So, I wrote the original rolling updates spec about a year ago, and the time has come to get serious about implementation. I went through it and basically rewrote the entire thing to reflect the knowledge I have gained from a year of working with Heat. Any and all comments are welcome. I intend to start implementation very soon, as this is an important component of the HA story for TripleO: https://wiki.openstack.org/wiki/Heat/Blueprints/RollingUpdates