事件处理框架介绍
Nginx基于事件驱动架构的Web服务器，负责这个功能的主要模块就是事件处理模块。事件处理模块主要解决如何收集、管理、分发事件（主要是网络事件和定时器事件）。由于网络事件与网卡中断处理程序，内核提供的系统调用密切相关，所以网络事件的驱动既取决与不同的操作系统，也取决于操作系统不同的操作系统内核版本。Nginx定义了一些列的事件驱动模块：ngx_devpoll_module，ngx_epoll_module，ngx_eventport_module，ngx_kqueue_module，ngx_poll_module，ngx_select_module，ngx_win32_poll_module，ngx_win32_select_module一共八个不同的事件驱动模块。在ngx_event_core_module模块的初始化过程中，将会从以上八个模块中选取1个作为Nginx进程的事件驱动模块。
1.事件驱动框架的处理流程
2.源码
void
ngx_event_accept(ngx_event_t *ev)
{
socklen_t socklen;
ngx_err_t err;
ngx_log_t *log;
ngx_uint_t level;
ngx_socket_t s;
ngx_event_t *rev, *wev;
ngx_sockaddr_t sa;
ngx_listening_t *ls;
ngx_connection_t *c, *lc;
ngx_event_conf_t *ecf;
#if (NGX_HAVE_ACCEPT4)
static ngx_uint_t use_accept4 = 1;
#endif
if (ev->timedout) {
if (ngx_enable_accept_events((ngx_cycle_t *) ngx_cycle) != NGX_OK) {
return;
}
ev->timedout = 0;
}
ecf = ngx_event_get_conf(ngx_cycle->conf_ctx, ngx_event_core_module);
if (!(ngx_event_flags & NGX_USE_KQUEUE_EVENT)) {
ev->available = ecf->multi_accept;
}
lc = ev->data;
ls = lc->listening;
ev->ready = 0;
ngx_log_debug2(NGX_LOG_DEBUG_EVENT, ev->log, 0,
"accept on %V, ready: %d", &ls->addr_text, ev->available);
do {
socklen = sizeof(ngx_sockaddr_t);
#if (NGX_HAVE_ACCEPT4)
if (use_accept4) {
s = accept4(lc->fd, &sa.sockaddr, &socklen, SOCK_NONBLOCK);
} else {
s = accept(lc->fd, &sa.sockaddr, &socklen);
}
#else
s = accept(lc->fd, &sa.sockaddr, &socklen);
#endif
if (s == (ngx_socket_t) -1) {
err = ngx_socket_errno;
if (err == NGX_EAGAIN) {
ngx_log_debug0(NGX_LOG_DEBUG_EVENT, ev->log, err,
"accept() not ready");
return;
}
level = NGX_LOG_ALERT;
if (err == NGX_ECONNABORTED) {
level = NGX_LOG_ERR;
} else if (err == NGX_EMFILE || err == NGX_ENFILE) {
level = NGX_LOG_CRIT;
}
#if (NGX_HAVE_ACCEPT4)
ngx_log_error(level, ev->log, err,
use_accept4 ? "accept4() failed" : "accept() failed");
if (use_accept4 && err == NGX_ENOSYS) {
use_accept4 = 0;
ngx_inherited_nonblocking = 0;
continue;
}
#else
ngx_log_error(level, ev->log, err, "accept() failed");
#endif
if (err == NGX_ECONNABORTED) {
if (ngx_event_flags & NGX_USE_KQUEUE_EVENT) {
ev->available--;
}
if (ev->available) {
continue;
}
}
if (err == NGX_EMFILE || err == NGX_ENFILE) {
if (ngx_disable_accept_events((ngx_cycle_t *) ngx_cycle, 1)
!= NGX_OK)
{
return;
}
if (ngx_use_accept_mutex) {
if (ngx_accept_mutex_held) {
ngx_shmtx_unlock(&ngx_accept_mutex);
ngx_accept_mutex_held = 0;
}
ngx_accept_disabled = 1;
} else {
ngx_add_timer(ev, ecf->accept_mutex_delay);
}
}
return;
}
#if (NGX_STAT_STUB)
(void) ngx_atomic_fetch_add(ngx_stat_accepted, 1);
#endif
ngx_accept_disabled = ngx_cycle->connection_n / 8
- ngx_cycle->free_connection_n;
c = ngx_get_connection(s, ev->log);
if (c == NULL) {
if (ngx_close_socket(s) == -1) {
ngx_log_error(NGX_LOG_ALERT, ev->log, ngx_socket_errno,
ngx_close_socket_n " failed");
}
return;
}
c->type = SOCK_STREAM;
#if (NGX_STAT_STUB)
(void) ngx_atomic_fetch_add(ngx_stat_active, 1);
#endif
c->pool = ngx_create_pool(ls->pool_size, ev->log);
if (c->pool == NULL) {
ngx_close_accepted_connection(c);
