177 lines
5.2 KiB
Python
177 lines
5.2 KiB
Python
# derived from https://pypi.python.org/pypi/locket/
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#
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# Copyright (c) 2012, Michael Williamson
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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#
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# 1. Redistributions of source code must retain the above copyright notice,
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# this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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#
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and documentation are
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# those of the authors and should not be interpreted as representing official
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# policies, either expressed or implied, of the FreeBSD Project.
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import errno
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import threading
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import time
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import weakref
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__all__ = ["lock_file"]
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import fcntl
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def _lock_file_blocking(file_):
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fcntl.flock(file_.fileno(), fcntl.LOCK_EX)
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def _lock_file_non_blocking(file_):
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try:
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fcntl.flock(file_.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
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return True
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except IOError as error:
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if error.errno in [errno.EACCES, errno.EAGAIN]:
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return False
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else:
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raise
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def _unlock_file(file_):
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fcntl.flock(file_.fileno(), fcntl.LOCK_UN)
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_locks_lock = threading.Lock()
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_locks = weakref.WeakValueDictionary()
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def lock_file(path, **kwargs):
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with _locks_lock:
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lock = _locks.get(path)
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if lock is None:
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lock = _create_lock_file(path, **kwargs)
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_locks[path] = lock
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return lock
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def _create_lock_file(path, **kwargs):
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thread_lock = _ThreadLock(path, **kwargs)
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file_lock = _LockFile(path, **kwargs)
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return _LockSet([thread_lock, file_lock])
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class LockError(Exception):
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pass
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def _acquire_non_blocking(acquire, timeout, retry_period, path):
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if retry_period is None:
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retry_period = 0.05
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start_time = time.time()
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while True:
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success = acquire()
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if success:
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return
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elif timeout is not None and time.time() - start_time > timeout:
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raise LockError("Couldn't lock {0}".format(path))
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else:
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time.sleep(retry_period)
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class _LockSet:
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def __init__(self, locks):
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self._locks = locks
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def acquire(self):
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acquired_locks = []
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try:
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for lock in self._locks:
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lock.acquire()
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acquired_locks.append(lock)
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except Exception:
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for acquired_lock in reversed(acquired_locks):
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# TODO: handle exceptions
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acquired_lock.release()
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raise
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def release(self):
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for lock in reversed(self._locks):
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# TODO: Handle exceptions
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lock.release()
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def __enter__(self):
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self.acquire()
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return self
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def __exit__(self, *args):
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self.release()
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class _ThreadLock:
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def __init__(self, path, timeout=None, retry_period=None):
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self._path = path
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self._timeout = timeout
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self._retry_period = retry_period
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self._lock = threading.Lock()
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def acquire(self):
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if self._timeout is None:
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self._lock.acquire() # pylint: disable=consider-using-with
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else:
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_acquire_non_blocking(
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acquire=lambda: self._lock.acquire(False), # pylint: disable=consider-using-with
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timeout=self._timeout,
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retry_period=self._retry_period,
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path=self._path,
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)
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def release(self):
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self._lock.release()
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class _LockFile:
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def __init__(self, path, timeout=None, retry_period=None):
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self._path = path
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self._timeout = timeout
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self._retry_period = retry_period
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self._file = None
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self._thread_lock = threading.Lock()
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def acquire(self):
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if self._file is None:
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self._file = open(self._path, "w") # pylint: disable=consider-using-with
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if self._timeout is None:
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_lock_file_blocking(self._file)
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else:
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_acquire_non_blocking(
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acquire=lambda: _lock_file_non_blocking(self._file),
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timeout=self._timeout,
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retry_period=self._retry_period,
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path=self._path,
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)
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def release(self):
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_unlock_file(self._file)
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self._file.close()
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self._file = None
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