def acquire(self):
logger.debug("Acquiring lock %s" % self.lock_id)
if not os.path.exists(self.path):
self._make_lockfile()
while True:
with open(self.path, "r+") as f:
fcntl.flock(f, fcntl.LOCK_EX)
pid = _readpid(f)
if pid==None:
_writepid(f)
fcntl.flock(f, fcntl.LOCK_UN)
logger.debug("%d got lock %s" % (os.getpid(), self.lock_id))
return
elif pid == os.getpid():
fcntl.flock(f, fcntl.LOCK_UN)
raise LockError("Process %d attempting to acquire lock %s which it already holds" %
(pid, self.lock_id))
elif not is_process_alive(pid):
logger.debug("%d: Lock holder %d of lock %s is dead, taking lock for myself" %
(os.getpid(), pid, self.lock_id))
_writepid(f)
fcntl.flock(f, fcntl.LOCK_UN)
return
else:
fcntl.flock(f, fcntl.LOCK_UN)
time.sleep(TIMEOUT)
def acquire_if_available(self):
"""Attempt to get the lock. Returns (True, mypid) if the attempt
was successful and (False, holder_pid) otherwise.
"""
logger.debug("Attepting to acquire lock %s" % self.lock_id)
mypid = os.getpid()
if not os.path.exists(self.path):
self._make_lockfile()
with open(self.path, "r+") as f:
fcntl.flock(f, fcntl.LOCK_EX)
pid = _readpid(f)
if pid==None:
_writepid(f)
fcntl.flock(f, fcntl.LOCK_UN)
logger.debug("%d got lock %s" % (mypid, self.lock_id))
return (True, mypid)
elif pid == mypid:
fcntl.flock(f, fcntl.LOCK_UN)
raise LockError("Process %d attempting to acquire lock %s which it already holds" %
(pid, self.lock_id))
elif not is_process_alive(pid):
logger.debug("%d: Lock holder %d of lock %s is dead, taking lock for myself" %
(mypid, pid, self.lock_id))
_writepid(f)
fcntl.flock(f, fcntl.LOCK_UN)
return (True, mypid)
else:
fcntl.flock(f, fcntl.LOCK_UN)
return (False, pid)
def is_locked(self):
if not os.path.exists(self.path):
return False
with open(self.path, "r") as f:
fcntl.flock(f, fcntl.LOCK_EX)
pid = _readpid(f)
fcntl.flock(f, fcntl.LOCK_UN)
if pid!=None and (pid==os.getpid() or is_process_alive(pid)):
return True
else:
return False
