We have an Azure FrontDoor (FD) configuration (backend pool and routing setup for https) that is returning 503 for our site that is hosted in a container in Azure Kubernetes Service (AKS).
We have an Azure front door configured to route to a backend that's hosted in AKS. The backend has an address of https://application-eastus2-01.application.com. We have configured the host header to send as www.application.com. I.e. it is different to the backend address.
We have setup the AKS to serve our website via a container and ingress if the host header www.application.com is used. If i run curl and postman against this AKS ingress ip and send the host header www.application.com in the request, it responds correctly with the site content. When i make the request to the address directly (from curl or postman wieh the correct host header), the site responds almosts immediately (i.e. it takes less than a second). I.e. i don't think this is a FrontDoor time out issue.
We have configured an FD backend pool so that the host header www.application.com is sent for requests to this backend ( https://application-eastus2-01.application.com). However, when i attempt to access https://www.application.com which is the address that is routed through FrontDoor for this DNS, FD responds with a 503 status. I don't think this is related to a timeout issue unless something else is misconfigured.
In looking at this Azure Monitor logs, it looks like everything is configured correctly.
I've studied this MS doc: https://docs.microsoft.com/en-us/azure/frontdoor/front-door-troubleshoot-routing
I'm at a loss as to what could be causing the 503 response. What else can we try to troubleshoot the issue?
