struct ngx_event_s {

void *data; //與事件關聯的對象，常指向事件所在的ngx_connection_t連接對象

unsigned write:1; //可寫標識位，1表示對應的tcp連接是可寫的

unsigned accept:1;// 1表示對應的連接是處于監聽狀態的連接，即可接收新的連接

/* used to detect the stale events in kqueue, rtsig, and epoll */

unsigned instance:1; //可來區分事件是否已過期

/*

* the event was passed or would be passed to a kernel;

* in aio mode - operation was posted.

*/

unsigned active:1;// 1表示事件活躍，即事件已添加到epoll中

unsigned disabled:1;//epoll中不使用該標識位

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

unsigned ready:1; //事件已就緒(即可讀或可寫)

unsigned oneshot:1;//epoll不使用該標識位

/* aio operation is complete */

unsigned complete:1;//aio中使用，表示 事件對應的aio異步操作已完成(io_getevents函數已成功返回)

unsigned eof:1;// 1表示當前處理的字符流已完成，如調用recv讀取連接數據時返回0，此時置該標識位為1

unsigned error:1;// 1表示事件處理過程中發生錯誤

unsigned timedout:1; //事件是否超時，1:表示超時。超時后事件對應的請求不需再被處理(對于http模塊來說事件超時后直接關閉請求)

unsigned timer_set:1; //為1時表示這個事件在定時器中

unsigned delayed:1;// 1表示 需延遲處理該事件，常用于限速功能中

unsigned deferred_accept:1;//延遲接收接連，即當連接中收到對象發送的數據后才真正建立連接

/* the pending eof reported by kqueue, epoll or in aio chain operation */

unsigned pending_eof:1;// 1表示TCP連接對向關閉讀端，即epoll返回EPOLLRDHUP

#if !(NGX_THREADS)

unsigned posted_ready:1;//該標識位在1.5.5版本源碼中只在ngx_epoll_process_events函數中有置位，其它地方并沒有用到

#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;// 1表示每次調用accept時盡可能多的接收TCP連接，與multi_accept配置項對應

#endif

ngx_event_handler_pt handler; // 事件產生后的回調函數句柄

#if (NGX_HAVE_AIO)

#if (NGX_HAVE_IOCP)

ngx_event_ovlp_t ovlp;

#else

struct aiocb aiocb;

#endif

#endif

ngx_uint_t index; //epoll中不使用

ngx_log_t *log; //ngx_log_t對象

ngx_rbtree_node_t timer;

unsigned closed:1; // 1表示事件已關閉

/* to test on worker exit */

unsigned channel:1;// 只在ngx_add_channel_event函數中有置位，其它地方沒用到

unsigned resolver:1; // resolver功能中使用?

#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

};

#if (NGX_HAVE_FILE_AIO)

struct ngx_event_aio_s {

void *data;

ngx_event_handler_pt handler;

ngx_file_t *file;

ngx_fd_t fd;

#if (NGX_HAVE_EVENTFD)

int64_t res;

#if (NGX_TEST_BUILD_EPOLL)

ngx_err_t err;

size_t nbytes;

#endif

#else

ngx_err_t err;

size_t nbytes;

#endif

#if (NGX_HAVE_AIO_SENDFILE)

off_t last_offset;

#endif

ngx_aiocb_t aiocb;

ngx_event_t event;

};

#endif

static ngx_command_t ngx_epoll_commands[] = {

{

/***epoll_events配置項表示epoll_wait函數每次最多返回多少個事件，在ngx_epoll_init函數中

會預先分配epoll_events配置項指定的epoll_event結構個數**/

ngx_string("epoll_events"),

NGX_EVENT_CONF|NGX_CONF_TAKE1,

ngx_conf_set_num_slot,

0,

offsetof(ngx_epoll_conf_t, events),

NULL },

{

/***worker_aio_requests配置項表示創建的aio context能并發處理異步事件的個數，即io_setup函數的第一個參數***/

ngx_string("worker_aio_requests"),

NGX_EVENT_CONF|NGX_CONF_TAKE1,

ngx_conf_set_num_slot,

0,

offsetof(ngx_epoll_conf_t, aio_requests),

NULL },

ngx_null_command

};

