Classic Two Generals. "No news is good news," generally isn't a good design philosophy for systems designed to detect trouble. How do we know that stealthy ninjas haven't assassinated our sentries? Well, we haven't heard anything wrong...
anycast "canary test in progress"
edge routers store new configs
anycast "canary test PASS"
edge routers activate new config
edge routers canary test new config (and pass or revert)
edge routers report home that all is well