Migrating brokers to KRaft

Migrating brokers to KRaft

Once the KRaft controller completes the metadata migration, the brokers will still be running in ZK mode. While the KRaft controller is in migration mode, it will continue sending controller RPCs to the ZK mode brokers. This includes RPCs like UpdateMetadata and LeaderAndIsr.

To migrate the brokers to KRaft, they simply need to be reconfigured as KRaft brokers and restarted. Using the above broker configuration as an example, we would replace the broker.id with node.id and add process.roles=broker. It is important that the broker maintain the same Broker/Node ID when it is restarted. The zookeeper configurations should be removed at this point.

# Sample KRaft broker server.properties listening on 9092
process.roles=broker
node.id=0
listeners=PLAINTEXT://:9092
advertised.listeners=PLAINTEXT://localhost:9092
listener.security.protocol.map=PLAINTEXT:PLAINTEXT,CONTROLLER:PLAINTEXT

# Don't set the IBP, KRaft uses "metadata.version" feature flag
# inter.broker.protocol.version=3.5

# Remove the migration enabled flag
# zookeeper.metadata.migration.enable=true

# Remove ZooKeeper client configuration
# zookeeper.connect=localhost:2181

# Keep the KRaft controller quorum configuration
controller.quorum.voters=3000@localhost:9093
controller.listener.names=CONTROLLER

Each broker is restarted with a KRaft configuration until the entire cluster is running in KRaft mode.