nginx 事件模块

2019独角兽企业重金招聘Python工程师标准>>>

操作系统和内核版本决定事件驱动机制，不同的操作系统对应不同的事件驱动机制，在Linux 2.6之后使用epoll机制，对应的事件驱动模块是ngx_epoll_module。Nginx的ngx_event_core_module模块根据操作系统确定使用哪一个事件驱动模块。

根据宏定义是否有值，确实使用哪种事件驱动模块，例如在编译后的文件NGINX/NGINX-1.6.2/objs/ngx_auto_config.h查找对应的宏定义，NGX_HAVE_EPOLL值为1，则使用epoll驱动。对应代码：

ngx_event_module_t  ngx_event_core_module_ctx = {
    &event_core_name,
    ngx_event_core_create_conf,            /* create configuration */
    ngx_event_core_init_conf,              /* init configuration */

    { NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL }
};


ngx_module_t  ngx_event_core_module = {
    NGX_MODULE_V1,
    &ngx_event_core_module_ctx,            /* module context */
    ngx_event_core_commands,               /* module directives */
    NGX_EVENT_MODULE,                      /* module type */
    NULL,                                  /* init master */
    ngx_event_module_init,                 /* init module */
    ngx_event_process_init,                /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};

static char *
ngx_event_core_init_conf(ngx_cycle_t *cycle, void *conf)
{
    ngx_event_conf_t  *ecf = conf;

#if (NGX_HAVE_EPOLL) && !(NGX_TEST_BUILD_EPOLL)
    int                  fd;
#endif
#if (NGX_HAVE_RTSIG)
    ngx_uint_t           rtsig;
    ngx_core_conf_t     *ccf;
#endif
    ngx_int_t            i;
    ngx_module_t        *module;
    ngx_event_module_t  *event_module;

    module = NULL;

#if (NGX_HAVE_EPOLL) && !(NGX_TEST_BUILD_EPOLL)

    fd = epoll_create(100);

    if (fd != -1) {
        (void) close(fd);
        module = &ngx_epoll_module;

    } else if (ngx_errno != NGX_ENOSYS) {
        module = &ngx_epoll_module;
    }

#endif

#if (NGX_HAVE_RTSIG)

    if (module == NULL) {
        module = &ngx_rtsig_module;
        rtsig = 1;

    } else {
        rtsig = 0;
    }

#endif

#if (NGX_HAVE_DEVPOLL)

    module = &ngx_devpoll_module;

#endif

#if (NGX_HAVE_KQUEUE)

    module = &ngx_kqueue_module;

#endif

#if (NGX_HAVE_SELECT)

    if (module == NULL) {
        module = &ngx_select_module;
    }

#endif

    if (module == NULL) {
        for (i = 0; ngx_modules[i]; i++) {

            if (ngx_modules[i]->type != NGX_EVENT_MODULE) {
                continue;
            }

            event_module = ngx_modules[i]->ctx;

            if (ngx_strcmp(event_module->name->data, event_core_name.data) == 0)
            {
                continue;
            }

            module = ngx_modules[i];
            break;
        }
    }

    if (module == NULL) {
        ngx_log_error(NGX_LOG_EMERG, cycle->log, 0, "no events module found");
        return NGX_CONF_ERROR;
    }

    ngx_conf_init_uint_value(ecf->connections, DEFAULT_CONNECTIONS);
    cycle->connection_n = ecf->connections;

    ngx_conf_init_uint_value(ecf->use, module->ctx_index);

    event_module = module->ctx;
    ngx_conf_init_ptr_value(ecf->name, event_module->name->data);

    ngx_conf_init_value(ecf->multi_accept, 0);
    ngx_conf_init_value(ecf->accept_mutex, 0);
    ngx_conf_init_msec_value(ecf->accept_mutex_delay, 500);


#if (NGX_HAVE_RTSIG)

    if (!rtsig) {
        return NGX_CONF_OK;
    }

    if (ecf->accept_mutex) {
        return NGX_CONF_OK;
    }

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

    if (ccf->worker_processes == 0) {
        return NGX_CONF_OK;
    }

    ngx_log_error(NGX_LOG_EMERG, cycle->log, 0,
                  "the "rtsig" method requires "accept_mutex" to be on");

    return NGX_CONF_ERROR;

#else

    return NGX_CONF_OK;

