Analyze the underlying implementation principles and advantages of Nginx's HTTP long connections and HTTP/2 multiplexing

Title: The underlying implementation principles and advantages of Nginx's HTTP long connection and HTTP/2 multiplexing

Abstract:
Nginx is a high-performance web server and reverse proxy server. It uses HTTP long connection and HTTP/2 multiplexing technologies during network transmission to improve performance and efficiency. This article will analyze the underlying implementation principles of Nginx's HTTP long connections and HTTP/2 multiplexing, and show relevant code examples.

1. The underlying implementation principle of HTTP long connection
1.1 What is HTTP long connection
HTTP long connection refers to the establishment of a persistent TCP connection between the client and the server. In a TCP connection Multiple HTTP requests and responses can be transmitted, thus avoiding the overhead of frequently creating and closing connections.

1.2 Implementation Principle of HTTP Long Connection
Nginx implements HTTP long connection by setting the "Connection" field of the HTTP header to "keep-alive". When the client sends an HTTP request with the "Connection: keep-alive" header, Nginx will also keep the connection open in the response until a certain time or the upper limit of the number of requests is reached before closing the connection.

1.3 Advantages of HTTP long connections

• Reduces the overhead of connection establishment and closing, improves performance;
• Can reuse TCP connections, reducing network transmission Consumption;
• Improves the concurrent processing capability of the server and reduces the load of the server.

The following is a simple Nginx configuration example that shows how to enable HTTP long connections:

http {
    keepalive_timeout 65;
    keepalive_requests 100;
    
    server {
        listen 80;
        server_name example.com;

        location / {
            proxy_pass http://backend;
            proxy_set_header Connection "keep-alive";
        }
    }
}

2. The underlying implementation principle of HTTP/2 multiplexing
2.1 What is HTTP/2 multiplexing
HTTP/2 multiplexing refers to the simultaneous transmission of multiple HTTP requests and responses on a single TCP connection, thus avoiding the head-of-line blocking in HTTP/1.x question.

2.2 Implementation Principle of HTTP/2 Multiplexing
Nginx implements HTTP/2 multiplexing by using the concepts of binary frames and streams. In a TCP connection, each HTTP request is assigned a unique stream identifier and transmitted in frames. Nginx can handle multiple streams simultaneously without waiting for the response from the previous request to return.

2.3 Advantages of HTTP/2 multiplexing

• Solve the head-of-line blocking problem in HTTP/1.x and improve transmission efficiency;
• It can better utilize the network bandwidth and reduce the waste of resources;
• improves the concurrent processing capability and reduces the load of the server.

The following is a simple Nginx configuration example showing how to enable HTTP/2 multiplexing:

http {
    listen 443 http2;
    server_name example.com;

    location / {
        proxy_pass http://backend;
        proxy_http_version 2.0;
    }
}

Conclusion:
Nginx’s HTTP long connections and HTTP/ 2Multiplexing technologies are designed to improve server performance and efficiency. HTTP long connections reduce the overhead of connection establishment and closing, and improve the server's concurrent processing capabilities; HTTP/2 multiplexing solves the head-of-line blocking problem of HTTP/1.x, improves transmission efficiency, and reduces resource waste. Proper use of these technologies can allow web applications to respond to client requests faster and improve user experience.

Reference materials:

1. Nginx official documentation: https://nginx.org/
2. "Nginx High-Performance Web Server Detailed Explanation"

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