def track_progress_less_iterations(self, server_had_bytes_before_attempt,
                                   roll_back_md5=True, debug=0):
    # At this point we had a re-tryable failure; see if made progress.
    if self.server_has_bytes > server_had_bytes_before_attempt:
        self.progress_less_iterations = 0   # If progress, reset counter.
    else:
        self.progress_less_iterations += 1
        if roll_back_md5:
            # Rollback any potential hash updates, as we did not
            # make any progress in this iteration.
            self.digesters = self.digesters_before_attempt

    if self.progress_less_iterations > self.num_retries:
        # Don't retry any longer in the current process.
        raise ResumableUploadException(
                'Too many resumable upload attempts failed without '
                'progress. You might try this upload again later',
                ResumableTransferDisposition.ABORT_CUR_PROCESS)

    # Use binary exponential backoff to desynchronize client requests.
    sleep_time_secs = random.random() * (2**self.progress_less_iterations)
    if debug >= 1:
        print('Got retryable failure (%d progress-less in a row).\n'
               'Sleeping %3.1f seconds before re-trying' %
               (self.progress_less_iterations, sleep_time_secs))
    time.sleep(sleep_time_secs)