Source code for galaxy.util.filelock

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import errno
import os
import time

[docs]class FileLockException(Exception): pass
[docs]class FileLock(object): """ A file locking mechanism that has context-manager support so you can use it in a with statement. This should be relatively cross compatible as it doesn't rely on msvcrt or fcntl for the locking. """ def __init__(self, file_name, timeout=10, delay=.05): """ Prepare the file locker. Specify the file to lock and optionally the maximum timeout and the delay between each attempt to lock. """ self.is_locked = False full_path = os.path.abspath(file_name) self.lockfile = "%s.lock" % full_path self.file_name = full_path self.timeout = timeout self.delay = delay
[docs] def acquire(self): """ Acquire the lock, if possible. If the lock is in use, it check again every `wait` seconds. It does this until it either gets the lock or exceeds `timeout` number of seconds, in which case it throws an exception. """ start_time = time.time() while True: try: self.fd =, os.O_CREAT | os.O_EXCL | os.O_RDWR) break except OSError as e: if e.errno != errno.EEXIST: raise if (time.time() - start_time) >= self.timeout: raise FileLockException("Timeout occured.") time.sleep(self.delay) self.is_locked = True
[docs] def release(self): """ Get rid of the lock by deleting the lockfile. When working in a `with` statement, this gets automatically called at the end. """ if self.is_locked: os.close(self.fd) os.unlink(self.lockfile) self.is_locked = False
def __enter__(self): """ Activated when used in the with statement. Should automatically acquire a lock to be used in the with block. """ if not self.is_locked: self.acquire() return self def __exit__(self, type, value, traceback): """ Activated at the end of the with statement. It automatically releases the lock if it isn't locked. """ if self.is_locked: self.release() def __del__(self): """ Make sure that the FileLock instance doesn't leave a lockfile lying around. """ self.release()