A Deep Dive into Kafka Consumer Rebalance Protocols: Mechanisms and Migration Process Insights

[KIP-848](https://cwiki.apache.org/confluence/display/KAFKA/KIP-848%3A+The+Next+Generation+of+the+Consumer+Rebalance+Protocol) introduces a new consumer rebalancing protocol to Kafka that differs significantly from its existing one. This session guides attendees through a detailed comparison of the existing and new consumer rebalance protocols and a thorough examination of the migration mechanisms involved in transitioning between them.

We offer a comprehensive overview of the fundamentals underlying the classic rebalancing protocols with different assignment strategies, as well as the newly introduced incremental rebalancing protocol. The overview includes the intricacies of group coordination, partition assignment strategies of each protocol.

Following the overview, we delve deeply into the mechanisms that drive the migration process between the old and new rebalance protocols. This includes exploration of stop-the-world offline migration methodologies and the more sophisticated online migration techniques that support non-empty group conversions. Detailed case studies illustrate the steps of upgrading and downgrading consumer groups, including handling the intermediate states where the group coordinator manages membership statuses across different protocols.

Through these insights, attendees will gain an understanding of the intricacies involved in seamlessly transitioning consumer groups and the improvements brought by the new rebalance protocol. This talk will also be of particular interest to distributed systems professionals who want to know more about the internals of Apache Kafka.