[KAFKA-15277] Design & implement support for internal Consumer delegates

• Type: Sub-task
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 3.7.0
• Component/s: clients, consumer
• Labels: consumer-threading-refactor kip-848-client-support kip-848-e2e kip-848-preview
• Assignee: Kirk True
• Reporter: Kirk True
• Created: 01/Aug/23 00:11
• Updated: 19/Dec/23 02:57
• Resolved: 15/Nov/23 13:01

Description

The consumer refactoring project introduced another Consumer implementation, creating two different, coexisting implementations of the Consumer interface:

• KafkaConsumer (AKA "existing", "legacy" consumer)
• PrototypeAsyncConsumer (AKA "new", "refactored" consumer)

The goal of this task is to refactor the code via the delegation pattern so that we can keep a top-level KafkaConsumer but then delegate to another implementation under the covers. There will be two delegates at first:

• LegacyKafkaConsumer
• AsyncKafkaConsumer

LegacyKafkaConsumer essentially be a renamed KafkaConsumer. That implementation handles the existing group protocol. AsyncKafkaConsumer is renamed from PrototypeAsyncConsumer and will implement the new consumer group protocol from KIP-848. Both of those implementations will live in the "internals" sub-package to discourage their use.

This task is part of the work to implement support for the new KIP-848 consumer group protocol.

Issue Links

• relates to: KAFKA-15284 Implement GroupProtocolResolver to dynamically determine consumer group protocol
• links to: GitHub Pull Request #14664
• links to: GitHub Pull Request #14670