Nginx源码学习(3)----Worker子进程

这次来看worker子进程。

ngx_spawn_process(cycle, ngx_worker_process_cycle, NULL,
                          "worker process", type);

 

在创建子进程的同时，注册了一个子进程要执行的函数：ngx_worker_process_cycle。

下面来看这个函数：

static void
ngx_worker_process_cycle(ngx_cycle_t *cycle, void *data)
{
    ngx_uint_t i;
    ngx_connection_t *c;

    ngx_process = NGX_PROCESS_WORKER;

    ngx_worker_process_init(cycle, 1);

    ngx_setproctitle("worker process");

#if (NGX_THREADS)
    {
    ngx_int_t n;
    ngx_err_t err;
    ngx_core_conf_t *ccf;

    ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);

    if (ngx_threads_n) {
        if (ngx_init_threads(ngx_threads_n, ccf->thread_stack_size, cycle)
            == NGX_ERROR)
        {
            /* fatal */
            exit(2);
        }

        err = ngx_thread_key_create(&ngx_core_tls_key);
        if (err != 0) {
            ngx_log_error(NGX_LOG_ALERT, cycle->log, err,
                          ngx_thread_key_create_n " failed");
            /* fatal */
            exit(2);
        }

        for (n = 0; n < ngx_threads_n; n++) {

            ngx_threads[n].cv = ngx_cond_init(cycle->log);

            if (ngx_threads[n].cv == NULL) {
                /* fatal */
                exit(2);
            }

            if (ngx_create_thread((ngx_tid_t *) &ngx_threads[n].tid,
                                  ngx_worker_thread_cycle,
                                  (void *) &ngx_threads[n], cycle->log)
                != 0)
            {
                /* fatal */
                exit(2);
            }
        }
    }
    }
#endif

    for ( ;; ) {

        if (ngx_exiting) {

            c = cycle->connections;

            for (i = 0; i < cycle->connection_n; i++) {

                /* THREAD: lock */

                if (c[i].fd != -1 && c[i].idle) {
                    c[i].close = 1;
                    c[i].read->handler(c[i].read);
                }
            }

            if (ngx_event_timer_rbtree.root == ngx_event_timer_rbtree.sentinel)
            {
                ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exiting");

                ngx_worker_process_exit(cycle);
            }
        }

        ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "worker cycle");

        ngx_process_events_and_timers(cycle);

        if (ngx_terminate) {
            ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exiting");

            ngx_worker_process_exit(cycle);
        }

        if (ngx_quit) {
            ngx_quit = 0;
            ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0,
                          "gracefully shutting down");
            ngx_setproctitle("worker process is shutting down");

            if (!ngx_exiting) {
                ngx_close_listening_sockets(cycle);
                ngx_exiting = 1;
            }
        }

        if (ngx_reopen) {
            ngx_reopen = 0;
            ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reopening logs");
            ngx_reopen_files(cycle, -1);
        }
    }
}

（1）函数首先执行了一个ngx_worker_process_init。这里不进去看了，说说大概的作用：设好进程环境，屏蔽一些信号，还有设好跟其他进程的通信（上次提到过的Unix域用于进程间通信）等等。

（2）接下来涉及线程：首先初始化线程属性、创建“线程标识号”（key）、每一个线程的pthread_cond_t的初始化、创建线程。线程执行的是ngx_worker_thread_cycle这个操作，我们来看看：

static ngx_thread_value_t
ngx_worker_thread_cycle(void *data)
{
    ngx_thread_t *thr = data;

    sigset_t set;
    ngx_err_t err;
    ngx_core_tls_t *tls;
    ngx_cycle_t *cycle;

    cycle = (ngx_cycle_t *) ngx_cycle;

    sigemptyset(&set);
    sigaddset(&set, ngx_signal_value(NGX_RECONFIGURE_SIGNAL));
    sigaddset(&set, ngx_signal_value(NGX_REOPEN_SIGNAL));
    sigaddset(&set, ngx_signal_value(NGX_CHANGEBIN_SIGNAL));

    err = ngx_thread_sigmask(SIG_BLOCK, &set, NULL);
    if (err) {
        ngx_log_error(NGX_LOG_ALERT, cycle->log, err,
                      ngx_thread_sigmask_n " failed");
        return (ngx_thread_value_t) 1;
    }

    ngx_log_debug1(NGX_LOG_DEBUG_CORE, cycle->log, 0,
                   "thread " NGX_TID_T_FMT " started", ngx_thread_self());

    ngx_setthrtitle("worker thread");

    tls = ngx_calloc(sizeof(ngx_core_tls_t), cycle->log);
    if (tls == NULL) {
        return (ngx_thread_value_t) 1;
    }

    err = ngx_thread_set_tls(ngx_core_tls_key, tls);
    if (err != 0) {
        ngx_log_error(NGX_LOG_ALERT, cycle->log, err,
                      ngx_thread_set_tls_n " failed");
        return (ngx_thread_value_t) 1;
    }

    ngx_mutex_lock(ngx_posted_events_mutex);

    for ( ;; ) {
        thr->state = NGX_THREAD_FREE;

        if (ngx_cond_wait(thr->cv, ngx_posted_events_mutex) == NGX_ERROR) {
            return (ngx_thread_value_t) 1;
        }

        if (ngx_terminate) {
            thr->state = NGX_THREAD_EXIT;

            ngx_mutex_unlock(ngx_posted_events_mutex);

            ngx_log_debug1(NGX_LOG_DEBUG_CORE, cycle->log, 0,
                           "thread " NGX_TID_T_FMT " is done",
                           ngx_thread_self());

            return (ngx_thread_value_t) 0;
        }

        thr->state = NGX_THREAD_BUSY;

        if (ngx_event_thread_process_posted(cycle) == NGX_ERROR) {
            return (ngx_thread_value_t) 1;
        }

        if (ngx_event_thread_process_posted(cycle) == NGX_ERROR) {
            return (ngx_thread_value_t) 1;
        }

        if (ngx_process_changes) {
            if (ngx_process_changes(cycle, 1) == NGX_ERROR) {
                return (ngx_thread_value_t) 1;
            }
        }
    }
}

这个函数的流程大概为：首先是屏蔽一些信号，接着上一个关于有没有事件的锁，接着进入一个for死循环，进入之后线程为free状态，等待事件到来也就是事件锁被打开，最后由ngx_event_thread_process_posted处理被post的事件（估计有一个全局的事件链表，暂未考证，待下面分析再看回来），注意每个线程每一次得到事件锁后处理两个事件。

（3）最后进程（其实应该是主线程，创建的线程都在忙着上面的事）进入死循环，等待一些事情的发生。