ngx_event_module_t ngx_epoll_module_ctx = {

&epoll_name,

ngx_epoll_create_conf, /* create configuration */

ngx_epoll_init_conf, /* init configuration */

{

//向epoll中添加事件時調用

ngx_epoll_add_event, /* add an event */

//從epoll中刪除事件時調用

ngx_epoll_del_event, /* delete an event */

/***epoll中不存在enable/disable事件的情況，這里默認設置成添加/刪除事件的函數***/

ngx_epoll_add_event, /* enable an event */

ngx_epoll_del_event, /* disable an event */

//向epoll中添加tcp連接時調用，每個tcp連接對象一個讀事件和一個寫事件

ngx_epoll_add_connection, /* add an connection */

//從epoll中刪除事件時調用

ngx_epoll_del_connection, /* delete an connection */

NULL, /* process the changes */

// epoll 事件處理函數

ngx_epoll_process_events, /* process the events */

//epoll模塊初始化函數

ngx_epoll_init, /* init the events */

//epoll模塊清理函數只在多線程模型中被調用

ngx_epoll_done, /* done the events */

}

};

static ngx_int_t

ngx_epoll_init(ngx_cycle_t *cycle, ngx_msec_t timer)

{

ngx_epoll_conf_t *epcf;

// 獲取ngx_epoll_module模塊存放配置項的結構

epcf = ngx_event_get_conf(cycle->conf_ctx, ngx_epoll_module);

if (ep == -1) {

// 創建epoll，成功返回描述符，失敗返回-1

ep = epoll_create(cycle->connection_n / 2);

if (ep == -1) {

ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,

"epoll_create() failed");

return NGX_ERROR;

}

/***如果系統支持aio , 這里初始化aio***/

#if (NGX_HAVE_FILE_AIO)

ngx_epoll_aio_init(cycle, epcf);

#endif

}

/***預分配events個epoll_event結構, epcf->events由epoll_events配置項指定，默認為512***/

if (nevents < epcf->events) {

if (event_list) {

ngx_free(event_list);

}

event_list = ngx_alloc(sizeof(struct epoll_event) * epcf->events,

cycle->log);

if (event_list == NULL) {

return NGX_ERROR;

}

}

nevents = epcf->events;

//指定I/O讀寫的方法

ngx_io = ngx_os_io;

// 設置ngx_event_actions接口，后續通過ngx_event_actions來調用epoll模塊中的方法

ngx_event_actions = ngx_epoll_module_ctx.actions;

/***nginx使用epoll事件模型時NGX_HAVE_CLEAR_EVENT宏被定義, NGX_USE_CLEAR_EVENT宏表示使用epoll的ET模式***/

#if (NGX_HAVE_CLEAR_EVENT)

ngx_event_flags = NGX_USE_CLEAR_EVENT

#else

ngx_event_flags = NGX_USE_LEVEL_EVENT

#endif

|NGX_USE_GREEDY_EVENT

|NGX_USE_EPOLL_EVENT;

return NGX_OK;

}

static ngx_int_t

ngx_epoll_add_event(ngx_event_t *ev, ngx_int_t event, ngx_uint_t flags)

{

int op;

uint32_t events, prev;

ngx_event_t *e;

ngx_connection_t *c;

struct epoll_event ee;

//獲取事件關聯的連接

c = ev->data;

events = (uint32_t) event;

/***根據event參數判斷當前是添加讀事件還是寫事件***/

if (event == NGX_READ_EVENT) {

e = c->write;

prev = EPOLLOUT;

#if (NGX_READ_EVENT != EPOLLIN|EPOLLRDHUP)

events = EPOLLIN|EPOLLRDHUP;

#endif

} else {

e = c->read;

prev = EPOLLIN|EPOLLRDHUP;

#if (NGX_WRITE_EVENT != EPOLLOUT)

events = EPOLLOUT;

#endif

}

/***如果當前需添加讀事件，就通過active標識判斷讀事件所關聯的連接對應的寫事件是否活躍(

活躍表示事件已添加到epoll中)。***/

if (e->active) {

op = EPOLL_CTL_MOD;

events |= prev;

} else {

op = EPOLL_CTL_ADD;

}

//將flags參數加入到epoll標志中

ee.events = events | (uint32_t) flags;

