We'll be upgrading the cloud services OpenStack install next Tuesday, beginning at 12:00 noon UTC The entire upgrade process may take an hour or two.  Early on in the process, Horizon (and associated OpenStack APIs) will be disabled (probably for 20 to 30 minutes.)  There may also be brief network interruptions during the upgrade. Toolforge and existing VMs should be largely unaffected apart from possible network hiccups.