return;
}
if (socklen > (socklen_t) sizeof(ngx_sockaddr_t)) {
socklen = sizeof(ngx_sockaddr_t);
}
c->sockaddr = ngx_palloc(c->pool, socklen);
if (c->sockaddr == NULL) {
ngx_close_accepted_connection(c);
return;
}
ngx_memcpy(c->sockaddr, &sa, socklen);
log = ngx_palloc(c->pool, sizeof(ngx_log_t));
if (log == NULL) {
ngx_close_accepted_connection(c);
return;
}
/* set a blocking mode for iocp and non-blocking mode for others */
if (ngx_inherited_nonblocking) {
if (ngx_event_flags & NGX_USE_IOCP_EVENT) {
if (ngx_blocking(s) == -1) {
ngx_log_error(NGX_LOG_ALERT, ev->log, ngx_socket_errno,
ngx_blocking_n " failed");
ngx_close_accepted_connection(c);
return;
}
}
} else {
if (!(ngx_event_flags & NGX_USE_IOCP_EVENT)) {
if (ngx_nonblocking(s) == -1) {
ngx_log_error(NGX_LOG_ALERT, ev->log, ngx_socket_errno,
ngx_nonblocking_n " failed");
ngx_close_accepted_connection(c);
return;
}
}
}
*log = ls->log;
c->recv = ngx_recv;
c->send = ngx_send;
c->recv_chain = ngx_recv_chain;
c->send_chain = ngx_send_chain;
c->log = log;
c->pool->log = log;
c->socklen = socklen;
c->listening = ls;
c->local_sockaddr = ls->sockaddr;
c->local_socklen = ls->socklen;
#if (NGX_HAVE_UNIX_DOMAIN)
if (c->sockaddr->sa_family == AF_UNIX) {
c->tcp_nopush = NGX_TCP_NOPUSH_DISABLED;
c->tcp_nodelay = NGX_TCP_NODELAY_DISABLED;
#if (NGX_SOLARIS)
/* Solaris's sendfilev() supports AF_NCA, AF_INET, and AF_INET6 */
c->sendfile = 0;
#endif
}
#endif
rev = c->read;
wev = c->write;
wev->ready = 1;
if (ngx_event_flags & NGX_USE_IOCP_EVENT) {
rev->ready = 1;
}
if (ev->deferred_accept) {
rev->ready = 1;
#if (NGX_HAVE_KQUEUE || NGX_HAVE_EPOLLRDHUP)
rev->available = 1;
#endif
}
rev->log = log;
wev->log = log;
/*
* TODO: MT: - ngx_atomic_fetch_add()
* or protection by critical section or light mutex
*
* TODO: MP: - allocated in a shared memory
* - ngx_atomic_fetch_add()
* or protection by critical section or light mutex
*/
c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);
#if (NGX_STAT_STUB)
(void) ngx_atomic_fetch_add(ngx_stat_handled, 1);
#endif
if (ls->addr_ntop) {
c->addr_text.data = ngx_pnalloc(c->pool, ls->addr_text_max_len);
if (c->addr_text.data == NULL) {
ngx_close_accepted_connection(c);
return;
}
c->addr_text.len = ngx_sock_ntop(c->sockaddr, c->socklen,
c->addr_text.data,
ls->addr_text_max_len, 0);
if (c->addr_text.len == 0) {
ngx_close_accepted_connection(c);
return;
}
}
#if (NGX_DEBUG)
{
ngx_str_t addr;
u_char text[NGX_SOCKADDR_STRLEN];
ngx_debug_accepted_connection(ecf, c);
if (log->log_level & NGX_LOG_DEBUG_EVENT) {
addr.data = text;
addr.len = ngx_sock_ntop(c->sockaddr, c->socklen, text,
NGX_SOCKADDR_STRLEN, 1);
ngx_log_debug3(NGX_LOG_DEBUG_EVENT, log, 0,
"*%uA accept: %V fd:%d", c->number, &addr, s);
}
}
#endif
if (ngx_add_conn && (ngx_event_flags & NGX_USE_EPOLL_EVENT) == 0) {
if (ngx_add_conn(c) == NGX_ERROR) {
ngx_close_accepted_connection(c);
return;
}
}
log->data = NULL;
log->handler = NULL;
ls->handler(c);
if (ngx_event_flags & NGX_USE_KQUEUE_EVENT) {
ev->available--;
}
} while (ev->available);
}