110 lines
3.8 KiB
Python
110 lines
3.8 KiB
Python
# -*- coding: utf-8 -*-
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#
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# Copyright (C) 2014 eNovance Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import abc
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import tooz
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from tooz import coordination
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class _LockProxy(object):
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def __init__(self, lock, *args, **kwargs):
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self.lock = lock
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self.args = args
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self.kwargs = kwargs
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def __enter__(self):
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return self.lock.__enter__(*self.args, **self.kwargs)
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def __exit__(self, exc_type, exc_val, exc_tb):
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self.lock.__exit__(exc_type, exc_val, exc_tb)
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class Lock(object, metaclass=abc.ABCMeta):
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def __init__(self, name):
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if not name:
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raise ValueError("Locks must be provided a name")
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self._name = name
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@property
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def name(self):
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return self._name
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def __call__(self, *args, **kwargs):
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return _LockProxy(self, *args, **kwargs)
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def __enter__(self, *args, **kwargs):
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acquired = self.acquire(*args, **kwargs)
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if not acquired:
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msg = u'Acquiring lock %s failed' % self.name
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raise coordination.LockAcquireFailed(msg)
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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self.release()
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def is_still_owner(self):
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"""Checks if the lock is still owned by the acquiree.
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:returns: returns true if still acquired (false if not) and
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false if the lock was never acquired in the first place
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or raises ``NotImplemented`` if not implemented.
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"""
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raise tooz.NotImplemented
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@abc.abstractmethod
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def release(self):
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"""Attempts to release the lock, returns true if released.
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The behavior of releasing a lock which was not acquired in the first
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place is undefined (it can range from harmless to releasing some other
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users lock)..
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:returns: returns true if released (false if not)
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:rtype: bool
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"""
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def break_(self):
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"""Forcefully release the lock.
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This is mostly used for testing purposes, to simulate an out of
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band operation that breaks the lock. Backends may allow waiters to
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acquire immediately if a lock is broken, or they should raise an
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exception. Releasing should be successful for objects that believe
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they hold the lock but do not have the lock anymore. However,
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they should be careful not to re-break the lock by releasing it,
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since they may not be the holder anymore.
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:returns: returns true if forcefully broken (false if not)
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or raises ``NotImplemented`` if not implemented.
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"""
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raise tooz.NotImplemented
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@abc.abstractmethod
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def acquire(self, blocking=True, shared=False):
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"""Attempts to acquire the lock.
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:param blocking: If True, blocks until the lock is acquired. If False,
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returns right away. Otherwise, the value is used as a
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timeout value and the call returns maximum after this
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number of seconds.
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:param shared: If False, the lock is exclusive. If True, the lock can
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be shareable or raises ``NotImplemented`` if not
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implemented.
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:returns: returns true if acquired (false if not)
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:rtype: bool
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"""
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