Nginx源码分析 - HTTP模块篇 - ngx_http_block函数和HTTP模块的初始化

前面几章整理了Nginx的事件模块，这一章开始整理HTTP模块。
HTTP模块的初始化工作，都在src/http/nginx_http.c 中的ngx_http_block函数中进行的。

http模块的配置

在看nginx_http_block之前，我们还必须看一下nginx.conf中 HTTP大模块的配置文件，只有理解了HTTP模块的配置，才能更好的理解HTTP模块如何初始化的。
配置如下：
http
{
include mime.types;
default_type application/octet-stream;

#charset gb2312;

server_names_hash_bucket_size 128;
client_header_buffer_size 32k;
large_client_header_buffers 4 32k;
client_max_body_size 8m;

sendfile on;
tcp_nopush on;

keepalive_timeout 60;

tcp_nodelay on;

fastcgi_connect_timeout 300;
fastcgi_send_timeout 300;
fastcgi_read_timeout 300;
fastcgi_buffer_size 64k;
fastcgi_buffers 4 64k;
fastcgi_busy_buffers_size 128k;
fastcgi_temp_file_write_size 128k;

gzip on;
gzip_min_length 1k;
gzip_buffers 4 16k;
gzip_http_version 1.0;
gzip_comp_level 2;
gzip_types text/plain application/x-javascript text/css application/xml;
gzip_vary on;

#limit_zone crawler $binary_remote_addr 10m;

server
{
listen 80;
#server_name blog.s135.com;
index index.html index.htm index.php;
root /home/wwwroot/;

#limit_conn crawler 20;

location ~ .*\.(php|php5)?$
{
#fastcgi_pass unix:/tmp/php-cgi.sock;
fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
include fcgi.conf;
}

location ~ .*\.(gif|jpg|jpeg|png|bmp|swf)$
{
expires 30d;
}

location ~ .*\.(js|css)?$
{
expires 1h;
}

log_format access '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" $http_x_forwarded_for';
access_log /usr/local/nginx-1.4.7/logs/access.log access;
}

server
{
listen 80;
server_name status.blog.s135.com;
location / {
stub_status on;
access_log off;
}
}
从上面的配置文件我们可以看到，HTTP的配置主要分为4层：
1. 最外层的http{} 模块。模块类型：NGX_CORE_MODULE （最外层的核心模块）

2. http核心模块中的main配置：http{include mine type; }。模块类型：NGX_HTTP_MODULE （全局的HTTP模块的配置信息）

3. http核心模块中的server配置：server{}。模块类型：NGX_HTTP_MODULE （主要是配置Server的信息）

4. http核心模块中的location本地信息配置：location{}。模块类型：NGX_HTTP_MODULE （主要一个server对应的本地资源信息：静态资源、反向代理端口地址、各种语言容器端口等）

最外层的http模块，类型NGX_CORE_MODULE，属于核心模块，核心模块在最开始配置文件初始化的时候，就会调用指令的命令集。所以在核心模块启动的时候就会调用http的模块配置解析指令函数：ngx_http_block

HTTP核心模块的数据结构

/**
* HTTP模块命令集
* HTTP模块也是一个大模块，最外层为：
* http {
* ....
* }
* ngx_http_block:该方法就是回调函数
* HTTP核心模块
*/
static ngx_command_t ngx_http_commands[] = {

{ ngx_string("http"),
NGX_MAIN_CONF|NGX_CONF_BLOCK|NGX_CONF_NOARGS,
ngx_http_block,
0,
0,
NULL },

ngx_null_command
};

/**
*HTTP核心模块上下文
*/
static ngx_core_module_t ngx_http_module_ctx = {
ngx_string("http"),
NULL,
NULL
};

