Nginx源码分析 - Event事件篇 - epoll事件模块
来源：互联网 发布：淘宝扎头皮筋价格 编辑：程序博客网 时间：2024/05/16 15:47
这一篇主要讲解一下epoll事件模块。Nginx支持多种事件模块：epoll/pool/select/kqueue等。epoll比较常用，我们也比较熟悉。
Nginx的epoll事件模块在/event/module/ngx_epoll_module.c
Epoll模块的数据结构
1. epoll模块命令集 ngx_epoll_commands
/** * epoll模块命令集 * epoll_events：这个配置项表示调用一次epoll_wait最多可以返回的事件数 * worker_aio_requests：指明在开启异步I/O且使用io_setup系统调用初始化异步I/O上下文环境时，初始分配的异步I/O事件个数 */static ngx_command_t ngx_epoll_commands[] = { { ngx_string("epoll_events"), NGX_EVENT_CONF|NGX_CONF_TAKE1, ngx_conf_set_num_slot, 0, offsetof(ngx_epoll_conf_t, events), NULL }, { 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};2. epoll模块上下文 ngx_epoll_module_ctx
/** * epoll模块上下文 * ngx_epoll_create_conf ： 配置文件创建 * ngx_epoll_init_conf ： 配置文件初始化 * ngx_event_actions_t actions ： 事件的action对象结构 */ngx_event_module_t ngx_epoll_module_ctx = { &epoll_name, ngx_epoll_create_conf, /* create configuration */ ngx_epoll_init_conf, /* init configuration */ { ngx_epoll_add_event, /* add an event */ ngx_epoll_del_event, /* delete an event */ ngx_epoll_add_event, /* enable an event */ ngx_epoll_del_event, /* disable an event */ ngx_epoll_add_connection, /* add an connection */ ngx_epoll_del_connection, /* delete an connection */#if (NGX_HAVE_EVENTFD) ngx_epoll_notify, /* trigger a notify */#else NULL, /* trigger a notify */#endif ngx_epoll_process_events, /* process the events */ ngx_epoll_init, /* init the events */ ngx_epoll_done, /* done the events */ }};3. epoll模块配置 ngx_epoll_module
/** * epoll模块配置 * ngx_epoll_module_ctx：epoll模块上下文 * ngx_epoll_commands：epoll模块上下文 * epoll/kqueue事件模块等没有初始化的方法 */ngx_module_t ngx_epoll_module = { NGX_MODULE_V1, &ngx_epoll_module_ctx, /* module context */ ngx_epoll_commands, /* module directives */ NGX_EVENT_MODULE, /* module type */ NULL, /* init master */ NULL, /* init module */ NULL, /* init process */ NULL, /* init thread */ NULL, /* exit thread */ NULL, /* exit process */ NULL, /* exit master */ NGX_MODULE_V1_PADDING};Epoll模块的初始化
1. 配置文件初始化
epool模块属于Event模块下面的子模块，配置文件初始化的时候，在Event解析配置文件的核心函数：ngx_events_block 中。
/* 模块初始化，如果是NGX_EVENT_MODULE，则调用模块的create_conf方法 */for (i = 0; cf->cycle->modules[i]; i++) {if (cf->cycle->modules[i]->type != NGX_EVENT_MODULE) {continue;}m = cf->cycle->modules[i]->ctx;if (m->create_conf) {(*ctx)[cf->cycle->modules[i]->ctx_index] = m->create_conf(cf->cycle);if ((*ctx)[cf->cycle->modules[i]->ctx_index] == NULL) {return NGX_CONF_ERROR ;}}}/* event*/pcf = *cf;cf->ctx = ctx;cf->module_type = NGX_EVENT_MODULE;cf->cmd_type = NGX_EVENT_CONF;/* 调用配置解析，这次解析的是 块中的内容，非文件内容 */rv = ngx_conf_parse(cf, NULL);*cf = pcf;if (rv != NGX_CONF_OK) {return rv;}/* 初始化 模块的init_conf 方法*/for (i = 0; cf->cycle->modules[i]; i++) {if (cf->cycle->modules[i]->type != NGX_EVENT_MODULE) {continue;}m = cf->cycle->modules[i]->ctx;if (m->init_conf) {rv = m->init_conf(cf->cycle,(*ctx)[cf->cycle->modules[i]->ctx_index]);if (rv != NGX_CONF_OK) {return rv;}}}配置文件初始化
/** * 创建配置 */static void *ngx_epoll_create_conf(ngx_cycle_t *cycle){ ngx_epoll_conf_t *epcf; epcf = ngx_palloc(cycle->pool, sizeof(ngx_epoll_conf_t)); if (epcf == NULL) { return NULL; } epcf->events = NGX_CONF_UNSET; epcf->aio_requests = NGX_CONF_UNSET; return epcf;}/** * 初始化配置 */static char *ngx_epoll_init_conf(ngx_cycle_t *cycle, void *conf){ ngx_epoll_conf_t *epcf = conf; ngx_conf_init_uint_value(epcf->events, 512); ngx_conf_init_uint_value(epcf->aio_requests, 32); return NGX_CONF_OK;}2. 模块初始化
epool模块属于Event模块下面的子模块，所以没有设置独立的init_process初始化回调函数。
epoll事件模块的初始化是在Event大模块初始化的时候进行初始化的。
初始化放在：ngx_event_process_init中进行
