What is ClickHouse Keeper?
ClickHouse Keeper is a built-in distributed coordination service designed specifically for ClickHouse clusters. It serves as an alternative to Apache ZooKeeper, providing essential functionality for managing distributed ClickHouse deployments. ClickHouse Keeper handles tasks such as cluster configuration storage, leader election, and distributed locking, ensuring consistency and reliability across the cluster.
Best Practices
- Use ClickHouse Keeper for new cluster deployments instead of ZooKeeper when possible.
- Deploy an odd number of Keeper nodes (e.g., 3 or 5) to ensure quorum and fault tolerance.
- Distribute Keeper nodes across different failure domains (e.g., racks or availability zones) to improve resilience.
- Monitor Keeper nodes regularly for performance and health.
- Implement proper backup and recovery strategies for Keeper data.
- Use secure communication protocols between ClickHouse nodes and Keeper instances.
Common Issues or Misuses
- Insufficient number of Keeper nodes, leading to reduced fault tolerance.
- Improper configuration of Keeper endpoints in ClickHouse server settings.
- Neglecting to monitor and maintain Keeper nodes, potentially leading to cluster instability.
- Mixing ZooKeeper and ClickHouse Keeper within the same cluster, which is not supported.
- Underestimating resource requirements for Keeper nodes in high-load scenarios.
Additional Information
ClickHouse Keeper is implemented using the RAFT consensus algorithm, which provides strong consistency guarantees. It is designed to be a drop-in replacement for ZooKeeper in ClickHouse deployments, offering improved performance and easier management due to its tight integration with ClickHouse.
Keeper supports all the necessary operations required by ClickHouse, including ephemeral nodes, sequential nodes, and watches. It also provides a compatible API for existing ZooKeeper clients, making migration from ZooKeeper to Keeper relatively straightforward.
Frequently Asked Questions
Q: How does ClickHouse Keeper compare to Apache ZooKeeper?
A: ClickHouse Keeper is specifically designed for ClickHouse and offers better integration, potentially higher performance, and easier management. It supports all necessary operations required by ClickHouse and provides a compatible API for existing ZooKeeper clients.
Q: Can I mix ZooKeeper and ClickHouse Keeper in the same cluster?
A: No, mixing ZooKeeper and ClickHouse Keeper within the same cluster is not supported. You should use either ZooKeeper or Keeper exclusively for a given ClickHouse cluster.
Q: How many ClickHouse Keeper nodes should I deploy?
A: It's recommended to deploy an odd number of Keeper nodes, typically 3 or 5, to ensure quorum and fault tolerance. The exact number depends on your cluster size and reliability requirements.
Q: Is ClickHouse Keeper suitable for large-scale production deployments?
A: Yes, ClickHouse Keeper is designed to handle large-scale production deployments. However, as with any critical component, proper planning, monitoring, and maintenance are essential for optimal performance and reliability.
Q: How do I migrate from ZooKeeper to ClickHouse Keeper?
A: Migration typically involves setting up Keeper nodes, updating ClickHouse configuration to use Keeper instead of ZooKeeper, and then gradually transitioning cluster nodes. ClickHouse provides tools and documentation to assist with this process, but it should be carefully planned and executed.
