@smarterclayton raised this issue in #199: how should Kubernetes support non-load-balanced and/or stateful services? Specifically, Zookeeper was the example.

Zookeeper (or etcd) exhibits 3 common problems:

1. Identification of the instance(s) clients should contact
2. Identification of peers
3. Stateful instances

And it enables master election for other replicated services, which typically share the same problems, and probably need to advertise the elected master to clients.