ZooKeeper is a distributed coordination service that plays a critical role in the management and coordination of Kafka clusters. ZooKeeper is used by Kafka to maintain the state of the cluster and to ensure that the cluster operates correctly.
In Kafka, ZooKeeper performs the following functions:
1. Cluster coordination: ZooKeeper is used to manage the configuration settings and metadata for the Kafka cluster. This includes the location of Kafka brokers, the number of partitions for each topic, and the assignment of partitions to brokers.
2. Leader election: When a broker fails or becomes unavailable, ZooKeeper is used to coordinate the election of a new leader for the partitions that were previously led by the failed broker. ZooKeeper ensures that only one broker is elected as the leader for each partition, and that all other brokers act as followers.
3. Broker registration and health checks: Kafka brokers register with ZooKeeper to announce their presence in the cluster. ZooKeeper monitors the health of each broker and is used to detect when a broker becomes unavailable or fails.
4. Config management: Kafka uses ZooKeeper to store and manage configuration settings for the cluster, including security settings, replication factors, and retention policies.
Overall, ZooKeeper plays a critical role in the management and coordination of Kafka clusters, providing a reliable and consistent way to manage the state of the cluster and ensure that it operates correctly. Without ZooKeeper, it would be much more difficult to manage and coordinate the complex interactions between Kafka brokers and clients.