Kubernetes: load-balance across two different namespaces - kubernetes

Question

I want to deploy different versions of the same application in production:
kubectl create deployment hello-server --image=gcr.io/google-samples/hello-app:1.0 -n test-a
kubectl create deployment hello-server --image=gcr.io/google-samples/hello-app:2.0 -n test-b
kubectl expose deployment hello-server --port 80 --target-port 8080 -n test-a
kubectl expose deployment hello-server --port 80 --target-port 8080 -n test-b
I've tried to load-balance it like this:
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
name: test
annotations:
kubernetes.io/ingress.class: "nginx"
nginx.org/server-snippets: |
upstream test-servers-upstream {
server hello-server.test-a:80;
server hello-server.test-b:80;
}
spec:
rules:
- host: test-servers.example.com
http:
paths:
- path: /
backend:
serviceName: test-servers-upstream
servicePort: 80
but it returns an error:
/ test-servers-upstream:80 (<error: endpoints "test-servers-upstream" not found>)
Services:
$ kubectl get services -n test-b
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
hello-server ClusterIP 10.128.199.113 <none> 80/TCP 75m
$ kubectl get services -n test-a
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
hello-server ClusterIP 10.128.207.6 <none> 80/TCP 75m
How can I load-balance it?

Answer 1

Fresh ingress-nginx supports weight-based canary deployments out of box.
Looks like what you're asking for.
https://kubernetes.github.io/ingress-nginx/user-guide/nginx-configuration/annotations/#canary.
Great example here.
https://medium.com/#domi.stoehr/canary-deployments-on-kubernetes-without-service-mesh-425b7e4cc862
Basically, you create 2 identical ingresses, one for each namespace.
They are different only in annotations and in pointing to different services.
# ingress for a service A in namespace A
kind: Ingress
metadata:
name: demo-ingress
namespace: demo-prod
spec:
rules:
- host: canary.example.com
http:
paths:
- backend:
serviceName: demo-prod
servicePort: 80
path: /
# ingress for a service B in namespace B
# note canary annotations
kind: Ingress
metadata:
annotations:
nginx.ingress.kubernetes.io/canary: "true"
nginx.ingress.kubernetes.io/canary-weight: "20"
name: demo-ingress
namespace: demo-canary
spec:
rules:
- host: canary.example.com
http:
paths:
- backend:
serviceName: demo-canary
servicePort: 80
path: /
Note, that ingress-nginx canary implementation actually requires your services to be in different namespaces.