golang http forwarding

In modern applications, it is rare for a single server to handle all requests. Often multiple servers are used to work together. This may be because the traffic is too large and too many requests cannot be processed, or it may be due to the separation of business logic. This means that a mechanism is needed to coordinate communication between servers.

HTTP forwarding is a solution. It helps forward requests from one server to another. This enables load balancing and improved efficiency without requiring changes to existing application code.

In this article, we will introduce how to write an HTTP forwarding program using Go language. We'll learn how to use Go's standard library to listen for HTTP requests and forward them to an upstream server.

Preparation

In order to implement a simple HTTP forwarding program, we need to install Golang. Golang is a compiled language, its compilation speed is very fast, and it also provides a rich standard library. You can download and install Golang by visiting Golang’s official website.

Step 1: Install dependencies

When developing using Go language, there are many third-party libraries available for us to use. We can use command line instructions to download the required dependencies from domestic mirror sites. This will speed up our development process. The following is the command to download dependencies:

go env -w GO111MODULE=on
go env -w GOPROXY=https://goproxy.cn,direct

After executing the above command, we can happily develop.

Step 2: Create a forwarder

We can create a basic HTTP forwarder using the following code:

package main

import (
    "fmt"
    "net/http"
)

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
        fmt.Fprintf(w, "Hello world")
    })
    http.ListenAndServe(":8080", nil)
}

This application listens for all HTTP requests on port 8080. It uses the http.HandleFunc method to handle HTTP requests. For any request, it writes "Hello world" in the response. This is an extremely simple example, but it can help us understand how to build an HTTP server using Go language.

Step 3: Forward HTTP requests

We need to modify the code in the previous step to realize the function of forwarding HTTP requests. We need to forward the received request to the upstream server. By modifying our method of processing requests, we implement the function of forwarding requests to the upstream server. The following is the modified code:

package main

import (
    "fmt"
    "net/http"
    "net/http/httputil"
    "net/url"
)

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
        proxy := httputil.NewSingleHostReverseProxy(&url.URL{
            Scheme: "http",
            Host:   "127.0.0.1:8081",
        })
        proxy.ServeHTTP(w, req)
    })
    http.ListenAndServe(":8080", nil)
}

In this example, we create a proxy object using the httputil.NewSingleHostReverseProxy method. This object can forward HTTP requests to the upstream server. We also need to specify the address and port of the upstream server (127.0.0.1:8081). Finally, we use the proxy.ServeHTTP method to forward the HTTP request.

The code in the above example is very simple and easy to understand. Through this example, you can learn how to use the httputil package in the Go language standard library to implement HTTP forwarding.

Summary

In this article, we introduced how to use the Go language standard library to implement HTTP forwarding. We've provided a simple example to illustrate how to do this. The code can be modified to adapt to more complex business scenarios. As a very flexible and powerful programming language, Go can be widely used in web development, cloud computing, network programming and other fields. Hope this article is useful to you.

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