How to implement Nginx's dynamic module loading configuration

Nginx is a high-performance web server and reverse proxy software. The recently released Nginx version 1.9.11 and later supports the loading of dynamic modules. This new feature allows users to extend and customize functionality by adding new dynamic modules without recompiling and reinstalling Nginx. This article will introduce how to implement dynamic module loading configuration in Nginx and give specific code examples.

The principle of Nginx dynamic module loading is to turn on support for dynamic modules through a new compilation mode--"--add-dynamic-module=module_path". When using this compilation mode, the compilation generates a dynamic link library (.so) file. This dynamic link library can be dynamically loaded and unloaded when Nginx starts and runs. Compared with static modules, dynamic modules have better flexibility.

The following is the specific implementation method:

1. Write the dynamic module source code

Take the implementation of adding the Header header as an example. The Header header refers to the request in the Web application And response headers, Nginx itself does not provide the function of adding Header headers, but it can be achieved through custom modules. The following code is a simple example of adding a Header header:

#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>

static ngx_int_t ngx_http_add_header_handler(ngx_http_request_t *r) {
    ngx_table_elt_t *h;
    h = ngx_list_push(&r->headers_out.headers);
    h->hash = 1;
    ngx_str_set(&h->key, "MyHeader");
    ngx_str_set(&h->value, "Hello Nginx!");
    r->headers_out.content_length_n = sizeof("Hello Nginx!") - 1;
    ngx_http_clear_content_length(r);
    ngx_http_header_filter(r);
    ngx_http_send_header(r);
    return NGX_OK;
}

static ngx_int_t ngx_http_add_header_init(ngx_conf_t *cf) {
    ngx_http_handler_pt *h;
    ngx_http_core_main_conf_t *cmcf;
    cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);
    h = ngx_array_push(&cmcf->phases[NGX_HTTP_CONTENT_PHASE].handlers);
    if(h == NULL) {
        return NGX_ERROR;
    }
    *h = ngx_http_add_header_handler;
    return NGX_OK;
}

static ngx_http_module_t ngx_http_add_header_module_ctx = {
    NULL, ngx_http_add_header_init, NULL, NULL, NULL, NULL, NULL, NULL
};

ngx_module_t ngx_http_add_header_module = {
    NGX_MODULE_V1, &ngx_http_add_header_module_ctx, NULL, NGX_HTTP_MODULE, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NGX_MODULE_V1_PADDING
};

This code implements the Nginx custom module ngx_http_add_header_module. This custom module has two functions ngx_http_add_header_handler and ngx_http_add_header_init. The former is used to implement the Header header. Add specific logic, which is used to initialize the module. Each module must define a module context ngx_http_add_header_module_ctx, and an ngx_module_t structure variable ngx_http_add_header_module, which contains the version number, context and other information of the module.

2. Compile and generate a dynamic link library

Use the following command to compile the code to generate a dynamic link library:

./configure --prefix=/usr/local/nginx --add-dynamic-module=./src/http/modules/my_module && make && make install

Executing the above command will create it under the HTTP module of Nginx The my_module directory contains the Makefile used to build dynamic modules and some necessary source code and header files. The generated dynamic link library file (.so) is in the objs/ directory.

3. Load dynamic modules

Add the following code to the Nginx configuration file nginx.conf to load the dynamic link library:

load_module modules/ngx_http_add_header_module.so;

http {
    server {
        listen 80;
        server_name myweb.com;
        location / {
            add_header MyHeader "Hello Nginx!";
            root /var/www/html;
        }
    }
}

Load through the load_module command under the http module ngx_http_add_header_module.so dynamic link library file, then define a server block, and specify the location configuration item in the server block to add the Header header.

4. Reload Nginx

Execute the following command to reload the Nginx server:

nginx -s reload

This command can reload the configuration, restart Nginx, shut down Nginx and other operations.

At this point, the process of implementing dynamic module loading configuration in Nginx is completed.

Summary:

Through the above introduction, we can briefly understand the dynamic module loading implementation method in Nginx 1.9.11 and later versions. During the implementation process, you need to write the dynamic module source code, compile and generate the dynamic link library, load the module library and reload Nginx in order. Using dynamic modules allows users to develop a certain function in the post-release stage, making product launch faster and more flexible.

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