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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
29import logging
30import time
31
32from webkitpy.thirdparty.autoinstalled import mechanize
33from webkitpy.common.system.deprecated_logging import log
34
35
36_log = logging.getLogger(__name__)
37
38
39class NetworkTimeout(Exception):
40    pass
41
42
43class 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