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      1 # Copyright (C) 2010 Google Inc. All rights reserved.
      2 # 
      3 # Redistribution and use in source and binary forms, with or without
      4 # modification, are permitted provided that the following conditions are
      5 # met:
      6 # 
      7 #     * Redistributions of source code must retain the above copyright
      8 # notice, this list of conditions and the following disclaimer.
      9 #     * Redistributions in binary form must reproduce the above
     10 # copyright notice, this list of conditions and the following disclaimer
     11 # in the documentation and/or other materials provided with the
     12 # distribution.
     13 #     * Neither the name of Google Inc. nor the names of its
     14 # contributors may be used to endorse or promote products derived from
     15 # this software without specific prior written permission.
     16 # 
     17 # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     18 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     19 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     20 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     21 # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     22 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     23 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     24 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     25 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     26 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     27 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     28 
     29 import logging
     30 import time
     31 
     32 from webkitpy.thirdparty.autoinstalled import mechanize
     33 from webkitpy.common.system.deprecated_logging import log
     34 
     35 
     36 _log = logging.getLogger(__name__)
     37 
     38 
     39 class NetworkTimeout(Exception):
     40     pass
     41 
     42 
     43 class NetworkTransaction(object):
     44     def __init__(self, initial_backoff_seconds=10, grown_factor=1.5, timeout_seconds=(10 * 60), convert_404_to_None=False):
     45         self._initial_backoff_seconds = initial_backoff_seconds
     46         self._grown_factor = grown_factor
     47         self._timeout_seconds = timeout_seconds
     48         self._convert_404_to_None = convert_404_to_None
     49 
     50     def run(self, request):
     51         self._total_sleep = 0
     52         self._backoff_seconds = self._initial_backoff_seconds
     53         while True:
     54             try:
     55                 return request()
     56             # FIXME: We should catch urllib2.HTTPError here too.
     57             except mechanize.HTTPError, e:
     58                 if self._convert_404_to_None and e.code == 404:
     59                     return None
     60                 self._check_for_timeout()
     61                 _log.warn("Received HTTP status %s loading \"%s\".  Retrying in %s seconds..." % (e.code, e.filename, self._backoff_seconds))
     62                 self._sleep()
     63 
     64     def _check_for_timeout(self):
     65         if self._total_sleep + self._backoff_seconds > self._timeout_seconds:
     66             raise NetworkTimeout()
     67 
     68     def _sleep(self):
     69         time.sleep(self._backoff_seconds)
     70         self._total_sleep += self._backoff_seconds
     71         self._backoff_seconds *= self._grown_factor
     72