@Service
public class OrderServiceImpl implements OrderService {
    ...
    @GlobalTransactional   ///  TM
    @Override
    public OperationResponse placeOrder(PlaceOrderRequestVO placeOrderRequestVO) throws Exception {
        ...

        // 扣减库存
        DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.STOCK);
        boolean operationStockResult = stockService.reduceStock(placeOrderRequestVO.getProductId(), amount);

        // 扣减余额
        DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.PAY);
        boolean operationBalanceResult = payService.reduceBalance(placeOrderRequestVO.getUserId(), price);

        ...
    }
}

@Service
@Slf4j
public class PayServiceImpl implements PayService {
    ...

    /**
     * 事务传播特性设置为 REQUIRES_NEW 开启新的事务
     *
     * @param userId 用户 ID
     * @param price  扣减金额
     */
    @Transactional(rollbackFor = Exception.class, propagation = Propagation.REQUIRES_NEW)   /// RM
    @Override
    public boolean reduceBalance(Long userId, Integer price) throws Exception {
        ...

        log.info("开始扣减用户 {} 余额", userId);
        Integer record = accountDao.reduceBalance(price);
        log.info("扣减用户 {} 余额结果:{}", userId, record > 0 ? "操作成功" : "扣减余额失败");

        return record > 0;

    }
    ...
}