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• Group (epoch=0)
• Empty
• Target Assignment (epoch=0)
• Empty
• Member Assignment
• Empty

* The above format represents the group state as it is persisted in the __consumer_offsets topic.

Member A joins the group. The coordinator bumps the group epoch to 1, adds A to the group, and creates an empty member assignment.

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At this point B can transitions to epoch 2 but cannot get foo-2 until A revokes it.

Note that the persisted target assignment of B already includes foo-2 here but B does not get it yet because foo-2 is not free.

• Group (epoch=2)
• A
• B
• Target Assignment (epoch=2)
• A - partitions=[foo-0, foo-1]
• B - partitions=[foo-2]
• Member Assignment
• A - epoch=1, partitions=[foo-0, foo-1, foo-2]
• B - epoch=2, partitions=[foo-2]

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