Elastic Bean Stalk showcasing No Data in Health for a running EC2 instance

The "No Data" status in AWS Elastic Beanstalk's health reporting for a running EC2 instance can be concerning, especially when the application appears to be functioning correctly. This status typically indicates that AWS Elastic Beanstalk and its health agent are not receiving the expected health data from your instance. Here are some potential reasons and steps to investigate:

1. Health Agent Issues: The Elastic Beanstalk health agent might not be running or communicating properly. Check if the health agent is installed and running on your EC2 instance.

2. Network Configuration: Even though you can ping external websites, there might be specific network configurations preventing the instance from communicating with Elastic Beanstalk's service endpoints. This is particularly important if you're not using a public IP address for your instance.

3. VPC Configuration: If you're using a custom VPC, ensure that it's properly configured to allow communication between your instance and Elastic Beanstalk. You might need to set up a NAT Gateway or VPC endpoints for Elastic Beanstalk to function correctly in a private subnet.

4. Security Group Settings: Verify that your security group allows outbound traffic to Elastic Beanstalk's service endpoints.

5. Instance Role Permissions: Ensure that the IAM role associated with your EC2 instance has the necessary permissions to communicate with Elastic Beanstalk.

6. Application Logs: Check your application logs for any errors that might prevent the health agent from reporting data.

7. Elastic Beanstalk Configuration: Review your environment's configuration to ensure health reporting is set up correctly.

8. Recent Changes: If this issue started recently, consider any recent changes to your application, environment, or AWS account that might have affected health reporting.

To resolve this:

1. Verify the health agent is running and properly configured.
2. Check and adjust your VPC and network settings if necessary.
3. Review security group and IAM role permissions.
4. Consider performing a rolling update of your environment to refresh the instances.
5. If the issue persists, you may need to redeploy your application to a new Elastic Beanstalk environment.

If these steps don't resolve the issue, it's advisable to contact AWS support for further assistance, as there might be underlying issues specific to your setup that require more in-depth investigation.

Sources
InstanceHealthSummary - AWS Elastic Beanstalk
Managed ALB for beanstalk | AWS re:Post
Load balancer health check fails on Elastic Beanstalk environment | AWS re:Post