HTTP verb and path based ACL configuration in Nginx reverse proxy

Nginx is a high-performance web server and reverse proxy server. Its powerful configuration capabilities enable Nginx to be used in a variety of different scenarios. Among them, ACL configuration based on HTTP verbs and paths is a commonly used method in Nginx reverse proxy. This article will introduce its principle and implementation method.

1. The concept of ACL

ACL (Access Control List) is an access control list, which is a rule-based access control technology. By defining some rules, different visitors can be distinguished and have different access controls.

In the Nginx reverse proxy, ACL can be used to distinguish different requests to implement different reverse proxy strategies. Specifically, requests can be classified and forwarded to different backend servers by matching the verbs and paths of HTTP requests.

2. Matching of HTTP verbs and paths

The HTTP protocol defines some commonly used HTTP verbs, such as GET, POST, PUT, DELETE, etc. HTTP verbs can be used to indicate the client's request type, which can be obtained through the $request_method variable in the Nginx configuration.

In addition to HTTP verbs, path is also an important factor in determining the request type. The path can be used to represent the requested resource location, which can be obtained through the $request_uri variable in the Nginx configuration.

3. ACL-based configuration method

In Nginx, you can use if statements to build ACL rules. The syntax of the if statement is as follows:

if (condition) {

// do something

}

where condition is an expression used to determine whether the current request complies with the rules. If the rules are met, the action in the block of code enclosed in curly braces is performed.

In ACL configuration based on HTTP verbs and paths, rule matching can be achieved through nesting of if statements. Specifically, you can first judge the HTTP verb, and then judge the path. The sample code is as follows:

if ($request_method = 'GET') {

if ($request_uri = '/users') {
    proxy_pass http://backend1;
}
if ($request_uri = '/orders') {
    proxy_pass http://backend2;
}

}
if ($request_method = 'POST') {

if ($request_uri = '/users') {
    proxy_pass http://backend3;
}
if ($request_uri = '/orders') {
    proxy_pass http://backend4;
}

}

In the above example code, first determine whether the HTTP verb is GET or POST, then determine the path, and finally select different back-end servers for forwarding based on the matching results.

4. Optimization of ACL rules

Although the if statement can be used to implement ACL configuration based on HTTP verbs and paths, the if statement also has some shortcomings. Specifically, the matching rules in the if statement are matched in order. If there are a large number of rules, the matching efficiency will become very low.

In order to solve this problem, you can use Nginx's map instruction for optimization. The map instruction can map different variables to different values, thereby simplifying the nesting relationship of if statements and thereby improving matching efficiency.

The following is an ACL configuration example code based on the map directive:

map $request_method$request_uri $backend {

default                     http://backend0;
GET/users                   http://backend1;
GET/orders                  http://backend2;
POST/users                  http://backend3;
POST/orders                 http://backend4;

}
server {

...
location / {
    proxy_pass              $backend;
}
...

}

In the above example code, the map directive maps the combination of $request_method and $request_uri variables to different $backend variable values. In the following proxy_pass directive, the $backend variable is used directly to forward the request.

5. Summary

ACL configuration based on HTTP verbs and paths is a commonly used technology in Nginx reverse proxy, which can be used to classify different requests and forward them to Different backend servers. In the specific implementation process, you can use if statements or map instructions to match rules. Especially for more complex ACL rules, using the map command can improve matching efficiency and thereby improve system performance.

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