Hi Team, I am currently operating a Kafka cluster in KRaft mode and would like to raise a few questions and suggestions regarding the cluster scale-down process.
Recently, I scaled down the cluster by removing one broker; however, I encountered a situation where the removed broker still appeared in the cluster, causing new partitions to be assigned to it. To address this, I was able to remove the broker from the controller metadata using the kafka-cluster.sh command. However, I could not find any documentation on this method, so I had to refer to the Kafka source code to discover this solution. The issue is now resolved, but I would like to ask if there is a more streamlined approach for scaling down. Additional Questions and Suggestions: 1. *Automatic Cluster Exclusion* I initially expected that a removed broker would be automatically excluded from the cluster after a certain period. However, the broker remained part of the cluster for quite some time. I am curious whether Kafka has a feature that automatically detects and excludes removed brokers from the cluster. 2. *Atomic Scale Down* If the above feature is not available, I would like to inquire if there is a way to atomically exclude a broker and simultaneously remove it from the cluster metadata. Since we manage a Kafka cluster with continuous topic creation, a non-atomic process might lead to new topics being assigned to the broker between its exclusion and metadata removal, necessitating manual partition reassignments. 3. *Documentation Enhancement (Suggestion)* While addressing the scale-down issue, I could not find any relevant information in the Kafka User Guide. I had to refer to the source code, specifically the unregister functionality, to learn that this could be done using kafka-cluster.sh. Including documentation on this process would likely make it easier for other users to manage their clusters effectively. Thank you, and I look forward to any guidance or recommendations. Best regards, hayoung
