nginx connections 介绍

       connection 主要负责连接，里面存放了很多的信息： 读事件、写事件、socket等。 

 

 

       一 获得一个connection 

       在nginx_event.c 中的ngx_event_process_init 函数中创建: //给connect 分配空间 cycle->connections = ngx_alloc(sizeof(ngx_connection_t) * cycle->connection_n, cycle->log); //给connect分配内存 if (cycle->connections == NULL) { return NGX_ERROR; } c = cycle->connections; //读取事件分配空间并初始化 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; #if (NGX_THREADS) rev[i].lock = &c[i].lock; rev[i].own_lock = &c[i].lock; #endif } //写事件分配空间并初始化 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; #if (NGX_THREADS) wev[i].lock = &c[i].lock; wev[i].own_lock = &c[i].lock; #endif } //初始化connection,并形成链表，并对每个connect关联 读取和写事件 i = cycle->connection_n; next = NULL; 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]; #if (NGX_THREADS) c[i].lock = 0; #endif } while (i); //所有分配的connection现在都是空闲的，放到空闲链表中，并初始化空闲数目 cycle->free_connections = next; cycle->free_connection_n = cycle->connection_n; 

 

整个过程就是 connnection 、 readevent、 writeevent 分配空间，把每个connection 和 read、write 事件关联，并把所有的connection组成链表，放在空闲的connection位置上。最后结构入下图：

 

 

     二 使用

     connection的使用在函数 ngx_get_connection 中实现 (ngx_connection.c)

     ngx_connection_t * ngx_get_connection(ngx_socket_t s, ngx_log_t *log) { ngx_uint_t instance; ngx_event_t *rev, *wev; ngx_connection_t *c; /* disable warning: Win32 SOCKET is u_int while UNIX socket is int */ //socket不能超过最大值 if (ngx_cycle->files && (ngx_uint_t) s >= ngx_cycle->files_n) { ngx_log_error(NGX_LOG_ALERT, log, 0, "the new socket has number %d, " "but only %ui files are available", s, ngx_cycle->files_n); return NULL; } /* ngx_mutex_lock */ //从空闲链表中拿一个connection c = ngx_cycle->free_connections; if (c == NULL) { ngx_log_error(NGX_LOG_ALERT, log, 0, "%ui worker_connections are not enough", ngx_cycle->connection_n); /* ngx_mutex_unlock */ return NULL; } //从空闲链表中删除，并更新空闲数量 ngx_cycle->free_connections = c->data; ngx_cycle->free_connection_n--; /* ngx_mutex_unlock */ //存放soket 和connenction 对应的关系 if (ngx_cycle->files) { ngx_cycle->files[s] = c; } //暂时保存事件，清空后再倒赋值回来 rev = c->read; wev = c->write; ngx_memzero(c, sizeof(ngx_connection_t)); c->read = rev; //和原来保持不变 c->write = wev; c->fd = s; //设置对应的socket c->log = log; instance = rev->instance; //读写事件初始化 ngx_memzero(rev, sizeof(ngx_event_t)); ngx_memzero(wev, sizeof(ngx_event_t)); rev->instance = !instance; wev->instance = !instance; rev->index = NGX_INVALID_INDEX; wev->index = NGX_INVALID_INDEX; rev->data = c; wev->data = c; wev->write = 1; return c; }

 

    整个过程验证socket大小、从空闲的connection链表中得到一个connection,并进行初始化，主要是清空除了读写事件以为的所有内容，并关联socket，最后对读写事件分别进行初始化。

 

    具体应用：

    1  创建listen socket的时候，需要和一个connenction关联，就是通过这个函数调用得到一个connection的。

    2  当一个连接到来的时候，需要一个connection进行服务， 这个在函数ngx_event_accept中调用

     其它我也不知道了。。。

 

 

    三 释放一个connect

    这个比较简单

  void ngx_free_connection(ngx_connection_t *c) { /* ngx_mutex_lock */ //放入到空闲链表中，并更新数量 c->data = ngx_cycle->free_connections; ngx_cycle->free_connections = c; ngx_cycle->free_connection_n++; /* ngx_mutex_unlock */ //删除socket 和 connection之间的关系 if (ngx_cycle->files) { ngx_cycle->files[c->fd] = NULL; } }

 

 四  注销所有的connection

       我也不知道在哪里？知道的告诉我下

 

 

总结： 1  通过预先分配，这样可以提高效率