Difference between the AckDeadline settings on the Subscription and Subscriber

[anuragm]

I am very confused by a similar setting on the Subscription and the Subscriber. This setting is the  ackDeadline.

I do understand the concept of ackDeadline as it pertains to a Subscription - acknowledge the message before a time limit or GCP will redeliver the same message. What is the concept of ackDeadline when it comes to the Subscriber?

I was reading lease management (https://cloud.google.com/pubsub/docs/lease-management) and it appears that this deadline can be extended by the Subscriber. This is a way to extend processing time of the message and asking the Subscription NOT to send the same message if the ackDeadline is extended.

1) Is my understanding correct? If so, what do these attributes in the

SubscriberClient.Settings- i) AckExtensionWindowdow ii)

MaxTotalAckExtension do?

 2) In my use-case I don't want to extend the deadline beyond a few secs and it is okay if the Subscription redelivers the message. I also want to know if I can discard the message if it goes beyond the ackDeadline in the Subscriber or the Subscription?

3)  How do these parameters behave when once delivery is set to true? Do I need to set any other attributes on the Subscription/Subscriber that affect Exactly-Once Delivery?

@ms4446 or anyone reading this can you please help? Thanks!