[KAFKA-15651] Investigate auto commit guarantees during Consumer.assign()

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Not A Problem
• Fix Version/s: 3.7.0
• Component/s: clients, consumer
• Labels: consumer-threading-refactor kip-848-preview
• Assignee: Kirk True
• Reporter: Kirk True
• Created: 19/Oct/23 21:57
• Updated: 20/Feb/24 20:46
• Resolved: 20/Oct/23 21:45

Description

In the assign() method implementation, both KafkaConsumer and PrototypeAsyncConsumer commit offsets asynchronously. Is this intentional? junrao asks in a recent PR review:

Do we guarantee that the new owner of the unsubscribed partitions could pick up the latest committed offset?

Let's confirm whether the asynchronous approach is acceptable and correct. If it is, great, let's enhance the documentation to briefly explain why. If it is not, let's correct the behavior if it's within the API semantic expectations.