docs: protected boolean onStageSingle(StageSingleEvent event) {
          Assert.notNull(event.getPipelineId());
          // 根据pipeline找到对应的实例
          FastRpcStageController controller = ArbitrateFactory.getInstance(event.getPipelineId(),
                                                                           FastRpcStageController.class);
          return controller.single(event.getStage(), (EtlEventData) event.getData());
      }