CR-16899-send-heartbeat (#200)

* send heartbeat

Author: ATGardner

server/application/application.go

@@ -1050,19 +1050,35 @@ func (s *Server) StartEventSource(es *events.EventSource, stream events.Eventing
 		}
 	}
 
-	events := make(chan *appv1.ApplicationWatchEvent, watchAPIBufferSize)
-
-	unsubscribe := s.appBroadcaster.Subscribe(events)
+	eventsChannel := make(chan *appv1.ApplicationWatchEvent, watchAPIBufferSize)
+	unsubscribe := s.appBroadcaster.Subscribe(eventsChannel)
+	ticker := time.NewTicker(5 * time.Second)
 	defer unsubscribe()
+	defer ticker.Stop()
 	for {
 		select {
-		case event := <-events:
+		case event := <-eventsChannel:
 			shouldProcess, ignoreResourceCache := s.applicationEventReporter.shouldSendApplicationEvent(event)
 			if !shouldProcess {
 				continue
 			}
 			ts := time.Now().Format("2006-01-02T15:04:05.000Z")
 			sendIfPermitted(event.Application, event.Type, ts, ignoreResourceCache)
+		case <-ticker.C:
+			var err error
+			ts := time.Now().Format("2006-01-02T15:04:05.000Z")
+			payload := events.EventPayload{Timestamp: ts}
+			payloadBytes, err := json.Marshal(&payload)
+			if err != nil {
+				log.Errorf("failed to marshal payload for heartbeat: %s", err.Error())
+				break
+			}
+
+			ev := &events.Event{Payload: payloadBytes, Name: es.Name}
+			if err = stream.Send(ev); err != nil {
+				log.Errorf("failed to send heartbeat: %s", err.Error())
+				break
+			}
 		case <-stream.Context().Done():
 			return nil
 		}