/*** ptr存儲事件關聯的連接對象(ngx_connection_t*)及事件過期比特位，

linux平臺中任何對象的地址最低位必定為零***/

ee.data.ptr = (void *) ((uintptr_t) c | ev->instance);

ngx_log_debug3(NGX_LOG_DEBUG_EVENT, ev->log, 0,

"epoll add event: fd:%d op:%d ev:%08XD",

c->fd, op, ee.events);

//向epoll中添加事件

if (epoll_ctl(ep, op, c->fd, &ee) == -1) {

ngx_log_error(NGX_LOG_ALERT, ev->log, ngx_errno,

"epoll_ctl(%d, %d) failed", op, c->fd);

return NGX_ERROR;

}

//標識事件活躍

ev->active = 1;

#if 0

ev->oneshot = (flags & NGX_ONESHOT_EVENT) ? 1 : 0;

#endif

return NGX_OK;

}

static ngx_int_t

ngx_epoll_del_event(ngx_event_t *ev, ngx_int_t event, ngx_uint_t flags)

{

int op;

uint32_t prev;

ngx_event_t *e;

ngx_connection_t *c;

struct epoll_event ee;

/*

* when the file descriptor is closed, the epoll automatically deletes

* it from its queue, so we do not need to delete explicitly the event

* before the closing the file descriptor

*/

/***上面的注釋說得很清楚了，當文件描述符被關閉后，epoll會自動將其刪除。***/

if (flags & NGX_CLOSE_EVENT) {

ev->active = 0;

return NGX_OK;

}

//獲取事件關聯的連接

c = ev->data;

/***根據event參數判斷當前是刪除讀事件還是寫事件***/

if (event == NGX_READ_EVENT) {

e = c->write;

prev = EPOLLOUT;

} else {

e = c->read;

prev = EPOLLIN|EPOLLRDHUP;

}

/***參考ngx_epoll_add_event函數***/

if (e->active) {

op = EPOLL_CTL_MOD;

ee.events = prev | (uint32_t) flags;

ee.data.ptr = (void *) ((uintptr_t) c | ev->instance);

} else {

op = EPOLL_CTL_DEL;

ee.events = 0;

ee.data.ptr = NULL;

}

ngx_log_debug3(NGX_LOG_DEBUG_EVENT, ev->log, 0,

"epoll del event: fd:%d op:%d ev:%08XD",

c->fd, op, ee.events);

//從epoll中刪除事件

if (epoll_ctl(ep, op, c->fd, &ee) == -1) {

ngx_log_error(NGX_LOG_ALERT, ev->log, ngx_errno,

"epoll_ctl(%d, %d) failed", op, c->fd);

return NGX_ERROR;

}

//清除事件活躍標識

ev->active = 0;

return NGX_OK;

}

static ngx_int_t

ngx_epoll_process_events(ngx_cycle_t *cycle, ngx_msec_t timer, ngx_uint_t flags)

{

int events;

uint32_t revents;

ngx_int_t instance, i;

ngx_uint_t level;

ngx_err_t err;

ngx_event_t *rev, *wev, **queue;

ngx_connection_t *c;

/* NGX_TIMER_INFINITE == INFTIM */

ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,

"epoll timer: %M", timer);

//調用epoll_wait獲取已準備就緒的事件

events = epoll_wait(ep, event_list, (int) nevents, timer);

err = (events == -1) ? ngx_errno : 0;

/***NGX_UPDATE_TIME標識在沒有設置timer_resolution配置項時有效表示每次調用epoll_wait函數返回會都更新時間。

ngx_event_timer_alarm變量在設置timer_resolution配置項時有效，每間隔timer_resolution配置項參數值就會設置

ngx_event_timer_alarm變量為1表示需更新時間。***/

if (flags & NGX_UPDATE_TIME || ngx_event_timer_alarm) {

ngx_time_update();

}

//err為非零指示epoll_wait失敗

if (err) {

if (err == NGX_EINTR) {

if (ngx_event_timer_alarm) {

ngx_event_timer_alarm = 0;

return NGX_OK;

}

level = NGX_LOG_INFO;

} else {

level = NGX_LOG_ALERT;

}

ngx_log_error(level, cycle->log, err, "epoll_wait() failed");

return NGX_ERROR;

}

if (events == 0) {

if (timer != NGX_TIMER_INFINITE) {

return NGX_OK;

}

ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,

"epoll_wait() returned no events without timeout");

return NGX_ERROR;

