Message retention and acknowledgment in GCP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is message retention in Google Cloud Pub/Sub?

Message retention is the time period during which Pub/Sub keeps a message available for delivery, even if it has been acknowledged. This allows subscribers to receive messages that were published before they subscribed or to reprocess messages if needed.

beginner

What does acknowledging a message mean in Pub/Sub?

Acknowledging a message means telling Pub/Sub that the message has been successfully received and processed. Once acknowledged, Pub/Sub stops delivering that message to the subscriber.

intermediate

How long is the default message retention period in Pub/Sub?

By default, Pub/Sub retains unacknowledged messages for 7 days. This means messages can be redelivered within this time if not acknowledged.

intermediate

What happens if a subscriber does not acknowledge a message within the ack deadline?

If a message is not acknowledged within the ack deadline (default 10 seconds), Pub/Sub considers it unacknowledged and will redeliver it to the same or another subscriber.

advanced

How can you extend the time a subscriber has to acknowledge a message?

Subscribers can modify the ack deadline by sending a ModifyAckDeadline request to extend the time before the message is redelivered, allowing more time to process the message.

What does acknowledging a message in Pub/Sub do?

A Extends the message retention period

B Stops redelivery of that message

C Deletes the message from the topic

D Publishes a new message

Acknowledging a message tells Pub/Sub that the message was processed successfully and should not be redelivered.

What is the default ack deadline for a message in Pub/Sub?

A 60 seconds

B 5 seconds

C 30 seconds

D 10 seconds

The default ack deadline is 10 seconds, after which unacknowledged messages are redelivered.

How long does Pub/Sub retain unacknowledged messages by default?

A 1 day

B 3 days

C 7 days

D 30 days

Pub/Sub retains unacknowledged messages for 7 days by default.

What happens if a message is not acknowledged before the ack deadline?

A It is redelivered

B It is sent to a dead-letter queue automatically

C It is archived

D It is deleted permanently

If not acknowledged in time, the message is redelivered to subscribers.

Which method allows a subscriber to extend the ack deadline?

A modifyAckDeadline

B extendMessageRetention

C acknowledgeMessage

D renewSubscription

The modifyAckDeadline method lets subscribers extend the time to acknowledge a message.

Explain how message retention and acknowledgment work together in Google Cloud Pub/Sub.

Think about how Pub/Sub ensures messages are not lost and are processed at least once.

Describe what happens when a subscriber does not acknowledge a message within the ack deadline.

Focus on the flow of message delivery and retry.