Cassandra Database Unavailability and Performance Issues

Problem:

The client reported instances of Cassandra databases experiencing unavailability and performance degradation, leading to application connection errors. Specifically, nodes were found to be unresponsive, and memory and CPU utilization spiked unexpectedly. Additionally, there were concerns about data inconsistencies between data centers and excessive tombstones affecting performance.

Process:

Initial Investigation:

Upon initial investigation, it was observed that while the Cassandra process was running, it was not listening on the expected port (9042) on certain nodes.
Network diagnostics were performed, including netstat commands to identify any issues with port listening.

Analysis and Troubleshooting Steps:

Node-specific diagnostics were conducted, including nodetool status and netstat commands.
Cassandra services were stopped, system logs were collected, and the logs were cleared before restarting the services to capture relevant information.
Logs and configuration files from affected nodes were analyzed to identify root causes.
Anomalies such as data inconsistencies between data centers, excessive tombstones, and unexpected memory and CPU spikes were identified.
Further investigation revealed additional processes consuming memory, such as the “pmd” process, which were identified as potential contributors to memory issues.

Solution:

Immediate Actions:

Restarting Cassandra services on affected nodes to restore availability.
Clearing logs and conducting repair and cleanup tasks to address data inconsistencies and performance issues.

Long-term Solutions:

Increasing disk sizes to accommodate compaction and repair tasks.
Optimizing JVM heap sizes and system resources to prevent memory and CPU spikes.
Ensuring exclusive system resource usage for Cassandra to avoid conflicts with other processes.

Conclusion:

Here are some of the most important steps to manage Cassandra databases smoothly and avoid performance problems:

• Monitor Proactively: Set up monitoring for CPU, memory, node responsiveness, and data consistency.
• Regular Maintenance: Conduct routine tasks like repair and cleanup to optimize performance.
• Resource Optimization: Allocate resources properly, adjusting JVM heap sizes and ensuring sufficient disk space.
• Isolate Resources: Ensure Cassandra has exclusive access to system resources.
• Thorough Analysis: Investigate root causes thoroughly during troubleshooting.
• Plan for Growth: Scale resources appropriately for future capacity needs.

With these steps, navigating the world of Cassandra databases will be a breeze, ensuring reliability and stability at every turn.