Celilo deploys a fleet to a known, declared state. Over time, reality drifts: someone edits a config by hand, a service is left stopped, a machine falls behind. Drift detection answers a question every operator eventually asks — “is the fleet still what I said it should be?” — without having to check each system by hand.
Desired state vs. deployed state
Celilo already holds the desired state: the declared configuration of every deployed module. Drift is simply the difference between that and what’s actually running out on the fleet. The point of surfacing it is to catch the quiet divergences — the manual tweak that never made it back into config, the change that silently didn’t take — before they become the thing you’re debugging at 3am. Knowing the fleet has drifted, and where, turns a mystery into a to-do list.