27.09.2024 Problem:
Client reported an issue with Cassandra version 4 after upgrading from version 3. Running the “nodetool repair” command on a cluster with 2 data centers (3 nodes each) resulted in an error indicating that the incremental repair session failed. This issue did not occur with version 3, and all nodes showed no pending compaction tasks.
Solution:
To address this issue, in-depth investigation took place. The team explored the information provided by client and proposed the following:
Step 1: Scrubbing Each Keyspace
Description: Scrubbing a keyspace in Cassandra checks and repairs any inconsistencies in the data files of that keyspace.
Command: nodetool scrub {KEYSPACE}
Purpose: This command ensures that data within each keyspace is validated and any corrupted or inconsistent data is repaired.
Step 2: Repairing Each Keyspace
Description: Repairing a keyspace in Cassandra synchronizes data across all nodes in the cluster, ensuring consistency and resolving any data inconsistencies.
Command: nodetool repair {KEYSPACE}
Purpose: Running this command after scrubbing ensures that data on each node is consistent with the rest of the cluster, addressing any issues caused by the upgrade to Cassandra version 4.
Step 3: Sharing Outputs for Analysis
Description: After executing the scrub and repair commands on each node for each keyspace, it’s crucial to gather and share the output and logs for further analysis.
Purpose: The outputs provide insights into the success of the operations and any errors encountered, helping diagnose and troubleshoot remaining issues.
Step 4: Providing Logs and Configurations
Description: Alongside the command outputs, sharing logs and configurations from all nodes in the Cassandra cluster is essential.
Purpose: Logs and configurations offer detailed information about the state of the cluster, potential errors, and settings that may affect performance or operation.
Conclusion:
After performing the recommended steps, the client successfully resolved the issue by running “nodetool repair” on all keyspaces. The expert highlighted the importance of following proper procedures during major version upgrades and regularly running “nodetool repair” to maintain cluster health. For future upgrades, the client was provided with detailed steps to ensure a smooth transition.