@Override
    public void transition(HostImpl host, HostEvent event) {
      HostHeartbeatLostEvent e = (HostHeartbeatLostEvent) event;
      // TODO Audit logs
      LOG.debug("Host transitioned to heartbeat lost state, host={}, lastHeartbeatTime={}", e.getHostName(), host.getLastHeartbeatTime());
      host.setHealthStatus(new HostHealthStatus(HealthStatus.UNKNOWN, host.getHealthStatus().getHealthReport()));
      host.setLastAgentStartTime(0);
      host.topologyManager.onHostHeartBeatLost(host);
    }
Used to publish events relating to host CRUD operations.
ambari-server/src/main/java/org/apache/ambari/server/state/host/HostImpl.java