分析线程池详解

Syntax: thread_pool name threads=number [max_queue=number];Default: thread_pool default threads=32 max_queue=65536;Context: main

/******************* nginx/src/core/ngx_thread_pool.c ************************///创建线程池所需的基础结构static void * ngx_thread_pool_create_conf(ngx_cycle_t *cycle){  ngx_thread_pool_conf_t *tcf;   //从cycle->pool指向的内存池中申请一块内存  tcf = ngx_pcalloc(cycle->pool, sizeof(ngx_thread_pool_conf_t));  if (tcf == NULL) {    return NULL;  }      //先申请包含4个ngx_thread_pool_t指针类型元素的数组   //ngx_thread_pool_t结构体中保存了一个线程池相关的信息  if (ngx_array_init(&tcf->pools, cycle->pool, 4,            sizeof(ngx_thread_pool_t *))    != NGX_OK)  {    return NULL;  }   return tcf;} //解析处理配置文件中thread_pool的配置，并将相关信息保存的ngx_thread_pool_t中static char * ngx_thread_pool(ngx_conf_t *cf, ngx_command_t *cmd, void *conf){  ngx_str_t     *value;  ngx_uint_t     i;  ngx_thread_pool_t *tp;   value = cf->args->elts;   //根据thread_pool配置中的name作为线程池的唯一标识（如果重名，只有第一个有效）  //申请ngx_thread_pool_t结构保存线程池的相关信息  //由此可见，nginx支持配置多个name不同的线程池  tp = ngx_thread_pool_add(cf, &value[1]);  .......  //处理thread_pool配置行的所有元素  for (i = 2; i < cf->args->nelts; i++) {    //检查配置的线程数    if (ngx_strncmp(value[i].data, "threads=", 8) == 0) {     .......    }         //检查配置的最大队列长度    if (ngx_strncmp(value[i].data, "max_queue=", 10) == 0) {     .......    }  }  ......} //判断包含多个线程池的数组中的各个线程池的配置是否正确static char * ngx_thread_pool_init_conf(ngx_cycle_t *cycle, void *conf){  ....  ngx_thread_pool_t **tpp;   tpp = tcf->pools.elts;  //遍历数组中所有的线程池配置，并检查其正确性  for (i = 0; i < tcf->pools.nelts; i++) {    .....  }   return NGX_CONF_OK;}

/******************* nginx/src/core/ngx_thread_pool.c ************************///创建线程池所需的基础结构static ngx_int_tngx_thread_pool_init_worker(ngx_cycle_t *cycle){  ngx_uint_t        i;  ngx_thread_pool_t    **tpp;  ngx_thread_pool_conf_t  *tcf;  //如果不是worker或者只有一个worker就不起用线程池  if (ngx_process != NGX_PROCESS_WORKER    && ngx_process != NGX_PROCESS_SINGLE)  {    return NGX_OK;  }     //初始化任务队列  ngx_thread_pool_queue_init(&ngx_thread_pool_done);   tpp = tcf->pools.elts;  for (i = 0; i < tcf->pools.nelts; i++) {    //初始化各个线程池    if (ngx_thread_pool_init(tpp[i], cycle->log, cycle->pool) != NGX_OK) {      return NGX_ERROR;    }  }   return NGX_OK;} //线程池初始化static ngx_int_t ngx_thread_pool_init(ngx_thread_pool_t *tp, ngx_log_t *log, ngx_pool_t *pool){  .....  //初始化任务队列  ngx_thread_pool_queue_init(&tp->queue);   //创建线程锁  if (ngx_thread_mutex_create(&tp->mtx, log) != NGX_OK) {    return NGX_ERROR;  }   //创建线程条件变量  if (ngx_thread_cond_create(&tp->cond, log) != NGX_OK) {    (void) ngx_thread_mutex_destroy(&tp->mtx, log);    return NGX_ERROR;  }  ......  for (n = 0; n < tp->threads; n++) {    //创建线程池中的每个线程    err = pthread_create(&tid, &attr, ngx_thread_pool_cycle, tp);    if (err) {      ngx_log_error(NGX_LOG_ALERT, log, err,             "pthread_create() failed");      return NGX_ERROR;    }  }  ......} //线程池中线程处理主函数static void *ngx_thread_pool_cycle(void *data){   ......   for ( ;; ) {    //阻塞的方式获取线程锁    if (ngx_thread_mutex_lock(&tp->mtx, tp->log) != NGX_OK) {      return NULL;    }     /* the number may become negative */    tp->waiting--;     //如果任务队列为空，就cond_wait阻塞等待有新任务时调用cond_signal/broadcast触发    while (tp->queue.first == NULL) {      if (ngx_thread_cond_wait(&tp->cond, &tp->mtx, tp->log)        != NGX_OK)      {        (void) ngx_thread_mutex_unlock(&tp->mtx, tp->log);        return NULL;      }    }    //从任务队列中获取task，并将其从队列中移除    task = tp->queue.first;    tp->queue.first = task->next;     if (tp->queue.first == NULL) {      tp->queue.last = &tp->queue.first;    }     if (ngx_thread_mutex_unlock(&tp->mtx, tp->log) != NGX_OK) {      return NULL;    }    ......    //task的处理函数    task->handler(task->ctx, tp->log);    .....     ngx_spinlock(&ngx_thread_pool_done_lock, 1, 2048);     //将经过预处理的任务添加到done队列中等待调用event的回调函数继续处理    *ngx_thread_pool_done.last = task;    ngx_thread_pool_done.last = &task->next;         //防止编译器优化，保证解锁操作是在上述语句执行完毕后再去执行的    ngx_memory_barrier();     ngx_unlock(&ngx_thread_pool_done_lock);         (void) ngx_notify(ngx_thread_pool_handler);  }} //处理pool_done队列上task中包含的每个event事件static void ngx_thread_pool_handler(ngx_event_t *ev){  .....  ngx_spinlock(&ngx_thread_pool_done_lock, 1, 2048);   //获取任务链表的头部  task = ngx_thread_pool_done.first;  ngx_thread_pool_done.first = NULL;  ngx_thread_pool_done.last = &ngx_thread_pool_done.first;   ngx_memory_barrier();   ngx_unlock(&ngx_thread_pool_done_lock);   while (task) {    ngx_log_debug1(NGX_LOG_DEBUG_CORE, ev->log, 0,            "run completion handler for task #%ui", task->id);    //遍历队列中的所有任务事件    event = &task->event;    task = task->next;     event->complete = 1;    event->active = 0;     //调用event对应的处理函数有针对性的进行处理    event->handler(event);  }} 

