@Override
    public void transition(HostImpl host, HostEvent event) {
      HostUnhealthyHeartbeatEvent e = (HostUnhealthyHeartbeatEvent) event;
      host.setLastHeartbeatTime(e.getHeartbeatTime());
      // TODO Audit logs
      LOG.debug("Host transitioned to an unhealthy state, host={}, heartbeatTime={}, healthStatus={}",
        e.getHostName(), e.getHeartbeatTime(), e.getHealthStatus());
      host.setHealthStatus(e.getHealthStatus());
    }
Used to publish events relating to host CRUD operations.
ambari-server/src/main/java/org/apache/ambari/server/state/host/HostImpl.java