大纲

1.生单链路的业务代码

2.生单链路中可能会出现数据不一致的问题

3.Seata AT模式下的分布式事务的原理

4.Seata AT模式下的分布式事务的读写隔离原理

5.Seata AT模式下的死锁问题以及超时机制

6.Seata AT模式下的读写隔离机制的影响

7.生单链路使用Seata AT模式的具体步骤

8.生单链路使用Seata AT模式时的原理流程

9.生单链路使用Seata AT模式时的并发问题

10.生单链路如何解决库存全局锁争用问题

1.生单链路的业务代码

(1)生成订单流程

(2)入参检查与风控检查

(3)获取商品信息与计算订单价格及验证价格

(4)锁定优惠券与商品库存

(5)新增订单到数据库

(6)发送延迟消息到MQ

(1)生成订单流程

@Service
public class OrderServiceImpl implements OrderService {...//提交订单/生成订单接口@GlobalTransactional(rollbackFor = Exception.class)@Overridepublic CreateOrderDTO createOrder(CreateOrderRequest createOrderRequest) {//1.入参检查checkCreateOrderRequestParam(createOrderRequest);//2.风控检查checkRisk(createOrderRequest);//3.获取商品信息List<ProductSkuDTO> productSkuList = listProductSkus(createOrderRequest);//4.计算订单价格CalculateOrderAmountDTO calculateOrderAmountDTO = calculateOrderAmount(createOrderRequest, productSkuList);//5.验证订单实付金额checkRealPayAmount(createOrderRequest, calculateOrderAmountDTO);//6.锁定优惠券lockUserCoupon(createOrderRequest);//7.锁定商品库存lockProductStock(createOrderRequest);//8.生成订单到数据库addNewOrder(createOrderRequest, productSkuList, calculateOrderAmountDTO);//9.发送订单延迟消息用于支付超时自动关单sendPayOrderTimeoutDelayMessage(createOrderRequest);//返回订单信息CreateOrderDTO createOrderDTO = new CreateOrderDTO();createOrderDTO.setOrderId(createOrderRequest.getOrderId());return createOrderDTO;}...
}

