[KAFKA-8386] Use COORDINATOR_NOT_AVAILABLE to replace UNKNOWN_MEMBER_ID when the group is not available

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.3.0
• Assignee: Boyang Chen
• Reporter: Boyang Chen
• Created: 17/May/19 22:43
• Updated: 05/Jun/19 21:41
• Resolved: 05/Jun/19 21:41

Description

When the group is dead or unavailable on the coordinator, current approach is to return `UNKNOWN_MEMBER_ID` to let the member reset generation and rejoin. It is not particularly safe for static members in this case, since resetting `member.id` could delay the detection for duplicate instance.id.

Also considering the fact that group unavailability could mostly be caused by migration, it is favorable to trigger a coordinator rediscovery immediately than one more bounce. Thus, we decide to use `COORDINATOR_NOT_AVAILABLE` as top line citizen.

Issue Links

• links to: GitHub Pull Request #6762