ACL configuration based on device identification in Nginx reverse proxy

Nginx is a high-performance web server, often used for reverse proxy or load balancing. In a reverse proxy scenario, Nginx can help us forward requests from multiple servers uniformly, thereby improving website access speed and stability. However, in some special scenarios, we may need to forward or process requests differently depending on the user's device. For example, for mobile device requests, we may need to forward them to a specially optimized mobile server to achieve a better page access experience. At this time, ACL configuration based on device identification is very useful. Here are some basic steps and sample code to help you use device-aware ACLs with Nginx.

Step 1: Install the device identification plug-in

Since Nginx does not support device identification by default, we need to install the relevant plug-ins first. The more commonly used plug-ins at present are ngx_http_browser_module and ngx_http_user_agent_module. They can both identify common user agent information and provide corresponding variables for us to use. The sample code given below is implemented based on ngx_http_user_agent_module.

First of all, we need to add this module when compiling Nginx. This can be achieved by adding the --with-http_user_agent_module option to the configure command:

./configure --with-http_stub_status_module --with-http_ssl_module --with-http_gzip_static_module --with-ipv6 --with- pcre --with-http_realip_module --with-http_geoip_module --with-http_user_agent_module

Step 2: Configure device identification judgment

In Nginx, device identification judgment can be made through the if statement and $ua variables to achieve. Specifically, we can use if statements to determine the device type based on the value of the $ua variable and perform different operations in the corresponding branches. Here is a simple example:

map $http_user_agent $is_mobile {

default        0;
~*mobile|android|ipod|iphone|blackberry|phone|playbook|tablet|kindle|silk     1;

}

server {

listen 80;
server_name example.com;

if ($is_mobile) {
    # 处理移动设备的请求
    proxy_pass http://mobile.example.com;
} else {
    # 处理桌面设备的请求
    proxy_pass http://www.example.com;
}

}

at In the above example, we first define a $is_mobile variable, whose value changes based on the value of the $http_user_agent variable. Specifically, if the value of $http_user_agent contains keywords such as mobile, android, ipod, iphone, blackberry, phone, playbook, tablet, kindle, or silk, the value of $is_mobile is 1; otherwise, it is 0. Next, use the if statement in the Nginx configuration file to determine the device type based on the value of the $is_mobile variable and forward the request to a different server.

It should be noted that the if statement itself will affect the performance of Nginx, so we should avoid using if statements in unnecessary places as much as possible. In addition, we can also use the ngx_http_map_module module to implement mapping of device types and forwarding addresses to further simplify configuration.

Step 3: Test and optimize configuration

The ACL configuration for device recognition is generally complex and needs to consider various device types and browser versions. In order to ensure the correctness and reliability of the configuration, we need to conduct sufficient testing and optimization. The following are some suggestions:

1. Understand user access through access logs and traffic monitoring, and optimize the hit rate of device identification based on data analysis.
2. Different device types and browser versions, especially browsers on mobile devices, require different processing and optimization. For example, you can use gzip-enabled pages for requests from mobile devices, thereby saving bandwidth and increasing page load speeds.
3. Since the if statement will affect the performance of Nginx, we can consider pre-processing some common user agent information and caching it into variables to avoid repeated calculations and judgments. This can be achieved through the ngx_http_map_module and ngx_http_upstream_hash_module modules.

Summary

With ACL configuration based on device identification, we can better handle requests from mobile devices and desktop devices in Nginx, thereby improving user experience and website performance. It should be noted that due to the diversity and complexity of device types and browser versions, we need to conduct sufficient testing and optimization to ensure the correctness and reliability of the configuration. In addition, we should avoid using if statements in unnecessary places as much as possible to improve the performance and stability of Nginx.

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