Rocky 9 Instance c7i.4xlarge freezes randomly

The issue you're experiencing with your Rocky 9 EC2 instance (c7i.4xlarge) freezing randomly is concerning, and there could be several potential causes. Here are some steps you can take to troubleshoot and potentially resolve the issue:

1. Check system resources: Although you mentioned there are no monitoring graphs available when the freeze occurs, it's important to monitor CPU, memory, and disk usage during normal operation. The c7i.4xlarge instance type is quite powerful, so resource exhaustion is less likely, but still possible depending on your workload.

2. Review logs: When the instance becomes responsive again, check system logs (/var/log/messages, /var/log/syslog) for any error messages or warnings that occurred just before the freeze.

3. Use EC2 Serial Console: This tool allows you to access your instance even when it's unresponsive to network connections. It can help you diagnose issues when the instance is frozen.

4. Consider using EC2Rescue: This is an AWS tool designed to help diagnose and troubleshoot issues on Linux instances.

5. Check for hardware issues: Sometimes, instance freezes can be caused by underlying hardware problems. If the issue persists, you may want to stop the instance and start it again (not just reboot) to move it to different underlying hardware.

6. Monitor CPU credits: Although c7i instances are not burstable and don't use CPU credits like t-series instances, it's worth checking if there are any unexpected performance limitations.

7. Investigate application-specific issues: The freeze could be caused by your application or database. Review your application logs and MySQL logs for any errors or unusual behavior.

8. Create a replacement instance: If the problem persists and you need a quick solution, you can create an AMI from the problematic instance and launch a new instance using this AMI. This can help determine if the issue is specific to the current instance or if it's related to your configuration or application.

If these steps don't resolve the issue, you may need to open a support case with AWS for further assistance. They can help investigate if there are any underlying infrastructure issues causing the freezes.

Remember to implement a robust monitoring and alerting system to catch these issues early and provide more diagnostic information when they occur.

Sources
Troubleshoot Amazon EC2 instance stop issues - Amazon Elastic Compute Cloud
Troubleshoot issues with Amazon EC2 instances - Amazon Elastic Compute Cloud