Building a High-Performance HTTP/2 Server in Go

Introduction to HTTP/2 and Go

When it comes to building high-performance web servers, the choice of protocol and programming language can make all the difference. HTTP/2, with its multiplexing, header compression, and server push capabilities, is a significant improvement over HTTP/1.1. Go, with its lightweight goroutines, efficient networking library, and robust standard library, is an ideal choice for developing such servers.

Why HTTP/2?

HTTP/2 offers several advantages over its predecessor, including:

• Multiplexing: Multiple requests can be sent over a single connection, reducing the overhead of multiple connections.
• Header Compression: HPACK compression reduces the size of headers, leading to faster transmission times.
• Server Push: Servers can proactively send resources to the client without waiting for a request.

Why Go?

Go’s strengths include:

• Concurrency: Goroutines and channels make it easy to handle multiple connections concurrently.
• Performance: Go’s lightweight threads and efficient garbage collection ensure high performance.
• Standard Library: Go’s net/http package provides robust support for HTTP/2 out of the box.

Setting Up an HTTP/2 Server in Go

To set up an HTTP/2 server in Go, you don’t need any third-party libraries if you’re using Go 1.6 or later. Here’s how you can do it:

Step 1: Generate TLS Certificates

HTTP/2 requires TLS. You can generate a private key and a certificate using OpenSSL:

openssl req -newkey rsa:2048 -nodes -keyout server.key -x509 -days 365 -out server.crt

Step 2: Create the Server

Here’s a simple example of an HTTP/2 server using Go’s standard library:

package main

import (
    "log"
    "net/http"
)

func handle(w http.ResponseWriter, r *http.Request) {
    log.Printf("Got connection: %s", r.Proto)
    w.Write([]byte("Hello"))
}

func main() {
    srv := &http.Server{
        Addr:    ":8000",
        Handler: http.HandlerFunc(handle),
    }
    log.Printf("Serving on https://0.0.0.0:8000")
    log.Fatal(srv.ListenAndServeTLS("server.crt", "server.key"))
}

Step 3: Enable Server Push

Server push is a powerful feature of HTTP/2 that allows the server to send resources to the client before they are requested. Here’s how you can implement it:

package main

import (
    "log"
    "net/http"
)

func handle(w http.ResponseWriter, r *http.Request) {
    log.Printf("Got connection: %s", r.Proto)
    pusher, ok := w.(http.Pusher)
    if !ok {
        log.Println("Can't push to client")
    } else {
        err := pusher.Push("/2nd", nil)
        if err != nil {
            log.Printf("Failed push: %v", err)
        }
    }
    w.Write([]byte("Hello"))
}

func main() {
    srv := &http.Server{
        Addr:    ":8000",
        Handler: http.HandlerFunc(handle),
    }
    log.Printf("Serving on https://0.0.0.0:8000")
    log.Fatal(srv.ListenAndServeTLS("server.crt", "server.key"))
}

Full-Duplex Communication

Full-duplex communication is another key feature of HTTP/2, allowing both the client and server to send data simultaneously over the same connection. Here’s an example using Go’s net/http package to demonstrate an echo server:

package main

import (
    "io"
    "log"
    "net/http"
)

func echoHandler(w http.ResponseWriter, r *http.Request) {
    log.Printf("Got connection: %s", r.Proto)
    if r.Method == "PUT" {
        buf := make([]byte, 1024)
        for {
            n, err := r.Body.Read(buf)
            if err != nil {
                if err != io.EOF {
                    log.Printf("Read error: %v", err)
                }
                break
            }
            w.Write(buf[:n])
        }
    }
}

func main() {
    http.HandleFunc("/ECHO", echoHandler)
    srv := &http.Server{
        Addr:    ":8000",
        Handler: http.DefaultServeMux,
    }
    log.Printf("Serving on https://0.0.0.0:8000")
    log.Fatal(srv.ListenAndServeTLS("server.crt", "server.key"))
}

You can test this using curl with HTTP/2 enabled:

curl -i -XPUT --http2 https://localhost:8000/ECHO -d hello

Diagram: HTTP/2 Server Setup

Here is a simple sequence diagram to illustrate the setup of an HTTP/2 server in Go:

Best Practices and Additional Features

Handling Different Protocols

When dealing with both HTTP/1.1 and HTTP/2 clients, it’s important to handle each protocol correctly. Here’s how you can check the protocol version and handle server push accordingly:

func handle(w http.ResponseWriter, r *http.Request) {
    log.Printf("Got connection: %s", r.Proto)
    if r.Proto == "HTTP/2.0" {
        pusher, ok := w.(http.Pusher)
        if !ok {
            log.Println("Can't push to client")
        } else {
            err := pusher.Push("/2nd", nil)
            if err != nil {
                log.Printf("Failed push: %v", err)
            }
        }
    }
    w.Write([]byte("Hello"))
}

Configuration and Customization

For more advanced configuration, such as setting up custom HTTP/2 settings, you might need to use the golang.org/x/net/http2 package until it is fully integrated into the standard library. Here’s an example of configuring the server using this package:

package main

import (
    "log"
    "net/http"
    "golang.org/x/net/http2"
)

func main() {
    srv := &http.Server{
        Addr: ":443",
        Handler: http.FileServer(http.Dir(".")),
    }
    http2.ConfigureServer(srv, &http2.Server{})
    log.Fatal(srv.ListenAndServeTLS("server.crt", "server.key"))
}

Conclusion

Building a high-performance HTTP/2 server in Go is straightforward and leverages the powerful features of both the protocol and the language. With Go’s standard library providing transparent support for HTTP/2, you can focus on writing efficient and scalable server code. By following the steps outlined here, you can create a robust and high-performance HTTP/2 server that takes full advantage of the protocol’s capabilities. Happy coding