目录
2. ngx_connection_s socket连接对象结构
前一章，我们讲解了《Nginx源码分析 - 主流程篇 - 多进程的惊群和进程负载均衡处理 》 中实际上已经涉及到了一部分事件模块的概念。细心的可以发现，Nginx的事件都是由nginx_event.c文件中的ngx_process_events_and_timers进程事件分发器这个函数开始的。
这一章开始，我们会详细透彻的分析Nginx的event模块。如果你还对网络IO模型不太熟悉的，建议先把这块熟悉，也可以参考我的文章《 转载和积累系列 - 网络IO模型 》
如果你对Linux下的epoll模型也不是很熟悉的，请先学习下epoll的原理，也可以参考我的文章《Linux c 开发 - libevent 》
一切准备就绪，我们就可以开始了。
一、event模块的概览
- ngx_event.c ：这个文件主要放置Nginx事件event模块的核心代码。包含：进程事件分发器（ngx_process_events_and_timers）、事件模块的模块和配置、模块初始化/配置初始化等事件模块初始化的核心函数。
- ngx_event_timer.c：定时器事件管理。主要放置定时器的代码。
- ngx_event_posted.c：主要用于 拿到accept锁的进程 处理accept和read事件的回调函数。上一章惊群处理中，有重点提到ngx_event_process_posted这个方法。
- ngx_event_pipe.c：主要用于处理管道。
- ngx_event_openssl.c：主要用于处理SSL通道。HTTPS协议。
- ngx_event_connect.c：主要用于处理TCP的连接通道。
- ngx_event_accept.c：核心是ngx_event_accept和ngx_event_recvmsg，主要是处理accept事件的回调函数handler。而后续的read事件被ngx_event_accept中回调ngx_listen_t结构中的ls->handler回调函数回调，并且将rev->handler修改成ngx_http_wait_request_handler方法。
- modules/xxxx.c：主要封装了各种平台的事件模型。我们这边主要看ngx_epoll_module.c模块。
二、重要数据结构
下面几个数据结构会在event模块中非常常见，必须得非常熟悉。
- ngx_listening_s：主要是监听套接字结构，存放socket的信息
- ngx_connection_s：存储连接有关的信息和读写事件。
- ngx_event_s：主要存放事件的数据结构。
1. ngx_listening_s 侦听结构
主要用于存放连接的socket的侦听结构。
/**
* socket侦听结构
*/
struct ngx_listening_s {
ngx_socket_t fd; /* 文件描述符,即socket */
struct sockaddr *sockaddr; /* socket地址 */
socklen_t socklen; /* size of sockaddr */
size_t addr_text_max_len;
ngx_str_t addr_text;
int type;
int backlog;/* 日志 */
int rcvbuf; /* 数据接收buffer */
int sndbuf; /* 数据发送的buffer */
#if (NGX_HAVE_KEEPALIVE_TUNABLE)
int keepidle;
int keepintvl;
int keepcnt;
#endif
/* handler of accepted connection */
ngx_connection_handler_pt handler; /* 接收连接后的回调函数，回调方法：ngx_http_init_connection */
void *servers; /* array of ngx_http_in_addr_t, for example */
ngx_log_t log;
ngx_log_t *logp;
size_t pool_size;
/* should be here because of the AcceptEx() preread */
size_t post_accept_buffer_size;
/* should be here because of the deferred accept */
ngx_msec_t post_accept_timeout;
ngx_listening_t *previous; /* 前一个ngx_listening_t */
ngx_connection_t *connection; /* 连接对象 */
ngx_uint_t worker;
unsigned open:1; /* 为1表示监听句柄有效，为0表示正常关闭 */
unsigned remain:1;/* 为1表示不关闭原先打开的监听端口，为0表示关闭曾经打开的监听端口 */
unsigned ignore:1; /* 为1表示跳过设置当前ngx_listening_t结构体中的套接字，为0时正常初始化套接字 */
unsigned bound:1; /* already bound */
unsigned inherited:1; /* inherited from previous process */
unsigned nonblocking_accept:1;
unsigned listen:1; /* 为1表示当前结构体对应的套接字已经监听 */
unsigned nonblocking:1;
unsigned shared:1; /* shared between threads or processes */
unsigned addr_ntop:1;
