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 '-'.
I achieve this using Istio. It's not the main reason why we are using it, but the traffic management features allows this kind of thing.
+--Namespace A-------------------------------+
| |
| +-------+ +-------+ +--------------+ |
| |Ingress+--->Service+--->VirtualService| |
| +-------+ +-------+ +------+-------+ |
| | |
+--------------------------------------------+
|
+---------------+
|
| +--Namespace B---------+
| | |
| | +-------+ +---+ |
+--------->Service+---->Pod| |
| +-------+ +---+ |
| |
+----------------------+
With Istio you can have your ingress in one namespace, a service without Selector (because there is no pod here) and a virtual service that route the traffic on service.namespaceA to service.namespaceB.
I'am using this to achieve blue-green deployment. Imagine the same principle than above but with 3 namespaces :
The switch between blue and green version is managed by the virtualService in the namespace-A. The advantage is that you can test the green version (smoke test) using routing features of istio before release it to everyone.
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.
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.