分布式事务 - AT模式Dubbo集成Seata

vlambda
2020-06-29

分布式事务 - AT模式Dubbo集成Seata

本篇基于Dubbo集成Seata实现一个分布式事务的解决方案，在整个业务流程中，会涉及如下三个服务：

订单服务：用于创建订单。
账户服务：从账户中扣减余额。
库存服务：扣减指定商品的库存数量。

下图是这三个微服务的整体架构图，用户执行下单请求时，会调用下单业务的REST接口，该接口会分别调用库存服务以及订单服务。另外，订单服务还会调用账户服务先进行资金冻结，整个流程涉及这三个服务的分布式事务问题。

项目准备

基于Spring Boot + Nacos + Dubbo构建项目，包含下面这些服务：

sample-order-service，订单服务
sample-repo-service，库存服务
sample-account-service，账户服务
sample-seata-common，公共服务组件
sample-rest-web，提供统一业务的REST接口服务

其中sample-order-service、sample-repo-service、sample-account-service是基于Spring Boot + Dubbo构建的微服务，sample-rest-web提供统一的业务服务入口，sample-seata-common提供公共组件。

数据库准备

创建三个数据库：seata_order、seata_repo、seata_account，并分别在这三个数据库中创建对应的业务表。

--对应seata_order数据库CREATE TABLE 'tbl_order' ( 'id' int(11) NOT NULL AUTO_INCREMENT, 'order_no' varchar(255) DEFAULT NULL, 'user_id' varchar(255) DEFAULT NULL, 'product_code' varchar(255) DEFAULT NULL, 'count' int(11) DEFAULT 0, 'amount' int(11) DEFAULT 0, PRIMARY KEY ('id')) ENGINE=InnoDB DEFAULT CHARSET=utf-8;
--对应seata_repo数据库CREATE TABLE 'tbl_repo' ( 'id' int(11) NOT NULL AUTO_INCREMENT, 'product_code' varchar(255) DEFAULT NULL, 'name' varchar(255) DEFAULT NULL, 'count' int(11) DEFAULT 0, PRIMARY KEY ('id'), UNIQUE KEY ('product_code')) ENGINE=InnoDB DEFAULT CHARSET=utf-8;
-- 初始数据INSERT INTO 'tbl_repo' VALUES (1, 'TEST20200606001', '键盘', '1000');INSERT INTO 'tbl_repo' VALUES (2, 'TEST20200606002', '鼠标', '100');
-- 对应seata_account数据库CREATE TABLE 'tbl_account' ( 'id' int(11) NOT NULL AUTO_INCREMENT, 'user_id' varchar(255) DEFAULT NULL, 'balance' int(11) DEFAULT 0, PRIMARY KEY ('id')) ENGINE=InnoDB DEFAULT CHARSET=utf-8;--初始数据INSERT INTO 'tbl_account' VALUES (1, '1001', '10000')

核心方法说明

下面介绍部分主要代码：
sample-account-service：账户服务提供余额扣减的功能，具体代码如下：

@Slf4j@Servicepublic class AccountServiceImpl implements IAccountService{
 @Autowired AccountMapper accountMapper;
 @Override public ObjectResponse decreaseAccount(AccountDto accountDto) { ObjectResponse response=new ObjectResponse(); try{ int rs=accountMapper.decreaseAccount(accountDto.getUserId(),accountDto.getBalance().doubleValue()); if(rs>0){ response.setMsg(ResCode.SUCCESS.getMessage()); response.setCode(ResCode.SUCCESS.getCode()); return response; } response.setMsg(ResCode.FAILED.getMessage()); response.setCode(ResCode.FAILED.getCode()); }catch (Exception e){ log.error("decreaseAccount Occur Exception:"+e); response.setCode(ResCode.SYSTEM_EXCEPTION.getCode()); response.setMsg(ResCode.SYSTEM_EXCEPTION.getMessage()+"-"+e.getMessage()); } return response; }}

