ngx_http_stub_status_module 是一个 Nginx 的内置 HTTP 模块，该模块可以提供 Nginx 的状态信息。默认情况下这个模块是不被编译进来的，所以在编译 Nginx 时要指定加载该模块：
--with-http_stub_status_module为什么拿它做例子？因为它也是个足够短小精悍的模块，是一个典型 handler 模块。那么以后我们讲解模块的过程，都是：
简要的介绍
使用的实例
指令介绍
源码分析
2 Simple example location /nginx_status { stub_status on; access_log off;access_log /usr/local/nginx/logs/status.log; #日志 allow SOME.IP.ADD.RESS; deny all; }
我们假设你是在本机上实验，并且开启的是 80 端口，那么在浏览器中输入：
会看到这样的信息：
Active connections: 291 server accepts handled requests 16630948 16630948 31070465 Reading: 6 Writing: 179 Waiting: 106其含义很容易理解：
第一行
当前的活跃连接数：291
第二行
服务器已接受的连接数：16630948（accepted connection #）
服务器已处理的连接数：16630948（handled connection #）
服务器已处理的请求：31070465（可以算出，平均每个连接有 1.8 个请求）（handled connection #）
第三行
Reading – Nginx 读取的请求头次数为 6；
Writting – Nginx 读取请求体、处理请求并发送响应给客户端的次数为 179；
Waiting – 当前活动的长连接数：106。
Nginx 官方的解释如下：
active connections – number of all open connections
server accepts handled requests – nginx accepted 16630948 connections, handled 16630948 connections (no one was closed just it was accepted), and handles 31070465 requests (1.8 requests per connection)
reading – nginx reads request header
writing – nginx reads request body, processes request, or writes response to a client
waiting – keep-alive connections, actually it is active - (reading + writing)
3 Directives这个模块中的唯一一个指令，是：
stub_status语法：stub_status on
作用域：location
功能：统计这个 location 的信息。
4 Source analysis先看完整代码：
/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> #include <ngx_http.h> static char *ngx_http_set_status(ngx_conf_t *cf, ngx_command_t *cmd, void *conf); static ngx_command_t ngx_http_status_commands[] = { { ngx_string("stub_status"), NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG, ngx_http_set_status, 0, 0, NULL }, ngx_null_command }; static ngx_http_module_t ngx_http_stub_status_module_ctx = { NULL, /* preconfiguration */ NULL, /* postconfiguration */ NULL, /* create main configuration */ NULL, /* init main configuration */ NULL, /* create server configuration */ NULL, /* merge server configuration */ NULL, /* create location configuration */ NULL /* merge location configuration */ }; ngx_module_t ngx_http_stub_status_module = { NGX_MODULE_V1, &ngx_http_stub_status_module_ctx, /* module context */ ngx_http_status_commands, /* module directives */ NGX_HTTP_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 }; static ngx_int_t ngx_http_status_handler(ngx_http_request_t *r) { size_t size; ngx_int_t rc; ngx_buf_t *b; ngx_chain_t out; ngx_atomic_int_t ap, hn, ac, rq, rd, wr; if (r->method != NGX_HTTP_GET && r->method != NGX_HTTP_HEAD) { return NGX_HTTP_NOT_ALLOWED; } rc = ngx_http_discard_request_body(r); if (rc != NGX_OK) { return rc; } ngx_str_set(&r->headers_out.content_type, "text/plain"); if (r->method == NGX_HTTP_HEAD) { r->headers_out.status = NGX_HTTP_OK; rc = ngx_http_send_header(r); if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) { return rc; } } size = sizeof("Active connections: \n") + NGX_ATOMIC_T_LEN + sizeof("server accepts handled requests\n") - 1 + 6 + 3 * NGX_ATOMIC_T_LEN + sizeof("Reading: Writing: Waiting: \n") + 3 * NGX_ATOMIC_T_LEN; b = ngx_create_temp_buf(r->pool, size); if (b == NULL) { return NGX_HTTP_INTERNAL_SERVER_ERROR; } out.buf = b; out.next = NULL; ap = *ngx_stat_accepted; hn = *ngx_stat_handled; ac = *ngx_stat_active; rq = *ngx_stat_requests; rd = *ngx_stat_reading; wr = *ngx_stat_writing; b->last = ngx_sprintf(b->last, "Active connections: %uA \n", ac); b->last = ngx_cpymem(b->last, "server accepts handled requests\n", sizeof("server accepts handled requests\n") - 1); b->last = ngx_sprintf(b->last, " %uA %uA %uA \n", ap, hn, rq); b->last = ngx_sprintf(b->last, "Reading: %uA Writing: %uA Waiting: %uA \n", rd, wr, ac - (rd + wr)); r->headers_out.status = NGX_HTTP_OK; r->headers_out.content_length_n = b->last - b->pos; b->last_buf = 1; rc = ngx_http_send_header(r); if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) { return rc; } return ngx_http_output_filter(r, &out); } static char *ngx_http_set_status(ngx_conf_t *cf, ngx_command_t *cmd, void *conf) { ngx_http_core_loc_conf_t *clcf; clcf = ngx_http_conf_get_module_loc_conf(cf, ngx_http_core_module); clcf->handler = ngx_http_status_handler; return NGX_CONF_OK; }