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解剖Nginx·模块开发篇(5)解读内置非默认模块 ngx_http_stub_status_module

2012-06-03 12:51 2446 查看

解剖Nginx·模块开发篇(5)解读内置非默认模块 ngx_http_stub_status_module

作者:柳大·Poechant(钟超)
邮箱:zhongchao.ustc#gmail.com(# -> @)
博客:Blog.CSDN.net/Poechant
日期:June 3nd, 2012

1 Background

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
当然了,如果你是重新编译,仅仅
-s reload
是不够的,可能需要用到平滑升级:《高性能Web服务器Nginx的配置与部署研究(14)平滑升级你的Nginx》。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
源码分析先上源码
分析

2 Simple example

location /nginx_status {
  # copied from http://blog.kovyrin.net/2006/04/29/monitoring-nginx-with-rrdtool/   stub_status on;
  access_log   off;
  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:
http://localhost/nginx_status
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;
}
的确够短小精悍吧?关键在于 Nginx 提供的模块扩展方式比较好,让你可以少写一些代码(NDK 可以让你写的更少,这是后话)。

4.1 模块定义 ngx_http_stub_status_module

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
};
与此前介绍的 ngx_http_hello_world_module 并无本质区别。

4.2 命令集定义 ngx_http_status_commands

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
};
命令集定义如上,得到如下信息:name:stub_statustype:server conf、location conf、conf flag,其中最后一个比较陌生,相似的取值有:
#define NGX_CONF_ARGS_NUMBER 0x000000ff

#define NGX_CONF_BLOCK 0x00000100

#define NGX_CONF_FLAG 0x00000200

#define NGX_CONF_ANY 0x00000400

#define NGX_CONF_1MORE 0x00000800

#define NGX_CONF_2MORE 0x00001000

#define NGX_CONF_MULTI 0x00002000


set:ngx_http_set_status
下面解释下一些 types:

4.2.1 NGX_CONF_XXX

以下宏定义来自 ngx_conf_file.h:
#define NGX_CONF_NOARGS      0x00000001 // 命令不接受参数
#define NGX_CONF_TAKE1       0x00000002 // 命令携带1个参数
#define NGX_CONF_TAKE2       0x00000004 // 命令携带2个参数
#define NGX_CONF_TAKE3       0x00000008 // 命令携带3个参数
#define NGX_CONF_TAKE4       0x00000010 // 命令携带4个参数
#define NGX_CONF_TAKE5       0x00000020 // 命令携带5个参数
#define NGX_CONF_TAKE6       0x00000040 // 命令携带6个参数
#define NGX_CONF_TAKE7       0x00000080 // 命令携带7个参数

#define NGX_CONF_TAKE12      (NGX_CONF_TAKE1|NGX_CONF_TAKE2) // 命令携带1个或2个参数
#define NGX_CONF_TAKE13      (NGX_CONF_TAKE1|NGX_CONF_TAKE3) // 命令携带1个或3个参数
#define NGX_CONF_TAKE23      (NGX_CONF_TAKE2|NGX_CONF_TAKE3) // 命令携带2个或3个参数
#define NGX_CONF_TAKE123     (NGX_CONF_TAKE1|NGX_CONF_TAKE2|NGX_CONF_TAKE3) // 命令携带1个、2个或3个参数
#define NGX_CONF_TAKE1234    (NGX_CONF_TAKE1|NGX_CONF_TAKE2|NGX_CONF_TAKE3|NGX_CONF_TAKE4) // 命令携带1个、2个、3个或4个参数

#define NGX_CONF_ARGS_NUMBER 0x000000ff // 命令
#define NGX_CONF_BLOCK       0x00000100 // 块域,后面跟 {…},比如 server {...}
#define NGX_CONF_FLAG        0x00000200 // 命令接受“on|off”参数
#define NGX_CONF_ANY         0x00000400
#define NGX_CONF_1MORE       0x00000800 // 命令携带至少1个参数
#define NGX_CONF_2MORE       0x00001000 // 命令携带至少2个参数
#define NGX_CONF_MULTI       0x00002000 // 命令携带多个参数

4.3 上下文定义 ngx_http_stub_status_module_ctx

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 */
};
这个都是 NULL,够简单,无话可说了⋯⋯

4.4 命令设置函数 ngx_http_set_status

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;
}
和 ngx_http_hello_world_module 对比下:
static char* ngx_http_hello_world(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_hello_world_handler;

    ngx_conf_set_str_slot(cf, cmd, conf);

    return NGX_CONF_OK;
}
唯一的区别,就是 ngx_http_hello_world_module 多了一句 ngx_conf_set_str_slot。这个先留做一个问题,后面会介绍,暂时与关键主题无关。

4.5 命令处理函数 ngx_http_status_handler

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;
这个模块要求接受的请求类是 GET、HEAD,其他类型的请求会被拒绝。
if (r->method != NGX_HTTP_GET && r->method != NGX_HTTP_HEAD) {
        return NGX_HTTP_NOT_ALLOWED;
    }
放弃请求体,因为这个模块用不上。
rc = ngx_http_discard_request_body(r);

    if (rc != NGX_OK) {
        return rc;
    }
如果请求是 HEAD 类型的,则直接设置响应头的 content_type、status 字段,并发送响应头。
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;
        }
    }
创建一个缓冲区,向缓冲区写入我们上面在浏览器中看到的东西。
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;

    // 封装了 sprintf
    b->last = ngx_sprintf(b->last, "Active connections: %uA \n", ac);

    // 封装了 memcpy
    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));
缓冲区写完了。然后设置下响应头的 status、content_length_n(还记得吗?b->last - b->pos 刚好是缓冲区的第二个区域,是已写入数据部分。)
r->headers_out.status = NGX_HTTP_OK;
    r->headers_out.content_length_n = b->last - b->pos;

    b->last_buf = 1;
发送响应头。
rc = ngx_http_send_header(r);

    if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {
        return rc;
    }
filter。
return ngx_http_output_filter(r, &out);
}

5 Reference

http://wiki.nginx.org/HttpStubStatusModule http://blog.csdn.net/lengzijian/article/details/7356064 http://www.codinglabs.org/html/intro-of-nginx-module-development.html

6 本节留下的问题:

ngx_conf_set_str_slot:你可以先去了解下,或者等待在后面的博文中看到 :)
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