http://cjhust.blog.163.com/blog/static/175827157201348112639361/
Hello world
模块功能：注册一个定时事件，每过一秒钟打印一次hello world。ngx_add_timer函数就是用来完成将一个新的定时事件加入定时器红黑树中，定时事件被执行后，就会从树中移除，因此要想不断的循环打印hello world，就需要在事件回调函数被调用后再将事件给添加到定时器红黑树中。 ngx_http_hello_process_init是注册在模块的进程初始化阶段的回调函数上。
static ngx_connection_t dummy;
static ngx_event_t ev;
static void
ngx_http_hello_print(ngx_event_t *ev)
{
printf("hello world\n");
ngx_add_timer(ev, 1000);
}
static ngx_int_t
ngx_http_hello_process_init(ngx_cycle_t *cycle)
{
dummy.fd = (ngx_socket_t) -1;
ngx_memzero(&ev, sizeof(ngx_event_t));
ev.handler = ngx_http_hello_print;
ev.log = cycle->log;
ev.data = &dummy;
ngx_add_timer(&ev, 1000);
return NGX_OK;
}
4、操作函数
ngx_event_timer_init
函数功能：完成定时器红黑树的建树操作。
ngx_int_t
ngx_event_timer_init(ngx_log_t *log)
{
ngx_rbtree_init(&ngx_event_timer_rbtree, &ngx_event_timer_sentinel,
ngx_rbtree_insert_timer_value);
#if (NGX_THREADS)
if (ngx_event_timer_mutex) {
ngx_event_timer_mutex->log = log;
return NGX_OK;
}
ngx_event_timer_mutex = ngx_mutex_init(log, 0);
if (ngx_event_timer_mutex == NULL) {
return NGX_ERROR;
}
#endif
return NGX_OK;
}
ngx_event_add_timer(ngx_event_t *ev, ngx_msec_t timer)
//timer就是一个int的值，表示超时的事件，用于表示红黑树节点的key
static ngx_inline void
ngx_event_add_timer(ngx_event_t *ev, ngx_msec_t timer)
{
ngx_msec_t key;
ngx_msec_int_t diff;
key = ngx_current_msec + timer; //现在时间+超时时间=过期时间
//已经设置了定时器
if (ev->timer_set) {
/*
* Use a previous timer value if difference between it and a new
* value is less than NGX_TIMER_LAZY_DELAY milliseconds: this allows
* to minimize the rbtree operations for fast connections.
*/
diff = (ngx_msec_int_t) (key - ev->timer.key);
//2次比较相近，则忽略这次的
if (ngx_abs(diff) < NGX_TIMER_LAZY_DELAY) { //300
ngx_log_debug3(NGX_LOG_DEBUG_EVENT, ev->log, 0,
"event timer: %d, old: %M, new: %M",
ngx_event_ident(ev->data), ev->timer.key, key);
return;
}
//否则，删除old
ngx_del_timer(ev);
}
ev->timer.key = key;
ngx_log_debug3(NGX_LOG_DEBUG_EVENT, ev->log, 0,
"event timer add: %d: %M:%M",
ngx_event_ident(ev->data), timer, ev->timer.key);
ngx_mutex_lock(ngx_event_timer_mutex);
//事件的timer域插入到红黑树当中
ngx_rbtree_insert(&ngx_event_timer_rbtree, &ev->timer); // ev->timer是node
ngx_mutex_unlock(ngx_event_timer_mutex);
ev->timer_set = 1;
}
ngx_event_del_timer(ngx_event_t *ev)
static ngx_inline void
ngx_event_del_timer(ngx_event_t *ev)
{
ngx_log_debug2(NGX_LOG_DEBUG_EVENT, ev->log, 0,
"event timer del: %d: %M",
ngx_event_ident(ev->data), ev->timer.key);
ngx_mutex_lock(ngx_event_timer_mutex);
ngx_rbtree_delete(&ngx_event_timer_rbtree, &ev->timer);
ngx_mutex_unlock(ngx_event_timer_mutex);
#if (NGX_DEBUG)
ev->timer.left = NULL;
ev->timer.right = NULL;
ev->timer.parent = NULL;
#endif
ev->timer_set = 0;
}
ngx_event_find_timer(void)
函数功能：用于获取当前事件红黑树中最小的超时时间，将其提供给epoll，让epoll的wait在这个时间内唤醒。
ngx_msec_t
ngx_event_find_timer(void)
{
ngx_msec_int_t timer;
ngx_rbtree_node_t *node, *root, *sentinel;
if (ngx_event_timer_rbtree.root == &ngx_event_timer_sentinel) {
return NGX_TIMER_INFINITE;
}
ngx_mutex_lock(ngx_event_timer_mutex);
root = ngx_event_timer_rbtree.root;
sentinel = ngx_event_timer_rbtree.sentinel;
node = ngx_rbtree_min(root, sentinel);
ngx_mutex_unlock(ngx_event_timer_mutex);
timer = (ngx_msec_int_t) (node->key - ngx_current_msec);
return (ngx_msec_t) (timer > 0 ? timer : 0);
}
ngx_event_expire_timers(void)
函数功能：处理红黑树中的所有超时事件。
void
ngx_event_expire_timers(void)
{
ngx_event_t *ev;
ngx_rbtree_node_t *node, *root, *sentinel;
sentinel = ngx_event_timer_rbtree.sentinel;
//找到所有的超时的timer，然后处理它们
for ( ;; ) {
ngx_mutex_lock(ngx_event_timer_mutex);
root = ngx_event_timer_rbtree.root;
if (root == sentinel) {
return;
}
//获取key最小的节点
node = ngx_rbtree_min(root, sentinel);
//该节点是否超时
if ((ngx_msec_int_t) (node->key - ngx_current_msec) <= 0) {
ev = (ngx_event_t *) ((char *) node - offsetof(ngx_event_t, timer));
…
//类似于ngx_event_del_timer
ngx_rbtree_delete(&ngx_event_timer_rbtree, &ev->timer);
ngx_mutex_unlock(ngx_event_timer_mutex);
ev->timer_set = 0;
ev->timedout = 1;
ev->handler(ev);
continue;
}
break;
}
ngx_mutex_unlock(ngx_event_timer_mutex);
}
5、一个例子
ngx_process_events_and_timers(ngx_cycle_t *cycle)
void
ngx_process_events_and_timers(ngx_cycle_t *cycle)
{
ngx_uint_t flags;
ngx_msec_t timer, delta;
if (ngx_timer_resolution) { //0
timer = NGX_TIMER_INFINITE;
flags = 0;
} else {
timer = ngx_event_find_timer(); //返回的是最小的超时时间，单位是毫秒
flags = NGX_UPDATE_TIME;// 1
#if (NGX_THREADS)
if (timer == NGX_TIMER_INFINITE || timer > 500) {
timer = 500;
}
#endif
}
。。。
delta = ngx_current_msec;
//下面这个函数就是处理事件的函数（包括新连接建立事件），网络IO事件等等
(void) ngx_process_events(cycle, timer, flags); //ngx_epoll_process_events
delta = ngx_current_msec - delta; //时间差，因为ngx_time_update已更新
。。。
if (delta) {
ngx_event_expire_timers(); //处理所有的超时事件
}
。。。
}