unsigned wildcard:1;
#if (NGX_HAVE_INET6 && defined IPV6_V6ONLY)
unsigned ipv6only:1;
#endif
#if (NGX_HAVE_REUSEPORT)
unsigned reuseport:1;
unsigned add_reuseport:1;
#endif
unsigned keepalive:2;
#if (NGX_HAVE_DEFERRED_ACCEPT)
unsigned deferred_accept:1;
unsigned delete_deferred:1;
unsigned add_deferred:1;
#ifdef SO_ACCEPTFILTER
char *accept_filter;
#endif
#endif
#if (NGX_HAVE_SETFIB)
int setfib;
#endif
#if (NGX_HAVE_TCP_FASTOPEN)
int fastopen;
#endif
};
ngx_http_init_connection */
void *servers; /* array of ngx_http_in_addr_t, for example */
ngx_log_t log;
ngx_log_t *logp;
size_t pool_size;
/* should be here because of the AcceptEx() preread */
size_t post_accept_buffer_size;
/* should be here because of the deferred accept */
ngx_msec_t post_accept_timeout;
ngx_listening_t *previous; /* 前一个ngx_listening_t */
ngx_connection_t *connection; /* 连接对象 */
ngx_uint_t worker;
unsigned open:1; /* 为1表示监听句柄有效，为0表示正常关闭 */
unsigned remain:1;/* 为1表示不关闭原先打开的监听端口，为0表示关闭曾经打开的监听端口 */
unsigned ignore:1; /* 为1表示跳过设置当前ngx_listening_t结构体中的套接字，为0时正常初始化套接字 */
unsigned bound:1; /* already bound */
unsigned inherited:1; /* inherited from previous process */
unsigned nonblocking_accept:1;
unsigned listen:1; /* 为1表示当前结构体对应的套接字已经监听 */
unsigned nonblocking:1;
unsigned shared:1; /* shared between threads or processes */
unsigned addr_ntop:1;
unsigned wildcard:1;
#if (NGX_HAVE_INET6 && defined IPV6_V6ONLY)
unsigned ipv6only:1;
#endif
#if (NGX_HAVE_REUSEPORT)
unsigned reuseport:1;
unsigned add_reuseport:1;
#endif
unsigned keepalive:2;
#if (NGX_HAVE_DEFERRED_ACCEPT)
unsigned deferred_accept:1;
unsigned delete_deferred:1;
unsigned add_deferred:1;
#ifdef SO_ACCEPTFILTER
char *accept_filter;
#endif
#endif
#if (NGX_HAVE_SETFIB)
int setfib;
#endif
#if (NGX_HAVE_TCP_FASTOPEN)
int fastopen;
#endif
};2. ngx_connection_s socket连接对象结构
存储连接有关的信息和读写事件。
struct ngx_connection_s {
/* 关联其它的 ngx_connection_s */
void *data;
/* 读取数据事件 */
ngx_event_t *read;
/* 写入事件*/
ngx_event_t *write;
/* socket句柄 */
ngx_socket_t fd;
/* 接收数据的函数指针 */
ngx_recv_pt recv;
/* 发送数据的函数指针 */
ngx_send_pt send;
/* 批量接收数据的函数指针 */
ngx_recv_chain_pt recv_chain;
/* 批量发送数据的函数指针 */
ngx_send_chain_pt send_chain;
/* 该连接的网络监听数据结构 */
ngx_listening_t *listening;
off_t sent;
/* 日志 */
ngx_log_t *log;
/* 内存池 */
ngx_pool_t *pool;
int type;
/* socket的地址结构 */
struct sockaddr *sockaddr;
socklen_t socklen;
ngx_str_t addr_text;
ngx_str_t proxy_protocol_addr;
in_port_t proxy_protocol_port;
#if (NGX_SSL)
ngx_ssl_connection_t *ssl;
#endif
/* 本地监听socket的地址结构 */
struct sockaddr *local_sockaddr;
