Request redirection control and best practices for http.Transport in Go language

Request redirection control and best practices of http.Transport in Go language

1. Introduction
When using Go language for network requests or Http service development, we often encounter request redirection Orientation situation. By default, http.Transport in the Go standard library automatically handles the redirection of requests, but sometimes we need to customize the redirection behavior to meet special needs. This article will introduce how to use http.Transport to control redirection and provide some best practices for your reference.

2. Redirection control of http.Transport

1. Principle
   When the status code returned by the request sent is 3xx (redirection status code), http.Transport defaults Will automatically follow the redirect and return the final response result. This is implemented by the CheckRedirect function in http.Transport. The default CheckRedirect function will return a nil error when encountering any redirection, allowing http.Transport to automatically follow the redirection.
2. Custom redirection behavior
   We can control redirection behavior by customizing the CheckRedirect function. The CheckRedirect function is defined as follows:

func(req *http.Request, via []*http.Request) error

where req is the current request object and via is all redirect requests that have passed.

We can decide whether to continue to follow the redirect by checking the status code of the current request, the number of jumps and other information. If you want to terminate following redirects, just return a non-empty error.

The following is an example. The CheckRedirect function in the code controls the limit of no more than 3 jumps:

package main

import (
    "net/http"
    "fmt"
)

func main() {
    client := &http.Client{
        CheckRedirect: func(req *http.Request, via []*http.Request) error {
            if len(via) >= 3 {
                return fmt.Errorf("stopped after %d redirects", len(via))
            }
            return nil
        },
    }
    
    resp, err := client.Get("http://example.com") // 发送一个GET请求
    if err != nil {
        fmt.Println("请求发生错误：", err)
        return
    }
    defer resp.Body.Close()
    
    fmt.Println("响应码：", resp.StatusCode)
}

In the above sample code, when the number of jumps reaches 3 , the CheckRedirect function returns a non-null error, indicating that the redirect will no longer be followed. In this way, we can flexibly control the number of jumps to avoid infinite jumps.

3. Best Practices
In actual projects, we should pay attention to the following points when using http.Transport to make network requests:

1. Set reasonable jump limit
   Excessive jumps may cause performance loss or fall into an endless redirect loop. Under normal circumstances, we should set a reasonable limit on the number of jumps based on actual needs.
2. Handling redirection loopback
   In some scenarios, the server will return a redirection address, but then return to the initial request address after the jump, forming a redirection loopback. We need to check whether there are duplicate URLs in the request history in CheckRedirect to avoid the infinite loop problem.
3. Security Considerations
   In the process of following the redirect, we need to pay attention to whether it is possible to jump to an unsafe URL to avoid causing security vulnerabilities.

4. Summary
This article introduces how to use http.Transport to control request redirection, and gives some best practices for your reference. I hope this article can help everyone better understand and use http.Transport in Go language. In actual projects, we should reasonably set the CheckRedirect function to meet special needs based on specific needs, and pay attention to security and other considerations.

The above is an introduction to the request redirection control and best practices of http.Transport in Go language. I hope it will be helpful to everyone. thanks for reading!

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