(2)入参检查与风控检查

@Service
public class OrderServiceImpl implements OrderService {...//检查创建订单请求参数private void checkCreateOrderRequestParam(CreateOrderRequest createOrderRequest) {ParamCheckUtil.checkObjectNonNull(createOrderRequest);//订单ID检查String orderId = createOrderRequest.getOrderId();ParamCheckUtil.checkStringNonEmpty(orderId, OrderErrorCodeEnum.ORDER_ID_IS_NULL);//业务线标识检查Integer businessIdentifier = createOrderRequest.getBusinessIdentifier();ParamCheckUtil.checkObjectNonNull(businessIdentifier, OrderErrorCodeEnum.BUSINESS_IDENTIFIER_IS_NULL);if (BusinessIdentifierEnum.getByCode(businessIdentifier) == null) {throw new OrderBizException(OrderErrorCodeEnum.BUSINESS_IDENTIFIER_ERROR);}//用户ID检查String userId = createOrderRequest.getUserId();ParamCheckUtil.checkStringNonEmpty(userId, OrderErrorCodeEnum.USER_ID_IS_NULL);//订单类型检查Integer orderType = createOrderRequest.getOrderType();ParamCheckUtil.checkObjectNonNull(businessIdentifier, OrderErrorCodeEnum.ORDER_TYPE_IS_NULL);if (OrderTypeEnum.getByCode(orderType) == null) {throw new OrderBizException(OrderErrorCodeEnum.ORDER_TYPE_ERROR);}//卖家ID检查String sellerId = createOrderRequest.getSellerId();ParamCheckUtil.checkStringNonEmpty(sellerId, OrderErrorCodeEnum.SELLER_ID_IS_NULL);//配送类型检查Integer deliveryType = createOrderRequest.getDeliveryType();ParamCheckUtil.checkObjectNonNull(deliveryType, OrderErrorCodeEnum.USER_ADDRESS_ERROR);if (DeliveryTypeEnum.getByCode(deliveryType) == null) {throw new OrderBizException(OrderErrorCodeEnum.DELIVERY_TYPE_ERROR);}//地址信息检查String province = createOrderRequest.getProvince();String city = createOrderRequest.getCity();String area = createOrderRequest.getArea();String streetAddress = createOrderRequest.getStreet();ParamCheckUtil.checkStringNonEmpty(province, OrderErrorCodeEnum.USER_ADDRESS_ERROR);ParamCheckUtil.checkStringNonEmpty(city, OrderErrorCodeEnum.USER_ADDRESS_ERROR);ParamCheckUtil.checkStringNonEmpty(area, OrderErrorCodeEnum.USER_ADDRESS_ERROR);ParamCheckUtil.checkStringNonEmpty(streetAddress, OrderErrorCodeEnum.USER_ADDRESS_ERROR);//区域ID检查String regionId = createOrderRequest.getRegionId();ParamCheckUtil.checkStringNonEmpty(regionId, OrderErrorCodeEnum.REGION_ID_IS_NULL);//经纬度检查BigDecimal lon = createOrderRequest.getLon();BigDecimal lat = createOrderRequest.getLat();ParamCheckUtil.checkObjectNonNull(lon, OrderErrorCodeEnum.USER_LOCATION_IS_NULL);ParamCheckUtil.checkObjectNonNull(lat, OrderErrorCodeEnum.USER_LOCATION_IS_NULL);//收货人信息检查String receiverName = createOrderRequest.getReceiverName();String receiverPhone = createOrderRequest.getReceiverPhone();ParamCheckUtil.checkStringNonEmpty(receiverName, OrderErrorCodeEnum.ORDER_RECEIVER_IS_NULL);ParamCheckUtil.checkStringNonEmpty(receiverPhone, OrderErrorCodeEnum.ORDER_RECEIVER_IS_NULL);//客户端设备信息检查String clientIp = createOrderRequest.getClientIp();ParamCheckUtil.checkStringNonEmpty(clientIp, OrderErrorCodeEnum.CLIENT_IP_IS_NULL);//商品条目信息检查List<CreateOrderRequest.OrderItemRequest> orderItemRequestList = createOrderRequest.getOrderItemRequestList();ParamCheckUtil.checkCollectionNonEmpty(orderItemRequestList, OrderErrorCodeEnum.ORDER_ITEM_IS_NULL);for (CreateOrderRequest.OrderItemRequest orderItemRequest : orderItemRequestList) {Integer productType = orderItemRequest.getProductType();Integer saleQuantity = orderItemRequest.getSaleQuantity();String skuCode = orderItemRequest.getSkuCode();ParamCheckUtil.checkObjectNonNull(productType, OrderErrorCodeEnum.ORDER_ITEM_PARAM_ERROR);ParamCheckUtil.checkObjectNonNull(saleQuantity, OrderErrorCodeEnum.ORDER_ITEM_PARAM_ERROR);ParamCheckUtil.checkStringNonEmpty(skuCode, OrderErrorCodeEnum.ORDER_ITEM_PARAM_ERROR);}//订单费用信息检查List<CreateOrderRequest.OrderAmountRequest> orderAmountRequestList = createOrderRequest.getOrderAmountRequestList();ParamCheckUtil.checkCollectionNonEmpty(orderAmountRequestList, OrderErrorCodeEnum.ORDER_AMOUNT_IS_NULL);for (CreateOrderRequest.OrderAmountRequest orderAmountRequest : orderAmountRequestList) {Integer amountType = orderAmountRequest.getAmountType();ParamCheckUtil.checkObjectNonNull(amountType, OrderErrorCodeEnum.ORDER_AMOUNT_TYPE_IS_NULL);if (AmountTypeEnum.getByCode(amountType) == null) {throw new OrderBizException(OrderErrorCodeEnum.ORDER_AMOUNT_TYPE_PARAM_ERROR);}}Map<Integer, Integer> orderAmountMap = orderAmountRequestList.stream().collect(Collectors.toMap(CreateOrderRequest.OrderAmountRequest::getAmountType, CreateOrderRequest.OrderAmountRequest::getAmount));//订单支付原价不能为空if (orderAmountMap.get(AmountTypeEnum.ORIGIN_PAY_AMOUNT.getCode()) == null) {throw new OrderBizException(OrderErrorCodeEnum.ORDER_ORIGIN_PAY_AMOUNT_IS_NULL);}//订单运费不能为空if (orderAmountMap.get(AmountTypeEnum.SHIPPING_AMOUNT.getCode()) == null) {throw new OrderBizException(OrderErrorCodeEnum.ORDER_SHIPPING_AMOUNT_IS_NULL);}//订单实付金额不能为空if (orderAmountMap.get(AmountTypeEnum.REAL_PAY_AMOUNT.getCode()) == null) {throw new OrderBizException(OrderErrorCodeEnum.ORDER_REAL_PAY_AMOUNT_IS_NULL);}if (StringUtils.isNotEmpty(createOrderRequest.getCouponId())) {//订单优惠券抵扣金额不能为空if (orderAmountMap.get(AmountTypeEnum.COUPON_DISCOUNT_AMOUNT.getCode()) == null) {throw new OrderBizException(OrderErrorCodeEnum.ORDER_DISCOUNT_AMOUNT_IS_NULL);}}//订单支付信息检查List<CreateOrderRequest.PaymentRequest> paymentRequestList = createOrderRequest.getPaymentRequestList();ParamCheckUtil.checkCollectionNonEmpty(paymentRequestList, OrderErrorCodeEnum.ORDER_PAYMENT_IS_NULL);for (CreateOrderRequest.PaymentRequest paymentRequest : paymentRequestList) {Integer payType = paymentRequest.getPayType();Integer accountType = paymentRequest.getAccountType();if (payType == null || PayTypeEnum.getByCode(payType) == null) {throw new OrderBizException(OrderErrorCodeEnum.PAY_TYPE_PARAM_ERROR);}if (accountType == null || AccountTypeEnum.getByCode(accountType) == null) {throw new OrderBizException(OrderErrorCodeEnum.ACCOUNT_TYPE_PARAM_ERROR);}}}//风控检查private void checkRisk(CreateOrderRequest createOrderRequest) {//调用风控服务进行风控检查CheckOrderRiskRequest checkOrderRiskRequest = createOrderRequest.clone(CheckOrderRiskRequest.class);JsonResult<CheckOrderRiskDTO> jsonResult = riskApi.checkOrderRisk(checkOrderRiskRequest);if (!jsonResult.getSuccess()) {throw new OrderBizException(jsonResult.getErrorCode(), jsonResult.getErrorMessage());}}...
}

