NOTE: As of version 2.6.1 of Puppet this function is part of the core functionality provided from Puppet Labs.
I wrote a data store for puppet called extlookup and blogged about it before. With the release of Puppet 2.6.1 today extlookup is now fully integrated upstream and the code is owned by Puppet Labs.
Very happy about this, looking forward to YAML and JSON support being added in the near future.
I’ve also just tested Puppet 2.6.1 on a number of my machines and so far no show stoppers and the basics all work with MCollective still. I’ll do some more thorough testing soon.