mirror of
https://github.com/SickGear/SickGear.git
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326 lines
8.9 KiB
Python
326 lines
8.9 KiB
Python
"""
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lockfile.py - Platform-independent advisory file locks.
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Requires Python 2.5 unless you apply 2.4.diff
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Locking is done on a per-thread basis instead of a per-process basis.
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Usage:
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>>> lock = LockFile('somefile')
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>>> try:
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... lock.acquire()
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... except AlreadyLocked:
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... print 'somefile', 'is locked already.'
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... except LockFailed:
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... print 'somefile', 'can\\'t be locked.'
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... else:
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... print 'got lock'
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got lock
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>>> print lock.is_locked()
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True
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>>> lock.release()
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>>> lock = LockFile('somefile')
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>>> print lock.is_locked()
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False
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>>> with lock:
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... print lock.is_locked()
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True
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>>> print lock.is_locked()
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False
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>>> lock = LockFile('somefile')
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>>> # It is okay to lock twice from the same thread...
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>>> with lock:
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... lock.acquire()
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...
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>>> # Though no counter is kept, so you can't unlock multiple times...
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>>> print lock.is_locked()
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False
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Exceptions:
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Error - base class for other exceptions
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LockError - base class for all locking exceptions
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AlreadyLocked - Another thread or process already holds the lock
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LockFailed - Lock failed for some other reason
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UnlockError - base class for all unlocking exceptions
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AlreadyUnlocked - File was not locked.
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NotMyLock - File was locked but not by the current thread/process
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"""
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from __future__ import absolute_import
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import sys
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import socket
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import os
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import threading
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import time
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import urllib
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import warnings
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import functools
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# Work with PEP8 and non-PEP8 versions of threading module.
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if not hasattr(threading, "current_thread"):
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threading.current_thread = threading.currentThread
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if not hasattr(threading.Thread, "get_name"):
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threading.Thread.get_name = threading.Thread.getName
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__all__ = ['Error', 'LockError', 'LockTimeout', 'AlreadyLocked',
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'LockFailed', 'UnlockError', 'NotLocked', 'NotMyLock',
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'LinkLockFile', 'MkdirLockFile', 'SQLiteLockFile',
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'LockBase', 'locked']
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class Error(Exception):
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"""
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Base class for other exceptions.
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>>> try:
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... raise Error
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... except Exception:
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... pass
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"""
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pass
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class LockError(Error):
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"""
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Base class for error arising from attempts to acquire the lock.
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>>> try:
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... raise LockError
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... except Error:
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... pass
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"""
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pass
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class LockTimeout(LockError):
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"""Raised when lock creation fails within a user-defined period of time.
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>>> try:
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... raise LockTimeout
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... except LockError:
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... pass
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"""
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pass
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class AlreadyLocked(LockError):
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"""Some other thread/process is locking the file.
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>>> try:
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... raise AlreadyLocked
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... except LockError:
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... pass
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"""
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pass
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class LockFailed(LockError):
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"""Lock file creation failed for some other reason.
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>>> try:
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... raise LockFailed
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... except LockError:
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... pass
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"""
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pass
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class UnlockError(Error):
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"""
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Base class for errors arising from attempts to release the lock.
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>>> try:
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... raise UnlockError
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... except Error:
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... pass
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"""
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pass
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class NotLocked(UnlockError):
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"""Raised when an attempt is made to unlock an unlocked file.
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>>> try:
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... raise NotLocked
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... except UnlockError:
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... pass
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"""
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pass
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class NotMyLock(UnlockError):
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"""Raised when an attempt is made to unlock a file someone else locked.
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>>> try:
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... raise NotMyLock
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... except UnlockError:
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... pass
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"""
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pass
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class LockBase:
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"""Base class for platform-specific lock classes."""
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def __init__(self, path, threaded=True, timeout=None):
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"""
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>>> lock = LockBase('somefile')
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>>> lock = LockBase('somefile', threaded=False)
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"""
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self.path = path
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self.lock_file = os.path.abspath(path) + ".lock"
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self.hostname = socket.gethostname()
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self.pid = os.getpid()
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if threaded:
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t = threading.current_thread()
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# Thread objects in Python 2.4 and earlier do not have ident
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# attrs. Worm around that.