/*********************** nginx/src/os/unix/ngx_files.c **********************///file_cache模块的处理函数（涉及到了线程池）static ssize_t ngx_http_file_cache_aio_read(ngx_http_request_t *r, ngx_http_cache_t *c){  .......#if (NGX_THREADS)   if (clcf->aio == NGX_HTTP_AIO_THREADS) {    c->file.thread_task = c->thread_task;    //这里注册的函数在下面语句中的ngx_thread_read函数中被调用    c->file.thread_handler = ngx_http_cache_thread_handler;    c->file.thread_ctx = r;    //根据任务的属性，选择正确的线程池，并初始化task结构体中的各个成员        n = ngx_thread_read(&c->file, c->buf->pos, c->body_start, 0, r->pool);     c->thread_task = c->file.thread_task;    c->reading = (n == NGX_AGAIN);     return n;  }#endif   return ngx_read_file(&c->file, c->buf->pos, c->body_start, 0);}  //task任务的处理函数static ngx_int_t ngx_http_cache_thread_handler(ngx_thread_task_t *task, ngx_file_t *file){  .......  tp = clcf->thread_pool;  .......     task->event.data = r;  //注册thread_event_handler函数，该函数在处理pool_done队列中event事件时被调用  task->event.handler = ngx_http_cache_thread_event_handler;   //将任务放到线程池的任务队列中  if (ngx_thread_task_post(tp, task) != NGX_OK) {    return NGX_ERROR;  }  ......} /*********************** nginx/src/core/ngx_thread_pool.c **********************///添加任务到队列中ngx_int_t ngx_thread_task_post(ngx_thread_pool_t *tp, ngx_thread_task_t *task){  //如果当前的任务正在处理就退出  if (task->event.active) {    ngx_log_error(NGX_LOG_ALERT, tp->log, 0,           "task #%ui already active", task->id);    return NGX_ERROR;  }   if (ngx_thread_mutex_lock(&tp->mtx, tp->log) != NGX_OK) {    return NGX_ERROR;  }     //判断当前线程池等待的任务数量与最大队列长度的关系  if (tp->waiting >= tp->max_queue) {    (void) ngx_thread_mutex_unlock(&tp->mtx, tp->log);     ngx_log_error(NGX_LOG_ERR, tp->log, 0,           "thread pool /"%V/" queue overflow: %i tasks waiting",           &tp->name, tp->waiting);    return NGX_ERROR;  }  //激活任务  task->event.active = 1;   task->id = ngx_thread_pool_task_id++;  task->next = NULL;     //通知阻塞的线程有新事件加入，可以解除阻塞  if (ngx_thread_cond_signal(&tp->cond, tp->log) != NGX_OK) {    (void) ngx_thread_mutex_unlock(&tp->mtx, tp->log);    return NGX_ERROR;  }   *tp->queue.last = task;  tp->queue.last = &task->next;   tp->waiting++;   (void) ngx_thread_mutex_unlock(&tp->mtx, tp->log);   ngx_log_debug2(NGX_LOG_DEBUG_CORE, tp->log, 0,          "task #%ui added to thread pool /"%V/"",          task->id, &tp->name);   return NGX_OK;}