(3)获取商品信息与计算订单价格及验证价格

@Service
public class OrderServiceImpl implements OrderService {...//获取订单条目商品信息private List<ProductSkuDTO> listProductSkus(CreateOrderRequest createOrderRequest) {List<CreateOrderRequest.OrderItemRequest> orderItemRequestList = createOrderRequest.getOrderItemRequestList();List<ProductSkuDTO> productSkuList = new ArrayList<>();for (CreateOrderRequest.OrderItemRequest orderItemRequest : orderItemRequestList) {String skuCode = orderItemRequest.getSkuCode();ProductSkuQuery productSkuQuery = new ProductSkuQuery();productSkuQuery.setSkuCode(skuCode);productSkuQuery.setSellerId(createOrderRequest.getSellerId());JsonResult<ProductSkuDTO> jsonResult = productApi.getProductSku(productSkuQuery);if (!jsonResult.getSuccess()) {throw new OrderBizException(jsonResult.getErrorCode(), jsonResult.getErrorMessage());}ProductSkuDTO productSkuDTO = jsonResult.getData();//sku不存在if (productSkuDTO == null) {throw new OrderBizException(OrderErrorCodeEnum.PRODUCT_SKU_CODE_ERROR, skuCode);}productSkuList.add(productSkuDTO);}return productSkuList;}//计算订单价格，如果使用了优惠券、红包、积分等，会一并进行扣减//@param createOrderRequest 订单信息//@param productSkuList     商品信息private CalculateOrderAmountDTO calculateOrderAmount(CreateOrderRequest createOrderRequest, List<ProductSkuDTO> productSkuList) {CalculateOrderAmountRequest calculateOrderPriceRequest = createOrderRequest.clone(CalculateOrderAmountRequest.class, CloneDirection.FORWARD);//订单条目补充商品信息Map<String, ProductSkuDTO> productSkuDTOMap = productSkuList.stream().collect(Collectors.toMap(ProductSkuDTO::getSkuCode, Function.identity()));calculateOrderPriceRequest.getOrderItemRequestList().forEach(item -> {String skuCode = item.getSkuCode();ProductSkuDTO productSkuDTO = productSkuDTOMap.get(skuCode);item.setProductId(productSkuDTO.getProductId());item.setSalePrice(productSkuDTO.getSalePrice());});//调用营销服务计算订单价格JsonResult<CalculateOrderAmountDTO> jsonResult = marketApi.calculateOrderAmount(calculateOrderPriceRequest);//检查价格计算结果if (!jsonResult.getSuccess()) {throw new OrderBizException(jsonResult.getErrorCode(), jsonResult.getErrorMessage());}CalculateOrderAmountDTO calculateOrderAmountDTO = jsonResult.getData();if (calculateOrderAmountDTO == null) {throw new OrderBizException(OrderErrorCodeEnum.CALCULATE_ORDER_AMOUNT_ERROR);}//订单费用信息List<OrderAmountDTO> orderAmountList = ObjectUtil.convertList(calculateOrderAmountDTO.getOrderAmountList(), OrderAmountDTO.class);if (orderAmountList == null || orderAmountList.isEmpty()) {throw new OrderBizException(OrderErrorCodeEnum.CALCULATE_ORDER_AMOUNT_ERROR);}//订单条目费用明细List<OrderAmountDetailDTO> orderItemAmountList = ObjectUtil.convertList(calculateOrderAmountDTO.getOrderAmountDetail(), OrderAmountDetailDTO.class);if (orderItemAmountList == null || orderItemAmountList.isEmpty()) {throw new OrderBizException(OrderErrorCodeEnum.CALCULATE_ORDER_AMOUNT_ERROR);}return calculateOrderAmountDTO;}//验证订单实付金额private void checkRealPayAmount(CreateOrderRequest createOrderRequest, CalculateOrderAmountDTO calculateOrderAmountDTO) {List<CreateOrderRequest.OrderAmountRequest> originOrderAmountRequestList = createOrderRequest.getOrderAmountRequestList();Map<Integer, CreateOrderRequest.OrderAmountRequest> originOrderAmountMap =originOrderAmountRequestList.stream().collect(Collectors.toMap(CreateOrderRequest.OrderAmountRequest::getAmountType, Function.identity()));//前端给的实付金额Integer originRealPayAmount = originOrderAmountMap.get(AmountTypeEnum.REAL_PAY_AMOUNT.getCode()).getAmount();List<CalculateOrderAmountDTO.OrderAmountDTO> orderAmountDTOList = calculateOrderAmountDTO.getOrderAmountList();Map<Integer, CalculateOrderAmountDTO.OrderAmountDTO> orderAmountMap =orderAmountDTOList.stream().collect(Collectors.toMap(CalculateOrderAmountDTO.OrderAmountDTO::getAmountType, Function.identity()));//营销计算出来的实付金额Integer realPayAmount = orderAmountMap.get(AmountTypeEnum.REAL_PAY_AMOUNT.getCode()).getAmount();if (!originRealPayAmount.equals(realPayAmount)) {//订单验价失败throw new OrderBizException(OrderErrorCodeEnum.ORDER_CHECK_REAL_PAY_AMOUNT_FAIL);}}...
}