socklen_t local_socklen;
/* 用于接收和缓存客户端发来的字符流 */
ngx_buf_t *buffer;
/* 该字段表示将该连接以双向链表形式添加到cycle结构体中的 cycle->free_connections*/
ngx_queue_t queue;
/* 建立一条与后端服务器的连接,number+1 */
ngx_atomic_uint_t number;
/* 处理请求的次数 */
ngx_uint_t requests;
unsigned buffered:8;
/* 日志级别 */
unsigned log_error:3; /* ngx_connection_log_error_e */
/* 不期待字符流结束 */
unsigned timedout:1;
/* 连接处理过程中出现错误 */
unsigned error:1;
/* 标识此链接已经销毁,内存池,套接字等都不可用 */
unsigned destroyed:1;
/* 连接处于空闲状态 */
unsigned idle:1;
/* 连接可以重用 */
unsigned reusable:1;
/* 连接关闭 */
unsigned close:1;
unsigned shared:1;
/* 正在将文件中的数据法网另一端 */
unsigned sendfile:1;
unsigned sndlowat:1;
/* 使用tcp的nodely特性 */
unsigned tcp_nodelay:2; /* ngx_connection_tcp_nodelay_e */
/* 使用tcp的nopush特性 */
unsigned tcp_nopush:2; /* ngx_connection_tcp_nopush_e */
unsigned need_last_buf:1;
#if (NGX_HAVE_IOCP)
unsigned accept_context_updated:1;
#endif
#if (NGX_HAVE_AIO_SENDFILE)
unsigned busy_count:2;
#endif
#if (NGX_THREADS)
ngx_thread_task_t *sendfile_task;
#endif
};3. ngx_event_s 事件数据结构
struct ngx_event_s {
/* 事件相关对象, 通常data指向ngx_connection_t连接对象. (开启异步IO后可能指向ngx_event_aio_t结构体) */
void *data;
unsigned write:1;
/* 标识是否可以建立连接 */
unsigned accept:1;
/* used to detect the stale events in kqueue and epoll */
unsigned instance:1;
/*
* the event was passed or would be passed to a kernel;
* in aio mode - operation was posted.
*/
/* 表示是否是活动状态 */
unsigned active:1;
unsigned disabled:1;
/* the ready event; in aio mode 0 means that no operation can be posted */
unsigned ready:1;
unsigned oneshot:1;
/* aio operation is complete */
unsigned complete:1;
unsigned eof:1;
unsigned error:1;
unsigned timedout:1;
unsigned timer_set:1;
unsigned delayed:1;
unsigned deferred_accept:1;
/* the pending eof reported by kqueue, epoll or in aio chain operation */
unsigned pending_eof:1;
unsigned posted:1;
unsigned closed:1;
/* to test on worker exit */
unsigned channel:1;
unsigned resolver:1;
unsigned cancelable:1;
#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
*
* epoll with EPOLLRDHUP:
* accept: 1 if accept many, 0 otherwise
* read: 1 if there can be data to read, 0 otherwise
*
* iocp: TODO
*
* otherwise:
* accept: 1 if accept many, 0 otherwise
*/
#if (NGX_HAVE_KQUEUE) || (NGX_HAVE_IOCP)
int available;
#else
unsigned available:1;
#endif
ngx_event_handler_pt handler;
#if (NGX_HAVE_IOCP)
ngx_event_ovlp_t ovlp;
#endif
ngx_uint_t index;
ngx_log_t *log;
ngx_rbtree_node_t timer;
/* the posted queue */
ngx_queue_t queue;
#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
};
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