/**
* HTTP核心模块 结构
* 模块类型：NGX_CORE_MODULE
* 通过调用ngx_http_block方法，解析{}中的HTTP模块配置
*/
ngx_module_t ngx_http_module = {
NGX_MODULE_V1,
&ngx_http_module_ctx, /* module context */
ngx_http_commands, /* module directives */
NGX_CORE_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
};
从上面的结构中可以看到http{} 是NGX_CORE_MODULE，在核心模块初始化的时候，会调用ngx_http_commands命令集中的回调函数，逐个解析核心模块的配置信息。
而HTTP模块的总入口就是这个http{}命令集的回调函数：ngx_http_block
如果对配置文件如何解析有遗忘，请回顾《 Nginx源码分析 - 主流程篇 - 解析配置文件 》

ngx_http_block函数详解

/**
*ngx_http_commands 命令集的回调函数
*HTTP模块初始化的入口函数
*
*/
static char *
ngx_http_block(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
char *rv;
ngx_uint_t mi, m, s;
ngx_conf_t pcf;
ngx_http_module_t *module;
ngx_http_conf_ctx_t *ctx;
ngx_http_core_loc_conf_t *clcf;
ngx_http_core_srv_conf_t **cscfp;
ngx_http_core_main_conf_t *cmcf;

if (*(ngx_http_conf_ctx_t **) conf) {
return "is duplicate";
}

/* the main http context */

/* 分配一块内存，存放http配置上下文 */
ctx = ngx_pcalloc(cf->pool, sizeof(ngx_http_conf_ctx_t));
if (ctx == NULL) {
return NGX_CONF_ERROR;
}

*(ngx_http_conf_ctx_t **) conf = ctx;

/* count the number of the http modules and set up their indices */

/* 计算http模块个数 */
ngx_http_max_module = ngx_count_modules(cf->cycle, NGX_HTTP_MODULE);

/* the http main_conf context, it is the same in the all http contexts */

/**
* 最外层的HTTP配置
* http
{
include mime.types;
default_type application/octet-stream;
*/
ctx->main_conf = ngx_pcalloc(cf->pool,
sizeof(void *) * ngx_http_max_module);
if (ctx->main_conf == NULL) {
return NGX_CONF_ERROR;
}

/*
* the http null srv_conf context, it is used to merge
* the server{}s' srv_conf's
*/
/**
* server层的配置
* server
{
listen 80;
#server_name blog.s135.com;
index index.html index.htm index.php;
root /home/wwwroot/;
*/
ctx->srv_conf = ngx_pcalloc(cf->pool, sizeof(void *) * ngx_http_max_module);
if (ctx->srv_conf == NULL) {
return NGX_CONF_ERROR;
}

/*
* the http null loc_conf context, it is used to merge
* the server{}s' loc_conf's
*/

/**
* location 层的配置
location ~ .*\.(php|php5)?$
{
#fastcgi_pass unix:/tmp/php-cgi.sock;
fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
include fcgi.conf;
}
*/
ctx->loc_conf = ngx_pcalloc(cf->pool, sizeof(void *) * ngx_http_max_module);
if (ctx->loc_conf == NULL) {
return NGX_CONF_ERROR;
}

/*
* create the main_conf's, the null srv_conf's, and the null loc_conf's
* of the all http modules
*/
/**
* 调用：create_main_conf、create_srv_conf、create_loc_conf
* 创建配置
*/
for (m = 0; cf->cycle->modules[m]; m++) {
if (cf->cycle->modules[m]->type != NGX_HTTP_MODULE) {
continue;
}

module = cf->cycle->modules[m]->ctx;
mi = cf->cycle->modules[m]->ctx_index;

if (module->create_main_conf) {
ctx->main_conf[mi] = module->create_main_conf(cf);
if (ctx->main_conf[mi] == NULL) {
return NGX_CONF_ERROR;
}
}

if (module->create_srv_conf) {
ctx->srv_conf[mi] = module->create_srv_conf(cf);
if (ctx->srv_conf[mi] == NULL) {
return NGX_CONF_ERROR;
}
}

if (module->create_loc_conf) {
ctx->loc_conf[mi] = module->create_loc_conf(cf);
if (ctx->loc_conf[mi] == NULL) {
return NGX_CONF_ERROR;
}
}
}

pcf = *cf;
cf->ctx = ctx;

