 
 module.exports = LockManager =
 	LOCK_TEST_INTERVAL: 50 # 50ms between each test of the lock
+	MAX_TEST_INTERVAL: 1000 # back off to 1s between each test of the lock
 	MAX_LOCK_WAIT_TIME: 10000 # 10s maximum time to spend trying to get the lock
 	LOCK_TTL: 30 # seconds. Time until lock auto expires in redis.
 


	getLock: (doc_id, callback = (error, lockValue) ->) ->
		startTime = Date.now()
		do attempt = () ->
			if Date.now() - startTime > LockManager.MAX_LOCK_WAIT_TIME
				e = new Error("Timeout")

				if gotLock
					callback(null, lockValue)
				else
					setTimeout attempt, testInterval
					# back off when the lock is taken to avoid overloading
					testInterval = Math.max(testInterval * 2, LockManager.MAX_TEST_INTERVAL)

	checkLock: (doc_id, callback = (err, isFree)->)->
		key = keys.blockingKey(doc_id:doc_id)
