http.py 文件源码

def next_chunk(self, num_retries=0):
    """Get the next chunk of the download.

    Args:
      num_retries: Integer, number of times to retry 500's with randomized
            exponential backoff. If all retries fail, the raised HttpError
            represents the last request. If zero (default), we attempt the
            request only once.

    Returns:
      (status, done): (MediaDownloadStatus, boolean)
         The value of 'done' will be True when the media has been fully
         downloaded.

    Raises:
      apiclient.errors.HttpError if the response was not a 2xx.
      httplib2.HttpLib2Error if a transport error has occured.
    """
    headers = {
        'range': 'bytes=%d-%d' % (
            self._progress, self._progress + self._chunksize)
        }
    http = self._request.http

    for retry_num in xrange(num_retries + 1):
      if retry_num > 0:
        self._sleep(self._rand() * 2**retry_num)
        logging.warning(
            'Retry #%d for media download: GET %s, following status: %d'
            % (retry_num, self._uri, resp.status))

      resp, content = http.request(self._uri, headers=headers)
      if resp.status < 500:
        break

    if resp.status in [200, 206]:
      if 'content-location' in resp and resp['content-location'] != self._uri:
        self._uri = resp['content-location']
      self._progress += len(content)
      self._fd.write(content)

      if 'content-range' in resp:
        content_range = resp['content-range']
        length = content_range.rsplit('/', 1)[1]
        self._total_size = int(length)

      if self._progress == self._total_size:
        self._done = True
      return MediaDownloadProgress(self._progress, self._total_size), self._done
    else:
      raise HttpError(resp, content, uri=self._uri)