[yourabi]

I use ZooKeeper in production for snitch.io.

There are some interesting new alternatives such as etcd / serf/consul - but at the time ZooKeeper had the best track record (under Jepsen analysis). Things might have changed since then.

Aphyr has done a bunch of analysis of these systems part of his Jepsen tool: http://aphyr.com/tags/jepsen and http://aphyr.com/posts/291-call-me-maybe-zookeepe

If you are going to use ZooKeeper I strongly suggest looking at both Apache Curator and Netflix Exhibitor (they are complimentary).

The examples bundled with ZK don't handle all errors/edge cases...

Curator is a library of common patterns available to use mostly out of the box.

Exhibitor is a ZooKeeper "aware" supervisor system: https://github.com/Netflix/exhibitor

Also always remember your ensemble should have an odd number of nodes (3,5,7)