KIP-1123 — Rack-aware partitioning for Kafka Producer

Accepted Producer

Adds rack-aware (AZ-aware) partitioning to the Kafka producer: when client.rack is set, the producer preferentially routes to partitions whose leaders reside in the same AZ, reducing cross-AZ network traffic and latency. The default adaptive partitioner rotated across all partitions without rack awareness, causing producers to regularly send records cross-AZ and incur inter-AZ data transfer costs in cloud deployments.

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