Nginx源码分析 - Event事件篇 - Event模块的进程初始化ngx_event_process_init
前面一篇我们讲解了《Nginx源码分析 - Event事件篇 - Event模块和配置的初始化 》 ，了解了整个Event模块分为：ngx_events_module 事件模块 、ngx_event_core_module 事件核心模块 和 epoll/queue/win32_select事件模型模块
这一篇，主要讲解一个重要的函数：ngx_event_process_init
Event事件模块的大部分初始化都在ngx_event_process_init中完成。
源码分析
1. ngx_event_core_module 模块中配置ngx_event_process_init
/**
* Event核心模块
* ngx_event_module_init：模块初始化
* ngx_event_process_init：进程初始化
* 类型：NGX_EVENT_MODULE
*/
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 };
我们可以看到，在ngx_event_core_module模块中，配置了init_process的回调函数。通过这个回调函数，进行event的初始化。
2. ngx_worker_process_init 工作进程初始化的时候，调用init_process的回调函数
/* 对模块进程初始化 - 这边初始化的是所有的模块有init_process回调函数的进行初始化工作 */
for (i = 0; cycle->modules[i]; i++) {
if (cycle->modules[i]->init_process) {
if (cycle->modules[i]->init_process(cycle) == NGX_ERROR) {
/* fatal */
exit(2);
}
}
}
在工作进程初始化的函数中，我们看到就会调用模块的init_process。这个函数，我们在前面的文章中也详细讲解过。
3. ngx_event_process_init 实现
/**
* Event模块的进程初始化
*/
static ngx_int_t ngx_event_process_init(ngx_cycle_t *cycle) {
ngx_uint_t m, i;
ngx_event_t *rev, *wev;
ngx_listening_t *ls;
ngx_connection_t *c, *next, *old;
ngx_core_conf_t *ccf;
ngx_event_conf_t *ecf;
ngx_event_module_t *module;
/* 获取event模块的配置 */
ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);
ecf = ngx_event_get_conf(cycle->conf_ctx, ngx_event_core_module);
/* 多进程情况下，进程数大于1的情况，使用accept_mutex锁。惊群的时候需要用到。*/
if (ccf->master && ccf->worker_processes > 1 && ecf->accept_mutex) {
ngx_use_accept_mutex = 1;
ngx_accept_mutex_held = 0;
ngx_accept_mutex_delay = ecf->accept_mutex_delay;
} else {
ngx_use_accept_mutex = 0;
}
#if (NGX_WIN32)
/*
* disable accept mutex on win32 as it may cause deadlock if
* grabbed by a process which can't accept connections
*/
ngx_use_accept_mutex = 0;
#endif
/* 初始化全局队列：ngx_posted_accept_events和ngx_posted_events */
ngx_queue_init(&ngx_posted_accept_events);
ngx_queue_init(&ngx_posted_events);
/* 初始化event模块的时间 */
if (ngx_event_timer_init(cycle->log) == NGX_ERROR) {
return NGX_ERROR;
}
/**
* 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;
}
#if !(NGX_WIN32)
if (ngx_timer_resolution && !(ngx_event_flags & NGX_USE_TIMER_EVENT)) {
struct sigaction sa;
struct itimerval itv;
ngx_memzero(&sa, sizeof(struct sigaction));
sa.sa_handler = ngx_timer_signal_handler;
sigemptyset(&sa.sa_mask);
if (sigaction(SIGALRM, &sa, NULL) == -1) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"sigaction(SIGALRM) failed");
return NGX_ERROR;
}
itv.it_interval.tv_sec = ngx_timer_resolution / 1000;
itv.it_interval.tv_usec = (ngx_timer_resolution % 1000) * 1000;
itv.it_value.tv_sec = ngx_timer_resolution / 1000;
itv.it_value.tv_usec = (ngx_timer_resolution % 1000) * 1000;
if (setitimer(ITIMER_REAL, &itv, NULL) == -1) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"setitimer() failed");
}
}
if (ngx_event_flags & NGX_USE_FD_EVENT) {
struct rlimit rlmt;
if (getrlimit(RLIMIT_NOFILE, &rlmt) == -1) {
ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
"getrlimit(RLIMIT_NOFILE) failed");
return NGX_ERROR;
}
cycle->files_n = (ngx_uint_t) rlmt.rlim_cur;
cycle->files = ngx_calloc(sizeof(ngx_connection_t *) * cycle->files_n,
cycle->log);
if (cycle->files == NULL) {
return NGX_ERROR;
}
}
#else
if (ngx_timer_resolution && !(ngx_event_flags & NGX_USE_TIMER_EVENT)) {
ngx_log_error(NGX_LOG_WARN, cycle->log, 0,
