Implement static membership support

[huszkacs]

Static membership requires setting of group.instance.id, which requires JoinGroup API key version 5 and Heartbeat API Key version 3.
Documentation

Validation of new member.id is changed in later releases. When a client tries to join to a consumer group for the first time with empty memberID, server will return with an error called MEMBER_ID_REQUIRED and a generated memberID for the client. That newly generated memberID needs to be passed to connection retry. Learn more here

Pull request

[achille-roussel]

Hello @huszkacs

I noticed you closed the pull request that you had opened in relation to this issue. Do you have an update to share on the topic?

[huszkacs]

Hello @achille-roussel!

Yes, I did close that issue, because a major refactor had been merged in and my previous implementation of static membership became outdated. I am working on a new implementation using the new structure. I hope I can get it done next week.

[huszkacs]

@achille-roussel I added a small change, you can find it in the referenced pull request.

[Tang8330]

Hey @huszkacs @rhansen2 - just came across this, I see the linked PR has been closed. Are there any plans to support static memberships?

[huszkacs]

Hi! Unfortunately, I didn't touch this project for a while, but if it is something that you would love to have, I might be able to implement, but I can't estimate how much time it would take, given the amount of features might have been introduced since

[Tang8330]

I think that'd be extremely helpful - I've been debugging one of our Prod Kafka clusters (3k+ topics) and we're getting constant rebalances (using GKE auto-pilot) and I suspect there's an eviction bug with reader's internal queue: #1398

Static groups will at least reduce the amount of rebalances