KIP-392 — Allow consumers to fetch from closest replica

Accepted Kafka 2.3 ConsumerBroker

Adds a `client.rack` consumer configuration and corresponding broker-side rack-aware fetch logic (`ReplicaSelector` plugin) that routes consumer fetch requests to the closest in-sync replica rather than always to the partition leader. In multi-AZ or multi-DC Kafka deployments, all consumer fetches go to the leader regardless of replica locality, incurring expensive cross-AZ network traffic and latency.

Protocol Impact

Fetch

Details