update

hub/internal/monitor/staleness.go

@@ -24,6 +24,7 @@ type StalenessChecker struct {
 
 	mu            sync.Mutex
 	states        map[string]string    // customerID → "ok" | "stale" | "down"
+	downtimeStart map[string]time.Time // customerID → when node first became unreachable
 }
 
 // NewStalenessChecker creates a checker and initializes state from current data.
@@ -37,6 +38,7 @@ func NewStalenessChecker(s *store.Store, threshold time.Duration, onEvent EventN
 		logger:        logger,
 		onEvent:       onEvent,
 		states:        make(map[string]string),
+		downtimeStart: make(map[string]time.Time),
 	}
 
 	// Seed states from current report timestamps — no events on init
@@ -116,13 +118,25 @@ func (sc *StalenessChecker) Check() {
 
 		// State transition — emit event
 		sc.states[c.CustomerID] = newState
-		sc.emitTransition(c.CustomerID, oldState, newState, age)
+		if newState == "stale" && oldState == "ok" {
+			// Record when node first became unreachable
+			sc.downtimeStart[c.CustomerID] = time.Now()
+		}
+		downtimeDur := age
+		if newState == "ok" {
+			if t, ok := sc.downtimeStart[c.CustomerID]; ok {
+				downtimeDur = time.Since(t)
+			}
+			delete(sc.downtimeStart, c.CustomerID)
+		}
+		sc.emitTransition(c.CustomerID, oldState, newState, downtimeDur)
 	}
 
 	// Clean up customers that no longer have reports
 	for id := range sc.states {
 		if !seen[id] {
 			delete(sc.states, id)
+			delete(sc.downtimeStart, id)
 		}
 	}
 }