Tomorrow I'm going to upgrade several of the OpenStack control nodes to Debian Buster.  Due to version incompatibilities, Buster and Stretch nodes can't cooperate in the same cluster, so I will need to switch service between clusters a couple of times.

If things go really well, this will cause only brief hiccups in the OpenStack APIs.  More likely, though, things will get a bit tangled up and Horizon will misbehave for 20-30 minutes during the transition.

The first switchover will happen between 14:00 and 15:00 tomorrow; the second switch will follow an hour or two later.

-Andrew