How to use Nginx for reverse proxy and load balancing

How to use Nginx for reverse proxy and load balancing

Introduction:
Nginx is a high-performance open source web server and reverse proxy server. It can not only provide static file services like a traditional web server, but also serve as a reverse proxy server, forwarding client requests to multiple back-end servers and achieving load balancing. This article will introduce how to use Nginx to implement reverse proxy and load balancing configuration.

1. Reverse proxy
Reverse proxy means that the web server receives the client's request and forwards it to multiple back-end servers. The client cannot establish a connection directly with the backend server and can only communicate with the backend server through the reverse proxy server. Reverse proxy can hide the real IP address of the backend server and improve the security of the system.

Configuration example:
In the Nginx configuration file, add a new server block to configure the reverse proxy:

server {
    listen       80;
    server_name  example.com;

    location / {
        proxy_pass http://backend_servers;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

In the above configuration, listen specifies the port that Nginx listens on. server_name specifies the domain name of the reverse proxy. location / means forwarding all requests to the backend server. proxy_pass configures the address of the backend server, which can be an IP address or domain name. proxy_set_header can set some HTTP header information, such as Host and X-Real-IP, etc.

2. Load Balancing
Load balancing refers to distributing requests to multiple back-end servers to improve system performance and availability. Nginx supports a variety of load balancing algorithms, such as polling, weighted polling, least connections, etc.

Configuration example:
In the Nginx configuration file, add a new upstream block to configure the backend server:

upstream backend_servers {
    server 192.168.0.1:8080;
    server 192.168.0.2:8080;
    server 192.168.0.3:8080;
    server 192.168.0.4:8080;
}

server {
    listen       80;
    server_name  example.com;

    location / {
        proxy_pass http://backend_servers;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

In the above configuration, the upstream block defines multiple backends The server's address and port. In the location block, proxy_pass configures the name of the upstream block, and Nginx will select the appropriate backend server based on the configured load balancing algorithm.

3. Implement health check
In order to ensure the availability of the backend server, you can add the health check function. When the backend server fails, Nginx will automatically forward the request to other normal servers.

Configuration example:
In the Nginx configuration file, you can add a new location block to implement health check:

location /check {
    access_log off;
    proxy_pass http://backend_servers;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_next_upstream error timeout invalid_header http_500 http_502 http_503 http_504;
}

In the above configuration, location /check means that when a request is made to access / When checking, Nginx will forward the request to the backend server and then check the status code returned. If the returned status code is error, timeout, invalid_header, http_500, http_502, http_503 or http_504, Nginx will forward the request to other normal servers.

Conclusion:
By using Nginx's reverse proxy and load balancing functions, the performance and availability of the system can be improved. Through the introduction and code examples of this article, I believe that readers have understood how to configure Nginx for reverse proxy and load balancing. I hope it will be helpful to readers in practice.

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