class AdaptiveLock:
timeout = 600
def __init__(self):
self.method = "hard_links"
self.lock_instance = None
def lock(self, lock_file):
if self.method == "hard_links":
self.lock_instance = FluflLock(
lock_file,
lifetime=60) # seconds after which the lock is broken
try:
self.lock_instance.lock(
timeout=self.timeout) # try for a long time
return
except TimeoutError:
pass
except OSError:
pass
except PermissionError:
pass
logger.warning(
"Unable to use hard link-based file locks. "
"Trying fcntl-based file locks",
exc_info=True)
self.method = "fcntl"
if self.method == "fcntl":
self.lock_instance = FcntlLock(lock_file)
acquired = self.lock_instance.acquire(timeout=self.timeout)
if acquired:
return
logger.warning(
"Unable to use fcntl-based file locks. "
"Disabling file locks",
exc_info=True)
self.method = None
self.delay = 10.0 # use a large delay to make write collisions unlikely
def unlock(self):
if self.method == "hard_links":
self.lock_instance.unlock(
unconditionally=True) # do not raise errors in unlock
self.lock_instance = None
elif self.method == "fcntl":
self.lock_instance.release()
class AdaptiveLock:
def __init__(self, timeout: int = 180):
self.timeout = timeout
self.methods: List[str] = ["fcntl", "hard_links", "delay"]
self.lock_instance = None
def lock(self, lock_file):
if self.methods[0] == "hard_links":
self.lock_instance = FluflLock(
lock_file, lifetime=self.timeout
) # seconds after which the lock is broken
try:
self.lock_instance.lock(
timeout=self.timeout) # try for a long time
return
except (FluflLockError, TimeOutError): # timeouts etc.
pass
except OSError: # such as PermissionError
pass
logger.warning("Unable to use hard link-based file locks",
exc_info=True)
self.methods.pop(0)
self.lock(lock_file)
elif self.methods[0] == "fcntl":
self.lock_instance = FcntlLock(lock_file)
acquired = self.lock_instance.acquire(timeout=self.timeout,
delay=1)
if acquired:
return
logger.warning("Unable to use fcntl-based file locks",
exc_info=True)
self.methods.pop(0)
self.lock(lock_file)
else:
# use a random delay to make write collisions unlikely
delay = gauss(20, 5)
if delay > 0:
sleep(delay)
def unlock(self):
if self.methods[0] == "hard_links":
assert isinstance(self.lock_instance, FluflLock)
self.lock_instance.unlock(
unconditionally=True) # do not raise errors in unlock
self.lock_instance = None
elif self.methods[0] == "fcntl":
assert isinstance(self.lock_instance, FcntlLock)
self.lock_instance.release()
