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ISR information returned from metadata requests can be inconsistent with that stored/ returned from Zookeeper. Metadata is only propagated from controller to the brokers when the controller changes the leader or the ISR. However, when a follower catches up, the leader (not the controller) adds it back to ISR and updates ZK. This information is not propagated to all brokers.

Status

Current state: WIP Discarded

Discussion thread: here

JIRA: KAFKA-1367

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