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# Copyright (C) 2011-2014 by the Free Software Foundation, Inc.
#
# This file is part of GNU Mailman.
#
# GNU Mailman is free software: you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option)
# any later version.
#
# GNU Mailman is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
# more details.
#
# You should have received a copy of the GNU General Public License along with
# GNU Mailman. If not, see <http://www.gnu.org/licenses/>.
"""Unique ID generation.
Use these functions to create unique ids rather than inlining calls to hashlib
and whatnot. These are better instrumented for testing purposes.
"""
from __future__ import absolute_import, unicode_literals
__metaclass__ = type
__all__ = [
'UniqueIDFactory',
'factory',
]
import os
import uuid
import errno
from flufl.lock import Lock
from mailman.config import config
from mailman.model.uid import UID
from mailman.testing import layers
class UniqueIDFactory:
"""A factory for unique ids."""
def __init__(self, context=None):
# We can't call reset() when the factory is created below, because
# config.VAR_DIR will not be set at that time. So initialize it at
# the first use.
self._uid_file = None
self._lock_file = None
self._lockobj = None
self._context = context
layers.MockAndMonkeyLayer.register_reset(self.reset)
@property
def _lock(self):
if self._lockobj is None:
# These will get automatically cleaned up by the test
# infrastructure.
self._uid_file = os.path.join(config.VAR_DIR, '.uid')
if self._context:
self._uid_file += '.' + self._context
self._lock_file = self._uid_file + '.lock'
self._lockobj = Lock(self._lock_file)
return self._lockobj
def new_uid(self):
"""Return a new UID.
:return: The new uid
:rtype: int
"""
if layers.is_testing():
# When in testing mode we want to produce predictable id, but we
# need to coordinate this among separate processes. We could use
# the database, but I don't want to add schema just to handle this
# case, and besides transactions could get aborted, causing some
# ids to be recycled. So we'll use a data file with a lock. This
# may still not be ideal due to race conditions, but I think the
# tests will be serialized enough (and the ids reset between
# tests) that it will not be a problem. Maybe.
return self._next_uid()
while True:
uid = uuid.uuid4()
try:
UID.record(uid)
except ValueError:
pass
else:
return uid
def _next_uid(self):
with self._lock:
try:
with open(self._uid_file) as fp:
uid = int(fp.read().strip())
next_uid = uid + 1
with open(self._uid_file, 'w') as fp:
fp.write(str(next_uid))
return uuid.UUID(int=uid)
except IOError as error:
if error.errno != errno.ENOENT:
raise
with open(self._uid_file, 'w') as fp:
fp.write('2')
return uuid.UUID(int=1)
def reset(self):
with self._lock:
with open(self._uid_file, 'w') as fp:
fp.write('1')
factory = UniqueIDFactory()
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