16.12.2024 Problem:
The client needed to add a new data center to their existing Cassandra DB cluster for a critical project. However, upon starting Cassandra on the new server, it encountered a shutdown error due to a required node being offline. The error message, “A node required to move the data consistently is down,” indicated an issue with data consistency, requiring urgent resolution to proceed with setup.
Process:
Upon analyzing the situation, our expert identified that the client might have attempted to add nodes with pre-existing data, which can interfere with Cassandra’s bootstrapping process for new data centers. Our expert advised the client to check that the new nodes had clean disks and followed the official DataStax procedure for adding a data center to an existing setup, as outlined in the Cassandra documentation.
Our expert recommended the following steps to ensure a smooth integration:
- Clear all data on new nodes to avoid conflicts during the addition.
- Follow the documented process precisely to align with Cassandra’s expectations for new data centers here.
- Ensure consistency in seed nodes by initially setting up only one IP as the seed to simplify network configuration.
Solution:
After a few restart attempts and modifying the seed node configuration to a single IP address, Cassandra successfully initiated. The client then reverted to the original three IPs, and the cluster remained stable. Continuous monitoring was advised to identify any other potential issues.
Conclusion:
The successful addition of the new data center highlights the importance of strictly following the recommended Cassandra setup procedures. Ensuring clean nodes and consistent configuration minimized conflicts, enabling the critical project to proceed as planned. This solution also reinforces the need for a careful approach when expanding Cassandra clusters to avoid disruptions and ensure reliable data movement.