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Files
quay/util/locking.py
2020-02-05 19:55:07 -08:00

76 lines
2.3 KiB
Python

import logging
from redis import RedisError
from redlock import RedLock, RedLockError
from app import app
logger = logging.getLogger(__name__)
class LockNotAcquiredException(Exception):
"""
Exception raised if a GlobalLock could not be acquired.
"""
class GlobalLock(object):
"""
A lock object that blocks globally via Redis.
Note that Redis is not considered a tier-1 service, so this lock should not be used for any
critical code paths.
"""
def __init__(self, name, lock_ttl=600):
self._lock_name = name
self._redis_info = dict(app.config["USER_EVENTS_REDIS"])
self._redis_info.update(
{"socket_connect_timeout": 5, "socket_timeout": 5, "single_connection_client": True}
)
self._lock_ttl = lock_ttl
self._redlock = None
def __enter__(self):
if not self.acquire():
raise LockNotAcquiredException()
def __exit__(self, type, value, traceback):
self.release()
def acquire(self):
logger.debug("Acquiring global lock %s", self._lock_name)
try:
self._redlock = RedLock(
self._lock_name, connection_details=[self._redis_info], ttl=self._lock_ttl
)
acquired = self._redlock.acquire()
if not acquired:
logger.debug("Was unable to not acquire lock %s", self._lock_name)
return False
logger.debug("Acquired lock %s", self._lock_name)
return True
except RedLockError:
logger.debug("Could not acquire lock %s", self._lock_name)
return False
except RedisError as re:
logger.debug("Could not connect to Redis for lock %s: %s", self._lock_name, re)
return False
def release(self):
if self._redlock is not None:
logger.debug("Releasing lock %s", self._lock_name)
try:
self._redlock.release()
except RedLockError:
logger.debug("Could not release lock %s", self._lock_name)
except RedisError as re:
logger.debug(
"Could not connect to Redis for releasing lock %s: %s", self._lock_name, re
)
logger.debug("Released lock %s", self._lock_name)
self._redlock = None