Apache ZooKeeper

Apache ZooKeeper at a glance

Apache ZooKeeper is a widely used coordination service for distributed systems, providing configuration, naming and synchronization — underpinning platforms like Kafka and Hadoop. ZooKeeper ships regular releases plus security fixes; as critical coordination infrastructure, careful updates matter.

For admins ZooKeeper is often a dependency of other systems (whose version requirements matter), so coordinate updates with them. It runs as an ensemble (odd number of nodes); upgrade node-by-node in the documented way to keep the quorum, and back up the data and configuration first. ZooKeeper must be secured — it belongs strictly on a protected network with authentication and access control, never exposed, since it holds coordination state and sometimes sensitive configuration. After upgrading each node, verify it rejoins and the quorum is healthy. Note that some systems (like Kafka with KRaft) are moving away from ZooKeeper. Track the version and its support window; patchletter surfaces new ZooKeeper releases.