Troubleshooting Connectivity Issues in a Cassandra Cluster

Problem:

The client encountered challenges connecting to the cqlsh on several nodes within their Cassandra cluster. Additionally, discrepancies were noted in the output of “nodetool status” across different nodes, with certain nodes appearing as down. Seeking assistance, the client provided output files for analysis, prompting intervention to rectify the connectivity issues.

Process:

1. Check Network Connectivity: Ensure there are no network barriers such as firewalls or other tools obstructing internode communication.
2. Monitor System Metrics: Examine Load Average, CPU, Memory, Disk IO usage on all systems to identify any resource bottlenecks or abnormalities.
3. Review Configuration Consistency: Verify that all nodes within the cluster have identical configurations to maintain consistency.
4. Collect Logs and Configs: Back up logs and configuration files from all nodes and share them for further analysis.
5. Clean Logs: Clear logs folders to remove clutter and facilitate easier troubleshooting.
6. Cold Restart of Cluster: Perform a systematic restart of all nodes in the cluster: stop each node individually, then start them again one by one. Allow a grace period of 20 minutes after the restart before collecting fresh logs.
7. Evaluate Third-Party Tools: Identify any third-party tools or programs running within the cluster, such as the identified “/opt/cassandra/cassandra-reaper-3.1.1”. Evaluate their impact on cluster operations and consider temporarily disabling them for troubleshooting purposes.
8. Manual Nodetool Repair: Execute nodetool repair manually on all nodes without relying on third-party tools to ensure proper cluster maintenance.

Solution:

In response to the expert’s recommendations, the client undertook the restart of a specific node within the cluster, leading to the successful resolution of the connectivity issues. Subsequently, the client confirmed the issue’s resolution.

Conclusion:

Through diligent analysis and methodical troubleshooting procedures, the connectivity issues within the Cassandra cluster were effectively identified and resolved. This successful resolution underscores the value of proactive monitoring and timely intervention in safeguarding cluster stability and performance. Collaboration between the client and expert played a pivotal role in expediting the resolution process, minimizing operational disruption, and restoring normalcy to cluster operations.