Reduce Downtime through Upgrade Orchestration [GA] #1314

Value Prop

Upgrading GitHub Enterprise Server now requires about 20 minutes less downtime. Starting with GHES 3.21, pre-upgrade steps that previously ran during the maintenance window can now be run beforehand, while the appliance is still serving traffic.

Expected Outcome

Downtime during upgrades is one of the most significant friction points for GHES customers. Starting in 3.21, the pre-upgrade steps run while the appliance is still live, moving ~20 minutes of work outside the maintenance window and reducing total downtime accordingly.