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
self.lockfile = "%s.lock" % file_name
self.file_name = file_name
self.timeout = timeout
self.delay = delay
self.jfile = JChartFile()
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.open(self.lockfile, os.O_CREAT|os.O_EXCL|os.O_RDWR)
self.jfile.change_perm(self.lockfile)
break
except OSError, e:
if e.errno != errno.EEXIST:
#raise
return False
try:
# check file creation/modification time
last_modified_time = os.path.getmtime(self.lockfile)
if (time.time() - last_modified_time) > 60 * 60 * 2:
# if file was created more than an two hours ago lets remove it. possibly it was not deleted
os.unlink(self.lockfile)
continue
except OSError:
return False
if (time.time() - start_time) >= self.timeout:
#raise FileLockException("Timeout occured.")
return False
time.sleep(self.delay)
self.is_locked = True
return True
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
self.lockfile = "%s.lock" % file_name
self.file_name = file_name
self.timeout = timeout
self.delay = delay
self.jfile = JChartFile()
