| # Copyright (C) 2010 Gabor Rapcsanyi (rgabor@inf.u-szeged.hu), University of Szeged |
| # |
| # All rights reserved. |
| # |
| # Redistribution and use in source and binary forms, with or without |
| # modification, are permitted provided that the following conditions |
| # are met: |
| # 1. Redistributions of source code must retain the above copyright |
| # notice, this list of conditions and the following disclaimer. |
| # 2. Redistributions in binary form must reproduce the above copyright |
| # notice, this list of conditions and the following disclaimer in the |
| # documentation and/or other materials provided with the distribution. |
| # |
| # THIS SOFTWARE IS PROVIDED BY UNIVERSITY OF SZEGED ``AS IS'' AND ANY |
| # EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| # PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL UNIVERSITY OF SZEGED OR |
| # CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
| # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| # PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
| # PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY |
| # OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| """This class helps to lock files exclusively across processes.""" |
| |
| import logging |
| import os |
| import sys |
| import time |
| |
| |
| _log = logging.getLogger(__name__) |
| |
| |
| class FileLock(object): |
| |
| def __init__(self, lock_file_path, max_wait_time_sec=20): |
| self._lock_file_path = lock_file_path |
| self._lock_file_descriptor = None |
| self._max_wait_time_sec = max_wait_time_sec |
| |
| def _create_lock(self): |
| if sys.platform.startswith('win'): |
| import msvcrt |
| msvcrt.locking(self._lock_file_descriptor, msvcrt.LK_NBLCK, 32) |
| else: |
| import fcntl |
| fcntl.flock(self._lock_file_descriptor, fcntl.LOCK_EX | fcntl.LOCK_NB) |
| |
| def _remove_lock(self): |
| if sys.platform.startswith('win'): |
| import msvcrt |
| msvcrt.locking(self._lock_file_descriptor, msvcrt.LK_UNLCK, 32) |
| else: |
| import fcntl |
| fcntl.flock(self._lock_file_descriptor, fcntl.LOCK_UN) |
| |
| def acquire_lock(self): |
| self._lock_file_descriptor = os.open(self._lock_file_path, os.O_TRUNC | os.O_CREAT) |
| start_time = time.time() |
| while True: |
| try: |
| self._create_lock() |
| return True |
| except IOError: |
| if time.time() - start_time > self._max_wait_time_sec: |
| _log.debug("File locking failed: %s" % str(sys.exc_info())) |
| os.close(self._lock_file_descriptor) |
| self._lock_file_descriptor = None |
| return False |
| # There's no compelling reason to spin hard here, so sleep for a bit. |
| time.sleep(0.01) |
| |
| def release_lock(self): |
| try: |
| if self._lock_file_descriptor: |
| self._remove_lock() |
| os.close(self._lock_file_descriptor) |
| self._lock_file_descriptor = None |
| os.unlink(self._lock_file_path) |
| except (IOError, OSError): |
| _log.debug("Warning in release lock: %s" % str(sys.exc_info())) |
