2 # Copyright (C) 2010 Gabor Rapcsanyi (rgabor@inf.u-szeged.hu), University of Szeged
6 # Redistribution and use in source and binary forms, with or without
7 # modification, are permitted provided that the following conditions
9 # 1. Redistributions of source code must retain the above copyright
10 # notice, this list of conditions and the following disclaimer.
11 # 2. Redistributions in binary form must reproduce the above copyright
12 # notice, this list of conditions and the following disclaimer in the
13 # documentation and/or other materials provided with the distribution.
15 # THIS SOFTWARE IS PROVIDED BY UNIVERSITY OF SZEGED ``AS IS'' AND ANY
16 # EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
18 # PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL UNIVERSITY OF SZEGED OR
19 # CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
20 # EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
21 # PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
22 # PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
23 # OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
25 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 """This class helps to lock files exclusively across processes."""
35 _log = logging.getLogger(__name__)
38 class FileLock(object):
40 def __init__(self, lock_file_path, max_wait_time_sec=20):
41 self._lock_file_path = lock_file_path
42 self._lock_file_descriptor = None
43 self._max_wait_time_sec = max_wait_time_sec
45 def _create_lock(self):
46 if sys.platform.startswith('linux') or sys.platform in ('darwin', 'cygwin'):
48 fcntl.flock(self._lock_file_descriptor, fcntl.LOCK_EX | fcntl.LOCK_NB)
49 elif sys.platform == 'win32':
51 msvcrt.locking(self._lock_file_descriptor, msvcrt.LK_NBLCK, 32)
53 def _remove_lock(self):
54 if sys.platform.startswith('linux') or sys.platform in ('darwin', 'cygwin'):
56 fcntl.flock(self._lock_file_descriptor, fcntl.LOCK_UN)
57 elif sys.platform == 'win32':
59 msvcrt.locking(self._lock_file_descriptor, msvcrt.LK_UNLCK, 32)
61 def acquire_lock(self):
62 self._lock_file_descriptor = os.open(self._lock_file_path, os.O_TRUNC | os.O_CREAT)
63 start_time = time.time()
69 if time.time() - start_time > self._max_wait_time_sec:
70 _log.debug("File locking failed: %s" % str(sys.exc_info()))
71 os.close(self._lock_file_descriptor)
72 self._lock_file_descriptor = None
75 def release_lock(self):
77 if self._lock_file_descriptor:
79 os.close(self._lock_file_descriptor)
80 self._lock_file_descriptor = None
81 os.unlink(self._lock_file_path)
82 except (IOError, OSError):
83 _log.debug("Warning in release lock: %s" % str(sys.exc_info()))