(4)锁定优惠券与商品库存

@Service
public class OrderServiceImpl implements OrderService {...//锁定用户优惠券private void lockUserCoupon(CreateOrderRequest createOrderRequest) {String couponId = createOrderRequest.getCouponId();if (StringUtils.isEmpty(couponId)) {return;}LockUserCouponRequest lockUserCouponRequest = createOrderRequest.clone(LockUserCouponRequest.class);//调用营销服务锁定用户优惠券JsonResult<Boolean> jsonResult = marketApi.lockUserCoupon(lockUserCouponRequest);//检查锁定用户优惠券结果if (!jsonResult.getSuccess()) {throw new OrderBizException(jsonResult.getErrorCode(), jsonResult.getErrorMessage());}}//锁定商品库存private void lockProductStock(CreateOrderRequest createOrderRequest) {String orderId = createOrderRequest.getOrderId();List<LockProductStockRequest.OrderItemRequest> orderItemRequestList = ObjectUtil.convertList(createOrderRequest.getOrderItemRequestList(), LockProductStockRequest.OrderItemRequest.class);LockProductStockRequest lockProductStockRequest = new LockProductStockRequest();lockProductStockRequest.setOrderId(orderId);lockProductStockRequest.setOrderItemRequestList(orderItemRequestList);JsonResult<Boolean> jsonResult = inventoryApi.lockProductStock(lockProductStockRequest);//检查锁定商品库存结果if (!jsonResult.getSuccess()) {throw new OrderBizException(jsonResult.getErrorCode(), jsonResult.getErrorMessage());}}...
}@DubboService(version = "1.0.0", interfaceClass = MarketApi.class, retries = 0)
public class MarketApiImpl implements MarketApi {...//锁定用户优惠券记录@Overridepublic JsonResult<Boolean> lockUserCoupon(LockUserCouponRequest lockUserCouponRequest) {try {Boolean result = couponService.lockUserCoupon(lockUserCouponRequest);return JsonResult.buildSuccess(result);} catch (MarketBizException e) {log.error("biz error", e);return JsonResult.buildError(e.getErrorCode(), e.getErrorMsg());} catch (Exception e) {log.error("system error", e);return JsonResult.buildError(e.getMessage());}}...
}@Service
public class CouponServiceImpl implements CouponService {...//锁定用户优惠券@Transactional(rollbackFor = Exception.class)@Overridepublic Boolean lockUserCoupon(LockUserCouponRequest lockUserCouponRequest) {//检查入参checkLockUserCouponRequest(lockUserCouponRequest);String userId = lockUserCouponRequest.getUserId();String couponId = lockUserCouponRequest.getCouponId();CouponDO couponDO = couponDAO.getUserCoupon(userId, couponId);if (couponDO == null) {throw new MarketBizException(MarketErrorCodeEnum.USER_COUPON_IS_NULL);}//判断优惠券是否已经使用了if (CouponUsedStatusEnum.USED.getCode().equals(couponDO.getUsed())) {throw new MarketBizException(MarketErrorCodeEnum.USER_COUPON_IS_USED);}couponDO.setUsed(CouponUsedStatusEnum.USED.getCode());couponDO.setUsedTime(new Date());couponDAO.updateById(couponDO);return true;}...
}@DubboService(version = "1.0.0", interfaceClass = InventoryApi.class, retries = 0)
public class InventoryApiImpl implements InventoryApi {@Autowiredprivate InventoryService inventoryService;//锁定商品库存@Overridepublic JsonResult<Boolean> lockProductStock(LockProductStockRequest lockProductStockRequest) {try {Boolean result = inventoryService.lockProductStock(lockProductStockRequest);return JsonResult.buildSuccess(result);} catch (InventoryBizException e) {log.error("biz error", e);return JsonResult.buildError(e.getErrorCode(), e.getErrorMsg());} catch (Exception e) {log.error("system error", e);return JsonResult.buildError(e.getMessage());}}...
}@Service
public class InventoryServiceImpl implements InventoryService {...//锁定商品库存@Transactional(rollbackFor = Exception.class)@Overridepublic Boolean lockProductStock(LockProductStockRequest lockProductStockRequest) {//检查入参checkLockProductStockRequest(lockProductStockRequest);List<LockProductStockRequest.OrderItemRequest> orderItemRequestList = lockProductStockRequest.getOrderItemRequestList();for (LockProductStockRequest.OrderItemRequest orderItemRequest : orderItemRequestList) {String skuCode = orderItemRequest.getSkuCode();ProductStockDO productStockDO = productStockDAO.getBySkuCode(skuCode);if (productStockDO == null) {throw new InventoryBizException(InventoryErrorCodeEnum.PRODUCT_SKU_STOCK_ERROR);}Integer saleQuantity = orderItemRequest.getSaleQuantity();//执行库存扣减，并需要解决防止超卖的问题int nums = productStockDAO.lockProductStock(skuCode, saleQuantity);if (nums <= 0) {throw new InventoryBizException(InventoryErrorCodeEnum.LOCK_PRODUCT_SKU_STOCK_ERROR);}}return true;}...
}

