Method executeMethod

api.go:667–834

executeMethod - instantiates a given method, and retries the request upon any error up to maxRetries attempts in a binomially delayed manner using a standard back off algorithm.

(ctx context.Context, method string, metadata requestMetadata)

// request upon any error up to maxRetries attempts in a binomially
// delayed manner using a standard back off algorithm.
func (c *Client) executeMethod(ctx context.Context, method string, metadata requestMetadata) (res *http.Response, err error) {
	if c.IsOffline() {
		return nil, errors.New(c.endpointURL.String() + " is offline.")
	}

	var retryable bool       // Indicates if request can be retried.
	var bodySeeker io.Seeker // Extracted seeker from io.Reader.
	reqRetry := c.maxRetries // Indicates how many times we can retry the request

	if metadata.contentBody != nil {
		// Check if body is seekable then it is retryable.
		bodySeeker, retryable = metadata.contentBody.(io.Seeker)
		switch bodySeeker {
		case os.Stdin, os.Stdout, os.Stderr:
			retryable = false
		}
		// Retry only when reader is seekable
		if !retryable {
			reqRetry = 1
		}

		// Figure out if the body can be closed - if yes
		// we will definitely close it upon the function
		// return.
		bodyCloser, ok := metadata.contentBody.(io.Closer)
		if ok {
			defer bodyCloser.Close()
		}
	}

	if metadata.addCrc != nil && metadata.contentLength > 0 {
		if metadata.trailer == nil {
			metadata.trailer = make(http.Header, 1)
		}
		crc := metadata.addCrc.Hasher()
		metadata.contentBody = newHashReaderWrapper(metadata.contentBody, crc, func(hash []byte) {
			// Update trailer when done.
			metadata.trailer.Set(metadata.addCrc.Key(), base64.StdEncoding.EncodeToString(hash))
		})
		metadata.trailer.Set(metadata.addCrc.Key(), base64.StdEncoding.EncodeToString(crc.Sum(nil)))
	}

	for range c.newRetryTimer(ctx, reqRetry, DefaultRetryUnit, DefaultRetryCap, MaxJitter) {
		// Retry executes the following function body if request has an
		// error until maxRetries have been exhausted, retry attempts are
		// performed after waiting for a given period of time in a
		// binomial fashion.
		if retryable {
			// Seek back to beginning for each attempt.
			if _, err = bodySeeker.Seek(0, 0); err != nil {
				// If seek failed, no need to retry.
				return nil, err
			}
		}

		// Instantiate a new request.
		var req *http.Request
		req, err = c.newRequest(ctx, method, metadata)