docs: @GlobalTransactional(timeoutMills = 300000, name = "dubbo-demo-tx")
      public void purchase(String userId, String commodityCode, int orderCount, boolean dofail) {
          log.info("purchase begin ... xid: " + RootContext.getXID());
          
          storageService.deduct(commodityCode, orderCount);
          orderService.create(userId, commodityCode, orderCount);
          
          // for test
          if (dofail)
              throw new RuntimeException("just make it failed");
      }