(5)新增订单到数据库

@Service
public class OrderServiceImpl implements OrderService {...//新增订单数据到数据库private void addNewOrder(CreateOrderRequest createOrderRequest, List<ProductSkuDTO> productSkuList, CalculateOrderAmountDTO calculateOrderAmountDTO) {//封装新订单数据NewOrderDataHolder newOrderDataHolder = new NewOrderDataHolder();//生成主订单FullOrderData fullMasterOrderData = addNewMasterOrder(createOrderRequest, productSkuList, calculateOrderAmountDTO);//封装主订单数据到NewOrderData对象中newOrderDataHolder.appendOrderData(fullMasterOrderData);//如果存在多种商品类型，需要按商品类型进行拆单Map<Integer, List<ProductSkuDTO>> productTypeMap = productSkuList.stream().collect(Collectors.groupingBy(ProductSkuDTO::getProductType));if (productTypeMap.keySet().size() > 1) {for (Integer productType : productTypeMap.keySet()) {//生成子订单FullOrderData fullSubOrderData = addNewSubOrder(fullMasterOrderData, productType);//封装子订单数据到NewOrderData对象中newOrderDataHolder.appendOrderData(fullSubOrderData);}}//保存订单到数据库//订单信息List<OrderInfoDO> orderInfoDOList = newOrderDataHolder.getOrderInfoDOList();if (!orderInfoDOList.isEmpty()) {orderInfoDAO.saveBatch(orderInfoDOList);}//订单条目List<OrderItemDO> orderItemDOList = newOrderDataHolder.getOrderItemDOList();if (!orderItemDOList.isEmpty()) {orderItemDAO.saveBatch(orderItemDOList);}//订单配送信息List<OrderDeliveryDetailDO> orderDeliveryDetailDOList = newOrderDataHolder.getOrderDeliveryDetailDOList();if (!orderDeliveryDetailDOList.isEmpty()) {orderDeliveryDetailDAO.saveBatch(orderDeliveryDetailDOList);}//订单支付信息List<OrderPaymentDetailDO> orderPaymentDetailDOList = newOrderDataHolder.getOrderPaymentDetailDOList();if (!orderPaymentDetailDOList.isEmpty()) {orderPaymentDetailDAO.saveBatch(orderPaymentDetailDOList);}//订单费用信息List<OrderAmountDO> orderAmountDOList = newOrderDataHolder.getOrderAmountDOList();if (!orderAmountDOList.isEmpty()) {orderAmountDAO.saveBatch(orderAmountDOList);}//订单费用明细List<OrderAmountDetailDO> orderAmountDetailDOList = newOrderDataHolder.getOrderAmountDetailDOList();if (!orderAmountDetailDOList.isEmpty()) {orderAmountDetailDAO.saveBatch(orderAmountDetailDOList);}//订单状态变更日志信息List<OrderOperateLogDO> orderOperateLogDOList = newOrderDataHolder.getOrderOperateLogDOList();if (!orderOperateLogDOList.isEmpty()) {orderOperateLogDAO.saveBatch(orderOperateLogDOList);}//订单快照数据List<OrderSnapshotDO> orderSnapshotDOList = newOrderDataHolder.getOrderSnapshotDOList();if (!orderSnapshotDOList.isEmpty()) {orderSnapshotDAO.saveBatch(orderSnapshotDOList);}}//新增主订单信息订单private FullOrderData addNewMasterOrder(CreateOrderRequest createOrderRequest, List<ProductSkuDTO> productSkuList, CalculateOrderAmountDTO calculateOrderAmountDTO) {NewOrderBuilder newOrderBuilder = new NewOrderBuilder(createOrderRequest, productSkuList, calculateOrderAmountDTO, orderProperties);FullOrderData fullOrderData = newOrderBuilder.buildOrder().buildOrderItems().buildOrderDeliveryDetail().buildOrderPaymentDetail().buildOrderAmount().buildOrderAmountDetail().buildOperateLog().buildOrderSnapshot().build();//订单信息OrderInfoDO orderInfoDO = fullOrderData.getOrderInfoDO();//订单条目信息List<OrderItemDO> orderItemDOList = fullOrderData.getOrderItemDOList();//订单费用信息List<OrderAmountDO> orderAmountDOList = fullOrderData.getOrderAmountDOList();//补全地址信息OrderDeliveryDetailDO orderDeliveryDetailDO = fullOrderData.getOrderDeliveryDetailDO();String detailAddress = getDetailAddress(orderDeliveryDetailDO);orderDeliveryDetailDO.setDetailAddress(detailAddress);//补全订单状态变更日志OrderOperateLogDO orderOperateLogDO = fullOrderData.getOrderOperateLogDO();String remark = "创建订单操作0-10";orderOperateLogDO.setRemark(remark);//补全订单商品快照信息List<OrderSnapshotDO> orderSnapshotDOList = fullOrderData.getOrderSnapshotDOList();for (OrderSnapshotDO orderSnapshotDO : orderSnapshotDOList) {//优惠券信息if (orderSnapshotDO.getSnapshotType().equals(SnapshotTypeEnum.ORDER_COUPON.getCode())) {...}//订单费用信息else if (orderSnapshotDO.getSnapshotType().equals(SnapshotTypeEnum.ORDER_AMOUNT.getCode())) {orderSnapshotDO.setSnapshotJson(JsonUtil.object2Json(orderAmountDOList));}//订单条目信息else if (orderSnapshotDO.getSnapshotType().equals(SnapshotTypeEnum.ORDER_ITEM.getCode())) {orderSnapshotDO.setSnapshotJson(JsonUtil.object2Json(orderItemDOList));}}return fullOrderData;}...
}

