Controller
A Kafka controller is a server role that manages cluster metadata and coordinates partition, replica, and leader state.
Apache Kafka in Action
A Kafka controller is a broker designated to manage partition and replica state, including partition assignments and leader selection.
- How it is used
- Uses the controller to coordinate partition assignments, leader selection and recovery when brokers fail.
- How deep it goes
- Explains active and standby controllers, failure takeover and deployment counts, but does not detail the election protocol.
- Examples
- Traces a failed partition leader through controller-triggered election, client metadata refresh and reconnection.
- What you can do after
- Operate/configure it by choosing one controller-broker for local development or three or five for failure tolerance.
Kafka for Architects
A KRaft controller is a Kafka controller implementation that uses the Raft consensus protocol to manage cluster metadata and coordination.
- How it is used
- Coordinates Kafka metadata, broker health, leadership, and cluster availability as part of the platform’s control plane.
- How deep it goes
- Explains active-controller failover, metadata replication, heartbeat monitoring, partition-scale implications, and upgrade sequencing.
- Examples
- Uses a broker-controller cluster diagram, heartbeat-based failure detection, enterprise deployment planning, and rolling upgrade sequencing.
- What you can do after
- Operate/configure controller placement, quorum planning, failure expectations, partition-scale decisions, and rolling upgrades.
Related concepts
- KRaftimplements · KRaft is Apache Kafka’s Raft-based metadata-management mode, using an internal controller quorum instead of ZooKeeper.
- leader electionuses · Leader election is a distributed coordination process that selects one eligible participant to act as leader or coordinator.
- in-sync replicauses · An in-sync replica is a Kafka partition replica sufficiently caught up with its leader to remain eligible for failover.
- Kafka clusterpart of · A Kafka cluster is a group of Kafka brokers that collectively store, distribute, and serve event streams.
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