Gateway HTTPRoutes entries are deleted when a specific kind is allowed on Gateway

[gmagniez]

What happened:
external-dns is deleting entries of existing Gateway API HTTPRoutes when handling an event with a new added route.
What you expected to happen:
external-dns adding a new entry for the new route and keeping existing ones

How to reproduce it (as minimally and precisely as possible):
Create a Gateway with an "allowedRoutes" filter of type kind: HTTPRoute

allowedRoutes:
      kinds:
      - kind: HTTPRoute
      namespaces:
        from: All

Anything else we need to know?:
After addind some debug logs and rebuild external-dns, it seems that the APIGroup and Kind fields of the handled HTTPRoute objects are present at external-dns startup but no more after while handling events. The problem is located here:
https://github.com/kubernetes-sigs/external-dns/blob/master/source/gateway.go#L442
But I did not find an explanation why gvk.Group and gvk.Kind are empty strings once a while.

I have added the following log line juste before the Kind check:
log.Debugf("Check for kind match for route %s/%s, gw kind: %s/%s rt kind: %s/%s", meta.Namespace, meta.Name, group, gk.Kind, gvk.Group, gvk.Kind)

At startup I see:
level=debug msg="Check for kind match for route nsA/routeA, gw kind: gateway.networking.k8s.io/HTTPRoute rt kind: gateway.networking.k8s.io/HTTPRoute"

After handling a new route:
"Check for kind match for route nsA/routeA, gw kind: gateway.networking.k8s.io/HTTPRoute rt kind: /"

Environment:

• External-DNS version (use external-dns --version): 0.12.2
• DNS provider: google
• Others: Using external-dns with gateway api v1beta1

[abursavich]

@gmagniez, thanks for the detailed issue.