Relates to How to call a service exposed by a Kubernetes cluster from another Kubernetes cluster in same project.

Asking again since Kubernetes has been changes a lot since July.

Context:

I'm working on an infrastructure with multiple clusters serving different purposes, e.g.:

• Cluster A runs services/apps creating data for consumption
• Cluster B runs services/apps consuming data created by apps in cluster A
• Cluster C runs data services like Redis, Memcache, etc.

All clusters are in the default namespace.

Problem:

In Kubernetes, each cluster gets its own kubernetes (in the default namespace) and kube-dns (in the kube-system namespace) service with a different IP.

What happens with this setup is that, services in cluster A and B above can't discover (in service discovery terminology), let's say, Redis in cluster C. So a nslookup redis.default.svc.cluster.local from one of the services in cluster A/B comes back with ** server can't find redis.default.svc.cluster.local: NXDOMAIN. Note: This works from within cluster C.

I've read as many documents as I found about kube-dns, and pretty much all assume one cluster setup.

Clusters info:

Here are /etc/resolv.conf from two different clusters showing DNS nameservers with no common kube-dns ancestor:

Cluster A:

nameserver 10.67.240.10
nameserver 169.254.169.254
nameserver 10.240.0.1
search default.svc.cluster.local svc.cluster.local cluster.local c.project-name.internal. 1025230764914.google.internal. google.internal.

Cluster C:

nameserver 10.91.240.10
nameserver 169.254.169.254
nameserver 10.240.0.1
search default.svc.cluster.local svc.cluster.local cluster.local c.project-name.internal. google.internal.
options ndots:5

Both clusters have these services running with their respective IPs for their cluster in the kube-system namespace:

NAME                  LABELS                                                                           SELECTOR           
kube-dns              k8s-app=kube-dns,kubernetes.io/cluster-service=true,kubernetes.io/name=KubeDNS   k8s-app=kube-dns
kube-ui               k8s-app=kube-ui,kubernetes.io/cluster-service=true,kubernetes.io/name=KubeUI     k8s-app=kube-ui
monitoring-heapster   kubernetes.io/cluster-service=true,kubernetes.io/name=Heapster                   k8s-app=heapster

What is the ideal fix/update to this setup that can get the shared services discovered across all Kubernetes clusters in a GCE environment?