OpenSearch not loading dashboards after version upgrade

I understand you're experiencing issues with OpenSearch dashboards not loading after upgrading from version 2.11 to 2.15. This can be frustrating, especially when there are no visible logs to help diagnose the problem. Let's go through some steps to troubleshoot this issue:

1. First, even though the cluster health is yellow due to using a single instance, it's important to ensure that this isn't causing any underlying issues. You can use the AWS Systems Manager Automation runbook "AWSSupport-TroubleshootOpenSearchRedYellowCluster" to diagnose any potential problems related to the cluster status.

2. Since you mentioned that logs are enabled but not visible, there might be an issue with log delivery or configuration. Double-check your log settings in the OpenSearch Service console to ensure they are correctly configured and being delivered to the intended destination.

3. The dashboard loading issue could be related to compatibility problems between your custom endpoint configuration and the new OpenSearch version. Verify that your custom endpoint settings are still valid for version 2.15.

4. Sometimes, cache-related issues can occur after an upgrade. Try clearing your browser cache and cookies, then attempt to access the dashboard again.

5. It's possible that the upgrade process didn't complete successfully or left some components in an inconsistent state. You might want to consider restarting the OpenSearch process on the node. To do this:

• Go to the OpenSearch Service console
• Navigate to your domain and open the "Instance health" tab
• Select your node under "Data nodes"
• Choose "Actions" and select "Restart OpenSearch/Elasticsearch process"
• Confirm the action

6. If the issue persists, you may need to run some OpenSearch APIs to gather more information about the cluster's state and any potential issues. You can use the AWS Lambda function created by the troubleshooting automation mentioned earlier to run these APIs safely.

7. As a last resort, if none of the above steps resolve the issue, you might need to consider rolling back to the previous version (2.11) if that's feasible for your use case, and then attempt the upgrade again after further investigation.

If you continue to face issues, it would be advisable to contact AWS Support for more in-depth assistance, as they can access more detailed information about your OpenSearch Service setup and help diagnose any underlying problems that might not be immediately apparent.
Sources
Restart the OpenSearch process on a node - Amazon OpenSearch Service
AWSSupport-TroubleshootOpenSearchRedYellowCluster - AWS Systems Manager Automation runbook reference