def acquire_lock(lock_file, max_try=10, delay=10, max_delay=3600):
"""Acquire a lock represented by a file on the file system
If the process written in lock file doesn't exist anymore, we remove the
lock file immediately
If age of the lock_file is greater than max_delay, then we raise a UserWarning
"""
count = abs(max_try)
while count:
try:
fd = os.open(lock_file, os.O_EXCL | os.O_RDWR | os.O_CREAT)
os.write(fd, str_to_bytes(str(os.getpid())))
os.close(fd)
return True
except OSError as e:
if e.errno == errno.EEXIST:
try:
fd = open(lock_file, "r")
pid = int(fd.readline())
pi = ProcInfo(pid)
age = (time.time() - os.stat(lock_file)[stat.ST_MTIME])
if age / max_delay > 1:
raise UserWarning(
"Command '%s' (pid %s) has locked the "
"file '%s' for %s minutes" %
(pi.name(), pid, lock_file, age / 60))
except UserWarning:
raise
except NoSuchProcess:
os.remove(lock_file)
except Exception:
# The try block is not essential. can be skipped.
# Note: ProcInfo object is only available for linux
# process information are not accessible...
# or lock_file is no more present...
pass
else:
raise
count -= 1
time.sleep(delay)
else:
raise Exception('Unable to acquire %s' % lock_file)
def acquire_lock(lock_file, max_try=10, delay=10, max_delay=3600):
"""Acquire a lock represented by a file on the file system
If the process written in lock file doesn't exist anymore, we remove the
lock file immediately
If age of the lock_file is greater than max_delay, then we raise a UserWarning
"""
count = abs(max_try)
while count:
try:
fd = os.open(lock_file, os.O_EXCL | os.O_RDWR | os.O_CREAT)
os.write(fd, str_to_bytes(str(os.getpid())) )
os.close(fd)
return True
except OSError as e:
if e.errno == errno.EEXIST:
try:
fd = open(lock_file, "r")
pid = int(fd.readline())
pi = ProcInfo(pid)
age = (time.time() - os.stat(lock_file)[stat.ST_MTIME])
if age / max_delay > 1 :
raise UserWarning("Command '%s' (pid %s) has locked the "
"file '%s' for %s minutes"
% (pi.name(), pid, lock_file, age/60))
except UserWarning:
raise
except NoSuchProcess:
os.remove(lock_file)
except Exception:
# The try block is not essential. can be skipped.
# Note: ProcInfo object is only available for linux
# process information are not accessible...
# or lock_file is no more present...
pass
else:
raise
count -= 1
time.sleep(delay)
else:
raise Exception('Unable to acquire %s' % lock_file)
def test_wrong_process_and_continue(self):
fd = os.open(self.lock, os.O_EXCL | os.O_RDWR | os.O_CREAT)
os.write(fd, str_to_bytes('1111111111'))
os.close(fd)
self.assertTrue(os.path.exists(self.lock))
self.assertTrue(acquire_lock(self.lock))
def test_wrong_process(self):
fd = os.open(self.lock, os.O_EXCL | os.O_RDWR | os.O_CREAT)
os.write(fd, str_to_bytes('1111111111'))
os.close(fd)
self.assertTrue(os.path.exists(self.lock))
self.assertRaises(Exception, acquire_lock, self.lock, 1, 1)
