how to monitor queue size of netty eventloop in netty 1.0.0

Before netty 1.0.0, we used tcpServer::bootstrap to register a gauge for pending task queue of the eventloop

factory.addServerCustomizers(httpServer -> httpServer.tcpConfiguration(
    tcpServer -> tcpServer.bootstrap(serverBootstrap -> {
          serverBootstrap.config().childGroup().forEach(eventExecutor -> {
            if (SingleThreadEventExecutor.class.isAssignableFrom(eventExecutor.getClass())) {
              SingleThreadEventExecutor singleThreadEventExecutor = (SingleThreadEventExecutor) eventExecutor;

          Gauge.builder(SERVER_PENDING_TASK_METRIC, singleThreadEventExecutor::pendingTasks)
              .description("Pending Tasks")
              .tag(SERVER_THREAD_NAME, singleThreadEventExecutor.threadProperties().name())
              .tag(SERVER_THREAD_STATE, singleThreadEventExecutor.threadProperties().state().name())
              .register(registry);
        }
      });
      return serverBootstrap;
    }
)));

starting with netty 1.0.0, bootstrap is not available anymore. how can this be done now? thx for help