(6)发送延迟消息到MQ

@Service
public class OrderServiceImpl implements OrderService {...//发送支付订单超时延迟消息，用于支付超时自动关单private void sendPayOrderTimeoutDelayMessage(CreateOrderRequest createOrderRequest) {PayOrderTimeoutDelayMessage message = new PayOrderTimeoutDelayMessage();message.setOrderId(createOrderRequest.getOrderId());message.setBusinessIdentifier(createOrderRequest.getBusinessIdentifier());message.setCancelType(OrderCancelTypeEnum.TIMEOUT_CANCELED.getCode());message.setUserId(createOrderRequest.getUserId());message.setOrderType(createOrderRequest.getOrderType());message.setOrderStatus(OrderStatusEnum.CREATED.getCode());String msgJson = JsonUtil.object2Json(message);defaultProducer.sendMessage(RocketMqConstant.PAY_ORDER_TIMEOUT_DELAY_TOPIC, msgJson,RocketDelayedLevel.DELAYED_30m, "支付订单超时延迟消息");}...
}@Component
public class DefaultProducer {private final DefaultMQProducer producer;@Autowiredpublic DefaultProducer(RocketMQProperties rocketMQProperties) {producer = new DefaultMQProducer(RocketMqConstant.ORDER_DEFAULT_PRODUCER_GROUP);producer.setNamesrvAddr(rocketMQProperties.getNameServer());start();}//对象在使用之前必须要调用一次，只能初始化一次public void start() {try {this.producer.start();} catch (MQClientException e) {log.error("producer start error", e);}}...//发送消息public void sendMessage(String topic, String message, Integer delayTimeLevel, String type) {Message msg = new Message(topic, message.getBytes(StandardCharsets.UTF_8));try {if (delayTimeLevel > 0) {msg.setDelayTimeLevel(delayTimeLevel);}SendResult send = producer.send(msg);if (SendStatus.SEND_OK == send.getSendStatus()) {log.info("发送MQ消息成功, type:{}, message:{}", type, message);} else {throw new OrderBizException(send.getSendStatus().toString());}} catch (Exception e) {log.error("发送MQ消息失败：", e);throw new OrderBizException(OrderErrorCodeEnum.SEND_MQ_FAILED);}}...
}

2.生单链路中可能会出现数据不一致的问题

在更新优惠券本地事务、更新库存本地事务、插入订单数据本地事务中，可能会出现优惠券和库存都已经更新成功了，但订单数据却插入失败，此时就会出现数据不一致的问题。

3.Seata AT模式下的分布式事务的原理

说明一：需要部署一个Seata Server服务器。

说明二：在各个服务的分支事务的数据库中，需要新增一张undo_log表，用来记录各个服务的分支事务失败时可以执行的回滚SQL。

说明三：当入口服务开启一个分布式事务时，需要向Seata Server开启一个全局事务。

说明四：各个服务对其分支事务的执行情况会同步给Seata Server服务器。

说明五：当Seata Server发现某分支事务失败时，便会通知各服务进行事务回滚。

说明六：当各个服务进行事务回滚时，会从undo_log表查出对应SQL去执行。

4.Seata AT模式下的分布式事务的读写隔离原理

为了避免有其他线程修改某数据后又进行回滚，就一定要加本地锁 + 全局锁。本地锁是为了避免当前机器的其他线程对数据进行修改并回滚，全局锁是为了避免分布式机器的线程对数据进行修改并回滚。

服务A在更新某数据之前，需要先获取本地锁。服务A在成功获取本地锁之后，需要插入undo log数据。接着，服务A需要向Seata Server服务器获取全局锁。服务A在成功获取全局锁之后，会提交本地事务并释放本地锁。

如果服务A对服务B进行RPC调用并提交其本地事务，则继续按前面的步骤处理服务B的数据更新。当服务B的本地事务也提交完成后，不需要继续执行其他分支事务了，服务A便可以提交分布式事务，并释放全局锁。