"the \"timer_resolution\" directive is not supported "
"with the configured event method, ignored");
ngx_timer_resolution = 0;
}
#endif
/* 分配一块内存，存储连接 */
cycle->connections = ngx_alloc(
sizeof(ngx_connection_t) * cycle->connection_n, cycle->log);
if (cycle->connections == NULL) {
return NGX_ERROR;
}
c = cycle->connections;
/* 分配一块内存，存放读取事件 */
cycle->read_events = ngx_alloc(sizeof(ngx_event_t) * cycle->connection_n,
cycle->log);
if (cycle->read_events == NULL) {
return NGX_ERROR;
}
rev = cycle->read_events;
for (i = 0; i < cycle->connection_n; i++) {
rev[i].closed = 1;
rev[i].instance = 1;
}
/* 分配一块内存，存储写入事件*/
cycle->write_events = ngx_alloc(sizeof(ngx_event_t) * cycle->connection_n,
cycle->log);
if (cycle->write_events == NULL) {
return NGX_ERROR;
}
wev = cycle->write_events;
for (i = 0; i < cycle->connection_n; i++) {
wev[i].closed = 1;
}
i = cycle->connection_n;
next = NULL;
/* 初始化连接数据 */
do {
i--;
c[i].data = next;
c[i].read = &cycle->read_events[i];
c[i].write = &cycle->write_events[i];
c[i].fd = (ngx_socket_t) -1;
next = &c[i];
} while (i);
/* 空闲的连接 */
cycle->free_connections = next;
cycle->free_connection_n = cycle->connection_n;
/* for each listening socket */
/* 初始化侦听器 */
ls = cycle->listening.elts;
for (i = 0; i < cycle->listening.nelts; i++) {
#if (NGX_HAVE_REUSEPORT)
if (ls[i].reuseport && ls[i].worker != ngx_worker) {
continue;
}
#endif
c = ngx_get_connection(ls[i].fd, cycle->log);
if (c == NULL) {
return NGX_ERROR;
}
c->type = ls[i].type;
c->log = &ls[i].log;
c->listening = &ls[i];
ls[i].connection = c;
rev = c->read;
rev->log = c->log;
rev->accept = 1;
#if (NGX_HAVE_DEFERRED_ACCEPT)
rev->deferred_accept = ls[i].deferred_accept;
#endif
if (!(ngx_event_flags & NGX_USE_IOCP_EVENT)) {
if (ls[i].previous) {
/*
* delete the old accept events that were bound to
* the old cycle read events array
*/
old = ls[i].previous->connection;
if (ngx_del_event(old->read, NGX_READ_EVENT,
NGX_CLOSE_EVENT) == NGX_ERROR) {
return NGX_ERROR;
}
old->fd = (ngx_socket_t) -1;
}
}
#if (NGX_WIN32)
if (ngx_event_flags & NGX_USE_IOCP_EVENT) {
ngx_iocp_conf_t *iocpcf;
rev->handler = ngx_event_acceptex;
if (ngx_use_accept_mutex) {
continue;
}
if (ngx_add_event(rev, 0, NGX_IOCP_ACCEPT) == NGX_ERROR) {
return NGX_ERROR;
}
ls[i].log.handler = ngx_acceptex_log_error;
iocpcf = ngx_event_get_conf(cycle->conf_ctx, ngx_iocp_module);
if (ngx_event_post_acceptex(&ls[i], iocpcf->post_acceptex)
== NGX_ERROR)
{
return NGX_ERROR;
}
} else {
rev->handler = ngx_event_accept;
if (ngx_use_accept_mutex) {
continue;
}
if (ngx_add_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
return NGX_ERROR;
}
}
#else
/* 事件ev的回调函数handler ngx_event_accept tcp 或者ngx_event_recvmsg udp */
rev->handler =
(c->type == SOCK_STREAM) ? ngx_event_accept : ngx_event_recvmsg;
if (ngx_use_accept_mutex
#if (NGX_HAVE_REUSEPORT)
&& !ls[i].reuseport
#endif
) {
continue;
}
if (ngx_add_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
return NGX_ERROR;
}
#endif
}
return NGX_OK;
}
module->actions.init 主要是调用epoll/kqueque等模型模块的init初始化方法。epoll调用是ngx_epoll_init这个方法。
ecf->use在配置文件中，我们配置了:“use epoll;”。但是这里存储的是 epoll/kqueue等模块是索引ID。通过索引ID就可以快速在cycle->modules找到对应的模块。
具体如何确定是哪一个Linux事件模型(select/kqueue/epoll)，是在ngx_event_core_init_conf方法中定义的。
* 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;
