Good day,
I was originally discussing this on the IRC channel, #openstack, and was advised to reach out to this mailing list. In short, does OpenStack (i.e. via Heat, Senlin, Masakari, or some other feature/plugin), have the ability to perform a rolling upgrade operation on a group of VMs (i.e. similar to the "rolling update" feature in K8S, or the "instance refresh" feature in AWS auto-scaling groups / ASGs). I've reviewed the available documentation, but all documents regarding "rolling upgrades" are with respect to a rolling upgrade of the OpenStack/IaaS stack itself (i.e. operator-level functionality) as opposed to groups of VMs managed by OpenStack (i.e. user-level functionality). I'd ideally like to use built-in functionality to handle this operation, rather than writing a service from scratch.
I've also looked into tools such as Spinnaker.io and Harness.io, but could not find any FOSS or COTS tools for implementing rolling upgrades on OpenStack out-of-the-box (though if there are any options I've overlooked, I'm all ears).
Thank you.