How to Solve Received Invalid Status Code: 404 in the Backend Server’s HTTP Response

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To resolve a 404 error in backend health for Azure Application Gateway, you should consider the following steps:

1. Check Backend Server Configuration: Ensure that the backend server is correctly configured to handle the requests being sent by the Application Gateway. A 404 error typically indicates that the requested resource is not found on the server.
2. Validate URL and Path: Confirm that the URL and path being probed by the Application Gateway are correct. If the path is incorrect or the resource does not exist, it will result in a 404 error.
3. Inspect Application Gateway Settings: Review the settings of the Application Gateway, particularly the HTTP settings and the backend pool configuration. Ensure that the backend pool is pointing to the correct server and port.
4. Check Health Probes: If you have configured custom health probes, verify that they are set up correctly and that they point to a valid endpoint on the backend server.
5. Review Application Logs: Check the logs on the backend server to see if there are any indications of why the resource is not found. This may provide insights into misconfigurations or missing resources.

By following these steps, you should be able to identify and resolve the issues causing the 404 error in backend health.

References:

• Troubleshoot backend health issues in Application Gateway

Please do not modify probes as it is showing as expected instead follow above steps to resolve backend issues

kindly accept if it helps and let us know if any further questions

Thanks
Deepanshu