How to use Go and http.Transport to implement a retry strategy for network requests?

When making network requests, we often encounter requests that fail due to network instability, server abnormalities, etc. In order to improve the success rate of the request, we can use the retry strategy to resend the request until the request succeeds or the maximum number of retries is reached. This article will introduce how to use http.Transport in the Go language to implement a retry strategy for network requests.

First, we need to import the following package:

import (
    "fmt"
    "net/http"
    "time"
)

Next, we need to create a custom http.RoundTripper to implement retry logic. We can create a custom RoundTripper based on http.Transport. For example:

type RetryTransport struct {
    Transport http.RoundTripper
    Retries   int
}

In the RetryTransport structure, we define two fields: Transport and Retries. Transport is an http.RoundTripper type used to send requests and receive responses. Retries represents the maximum number of retries.

Next, we need to implement the RoundTrip method in the RoundTripper interface, which is used to send requests and receive responses. In this method, we can implement retry logic. For example:

func (r *RetryTransport) RoundTrip(req *http.Request) (*http.Response, error) {
    var resp *http.Response
    var err error

    for i := 0; i <= r.Retries; i++ {
        resp, err = r.Transport.RoundTrip(req)
        
        if err == nil && resp.StatusCode < 500 {
            break
        }
        
        time.Sleep(1 * time.Second)
    }

    return resp, err
}

In the RoundTrip method, we use a loop to perform the sending and receiving of requests. The number of loops is determined by the maximum number of retries. After each request is sent, we check whether an error occurred and the response status code is less than 500 (indicating a server-side exception). If the conditions are met, the request is successful and the loop is jumped out; otherwise, the request is sent again after waiting for 1 second.

Finally, we need to use a custom RetryTransport to create an http.Client for sending requests. For example:

func main() {
    retryTransport := &RetryTransport{
        Transport: http.DefaultTransport,
        Retries:   3,
    }

    client := &http.Client{
        Transport: retryTransport,
    }

    resp, err := client.Get("https://example.com")
    if err != nil {
        fmt.Println("請求出錯(cuò)：", err)
        return 
    }

    defer resp.Body.Close()

    // 處理響應(yīng)
    // ...
}

In the above example, we created a RetryTransport and designated it as the Transport of http.Client. We set the maximum number of retries to 3 times. We then use the client.Get method to send the request and process the returned response.

By using a custom RetryTransport, we can implement a retry strategy for network requests. When a request fails, it will automatically retry the specified number of times to improve the success rate of network requests.

To summarize, this article introduces how to use http.Transport and custom RoundTripper in Go language to implement a retry strategy for network requests. By defining the number of retries and waiting time, we can better cope with network instability and server exceptions, and improve the success rate of requests.

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