/** * 找到事件模型的模块，例如epoll/kqueue */for (m = 0; cycle->modules[m]; m++) {if (cycle->modules[m]->type != NGX_EVENT_MODULE) {continue;}if (cycle->modules[m]->ctx_index != ecf->use) {continue;}module = cycle->modules[m]->ctx;/** * 调用epoll/kqueue等模型模块的init初始化函数 * epoll调用的是ngx_epoll_init这个方法 */if (module->actions.init(cycle, ngx_timer_resolution) != NGX_OK) {/* fatal */exit(2);}break;}ngx_epoll_init 模块初始化：
/** * epoll模块初始化 */static ngx_int_tngx_epoll_init(ngx_cycle_t *cycle, ngx_msec_t timer){/* 存储配置项的结构体 */ ngx_epoll_conf_t *epcf; /* 获取配置文件 */ epcf = ngx_event_get_conf(cycle->conf_ctx, ngx_epoll_module); if (ep == -1) { /* 创建epoll对象，在很多Linux内核版本中，并不处理这个函数的参数 */ 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; }#if (NGX_HAVE_EVENTFD) if (ngx_epoll_notify_init(cycle->log) != NGX_OK) { ngx_epoll_module_ctx.actions.notify = NULL; }#endif#if (NGX_HAVE_FILE_AIO) ngx_epoll_aio_init(cycle, epcf);#endif#if (NGX_HAVE_EPOLLRDHUP) ngx_epoll_test_rdhup(cycle);#endif } /* 解析配置项所得的epoll_wait一次可最多返回的时间个数较大 */ 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; } } /* 更新全局变量 */ nevents = epcf->events; ngx_io = ngx_os_io; ngx_event_actions = ngx_epoll_module_ctx.actions;#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;}核心函数
1. ngx_epoll_process_events 实现了收集、分发事件接口
/** * 处理事件 ==> ngx_process_events * 实现了收集、分发事件接口(void) ngx_process_events(cycle, timer, flags); */static ngx_int_tngx_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; ngx_queue_t *queue; ngx_connection_t *c; /* NGX_TIMER_INFINITE == INFTIM */ ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "epoll timer: %M", timer); /* 调用epoll_wait获取事件 */ events = epoll_wait(ep, event_list, (int) nevents, timer); err = (events == -1) ? ngx_errno : 0; /* 更新时间 */ if (flags & NGX_UPDATE_TIME || ngx_event_timer_alarm) { ngx_time_update(); } /* epoll_wait出错处理 */ 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; } /* 本次调用没有事件发生 */ 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; } /* 遍历本次epoll_wait返回的所有事件 */ for (i = 0; i < events; i++) { /* 获取连接ngx_connection_t的地址 */ c = event_list[i].data.ptr; instance = (uintptr_t) c & 1; c = (ngx_connection_t *) ((uintptr_t) c & (uintptr_t) ~1); /* 取出读事件 */ rev = c->read; 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; } /* 取出事件类型 */ 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); 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 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; } /* 读取事件 EPOLLIN */ if ((revents & EPOLLIN) && rev->active) {#if (NGX_HAVE_EPOLLRDHUP) if (revents & EPOLLRDHUP) { rev->pending_eof = 1; } rev->available = 1;#endif rev->ready = 1; /* 如果事件抢到锁，则放入事件队列 */ if (flags & NGX_POST_EVENTS) { queue = rev->accept ? &ngx_posted_accept_events : &ngx_posted_events; ngx_post_event(rev, queue); } else { /* 没有抢到锁，立即调用事件回调方法来处理这个事件 */ rev->handler(rev); } } wev = c->write; /* 写事件 EPOLLOUT*/ if ((revents & EPOLLOUT) && wev->active) { 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; } wev->ready = 1;#if (NGX_THREADS) wev->complete = 1;#endif if (flags & NGX_POST_EVENTS) { ngx_post_event(wev, &ngx_posted_events); } else { wev->handler(wev); } } } return NGX_OK;}2. ngx_epoll_add_event 添加一个事件
/** * 添加一个事件 */static ngx_int_tngx_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; /* 每个事件的data成员存放着其对应的ngx_connection_t连接 */ c = ev->data; events = (uint32_t) event; /* 判断事件类型。如果是写事件，c->write 如果是读事件，c->read*/ 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 } /* 依据active标志位确定是否为活跃事件 */ if (e->active) { op = EPOLL_CTL_MOD; events |= prev; } else { op = EPOLL_CTL_ADD; } ee.events = events | (uint32_t) flags; 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); /* 新增一个事件 */ 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; } ev->active = 1;#if 0 ev->oneshot = (flags & NGX_ONESHOT_EVENT) ? 1 : 0;#endif return NGX_OK;} 0 0
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