nginx add dynamic module

nginx 动态添加模块

前言

1.9.11 版本前的 nginx 增加一个第三方模块，需要重新编译源代码，所有的模块都是用静态链接的形式组织起来的。而 Tengine 可以实现运行时动态加载模块，而不用每次都要重新编译Tengine。
Nginx 官方发布的 Nginx-1.9.11 版本，增加了此功能。
openresty 的 1.9.15.1 版本增加了此功能。

今天我将代码也更新到了 1.9.15.1 版本，试着动态加载自己编写的第三方模块

参考官方文档：

Converting Static Modules to Dynamic Modules

Old Config Shell File

New Config Shell File

Converting a config file

old-config

ngx_addon_name=ngx_http_xxx_filter_module
HTTP_AUX_FILTER_MODULES="$HTTP_AUX_FILTER_MODULES\              
                    ngx_http_xxx_filter_module"
NGX_ADDON_SRCS="$NGX_ADDON_SRCS \
                   $ngx_addon_dir/ngx_http_xxx_filter_module.c"

new-config

要考虑nginx版本，也要考虑是否为动态模块

ngx_addon_name=ngx_http_xxx_filter_module
#nginx version >= 1.9.11
if test -n "$ngx_module_link"; then   
    if [ $ngx_module_link = ADDON ] ; then          
        ngx_module_type=HTTP_AUX_FILTER   
    fi       
    ngx_module_name=ngx_http_xxx_filter_module    
 ngx_module_srcs="$ngx_addon_dir/ngx_http_xxx_filter_module.c"       
    . auto/module  
#nginx version < 1.9.11
else   
    HTTP_AUX_FILTER_MODULES="$HTTP_AUX_FILTER_MODULES \               
                     ngx_http_xxx_filter_module"    
     NGX_ADDON_SRCS="$NGX_ADDON_SRCS \           
                    $ngx_addon_dir/ngx_http_xxx_filter_module.c"
fi

Compiling a Dynamic Module

A new configure option has been created to add a module as a dynamic module. Instead of using --add-module you use --add-dynamic-module. For example:

./configure --add-dynamic-module=/opt/source/ngx_http_xxx_filter_module/

Modules are compiled along with NGINX by running the make command. Alternatively you can ask NGINX to just build the modules by doing:

$ make -f objs/Makefile modules

With NGINX 1.9.13 the following is another way of doing this:

$ make modules

Loading a Dynamic Module

Modules can be loaded into NGINX with the new load_module directive.

For example:(main级别)

load_module modules/ngx_http_xxx_filter_module.so;

ps: 虽说是 main 级别的，但是要其他块之上，如：

    user root root;
    worker_processes 2;
    pid /var/run/nginx.pid;

    load_module modules/ngx_http_xxx_filter_module.so;

    events {
        ...​
    }​
    http {
        ...​
    }​

若 load_module 用在 events 与 http 之间，则会提示：

"load_module" directive is specified too late

note

1. There is a hard limit of 128 dynamic modules that can be loaded at one time, as defined by NGX_MAX_DYNAMIC_MODULES in the NGINX source. This hard limit can be increased by editing this constant.

2. 新旧模块的兼容

   上面已经提到了新旧模块编译脚本的兼容

   同时也要考虑 c 语言层面的兼容，要关注动态模块对于 Nginx 框架的调整

   例如之前凡是用到全局变量 ngx_modules 的地方，要修改为 cycle->modules

    #if defined(nginx_version) && nginx_version >= 1009011
        modules = cf->cycle->modules;
    #else
        modules = ngx_modules;
    #endif