#endif
}

事件驱动模块在ngx_module_t的ctx通用接口是ngx_event_module_t，定义如下所示：

typedef struct {
    ngx_str_t              *name;

    void                 *(*create_conf)(ngx_cycle_t *cycle);
    char                 *(*init_conf)(ngx_cycle_t *cycle, void *conf);

    ngx_event_actions_t     actions;
} ngx_event_module_t;

typedef struct {
    ngx_int_t  (*add)(ngx_event_t *ev, ngx_int_t event, ngx_uint_t flags);
    ngx_int_t  (*del)(ngx_event_t *ev, ngx_int_t event, ngx_uint_t flags);

    ngx_int_t  (*enable)(ngx_event_t *ev, ngx_int_t event, ngx_uint_t flags);
    ngx_int_t  (*disable)(ngx_event_t *ev, ngx_int_t event, ngx_uint_t flags);

    ngx_int_t  (*add_conn)(ngx_connection_t *c);
    ngx_int_t  (*del_conn)(ngx_connection_t *c, ngx_uint_t flags);

    ngx_int_t  (*process_changes)(ngx_cycle_t *cycle, ngx_uint_t nowait);
    ngx_int_t  (*process_events)(ngx_cycle_t *cycle, ngx_msec_t timer,
                   ngx_uint_t flags);

    ngx_int_t  (*init)(ngx_cycle_t *cycle, ngx_msec_t timer);
    void       (*done)(ngx_cycle_t *cycle);
} ngx_event_actions_t;

事件由ngx_event_t结构体定义：

struct ngx_event_s{
    void            *data;

    unsigned         write:1;

    unsigned         accept:1;

    /* used to detect the stale events in kqueue, rtsig, and epoll */
    unsigned         instance:1;

    /*
     * the event was passed or would be passed to a kernel;
     * in aio mode - operation was posted.
     */
    unsigned         active:1;

    unsigned         disabled:1;

    /* the ready event; in aio mode 0 means that no operation can be posted */
    unsigned         ready:1;

    unsigned         oneshot:1;

    /* aio operation is complete */
    unsigned         complete:1;

    unsigned         eof:1;
    unsigned         error:1;

    unsigned         timedout:1;
    unsigned         timer_set:1;

    unsigned         delayed:1;

    unsigned         deferred_accept:1;

    /* the pending eof reported by kqueue, epoll or in aio chain operation */
    unsigned         pending_eof:1;

#if !(NGX_THREADS)
    unsigned         posted_ready:1;
#endif

#if (NGX_WIN32)
    /* setsockopt(SO_UPDATE_ACCEPT_CONTEXT) was successful */
    unsigned         accept_context_updated:1;
#endif

#if (NGX_HAVE_KQUEUE)
    unsigned         kq_vnode:1;

    /* the pending errno reported by kqueue */
    int              kq_errno;
#endif

    /*
     * kqueue only:
     *   accept:     number of sockets that wait to be accepted
     *   read:       bytes to read when event is ready
     *               or lowat when event is set with NGX_LOWAT_EVENT flag
     *   write:      available space in buffer when event is ready
     *               or lowat when event is set with NGX_LOWAT_EVENT flag
     *
     * iocp: TODO
     *
     * otherwise:
     *   accept:     1 if accept many, 0 otherwise
     */

#if (NGX_HAVE_KQUEUE) || (NGX_HAVE_IOCP)
    int              available;
#else
    unsigned         available:1;
#endif

    ngx_event_handler_pt  handler;


#if (NGX_HAVE_AIO)

#if (NGX_HAVE_IOCP)
    ngx_event_ovlp_t ovlp;
#else
    struct aiocb     aiocb;
#endif

#endif

    ngx_uint_t       index;

    ngx_log_t       *log;

    ngx_rbtree_node_t   timer;

    unsigned         closed:1;

    /* to test on worker exit */
    unsigned         channel:1;
    unsigned         resolver:1;

#if (NGX_THREADS)

    unsigned         locked:1;

    unsigned         posted_ready:1;
    unsigned         posted_timedout:1;
    unsigned         posted_eof:1;

#if (NGX_HAVE_KQUEUE)
    /* the pending errno reported by kqueue */
    int              posted_errno;
#endif

#if (NGX_HAVE_KQUEUE) || (NGX_HAVE_IOCP)
    int              posted_available;
#else
    unsigned         posted_available:1;
#endif

    ngx_atomic_t    *lock;
    ngx_atomic_t    *own_lock;

#endif

    /* the links of the posted queue */
    ngx_event_t     *next;
    ngx_event_t    **prev;


#if 0

    /* the threads support */

    /*
     * the event thread context, we store it here
     * if $(CC) does not understand __thread declaration
     * and pthread_getspecific() is too costly
     */

    void            *thr_ctx;

#if (NGX_EVENT_T_PADDING)

    /* event should not cross cache line in SMP */

    uint32_t         padding[NGX_EVENT_T_PADDING];
#endif
#endif
}

在ngx_event_t中，我们最关心handler成员，它决定了它所属的事件发生时的处理方法。

转载于:https://my.oschina.net/u/2326611/blog/847236