def txn():
""" lock in transaction to avoid races between Tasks """
entity = _FantasmTaskSemaphore.get_by_key_name(self.semaphoreKey)
if entity:
if entity.payload != payload:
self.logger.critical("Run-once semaphore datastore payload read error.")
return entity.payload
def __isFirstExecution(self, taskName, retryCount):
""" Ensures that the task has not been executed before. Meant to be run in a transaction. """
firstExecution = False
keyName = '%s--%s' % (taskName, retryCount)
existingTaskName = _FantasmTaskSemaphore.get_by_key_name(keyName)
if not existingTaskName:
_FantasmTaskSemaphore(key_name=keyName).put()
firstExecution = True
return firstExecution
def txn():
""" lock in transaction to avoid races between Tasks """
entity = _FantasmTaskSemaphore.get_by_key_name(self.semaphoreKey)
if not entity:
_FantasmTaskSemaphore(key_name=self.semaphoreKey, payload=payload).put()
memcache.set(self.semaphoreKey, payload)
return (True, payload)
else:
if entity.payload != payload:
self.logger.critical("Run-once semaphore datastore payload write error.")
memcache.set(self.semaphoreKey, entity.payload) # maybe reduces chance of ejection???
return (False, entity.payload)
