Virtualservice: HTTP multi-match and fallback

1

Hi Guys,
I’m trying to manage 2 “hosts” on my VS and then, depending on which “host” the request is for, route to different backends versions.

So, the expected behavior is that, if I make this call I get to the v2 backend app, which is working.
curl http://$INGRESS_HOST:$INGRESS_PORT -H "Host: xp.example.com"

I would then expect that if I make the following request, I would get to the v1 backend app as a fallback but this is not working, I get a 404.
curl http://$INGRESS_HOST:$INGRESS_PORT -H "Host: www.example.com"

Here the Virtualservice configuration:

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: backend-vs
  namespace: default
spec:
  gateways: 
  - demo-gateway
  hosts:
  - "www.example.com"
  - "xp.example.com"
  http:
  - match:
    - authority: 
        exact: xp.example.com
        #regex: ^(?!.*www\.example\.com).*$
      uri:
        prefix: /
    route:
    - destination:
        host: backend.default.svc.cluster.local
        subset: v2
        port:
          number: 80
  - match:
    - uri:
        prefix: /
    route:
    - destination:
        host: backend.default.svc.cluster.local
        subset: v1
        port:
          number: 80

After few hours of attempts I’m starting wondering if this is even “supported” or if I simply miss some concept.

Could someone give me an hints?
Here I’ve created a repo to reproduce the issue on minikube, it takes 2 minutes of copy&paste to see the issue:
https://github.com/binc75/istio-vs

Thanks. Cheers
Nicola

k8s version: 1.17.0
Istio: 1.5.1