sample-order-service：订单服务负责创建订单，并且在创建订单之前先基于Dubbo协议调用账户服务的资金扣减接口。

@Slf4j@Servicepublic class OrderServiceImpl implements IOrderService{
 @Autowired OrderMapper orderMapper; @Autowired OrderConvert orderConvert; @Reference IAccountService accountService; @Override public ObjectResponse<OrderDto> createOrder(OrderDto orderDto) { log.info("全局事务ID："+ RootContext.getXID()); ObjectResponse response=new ObjectResponse(); try { //账户扣款 AccountDto accountDto = new AccountDto(); accountDto.setUserId(orderDto.getUserId()); accountDto.setBalance(orderDto.getOrderAmount()); ObjectResponse accountRes = accountService.decreaseAccount(accountDto); //创建订单 Order order=orderConvert.dto2Order(orderDto); order.setOrderNo(UUID.randomUUID().toString()); orderMapper.createOrder(order); //判断扣款状态(判断可以前置） if(accountRes.getCode()!=ResCode.SUCCESS.getCode()){ response.setMsg(ResCode.FAILED.getMessage()); response.setCode(ResCode.FAILED.getCode()); return response; } response.setMsg(ResCode.SUCCESS.getMessage()); response.setCode(ResCode.SUCCESS.getCode()); }catch (Exception e){ log.error("createOrder Occur Exception:"+e); response.setCode(ResCode.SYSTEM_EXCEPTION.getCode()); response.setMsg(ResCode.SYSTEM_EXCEPTION.getMessage()+"-"+e.getMessage()); } return response; }}

sample-repo-service：库存服务提供库存扣减功能：

@Slf4j@Servicepublic class RepoServiceImpl implements IRepoService{ @Autowired RepoMapper repoMapper;
 @Override public ObjectResponse decreaseRepo(ProductDto productDto) { ObjectResponse response=new ObjectResponse(); try { int repo = repoMapper.decreaseRepo(productDto.getProductCode(), productDto.getCount()); if(repo>0){ response.setMsg(ResCode.SUCCESS.getMessage()); response.setCode(ResCode.SUCCESS.getCode()); return response; } response.setMsg(ResCode.FAILED.getMessage()); response.setCode(ResCode.FAILED.getCode()); }catch (Exception e){ log.error("decreaseRepo Occur Exception:"+e); response.setCode(ResCode.SYSTEM_EXCEPTION.getCode()); response.setMsg(ResCode.SYSTEM_EXCEPTION.getMessage()+"-"+e.getMessage()); } return response; }}

sample-rest-web: 基于Spring Boot的web项目，主要用于对外提供以业务为维度的REST接口，会分别调用库存服务和订单服务，实现库存扣减及创建订单的功能。

@Slf4j@RestControllerpublic class OrderController {
 @Autowired IRestOrderService restOrderService;
 @PostMapping("/order") ObjectResponse order(@RequestBody OrderRequest orderRequest) throws Exception { return restOrderService.handleBusiness(orderRequest); }}

RestOrderServiceImpl的具体实现如下：

@Slf4j@Servicepublic class RestOrderServiceImpl implements IRestOrderService { @Reference IRepoService repoService; @Reference IOrderService orderService;
 @Override @GlobalTransactional(timeoutMills = 300000, name = "sample-rest-web") public ObjectResponse handleBusiness(OrderRequest orderRequest) throws Exception { log.info("开始全局事务:xid="+ RootContext.getXID()); log.info("begin order: "+orderRequest); //1. 扣减库存 ProductDto productDto=new ProductDto(); productDto.setProductCode(orderRequest.getProductCode()); productDto.setCount(orderRequest.getCount()); ObjectResponse repoRes=repoService.decreaseRepo(productDto); //2. 创建订单 OrderDto orderDto=new OrderDto(); orderDto.setUserId(orderRequest.getUserId()); orderDto.setOrderAmount(orderRequest.getAmount()); orderDto.setOrderCount(orderRequest.getCount()); orderDto.setProductCode(orderRequest.getProductCode()); ObjectResponse orderRes=orderService.createOrder(orderDto); if(orderRequest.getProductCode().equals("GP20200202002")){ throw new Exception("系统异常"); } ObjectResponse response=new ObjectResponse(); response.setMsg(ResCode.SUCCESS.getMessage()); response.setCode(ResCode.SUCCESS.getCode()); response.setData(orderRes.getData()); return response; }}

项目启动顺序及访问

这几个项目彼此之间存在依赖关系，项目的启动顺序为：

sample-seata-common为公共组件，需要先通过mvn install到本地仓库给其他服务依赖。
启动sample-account-service，它会被订单服务调用。
启动订单服务sample-order-service。
启动库存服务sample-repo-service。
启动sample-rest-web，它作为REST的业务入口。

整合Seata实现分布式事务

在上述流程中，加入库存扣减成功了，但是在创建订单的时候，入股由于账户资金不足导致失败，就会出现数据不一致的场景。按照正常的流程来说，被扣减的库存需要加回去，这就是一个分布式事务的场景。接下来我们在项目中整合Seata来解决该问题。

