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