Is it possible to have an Ingress point to a Service from another namespace?

Question

What I want to do is have a service in the default namespace and ingresses in my other namespaces, which point to that service. I tried implementing the service and Ingress shown below, but it didn't work.

kind: Service
apiVersion: v1
metadata:
  name: serviceX
  namespace: default
spec:
  type: ExternalName
  externalName: serviceX.default.svc.cluster.local
ports:
- port: 123


kind: Ingress
apiVersion: extensions/v1beta1
metadata:
  name: web-ingress-test-vpndev
  namespace: my-namespace
spec:
  tls:
  - hosts:
    - abc.my-namespace.domain.com
    secretName: tls-secret-my-namespace
  rules:
  - http:
      paths:
      - path: "/"
        backend:
          serviceName: serviceX
          servicePort: 123
status:
  loadBalancer:
    ingress: {}

I know that I could implement the service in every namespace, but I was wondering if it's possible to have a single service. If I try to type the externalName of the service in the backend->serviceName handler of the ingress, I get and error saying that the name of the service can only contain numbers, letter and '-'.

Answer 1

I don't think this is possible and also don't think it's a good idea. Ingress is not a cluster level resource. Each namespace should have its own instance.

Answer 2

I would have to say that this isnt a good way. as all of ingress in different NS would be convert to Nginx Rule and take effect in ingress-controller pod.

And if you take a look the Nginx Rule(nginx.conf in ingress-controller pod), you will see each block of location in nginx.conf has variable set $namespace "****"; which means the ingress has been isolated by NS

Also, if you still want to implement your idea, might need to modify the ingress-contoller.