添加Seata Jar包依赖
分别在4个项目中添加Seata的starter组件依赖：

<dependency> <groupId>io.seata</groupId> <artifactId>seata-spring-boot-starter</artifactId> <version>1.0.0</version></dependency>

添加Seata配置项目
同样分别在4个项目中的application.yml文件中添加Seata的配置项：

seata: enabled: true tx-service-group: sample-rest-web transport: type: TCP server: NIO heartbeat: true #client和server通信心跳检测开关(默认为true) enable-client-batch-send-request: true thread-factory: boss-thread-prefix: NettyBoss worker-thread-prefix: NettyServerNIOWorker server-executor-thread-prefix: NettyServerBizHandler share-boss-worker: false client-selector-thread-prefix: NettyClientSelector client-selector-thread-size: 1 client-worker-thread-prefix: NettyClientWorkerThread boss-thread-size: 1 worker-thread-size: 8 shutdown: wait: 3 serialization: seata #client和server通信编解码方式 compressor: none service: vgroup-mapping: default #TC集群，需要和Seata-Server保持一致 enable-degrade: false #降级开关，默认为false，业务根据连续错误数自动降级，不走Seata事务 disable-global-transaction: false #全局事务开关，默认为false，false为开启，true为关闭 #grouplist: 192.168.216.128:8091 #TC服务列表，也就是Seata服务端地址，只有当注册中心为file时使用  client: rm: lock: lock-retry-interval: 10 lock-retry-policy-branch-rollback-on-conflict: true lock-retry-times: 30 rm-async-commit-buffer-limit: 10000 rm-report-retry-count: 5 rm-table-meta-check-enable: false rm-report-success-enable: true tm-commit-retry-count: 5 tm-rollback-retry-count: 5 undo: undo-log-table: undo_log undo-data-validation: true undo-log-serialization: jackson log: exception-rate: 100 support: spring: datasource-autoproxy: false registry: type: nacos nacos: cluster: default server-addr: 192.168.216.128:8848

上述配置中有几个配置项需要注意：

seata.support.spring.datasource-autoproxy: true 属性表示数据源自动代理开关，在sample-order-service、sample-account-service、sample-repo-service中设置为true，在sample-rest-web中设置为false，因为该项目并没有访问数据源，不需要代理。

seata: registry: type: nacos nacos: cluster: default server-addr: 192.168.216.127:8848

tx-service-group表示指定服务所属的事务分组，如果没有指定，默认使用spring.application.name加上字符串-seata-service-group。需要注意这两项配置必须要配置一项，否则会报错。

添加回滚日志表
分别在3个数据库seata-account、seata-repo、seata-order中添加一张回滚日志表，用于记录每个数据库表操作的回滚日志，当某个服务的事务出现异常时会根据该日志进行回滚。

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 DEFAULT CHARSET=utf-8;

sample-rest-web增加全局事务控制
修改sample-rest-web工程的RestOrderServiceImpl，做两件事情：

增加@GlobalTransactional全局事务注解
模拟一个异常处理，当商品编号等于某个指定的值时抛出异常，触发整个事务的回滚。

@Slf4j@Servicepublic class RestOrderServiceImpl implements IRestOrderService { @Reference IRepoService repoService; @Reference IOrderService orderService;
 @Override @GlobalTransactional(timeoutMills = 300000, name = "sample-rest-web") public ObjectResponse handleBusiness(OrderRequest orderRequest) throws Exception { log.info("开始全局事务:xid="+ RootContext.getXID()); log.info("begin order: "+orderRequest); //1. 扣减库存 ProductDto productDto=new ProductDto(); productDto.setProductCode(orderRequest.getProductCode()); productDto.setCount(orderRequest.getCount()); ObjectResponse repoRes=repoService.decreaseRepo(productDto); //2. 创建订单 OrderDto orderDto=new OrderDto(); orderDto.setUserId(orderRequest.getUserId()); orderDto.setOrderAmount(orderRequest.getAmount()); orderDto.setOrderCount(orderRequest.getCount()); orderDto.setProductCode(orderRequest.getProductCode()); ObjectResponse orderRes=orderService.createOrder(orderDto); if(orderRequest.getProductCode().equals("GP20200202002")){ throw new Exception("系统异常"); } ObjectResponse response=new ObjectResponse(); response.setMsg(ResCode.SUCCESS.getMessage()); response.setCode(ResCode.SUCCESS.getCode()); response.setData(orderRes.getData()); return response; }}