0.1.52 Gateway

server/internal/api/server_alerts.go

@@ -112,27 +112,34 @@ func librarySyncTitle(changed int) string {
 //
 // Only *transitions* are announced. A server that is down stays down, and repeating it
 // every minute would bury everything else.
-func (s *Server) WatchEmbyReachability(ctx context.Context, interval time.Duration) {
-	if interval <= 0 {
-		return
-	}
-	ticker := time.NewTicker(interval)
-	defer ticker.Stop()
-
+// The cadence is read on every tick rather than fixed at start-up, because it is an
+// operator setting the console can change: a loop that captured it would leave the one
+// probe an operator is most likely to want to slow down or switch off needing a restart
+// of the gateway to do either. A probe that is off still ticks, slowly, so that turning
+// it back on does not need one either.
+func (s *Server) WatchEmbyReachability(ctx context.Context) {
 	// Start out assuming reachable: a gateway booting while Emby is down should not
 	// open with a banner about a state nobody has seen change.
 	reachable := true
 	failures := 0
+	interval := s.embyHealthInterval()
 	// The same probe feeds the live state on /v1/status, so one request to Emby answers
 	// both "did this just change" and "is it working right now". Declared before the
 	// first tick so a client asking during the opening minute learns the retry interval.
-	s.embyHealth.begin(interval, time.Now().UTC())
+	s.embyHealth.retune(interval, time.Now().UTC())
+	timer := time.NewTimer(embyProbeDelay(interval))
+	defer timer.Stop()
 	for {
 		select {
 		case <-ctx.Done():
 			return
-		case <-ticker.C:
-			if s.quietTimeActive() {
+		case <-timer.C:
+			if next := s.embyHealthInterval(); next != interval {
+				interval = next
+				s.embyHealth.retune(interval, time.Now().UTC())
+			}
+			timer.Reset(embyProbeDelay(interval))
+			if interval <= 0 || s.quietTimeActive() {
 				continue
 			}
 			probeCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
@@ -160,6 +167,16 @@ func (s *Server) WatchEmbyReachability(ctx context.Context, interval time.Durati
 	}
 }
 
+// embyProbeDelay is how long to wait before looking again. With the probe switched off it
+// is the interval at which the loop asks whether it has been switched back on, which is a
+// minute because nothing is watching and nothing is being asked of Emby.
+func embyProbeDelay(interval time.Duration) time.Duration {
+	if interval <= 0 {
+		return time.Minute
+	}
+	return interval
+}
+
 // reachabilityAlert is timestamped per transition, so the "back online" banner never
 // collides with the "not responding" one it replaces.
 func (s *Server) reachabilityAlert(up bool) clientAlert {