@RequestMapping("/status")
 public String status() throws Exception {
   StringBuilder res = new StringBuilder(navigation());
   for (ContainerStatus status : appMaster.status()) {
     res.append(status).append("<br/>");
   }
   return res.toString();
 }
 @RequestMapping("/exit")
 public void exit() throws Exception {
   appMaster.stop();
   System.exit(0);
 }
 @RequestMapping("/submit")
 public String submit() throws Exception {
   String containerId = appMaster.startNewContainer();
   return navigation() + "Container has been submitted. Id: " + containerId;
 }