code: public void removeService(ServiceReference reference, Object service) {
          if (serviceRegistration != null) {
              serviceRegistration.unregister();
              serviceRegistration = null;
          }
  
          String alias = this.getAlias();
          ((HttpService) service).unregister(alias);
          if (servlet instanceof WebappServlet)
              ((WebappServlet)servlet).free();
          servlet = null;
      }
docs: Http Service is down, remove my servlet.