Status

Current state: Under Discussion

Discussion thread: TBD

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Motivation

As we are rolling out static membership for general Kafka client applications, we need to have persistent `group.instance.id` throughout restarts. One of the edge case is that we are currently using shared static integer field for thread-id incrementation for multiple stream instances on one single JVM. So it is very easily to fall into this example scenario with two stream instance A, B:

Instance A init one stream thread → Instance A init one stream thread → Instance B init one stream thread → Instance B init one stream thread

So instance ids being generated when two instances starts are : A-1, A-2, B-3, B-4

During one bounce, the order of initialization could change to:

Instance A init one stream thread → Instance B init one stream thread → Instance A init one stream thread → Instance B init one stream thread

And then change instance ids to : A-1, A-3, B-2, B-4

This means we are creating 4 new instance ids compared with previous round, so broker could no longer leverage the static information it stored. Basically, the scenario invalidates static membership effectiveness.

Proposed Changes

Describe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.

Public Interfaces

Compatibility, Deprecation, and Migration Plan

• There is no anticipated broken  

Rejected Alternatives

N/A