A similar kind of automated mechanism is required in distributed systems that allow for rolling upgrades. New functionality in upgraded nodes can't break not-ye

A similar kind of automated mechanism is required in distributed systems that allow for rolling upgrades. New functionality in upgraded nodes can't break not-yet-upgraded nodes and legacy behavior in not-yet-upgraded nodes has to be tolerated in upgraded nodes but only until the entire system is upgraded and then it is prohibited. Doing this wrong results in some really hard to fix production states.