Failed to verify the reachability of the instance - Urgent Help

Hi,

Amazon EC2 monitors the health of each EC2 instance with two status checks:

System status check

The system status check detects issues with the underlying host that your instance runs on. If the underlying host is unresponsive or unreachable due to network, hardware or software issues, then this status check fails.

Instance status check

The instance status check failure indicates an issue with the reachability of the instance. This issue occurs due to operating system-level errors such as the following:

1. Failure to boot the operating system
2. Failure to mount the volumes correctly
3. Exhausted CPU and memory
4. Kernel panic

To answer your question,

Unless you're using Route 53, you don't need to worry about it. but if you're using route53 then you might be required to update the Route 53 DNS records when the public IP changes.

Before you reboot an EC2 instance, Make sure you stop all your docker containers. Or If you rebooted your EC2 instance (without stopping docker containers), your docker containers wont get deleted, instead they get stopped (existed) status.

You can verify using ***docker ps -a *** that will show you all the docker container running/stopped stage.

Please also check the AWS knowledge Center Article that shares what to check when you get such status check error:

https://aws.amazon.com/premiumsupport/knowledge-center/ec2-linux-status-check-failure/

AWS documentation on Troubleshoot instances with failed status checks:

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/TroubleshootingInstances.html

hope this helps.

I strongly recommend you not to provide any resource details like EC2 instance id in "re:Post" since it is completely a community driven discussions and not a support center. If the issue is critical then reach out to AWS support via AWS support console.

Now coming back to your issue, I understand that the issue is intermittent. The best place to start investigating with is the OS logs, if this instance is Ubuntu, then check the log file /var/log/syslog for example,

$ sudo grep -i oom /var/log/syslog

If you find any error like below,

Out of memory: Killed process xxx(mongod) total-vm:xxx, anon-rss:xx, file-rss:0kB, shmem-rss:0kB, UID:xxpgtables:xx oom_score_adj:0 

then this means that, you EC2 instance suffered with memory. There are 2 ways to resolve the issue;

1. Identify the application and fine tune the application not to use memory more than the EC2 instance memory. You might still have performance issues with this options.
2. Upgrade the EC2 instance to next higher instance type with more memory and monitor the OS logs for memory usage.