}

//僅在多線程環境下此鎖才有效

ngx_mutex_lock(ngx_posted_events_mutex);

/***循環處理已就緒的事件***/

for (i = 0; i < events; i++) {

//獲取事件關聯的連接對象，對象地址最低位保存有在事件添加時設置的事件過期位

c = event_list[i].data.ptr;

//取事件過期位

instance = (uintptr_t) c & 1;

//屏蔽掉連接對象的最低位

c = (ngx_connection_t *) ((uintptr_t) c & (uintptr_t) ~1);

rev = c->read;

/***同一條連接的讀/寫事件的instance位值相同，由于下面先處理讀事件這里通過讀事件

的過期位來判斷連接是否過期，當fd為-1時也表示連接過期。***/

if (c->fd == -1 || rev->instance != instance) {

/*

* the stale event from a file descriptor

* that was just closed in this iteration

*/

ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,

"epoll: stale event %p", c);

continue;

}

//獲取連接已就緒的事件類型

revents = event_list[i].events;

ngx_log_debug3(NGX_LOG_DEBUG_EVENT, cycle->log, 0,

"epoll: fd:%d ev:%04XD d:%p",

c->fd, revents, event_list[i].data.ptr);

/***連接出現錯誤,EPOLLHUP標識表示收到RST報文。檢測到這兩種類型時 tcp連接中可能還有

數據未被讀取***/

if (revents & (EPOLLERR|EPOLLHUP)) {

ngx_log_debug2(NGX_LOG_DEBUG_EVENT, cycle->log, 0,

"epoll_wait() error on fd:%d ev:%04XD",

c->fd, revents);

}

#if 0

if (revents & ~(EPOLLIN|EPOLLOUT|EPOLLERR|EPOLLHUP)) {

ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,

"strange epoll_wait() events fd:%d ev:%04XD",

c->fd, revents);

}

#endif

/***如果連接發生錯誤但未置EPOLLIN及EPOLLOUT，這時我們加上EPOLLIN和EPOLLOUT，在調用讀/寫事件的

回調函數時就會知道為什么出現錯誤。 如果不加EPOLLIN和EPOLLOUT，后面就沒法調用讀/寫事件的

回調函數也就無法處理該連接了。***/

if ((revents & (EPOLLERR|EPOLLHUP))

&& (revents & (EPOLLIN|EPOLLOUT)) == 0)

{

/*

* if the error events were returned without EPOLLIN or EPOLLOUT,

* then add these flags to handle the events at least in one

* active handler

*/

revents |= EPOLLIN|EPOLLOUT;

}

/***連接可讀且活躍***/

if ((revents & EPOLLIN) && rev->active) {

#if (NGX_HAVE_EPOLLRDHUP)

//EPOLLRDHUP表示連接對方關閉了讀端

if (revents & EPOLLRDHUP) {

rev->pending_eof = 1;

}

#endif

//NGX_POST_THREAD_EVENTS宏末被使用

if ((flags & NGX_POST_THREAD_EVENTS) && !rev->accept) {

rev->posted_ready = 1;

} else {

//標識事件已就緒

rev->ready = 1;

}

/***NGX_POST_EVENTS表示事件需要延后處理，這里根據accept標識位將事件加入到相應隊列中***/

if (flags & NGX_POST_EVENTS) {

queue = (ngx_event_t **) (rev->accept ?

&ngx_posted_accept_events : &ngx_posted_events);

ngx_locked_post_event(rev, queue);

} else {

//調用事件的回調函數

rev->handler(rev);

}

}

wev = c->write;

/***連接可寫且活躍***/

if ((revents & EPOLLOUT) && wev->active) {

//重新檢查事件是否過期，因為在處理讀事件過程中該事件可能已結束。

if (c->fd == -1 || wev->instance != instance) {

/*

* the stale event from a file descriptor

* that was just closed in this iteration

*/

ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,

"epoll: stale event %p", c);

continue;

}

if (flags & NGX_POST_THREAD_EVENTS) {

wev->posted_ready = 1;

} else {

wev->ready = 1;

}

if (flags & NGX_POST_EVENTS) {

ngx_locked_post_event(wev, &ngx_posted_events);

} else {

wev->handler(wev);

}

}

}

ngx_mutex_unlock(ngx_posted_events_mutex);

return NGX_OK;

}