这个时候全局事务的提交就变得十分轻量级，就是把 undo_log 对应的记录删掉即可，即使是当时删除失败了，也已经不会影响全局事 务的最终结果，这次删不了，那就待会再删，程序删不了，没事，顶多人工删。

1.4.全局事务回滚流程

如果全局事务的任何一个事务分支失败了，那么全局事务就进入“回滚“流程，回滚时依据先前保存好数据镜像，将原来的数据回放回去。

如果全局回放成功，那么数据的一致性也就得到了保证，如果回放不成功，那么事务就进入异常。应对异常，可能需要重试，可能需要人工介入。

2.Seata 在 dubbo 中的使用

2.1.新增 mvn 依赖

在需要增加分布式事务的模块加上相关依赖

1. <dependency>
   

2. <groupId>io.seata</groupId>
   

3. <artifactId>seata-spring-boot-starter</artifactId>
   

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<version>1.1.0</version>

5. </dependency>
   

2.2.修改 properties 文件

1. #服务名称
   

2. dubbo.application.name=service
   

3. #注册中心地址
   

4. dubbo.registry.address=127.0.0.1:2181
   

5. #注册中心类型
   

6. dubbo.registry.protocol=zookeeper
   

7. #版本号
   

8. dubbo.application.version=3
   

9. # Dubbo Protocol
   

10. #协议名称
    

11. dubbo.protocol.name=dubbo
    

12. #服务暴露端口
    

13. dubbo.protocol.port=20880
    

14. seata.enabled=true
    

15. seata.application-id=biz-service
    

16. seata.tx-service-group=my_test_tx_group
    

17. seata.client.rm.async-commit-buffer-limit=1000
    

18. seata.client.rm.report-retry-count=5
    

19. seata.client.rm.table-meta-check-enable=false
    

20. seata.client.rm.report-success-enable=false
    

21. seata.client.rm.lock.retry-interval=10
    

22. seata.client.rm.lock.retry-times=30
    

23. seata.client.rm.lock.retry-policy-branch-rollback-on-conflict=true
    

24. seata.client.tm.commit-retry-count=5
    

25. seata.client.tm.rollback-retry-count=5
    

26. seata.client.undo.data-validation=true
    

27. seata.client.undo.log-serialization=jackson
    

28. seata.client.undo.log-table=undo_log
    

29. seata.client.log.exceptionRate=100
    

30. seata.service.vgroup-mapping.my_test_tx_group=default
    

31. seata.service.grouplist.default=127.0.0.1:8091
    

32. seata.transport.shutdown.wait=3
    

33. seata.transport.thread-factory.boss-thread-prefix=NettyBoss
    

34. seata.transport.thread-factory.worker-thread-prefix=NettyServerNIOWorker
    

35. seata.transport.thread-factory.server-executor-thread-prefix=NettyServerBizHandler
    

36. seata.transport.thread-factory.share-boss-worker=false
    

37. seata.transport.thread-factory.client-selector-thread-prefix=NettyClientSelector
    

38. seata.transport.thread-factory.client-selector-thread-size=1
    

39. seata.transport.thread-factory.client-worker-thread-prefix=NettyClientWorkerThread
    

40. seata.transport.thread-factory.worker-thread-size=default
    

41. seata.transport.thread-factory.boss-thread-size=1
    

42. seata.transport.type=TCP
    

43. seata.transport.server=NIO
    

44. seata.transport.heartbeat=true
    

45. seata.transport.serialization=seata
    

46. seata.transport.compressor=none
    

47. seata.transport.enable-client-batch-send-request=true
    

48. seata.config.type=file
    

49. seata.registry.type=file
    

2.3.新增配置类

1. package cn.enjoy.mt.order.config;
   

2. import com.alibaba.druid.pool.DruidDataSource;
   

3. import org.apache.ibatis.session.SqlSessionFactory;
   

4. import org.mybatis.spring.SqlSessionFactoryBean;
   

5. import org.springframework.boot.context.properties.ConfigurationProperties;
   

6. import org.springframework.context.annotation.Bean;
   

7. import org.springframework.context.annotation.Configuration;
   

8. import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
   

9. import javax.sql.DataSource;
   

10. @Configuration
    

11. public class SeataConfiguration {
    

12. @Bean
    

13. @ConfigurationProperties(prefix = "spring.datasource")
    

14. public DataSource druidDataSource() {
    

15. DruidDataSource druidDataSource = new DruidDataSource();
    

16. return druidDataSource;
    

17. }
    

18. @Bean
    

19. public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
    

20. SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
    

21. factoryBean.setDataSource(dataSource);
    

22. factoryBean.setMapperLocations(new PathMatchingResourcePatternResolver()
    

23. .getResources("classpath:/mapping/.xml"));
    

24. return factoryBean.getObject();
    

25. }
    

26. }
    

2.4.新增 undo_log 日志表

1. CREATE TABLE undo_log (
   

2. id bigint(20) NOT NULL AUTO_INCREMENT,
   

3. branch_id bigint(20) NOT NULL,
   

4. xid varchar(100) NOT NULL,
   

5. context varchar(128) NOT NULL,
   

6. rollback_info longblob NOT NULL,
   

7. log_status int(11) NOT NULL,
   

8. log_created datetime NOT NULL,
   

9. log_modified datetime NOT NULL,
   

10. ext varchar(100) DEFAULT NULL,
    

11. PRIMARY KEY (id),
    

12. UNIQUE KEY ux_undo_log (xid,branch_id)
    

13. ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
    

2.5.SeataProperties

1. package cn.enjoy.mt.order.config;
   

2. import org.springframework.boot.context.properties.ConfigurationProperties;
   

3. @ConfigurationProperties("spring.cloud.alibaba.seata")
   

4. public class SeataProperties {
   

5. private String txServiceGroup;
   

6. public SeataProperties() {
   

7. }
   

8. public String getTxServiceGroup() {
   

9. return this.txServiceGroup;
   

10. }
    

11. public void setTxServiceGroup(String txServiceGroup) {
    

12. this.txServiceGroup = txServiceGroup;
    

13. }
    

14. }
    

2.6.修改启动类

1. package cn.enjoy.mt.order;
   

2. import org.apache.dubbo.config.spring.context.annotation.EnableDubbo;
   

3. import org.mybatis.spring.annotation.MapperScan;