Understand how Nginx load balancing algorithm fair works

The working principle and code examples of Nginx load balancing algorithm fair

Introduction:
In high concurrency scenarios, a single server may not be able to satisfy user requests. In order to improve the processing power and stability of the server, load balancing technology is often used. As a high-performance web server and reverse proxy server, Nginx's built-in load balancing module provides a variety of algorithms to choose from. The "fair" algorithm is a dynamic algorithm that is scheduled based on the processing time of the request. This article will provide an in-depth understanding of the working principle of the Nginx load balancing algorithm fair and provide specific code examples.

1. The working principle of Nginx load balancing algorithm fair
The load balancing module of Nginx implements a variety of load balancing algorithms, of which the fair algorithm is one of them. The core idea of ​​the fair algorithm is to dynamically schedule requests based on the average response time of each background server. The specific working principle is as follows:

1. First visit: When a user visits for the first time, Nginx will forward the request to different backend servers in sequence in a polling manner.
2. Statistical processing time: Each backend server will send processing time information to Nginx after responding to the request.
3. Average response time calculation: Nginx will calculate the average response time based on the processing time statistics of each server.
4. Response time weight calculation: Nginx will calculate the corresponding weight based on the average response time of each server. The longer the response time, the lower the weight.
5. Request scheduling: When a new request arrives, Nginx will select the appropriate backend server to forward the request based on the weight of the server.
6. Dynamic adjustment: When the response time of the background server changes, Nginx will recalculate the average response time based on the new processing time and adjust the weight accordingly.

2. Code example of Nginx load balancing algorithm fair
In order to demonstrate the working principle of Nginx load balancing algorithm fair, the following is an example of an Nginx configuration file:

http {
upstream backend {

fair;
server 192.168.1.1;
server 192.168.1.2;
server 192.168.1.3;

}

server {

listen 80;
server_name example.com;

location / {
  proxy_pass http://backend;
}

}
}

In the above example, by The upstream directive defines a background server group backend and specifies the use of the fair algorithm for load balancing. Among them, the server directive is used to specify the IP address of the backend server. In an actual production environment, more servers can be added as needed.

In the server block, use the location directive to configure the request forwarding rules. In the example, all requests will be forwarded to the backend server group for processing.

3. Summary
As a high-performance web server and reverse proxy server, Nginx’s built-in load balancing module provides a variety of algorithms to choose from. The fair algorithm is a dynamic algorithm that schedules based on the processing time of the request. It dynamically adjusts the weight of request forwarding by counting the average response time of each background server. Through the introduction of this article, we have an in-depth understanding of the working principle of Nginx load balancing algorithm fair and give specific code examples.

Using Nginx load balancing algorithm fair can improve the processing power and stability of the server, thereby improving the user experience. In practical applications, we can choose appropriate load balancing algorithms based on specific business needs to meet the needs of different scenarios.

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