func()

in client.go [588:756]

• 132 lines of code
• 40 McCabe index (conditional complexity)

func (c *Client) Do(req *Request) (*http.Response, error) {
	c.clientInit.Do(func() {
		if c.HTTPClient == nil {
			c.HTTPClient = cleanhttp.DefaultPooledClient()
		}
	})

	logger := c.logger()

	if logger != nil {
		switch v := logger.(type) {
		case LeveledLogger:
			v.Debug("performing request", "method", req.Method, "url", req.URL)
		case Logger:
			v.Printf("[DEBUG] %s %s", req.Method, req.URL)
		}
	}

	var resp *http.Response
	var attempt int
	var shouldRetry bool
	var doErr, respErr, checkErr error

	for i := 0; ; i++ {
		doErr, respErr = nil, nil
		attempt++

		// Always rewind the request body when non-nil.
		if req.body != nil {
			body, err := req.body()
			if err != nil {
				c.HTTPClient.CloseIdleConnections()
				return resp, err
			}
			if c, ok := body.(io.ReadCloser); ok {
				req.Body = c
			} else {
				req.Body = ioutil.NopCloser(body)
			}
		}

		if c.RequestLogHook != nil {
			switch v := logger.(type) {
			case LeveledLogger:
				c.RequestLogHook(hookLogger{v}, req.Request, i)
			case Logger:
				c.RequestLogHook(v, req.Request, i)
			default:
				c.RequestLogHook(nil, req.Request, i)
			}
		}

		// Attempt the request
		resp, doErr = c.HTTPClient.Do(req.Request)

		// Check if we should continue with retries.
		shouldRetry, checkErr = c.CheckRetry(req.Context(), resp, doErr)
		if !shouldRetry && doErr == nil && req.responseHandler != nil {
			respErr = req.responseHandler(resp)
			shouldRetry, checkErr = c.CheckRetry(req.Context(), resp, respErr)
		}

		err := doErr
		if respErr != nil {
			err = respErr
		}
		if err != nil {
			switch v := logger.(type) {
			case LeveledLogger:
				v.Error("request failed", "error", err, "method", req.Method, "url", req.URL)
			case Logger:
				v.Printf("[ERR] %s %s request failed: %v", req.Method, req.URL, err)
			}
		} else {
			// Call this here to maintain the behavior of logging all requests,
			// even if CheckRetry signals to stop.
			if c.ResponseLogHook != nil {
				// Call the response logger function if provided.
				switch v := logger.(type) {
				case LeveledLogger:
					c.ResponseLogHook(hookLogger{v}, resp)
				case Logger:
					c.ResponseLogHook(v, resp)
				default:
					c.ResponseLogHook(nil, resp)
				}
			}
		}

		if !shouldRetry {
			break
		}

		// We do this before drainBody because there's no need for the I/O if
		// we're breaking out
		remain := c.RetryMax - i
		if remain <= 0 {
			break
		}

		// We're going to retry, consume any response to reuse the connection.
		if doErr == nil {
			c.drainBody(resp.Body)
		}

		wait := c.Backoff(c.RetryWaitMin, c.RetryWaitMax, i, resp)
		if logger != nil {
			desc := fmt.Sprintf("%s %s", req.Method, req.URL)
			if resp != nil {
				desc = fmt.Sprintf("%s (status: %d)", desc, resp.StatusCode)
			}
			switch v := logger.(type) {
			case LeveledLogger:
				v.Debug("retrying request", "request", desc, "timeout", wait, "remaining", remain)
			case Logger:
				v.Printf("[DEBUG] %s: retrying in %s (%d left)", desc, wait, remain)
			}
		}
		timer := time.NewTimer(wait)
		select {
		case <-req.Context().Done():
			timer.Stop()
			c.HTTPClient.CloseIdleConnections()
			return nil, req.Context().Err()
		case <-timer.C:
		}

		// Make shallow copy of http Request so that we can modify its body
		// without racing against the closeBody call in persistConn.writeLoop.
		httpreq := *req.Request
		req.Request = &httpreq
	}

	// this is the closest we have to success criteria
	if doErr == nil && respErr == nil && checkErr == nil && !shouldRetry {
		return resp, nil
	}

	defer c.HTTPClient.CloseIdleConnections()

	var err error
	if checkErr != nil {
		err = checkErr
	} else if respErr != nil {
		err = respErr
	} else {
		err = doErr
	}

	if c.ErrorHandler != nil {
		return c.ErrorHandler(resp, err, attempt)
	}

	// By default, we close the response body and return an error without
	// returning the response
	if resp != nil {
		c.drainBody(resp.Body)
	}

	// this means CheckRetry thought the request was a failure, but didn't
	// communicate why
	if err == nil {
		return nil, fmt.Errorf("%s %s giving up after %d attempt(s)",
			req.Method, req.URL, attempt)
	}

	return nil, fmt.Errorf("%s %s giving up after %d attempt(s): %w",
		req.Method, req.URL, attempt, err)
}