Next Wednesday, December 4th, at 00:00 UTC (4pm San Francisco) there will be a Phabricator upgrade window that might last up to 2 hours.

While we expect downtime to be much shorter than that Phabricator might be unreachable in that time frame.

We are switching the production Phabricator server to a buster (Debian stable) machine.

https://phabricator.wikimedia.org/T238956