Cooperative Rebalancing in the Kafka Consumer, Streams & ksqlDB

What this post added

Introduces and explains the incremental cooperative rebalancing protocol for Kafka consumers, contrasting it with the eager rebalancing protocol. Details the mechanics of the JoinGroup and SyncGroup requests, the roles of group coordinator and leader, and the partition assignor's function in the new protocol. Explains how this protocol minimizes downtime by allowing consumers to retain ownership of unassigned partitions, benefiting Kafka Streams and ksqlDB.