分布式事务的全链路在执行完毕前，对应数据的全局锁是不会释放的。

5.Seata AT模式下的死锁问题以及超时机制

Seata的一条事务链路里，每一个事务都会按如下顺序执行：首先获取本地锁更新本地数据，然后插入undo log记录，接着获取本地数据对应的全局锁，最后提交本地事务并释放本地锁。

Seata的一条事务链路里，一个事务执行完就会继续执行下一个事务。如果事务链路里的所有事务都执行完成了，那么就提交事务，并释放全局锁。如果某个事务需要回滚，那么就需要获取该事务本地数据的本地锁，然后获取undo log记录生成逆向操作的SQL语句来进行补偿和更新，补偿完毕才能释放本地数据的全局锁。

由于Seata AT模式的写隔离是通过本地数据的全局锁来实现的，所以写隔离的过程中，就涉及到了本地数据的本地锁和全局锁两把锁，这时候就很容易导致出现死锁的情况。

比如当事务1的分支事务提交数据1的本地事务后，会释放数据1的本地锁。此时事务2的分支事务就可以获取数据1的本地锁，但要等待获取事务1释放数据1的全局锁后，才能释放数据1的本地锁。如果事务1的后续分支事务出现异常需要进行回滚，那么事务1就需要获取数据1的本地锁，执行回滚补偿处理。事务1执行完分支事务的回滚补偿处理后，才能释放数据1的全局锁。

于是就出现了这样的死锁场景：事务1对数据1的回滚，占用了数据1的全局锁，需等待获取数据1的本地锁。事务2对数据1的更新，占用了数据1的本地锁，需等待获取数据1的全局锁。

Seata为了解决这个问题，会引入等待全局锁的超时机制。如果事务2在等待数据1的全局锁时出现超时，就会释放其占用的本地锁。从而让事务1能获取到数据1的本地锁，完成其事务操作，而不用一直等待。

6.Seata AT模式下的读写隔离机制的影响

由于全局锁的存在，会严重影响Seata AT分布式事务的并发吞吐量。所以除非是金融级别的系统，才会使用像Seata AT模式这么严格的事务来保证数据的强一致性。

当然，通常情况下分布式事务基本都是更新不同的数据。只要更新不同的数据，那么Seata AT分布式事务也不会出现全局锁等待。只有一些特殊情况下，才可能会出现大量分布式事务更新同一条数据。当使用Seata AT分布式事务时，特别注意尽量不要让全局锁等待。

如果不使用全局锁，那么Seata AT模式的分布式事务就会出现写未提交。就可能出现分支事务更新失败时无法回滚，因为回滚的数据已被覆盖。

Seata AT模式的分布式事务默认是读未提交的，即分布式事务在未提交前，分支事务更新的数据是可被其他事务读到的。

此外，很多公司都是使用基于RocketMQ的柔性事务来实现分布式事务。

7.生单链路使用Seata AT模式的具体步骤

(1)生单链路中分布式事务的主要分支事务

(2)订单系统 + 优惠券系统 + 商品库存系统都需要在pom.xml文件中引入Seata

(3)订单系统的生单接口作为分布式事务入口需添加@GlobalTransactional注解开启全局事务

(4)优惠券系统的锁定优惠券接口需添加Spring的事务注解@Transactional

(5)商品库存系统的锁定库存接口需添加Spring的事务注解@Transactional

(6)各分支事务操作的数据库需要添加undo log表

(1)生单链路中分布式事务的主要分支事务

分布式事务入口：订单系统的生单接口

分支事务1：优惠券系统锁定优惠券

分支事务2：商品库存系统锁定商品库存

分支事务3：订单系统创建订单数据

(2)订单系统 + 优惠券系统 + 商品库存系统都需要在pom.xml文件中引入Seata

<!-- 引入seata整合分布式事务 -->
<dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-seata</artifactId><exclusions><exclusion><groupId>io.seata</groupId><artifactId>seata-spring-boot-starter</artifactId></exclusion></exclusions>
</dependency><!-- 跟安装的seata-server需要保持版本一致 -->
<dependency><groupId>io.seata</groupId><artifactId>seata-spring-boot-starter</artifactId><version>1.3.0</version>
</dependency>

(3)订单系统的生单接口作为分布式事务入口需添加@GlobalTransactional注解开启全局事务

通过添加Seata提供的注解@GlobalTransactional来开启全局事务。

@Service
public class OrderServiceImpl implements OrderService {...//提交订单/生成订单接口//@param createOrderRequest 提交订单请求入参//@return 订单号@GlobalTransactional(rollbackFor = Exception.class)@Overridepublic CreateOrderDTO createOrder(CreateOrderRequest createOrderRequest) {//1.入参检查checkCreateOrderRequestParam(createOrderRequest);//2.风控检查checkRisk(createOrderRequest);//3.获取商品信息List<ProductSkuDTO> productSkuList = listProductSkus(createOrderRequest);//4.计算订单价格CalculateOrderAmountDTO calculateOrderAmountDTO = calculateOrderAmount(createOrderRequest, productSkuList);//5.验证订单实付金额checkRealPayAmount(createOrderRequest, calculateOrderAmountDTO);//6.锁定优惠券lockUserCoupon(createOrderRequest);//7.锁定商品库存lockProductStock(createOrderRequest);//8.生成订单到数据库addNewOrder(createOrderRequest, productSkuList, calculateOrderAmountDTO);//9.发送订单延迟消息用于支付超时自动关单sendPayOrderTimeoutDelayMessage(createOrderRequest);//返回订单信息CreateOrderDTO createOrderDTO = new CreateOrderDTO();createOrderDTO.setOrderId(createOrderRequest.getOrderId());return createOrderDTO;}...
}

