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def handleJoinGroup(...)

def handleSyncGroup(...)

where we shall enforce the group size capping rules upon requests.

Proposed Changes

We shall add a config called group.max.size on the coordinator side.

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The default value 1_000_000 proposed here is based on a rough size estimation of member metadata (100B120B), so the max allowed memory usage per group is 100B 120B * 1_000_000 = 100 MB which should be sufficient large number for of 5X~10X for most use cases I know. Welcome Further discussion on this number.is welcomed on defining the default value!

Implementation wise we shall block registration of new member once a group reaches its capacity, and define a new error type:

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