def __init__(self, redisSettings=globalRedisSettings):
self.redisHostname = redisSettings['redisHostname']
self.redisPort = redisSettings['redisPort']
self.redisDb = redisSettings['redisDb']
self.prefixInRedis = redisSettings['prefixInRedis']
self.checkInterval = redisSettings['checkInterval']
self.redisConnection = redis.Redis(host=self.redisHostname,
port=self.redisPort,
db=self.redisDb)
self.lock = RedisLock(self.redisConnection,
lock_key='LOCK:WebSiteStatusService')
def _do_execute_query(parameterized_query, wlm_queue=None):
# This method should always be getting executed within a Lambda context
# Distributed dog pile lock pattern
# From: https://pypi.python.org/pypi/python-redis-lock
log.info("About to attempt acquiring lock...")
redis_client = redshift.get_redshift_cache_redis_client()
with RedisLock(redis_client, parameterized_query.cache_key, expire=300):
# Get a lock with a 5-minute lifetime since that's the maximum duration of a Lambda
# to ensure the lock is held for as long as the Python process / Lambda is running.
log.info("Lock acquired.")
return _do_execute_query_work(parameterized_query, wlm_queue)
def set(self, key, expiration):
self.lock = RedisLock(self.redis, lock_key='cyclops:lock:%s' % key, lock_timeout=5*60)
if not self.lock.acquire():
return
try:
self.redis.setex(
key,
expiration,
0
)
finally:
self.lock.release()
