如何重试HTTP POST请求

Question

我已经实现了以下代码，用于在Go中重试http发布请求。

在第二次重试尝试中，我总是将请求正文设为null。我试过推迟req.body.close（），但是它不起作用。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

}

请在下面找到错误详细信息

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 []错误的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

为了能够重用主体为非零的请求，首先需要确保主体（不是由您而是由客户端的RoundTripper）已关闭。

文档的相关部分：

RoundTrip必须始终关闭主体，包括发生错误时，但根据实现的不同，即使在RoundTrip返回之后，也可以在单独的goroutine中关闭它。这意味着希望重用主体以用于后续请求的调用者必须安排在等待Close调用之后再这样做。

重用没有正文的请求（如GET）时，您仍然需要小心：

如果请求没有主体，则只要调用方在RoundTrip失败或Response.Body关闭之前不更改请求，就可以重用该请求。

取自这里。

因此，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 ...

    }

    // ...
}