| # Copyright (C) 2010 Google Inc. All rights reserved. |
| # |
| # Redistribution and use in source and binary forms, with or without |
| # modification, are permitted provided that the following conditions are |
| # met: |
| # |
| # * Redistributions of source code must retain the above copyright |
| # notice, this list of conditions and the following disclaimer. |
| # * Redistributions in binary form must reproduce the above |
| # copyright notice, this list of conditions and the following disclaimer |
| # in the documentation and/or other materials provided with the |
| # distribution. |
| # * Neither the name of Google Inc. nor the names of its |
| # contributors may be used to endorse or promote products derived from |
| # this software without specific prior written permission. |
| # |
| # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| import logging |
| import time |
| import urllib2 |
| |
| _log = logging.getLogger(__name__) |
| |
| |
| class NetworkTimeout(Exception): |
| def __str__(self): |
| return 'NetworkTimeout' |
| |
| |
| class NetworkTransaction(object): |
| def __init__(self, initial_backoff_seconds=10, grown_factor=1.5, timeout_seconds=(10 * 60), convert_404_to_None=False): |
| self._initial_backoff_seconds = initial_backoff_seconds |
| self._grown_factor = grown_factor |
| self._timeout_seconds = timeout_seconds |
| self._convert_404_to_None = convert_404_to_None |
| |
| def run(self, request): |
| self._total_sleep = 0 |
| self._backoff_seconds = self._initial_backoff_seconds |
| while True: |
| try: |
| return request() |
| except urllib2.HTTPError, e: |
| if self._convert_404_to_None and e.code == 404: |
| return None |
| self._check_for_timeout() |
| _log.warn("Received HTTP status %s loading \"%s\". Retrying in %s seconds..." % (e.code, e.filename, self._backoff_seconds)) |
| self._sleep() |
| |
| def _check_for_timeout(self): |
| if self._total_sleep + self._backoff_seconds > self._timeout_seconds: |
| raise NetworkTimeout() |
| |
| def _sleep(self): |
| time.sleep(self._backoff_seconds) |
| self._total_sleep += self._backoff_seconds |
| self._backoff_seconds *= self._grown_factor |