}
事件event的回调函数，主要包含两个：ngx_event_accept或者ngx_event_recvmsg。一个是TCP接收连接，一个是UDP方式接收连接。
TCP连接和读取事件逻辑：
在 Nginx 的初始化启动过程中，worker 工作进程会调用事件模块的ngx_event_process_init 方法为每个监听套接字ngx_listening_t 分配一个 ngx_connection_t 连接，并设置该连接上读事件的回调方法handler 为ngx_event_accept，同时将读事件挂载到epoll 事件机制中等待监听套接字连接上的可读事件发生，到此，Nginx 就可以接收并处理来自客户端的请求。当监听套接字连接上的可读事件发生时，即该连接上有来自客户端发出的连接请求，则会启动读事件的handler 回调方法ngx_event_accept，在ngx_event_accept 方法中调用accept() 函数接收来自客户端的连接请求，成功建立连接之后，ngx_event_accept 函数调用监听套接字上的handler 回调方法ls->handler(c)（该回调方法就是ngx_http_init_connection）。ngx_http_init_connection 会将rev->handler的回调函数修改成： ngx_http_wait_request_handler，该回调函数主要用于处理read事件的数据读取。
1. ngx_event_process_init 初始化的时候，rev->handler的回调函数是ngx_event_accept
/* 事件ev的回调函数handler ngx_event_accept或者ngx_event_recvmsg */
rev->handler =
(c->type == SOCK_STREAM) ? ngx_event_accept : ngx_event_recvmsg;
2. ngx_event_accept中会调用ls->handler回调函数ngx_http_init_connection
log->data = NULL;
log->handler = NULL;
/* 回调函数 ngx_http_init_connection */
ls->handler(c);
if (ngx_event_flags & NGX_USE_KQUEUE_EVENT) {
ev->available--;
}3. ngx_http_init_connection初始化一个http的连接，并且将rev->handler回调函数修改成ngx_http_wait_request_handler，主要用于接收read事件数据
void
ngx_http_init_connection(ngx_connection_t *c)
{
....
rev = c->read;
rev->handler = ngx_http_wait_request_handler;
c->write->handler = ngx_http_empty_handler;
}
4. ls->handler的回调函数是如何赋值的？
你需要看一下ngx_http.c中的ngx_http_block函数，该函数在模块命令初始化的时候会回调，并且调用 ngx_http_optimize_servers方法，并且进一步调用ngx_http_init_listening初始化http的监听器，然后最终调用ngx_http_add_listening方法。
static ngx_listening_t *
ngx_http_add_listening(ngx_conf_t *cf, ngx_http_conf_addr_t *addr)
{
ngx_listening_t *ls;
ngx_http_core_loc_conf_t *clcf;
ngx_http_core_srv_conf_t *cscf;
ls = ngx_create_listening(cf, &addr->opt.sockaddr.sockaddr,
addr->opt.socklen);
if (ls == NULL) {
return NULL;
}
ls->addr_ntop = 1;
ls->handler = ngx_http_init_connection;
cscf = addr->default_server;
ls->pool_size = cscf->connection_pool_size;
ls->post_accept_timeout = cscf->client_header_timeout;
clcf = cscf->ctx->loc_conf[ngx_http_core_module.ctx_index];
ls->logp = clcf->error_log;
ls->log.data = &ls->addr_text;
ls->log.handler = ngx_accept_log_error;
#if (NGX_WIN32)
{
ngx_iocp_conf_t *iocpcf = NULL;
if (ngx_get_conf(cf->cycle->conf_ctx, ngx_events_module)) {
iocpcf = ngx_event_get_conf(cf->cycle->conf_ctx, ngx_iocp_module);
}
if (iocpcf && iocpcf->acceptex_read) {
ls->post_accept_buffer_size = cscf->client_header_buffer_size;
}
}
#endif
ls->backlog = addr->opt.backlog;
ls->rcvbuf = addr->opt.rcvbuf;
ls->sndbuf = addr->opt.sndbuf;
ls->keepalive = addr->opt.so_keepalive;
#if (NGX_HAVE_KEEPALIVE_TUNABLE)
ls->keepidle = addr->opt.tcp_keepidle;
ls->keepintvl = addr->opt.tcp_keepintvl;
ls->keepcnt = addr->opt.tcp_keepcnt;
#endif
#if (NGX_HAVE_DEFERRED_ACCEPT && defined SO_ACCEPTFILTER)
ls->accept_filter = addr->opt.accept_filter;
#endif
#if (NGX_HAVE_DEFERRED_ACCEPT && defined TCP_DEFER_ACCEPT)
ls->deferred_accept = addr->opt.deferred_accept;
#endif
#if (NGX_HAVE_INET6 && defined IPV6_V6ONLY)
ls->ipv6only = addr->opt.ipv6only;
#endif
#if (NGX_HAVE_SETFIB)
ls->setfib = addr->opt.setfib;
#endif
#if (NGX_HAVE_TCP_FASTOPEN)
ls->fastopen = addr->opt.fastopen;
#endif
#if (NGX_HAVE_REUSEPORT)
ls->reuseport = addr->opt.reuseport;
#endif
return ls;
}
下一篇，我们就可以具体看一下，ngx_epoll_module.c具体实现。