Acknowledging a message in Pub/Sub means that you are done with it, and it will not be delivered
to this subscription again. You should avoid acknowledging messages until you have finished
processing them, so that in the event of a failure, you receive the message again.
If exactly-once delivery is enabled on the subscription, the future returned by the ack/nack
methods track the state of acknowledgement operation by the server. If the future completes
successfully, the message is guaranteed NOT to be re-delivered. Otherwise, the future will
contain an exception with more details about the failure and the message may be re-delivered.
If exactly-once delivery is NOT enabled on the subscription, the future returns immediately
with an AckResponse.SUCCESS. Because re-deliveries are possible, you should ensure that your
processing code is idempotent, as you may receive any given message more than once.
Methods
ack()
publicabstractApiFuture<AckResponse>ack()
Acknowledges that the message has been successfully processed. The service will not send the
message again.
A future representing the server response is returned
