KIP-966 — Eligible Leader Replicas

Accepted Kafka 3.7 Broker

Introduces Eligible Leader Replicas (ELR), a per-partition set of replicas that lost data in an unclean shutdown but are still eligible for leader election under KRaft, providing minISR-1 tolerance to data-loss unclean shutdowns. The last-replica-standing scenario allowed a single replica that suffered an unclean shutdown and lost committed data to be re-elected as leader, causing surviving replicas to truncate their logs and produce cluster-wide committed data loss.

Protocol Impact

BrokerRegistration v3/v2 · ElectLeaders · DescribeTopicPartitions

Details