/**
* preconfiguration 预先初始化配置信息
*/
for (m = 0; cf->cycle->modules[m]; m++) {
if (cf->cycle->modules[m]->type != NGX_HTTP_MODULE) {
continue;
}

module = cf->cycle->modules[m]->ctx;

if (module->preconfiguration) {
if (module->preconfiguration(cf) != NGX_OK) {
return NGX_CONF_ERROR;
}
}
}

/* parse inside the http{} block */

cf->module_type = NGX_HTTP_MODULE;
cf->cmd_type = NGX_HTTP_MAIN_CONF;
rv = ngx_conf_parse(cf, NULL);

if (rv != NGX_CONF_OK) {
goto failed;
}

/*
* init http{} main_conf's, merge the server{}s' srv_conf's
* and its location{}s' loc_conf's
*/

/**
* 初始化main配置
* 合并 server srv_conf
* 合并location loc_conf
*/
cmcf = ctx->main_conf[ngx_http_core_module.ctx_index];
cscfp = cmcf->servers.elts;

for (m = 0; cf->cycle->modules[m]; m++) {
if (cf->cycle->modules[m]->type != NGX_HTTP_MODULE) {
continue;
}

module = cf->cycle->modules[m]->ctx;
mi = cf->cycle->modules[m]->ctx_index;

/* init http{} main_conf's */

if (module->init_main_conf) {
rv = module->init_main_conf(cf, ctx->main_conf[mi]);
if (rv != NGX_CONF_OK) {
goto failed;
}
}

rv = ngx_http_merge_servers(cf, cmcf, module, mi);
if (rv != NGX_CONF_OK) {
goto failed;
}
}

/* create location trees */

/**
* 创建 location模块的trees
*/
for (s = 0; s < cmcf->servers.nelts; s++) {

clcf = cscfp[s]->ctx->loc_conf[ngx_http_core_module.ctx_index];

if (ngx_http_init_locations(cf, cscfp[s], clcf) != NGX_OK) {
return NGX_CONF_ERROR;
}

if (ngx_http_init_static_location_trees(cf, clcf) != NGX_OK) {
return NGX_CONF_ERROR;
}
}

if (ngx_http_init_phases(cf, cmcf) != NGX_OK) {
return NGX_CONF_ERROR;
}

if (ngx_http_init_headers_in_hash(cf, cmcf) != NGX_OK) {
return NGX_CONF_ERROR;
}

for (m = 0; cf->cycle->modules[m]; m++) {
if (cf->cycle->modules[m]->type != NGX_HTTP_MODULE) {
continue;
}

module = cf->cycle->modules[m]->ctx;

if (module->postconfiguration) {
if (module->postconfiguration(cf) != NGX_OK) {
return NGX_CONF_ERROR;
}
}
}

if (ngx_http_variables_init_vars(cf) != NGX_OK) {
return NGX_CONF_ERROR;
}

/*
* http{}'s cf->ctx was needed while the configuration merging
* and in postconfiguration process
*/

*cf = pcf;

if (ngx_http_init_phase_handlers(cf, cmcf) != NGX_OK) {
return NGX_CONF_ERROR;
}

/* optimize the lists of ports, addresses and server names */

/* ngx_http_optimize_servers 初始化listen 端口号 ip地址 服务器等监听信息*/
if (ngx_http_optimize_servers(cf, cmcf, cmcf->ports) != NGX_OK) {
return NGX_CONF_ERROR;
}

return NGX_CONF_OK;

failed:

*cf = pcf;

return rv;
}
下一章会详细讲解：ngx_http_optimize_servers