如何重试 HTTP POST 请求

Question

我已经实现了以下代码以在 Go 中重试 http post 请求。

在第二次重试尝试中，我总是将请求正文设为空。我试过 defer req.body.close() 但它不起作用。谁能帮我解决这个问题？

func httpRetry(req *http.Request, timeOut time.Duration, retryAttempts int, retryDelay time.Duration) (*http.Response, error) {

    attempts := 0

    for {
        attempts++
        fmt.Println("Attempt - ", attempts)
        statusCode := 0

        tr := &http.Transport{
            TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
        }
        var netClient = &http.Client{
            Timeout:   time.Second * timeOut,
            Transport: tr,
        }
        fmt.Println("ret 88888 ", req)
        response, err := netClient.Do(req)

        //defer req.Body.Close()

        fmt.Println(response, "  dd", err)

        if response != nil {
            fmt.Println(response.StatusCode)
            statusCode = response.StatusCode
        }

        if err != nil {
            fmt.Println(err)
            //return response, err
        }

        if err == nil && statusCode == http.StatusOK {
            return response, nil
        }

        if err == nil && response != nil {
            defer req.Body.Close()
        }

        retry := retryDecision(statusCode, attempts, retryAttempts)
        if !retry {
            return response, err
        }

        fmt.Println("Retry Attempt number", attempts)
        time.Sleep(retryDelay * time.Second)
        fmt.Println("After Delay")
    }
}

func retryDecision(responseStatusCode int, attempts int, retryAttempts int) bool {

    retry := false
    fmt.Println("Retry Decision 0 ", responseStatusCode, attempts, retryAttempts)
    errorCodeForRetry :=
        []int{http.StatusInternalServerError, http.StatusUnauthorized, http.StatusNotImplemented, http.StatusBadGateway, http.StatusServiceUnavailable, http.StatusGatewayTimeout}

    for _, code := range errorCodeForRetry {
        if code == responseStatusCode && attempts <= retryAttempts {
            retry = true
        }
    }

    fmt.Println("Retry Decision ", retry)

    return retry

}

请在下方查找错误详细信息

Attempt -  1
ret 88888  &{POST https://localhost:8080/logs/ HTTP/1.1 1 1 map[] {{"converstnId":"","boId":"","msgId":"","serviceName":"","headers":"","properties":"","message":"","body":"aa","exceptionMessage":"","logType":"","exceptionStackTrace":""}}

0x5ec890 170 [] false map[] map[] map[]
}

Attempt -  2
ret 88888  &{POST https://localhost:8080/logs/ HTTP/1.1 1 1 map[] {} 0x5ec890 170 [] false  map[] map[] <nil> map[]

}

Answer 1

为了能够重用body 非nil 的请求，您首先需要确保body 已经关闭，不是由您关闭，而是由客户端的RoundTripper.

文档的相关部分：

RoundTrip must always close the body, including on errors, but depending on the implementation may do so in a separate goroutine even after RoundTrip returns. This means that callers wanting to reuse the body for subsequent requests must arrange to wait for the Close call before doing so.

重用没有body的请求时，比如GET，还是要小心：

If the request does not have a body, it can be reused as long as the caller does not mutate the Request until RoundTrip fails or the Response.Body is closed.

摘自 here.

所以只要您确定 RoundTripper 关闭了主体，您可以做的就是在每次迭代的顶部重置请求的主体。像这样：

func httpRetry(req *http.Request, timeOut time.Duration, retryAttempts int, retryDelay time.Duration) (*http.Response, error) {

    // ...

    data, err := ioutil.ReadAll(req.Body)
    if err != nil {
        return nil, err
    }

    // close the original body, we don't need it anymore
    if err := req.Body.Close(); err != nil {
        return err
    }

    for {

        req.Body = ioutil.NopCloser(bytes.NewReader(data)) // reset the body

        // ... your code ...

    }

    // ...
}

如何重试 HTTP POST 请求

How to retry HTTP POST requests

http

go

retry-logic