(4)优惠券系统的锁定优惠券接口需添加Spring的事务注解@Transactional

通过添加Spring提供的@Transactional注解来开启本地事务。Seata会代理Spring的事务，进行本地锁申请 + undo log写入 + 全局锁请求 + 提交/回滚本地事务等操作。

@Service
public class CouponServiceImpl implements CouponService {...//锁定用户优惠券@Transactional(rollbackFor = Exception.class)@Overridepublic Boolean lockUserCoupon(LockUserCouponRequest lockUserCouponRequest) {//检查入参checkLockUserCouponRequest(lockUserCouponRequest);String userId = lockUserCouponRequest.getUserId();String couponId = lockUserCouponRequest.getCouponId();CouponDO couponDO = couponDAO.getUserCoupon(userId, couponId);if (couponDO == null) {throw new MarketBizException(MarketErrorCodeEnum.USER_COUPON_IS_NULL);}//判断优惠券是否已经使用了if (CouponUsedStatusEnum.USED.getCode().equals(couponDO.getUsed())) {throw new MarketBizException(MarketErrorCodeEnum.USER_COUPON_IS_USED);}couponDO.setUsed(CouponUsedStatusEnum.USED.getCode());couponDO.setUsedTime(new Date());couponDAO.updateById(couponDO);return true;}...
}

(5)商品库存系统的锁定库存接口需添加Spring的事务注解@Transactional

通过添加Spring提供的@Transactional注解来开启本地事务。Seata会代理Spring的事务，进行本地锁申请 + undo log写入 + 全局锁请求 + 提交/回滚本地事务等操作。

@Service
public class InventoryServiceImpl implements InventoryService {...//锁定商品库存@Transactional(rollbackFor = Exception.class)@Overridepublic Boolean lockProductStock(LockProductStockRequest lockProductStockRequest) {//检查入参checkLockProductStockRequest(lockProductStockRequest);List<LockProductStockRequest.OrderItemRequest> orderItemRequestList = lockProductStockRequest.getOrderItemRequestList();for (LockProductStockRequest.OrderItemRequest orderItemRequest : orderItemRequestList) {String skuCode = orderItemRequest.getSkuCode();ProductStockDO productStockDO = productStockDAO.getBySkuCode(skuCode);if (productStockDO == null) {throw new InventoryBizException(InventoryErrorCodeEnum.PRODUCT_SKU_STOCK_ERROR);}Integer saleQuantity = orderItemRequest.getSaleQuantity();//执行库存扣减，并需要解决防止超卖的问题int nums = productStockDAO.lockProductStock(skuCode, saleQuantity);if (nums <= 0) {throw new InventoryBizException(InventoryErrorCodeEnum.LOCK_PRODUCT_SKU_STOCK_ERROR);}}return true;}...
}

(6)各分支事务操作的数据库需要添加undo log表

订单系统的数据库 + 优惠券系统的数据库 + 库存系统的数据库，都需要添加如下一张undo_log表，提供给Seata使用。

CREATE TABLE `undo_log` (`id` bigint(20) NOT NULL AUTO_INCREMENT,`branch_id` bigint(20) NOT NULL,`xid` varchar(100) NOT NULL,`context` varchar(128) NOT NULL,`rollback_info` longblob NOT NULL,`log_status` int(11) NOT NULL,`log_created` datetime NOT NULL,`log_modified` datetime NOT NULL,PRIMARY KEY (`id`),UNIQUE KEY `ux_undo_log` (`xid`,`branch_id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

8.生单链路使用Seata AT模式时的原理流程

(1)undo log的生成

(2)生单链路使用Seata AT模式时的原理流程

(1)undo log的生成

首先根据更新字段查询出前镜像Before Image，然后进行本地事务的更新，接着根据更新字段查询出更新后的后镜像After Image，这样就可以根据前后镜像 + 执行SQL语句的基本信息拼成一条undo log。

分布式事务入口会向Seata Server注册一个全局事务XID，分支事务会向Seata Server注册一个分支事务Branch ID。

如下是Seata官网提供的一条undo log数据示例：

{"branchId": 641789253,"undoItems": [{"afterImage": {"rows": [{"fields": [{"name": "id","type": 4,"value": 1}, {"name": "name","type": 12,"value": "GTS"}, {"name": "since","type": 12,"value": "2014"}]}],"tableName": "product"},"beforeImage": {"rows": [{"fields": [{"name": "id","type": 4,"value": 1}, {"name": "name","type": 12,"value": "TXC"}, {"name": "since","type": 12,"value": "2014"}]}],"tableName": "product"},"sqlType": "UPDATE"}],"xid": "xid:xxx"
}

(2)生单链路使用Seata AT模式时的原理流程