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ident = getattr(t, "ident", hash(t))
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self.tname = "-%x" % (ident & 0xffffffff)
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else:
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self.tname = ""
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dirname = os.path.dirname(self.lock_file)
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# unique name is mostly about the current process, but must
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# also contain the path -- otherwise, two adjacent locked
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# files conflict (one file gets locked, creating lock-file and
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# unique file, the other one gets locked, creating lock-file
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# and overwriting the already existing lock-file, then one
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# gets unlocked, deleting both lock-file and unique file,
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# finally the last lock errors out upon releasing.
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self.unique_name = os.path.join(dirname,
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"%s%s.%s%s" % (self.hostname,
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self.tname,
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self.pid,
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hash(self.path)))
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self.timeout = timeout
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def acquire(self, timeout=None):
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"""
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Acquire the lock.
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* If timeout is omitted (or None), wait forever trying to lock the
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file.
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* If timeout > 0, try to acquire the lock for that many seconds. If
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the lock period expires and the file is still locked, raise
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LockTimeout.
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* If timeout <= 0, raise AlreadyLocked immediately if the file is
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already locked.
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"""
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raise NotImplemented("implement in subclass")
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def release(self):
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"""
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Release the lock.
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If the file is not locked, raise NotLocked.
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"""
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raise NotImplemented("implement in subclass")
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def is_locked(self):
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"""
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Tell whether or not the file is locked.
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"""
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raise NotImplemented("implement in subclass")
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def i_am_locking(self):
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"""
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Return True if this object is locking the file.
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"""
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raise NotImplemented("implement in subclass")
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def break_lock(self):
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"""
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Remove a lock. Useful if a locking thread failed to unlock.
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"""
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raise NotImplemented("implement in subclass")
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def __enter__(self):
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"""
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Context manager support.
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"""
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self.acquire()
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return self
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def __exit__(self, *_exc):
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"""
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Context manager support.
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"""
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self.release()
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def __repr__(self):
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return "<%s: %r -- %r>" % (self.__class__.__name__, self.unique_name,
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self.path)
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def _fl_helper(cls, mod, *args, **kwds):
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warnings.warn("Import from %s module instead of lockfile package" % mod,
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DeprecationWarning, stacklevel=2)
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# This is a bit funky, but it's only for awhile. The way the unit tests
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# are constructed this function winds up as an unbound method, so it
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# actually takes three args, not two. We want to toss out self.
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if not isinstance(args[0], str):
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# We are testing, avoid the first arg
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args = args[1:]
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if len(args) == 1 and not kwds:
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kwds["threaded"] = True
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return cls(*args, **kwds)
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def LinkFileLock(*args, **kwds):
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"""Factory function provided for backwards compatibility.
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Do not use in new code. Instead, import LinkLockFile from the
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lockfile.linklockfile module.
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"""
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from . import linklockfile
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return _fl_helper(linklockfile.LinkLockFile, "lockfile.linklockfile",
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*args, **kwds)
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def MkdirFileLock(*args, **kwds):
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"""Factory function provided for backwards compatibility.
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Do not use in new code. Instead, import MkdirLockFile from the
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lockfile.mkdirlockfile module.
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"""
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from . import mkdirlockfile
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return _fl_helper(mkdirlockfile.MkdirLockFile, "lockfile.mkdirlockfile",
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*args, **kwds)
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def SQLiteFileLock(*args, **kwds):
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"""Factory function provided for backwards compatibility.
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Do not use in new code. Instead, import SQLiteLockFile from the
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lockfile.mkdirlockfile module.
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"""
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from . import sqlitelockfile
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return _fl_helper(sqlitelockfile.SQLiteLockFile, "lockfile.sqlitelockfile",
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*args, **kwds)
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def locked(path, timeout=None):
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"""Decorator which enables locks for decorated function.
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Arguments:
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- path: path for lockfile.
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- timeout (optional): Timeout for acquiring lock.
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Usage:
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@locked('/var/run/myname', timeout=0)
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def myname(...):
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...
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"""
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def decor(func):
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@functools.wraps(func)
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def wrapper(*args, **kwargs):
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lock = FileLock(path, timeout=timeout)
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lock.acquire()
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try:
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return func(*args, **kwargs)
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finally:
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lock.release()
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return wrapper
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return decor
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if hasattr(os, "link"):
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from . import linklockfile as _llf
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LockFile = _llf.LinkLockFile
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else:
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from . import mkdirlockfile as _mlf
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LockFile = _mlf.MkdirLockFile
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FileLock = LockFile
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