140 lines
4.2 KiB
Python
140 lines
4.2 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 six
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import threading
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import weakref
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from tooz import coordination
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class _LockProxy(object):
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def __init__(self, lock, blocking=True):
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self.lock = lock
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self.blocking = blocking
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def __enter__(self):
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return self.lock.__enter__(self.blocking)
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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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@six.add_metaclass(abc.ABCMeta)
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class Lock(object):
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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, blocking=True):
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return _LockProxy(self, blocking)
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def __enter__(self, blocking=True):
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acquired = self.acquire(blocking)
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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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@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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@abc.abstractmethod
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def acquire(self, blocking=True):
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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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:returns: returns true if acquired (false if not)
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:rtype: bool
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"""
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class SharedWeakLockHelper(Lock):
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"""Helper for lock that need to rely on a state in memory and
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be the same object across each coordinator.get_lock(...)
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"""
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LOCKS_LOCK = threading.Lock()
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ACQUIRED_LOCKS = dict()
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RELEASED_LOCKS = weakref.WeakValueDictionary()
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def __init__(self, namespace, lockclass, name, *args, **kwargs):
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super(SharedWeakLockHelper, self).__init__(name)
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self._lock_key = "%s:%s" % (namespace, name)
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self._newlock = lambda: lockclass(
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self.name, *args, **kwargs)
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@property
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def lock(self):
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"""Access the underlying lock object.
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For internal usage only.
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"""
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with self.LOCKS_LOCK:
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try:
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l = self.ACQUIRED_LOCKS[self._lock_key]
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except KeyError:
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l = self.RELEASED_LOCKS.setdefault(
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self._lock_key, self._newlock())
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return l
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def acquire(self, blocking=True):
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l = self.lock
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if l.acquire(blocking):
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with self.LOCKS_LOCK:
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self.RELEASED_LOCKS.pop(self._lock_key, None)
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self.ACQUIRED_LOCKS[self._lock_key] = l
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return True
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return False
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def release(self):
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with self.LOCKS_LOCK:
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try:
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l = self.ACQUIRED_LOCKS.pop(self._lock_key)
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except KeyError:
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return False
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else:
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if l.release():
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self.RELEASED_LOCKS[self._lock_key] = l
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return True
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else:
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# Put it back...
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self.ACQUIRED_LOCKS[self._lock_key] = l
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return False
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