分布式事务之Seata AT
文章目录
- AT简介
- AT模式原理
- AT项目实战
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- 账户服务
- 积分服务
- 聚合服务
- 查看回滚日志
AT简介
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AT模式是基于XA演进而来的一种分布式事务模式，是Seata主推的分布式事务解决方案。它也分为三大模块，分别是TM、RM和TC，TM和RM作为客户端与业务系统集成，TC作为Seata服务器单独部署
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AT模式采用的是 Write Ahead Log 思想，即把事务的信息以事务日志的方式记录下来。
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概念
- TM(Transaction Manager):表示事务管理器，负责向TC注册一个全局事务，并生成一个全局唯一的XID。
- RM（Resource Manager）:表示数据库资源，业务层通过JDBC接口访问RM时，Seata会对所有请求进行拦截。每个本地事务进行提交时，RM都会向TC（Transaction Coordinator事务协调器）注册一个分支事务
- TC(Transaction Coordinator): 这是一个独立的服务，是一个独立的 JVM 进程，里面不包含任何业务代码，它的主要职责：维护着整个事务的全局状态，负责通知 RM 执行回滚或提交；
AT模式原理
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AT模式工作流程分为两个阶段
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一阶段：（1）拦截并解析SQL，查询前置快照。（2）执行业务SQL。（3）查询后置快照。（4）将前置快照和后置快照数据整合并生成undo Log。（5）向服务端注册分支事务 （6）插入Undo Log ，提交事务
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二阶段（提交）：一阶段成功，二阶段插入待删除队列，异步删除一阶段的Undo Log
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二阶段（回滚）：生成反向SQL，删除Undo log
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AT项目实战
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项目源码：https://github.com/jannal/transaction/tree/master/seata-at
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服务模块
服务 描述 service-account 账户服务 service-points 积分服务 service-aggregation 聚合服务
账户服务
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SQL脚本
CREATE DATABASE IF NOT EXISTS seata_account DEFAULT CHARSET utf8mb4 COLLATE utf8mb4_bin; DROP TABLE IF EXISTS `t_user`; CREATE TABLE `t_user` ( `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT COMMENT '主键', `user_id` varchar(50) COLLATE utf8mb4_bin NOT NULL COMMENT '用户唯一标识', `username` varchar(50) COLLATE utf8mb4_bin NOT NULL COMMENT '用户名', `password` varchar(50) COLLATE utf8mb4_bin NOT NULL COMMENT '密码', `create_time` datetime NOT NULL COMMENT '创建时间', `update_time` datetime NOT NULL COMMENT '更新时间', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin COMMENT='用户'; DROP TABLE IF EXISTS `undo_log`; 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, `ext` varchar(100) DEFAULT NULL, PRIMARY KEY (`id`), UNIQUE KEY `ux_undo_log` (`xid`,`branch_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4; -
服务接口
public interface AccountFacadeService { public void registerUser(UserRequestDTO userRequestDTO); } @Slf4j @DubboService(version = "1.0.0") public class AccountFacadeServiceImpl implements AccountFacadeService { @Autowired private UserService userService; @Override public void registerUser(UserRequestDTO userRequestDTO) { log.info("全局事务id:{}", RootContext.getXID()); User user = new User(); BeanUtils.copyProperties(userRequestDTO, user); userService.register(user); } } -
配置代理数据源
@Configuration @Slf4j public class DataSourceProxyConfig { @Bean public SqlSessionFactory sqlSessionFactoryBean(DataSource dataSource) throws Exception { log.info("代理的原始数据源类:{}", dataSource.getClass().getName()); //seata数据源代理类代理原始的DataSource DataSourceProxy dataSourceProxy = new DataSourceProxy(dataSource); SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean(); sqlSessionFactoryBean.setDataSource(dataSourceProxy); sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver() .getResources("classpath*:/mapper/*Mapper.xml")); sqlSessionFactoryBean.setTransactionFactory(new SpringManagedTransactionFactory()); return sqlSessionFactoryBean.getObject(); } } -
seata配置
seata.enabled=true #写成这样不生效 #seata.enable-auto-data-source-proxy=true #seata.enableAutoDataSourceProxy=true seata.application-id=account-provider-seata seata.registry.type=nacos # Server和Client端的值需一致，默认seata-server seata.registry.nacos.application=seata-server seata.registry.nacos.server-addr=192.168.101.8:8848 seata.registry.nacos.group=DEFAULT_GROUP seata.registry.nacos.cluster=default seata.registry.nacos.username=root seata.registry.nacos.password=root seata.registry.nacos.namespace=e489e0de-8001-41b8-83a6-3241d426a9f7 seata.config.type=nacos seata.config.nacos.data-id=seataServer.properties seata.config.nacos.server-addr=192.168.101.8:8848 seata.config.nacos.group=DEFAULT_GROUP seata.config.nacos.username=root seata.config.nacos.password=root seata.config.nacos.namespace=e489e0de-8001-41b8-83a6-3241d426a9f7 # nacos server默认值是my_test_tx_group seata.tx-service-group=my_test_tx_group seata.service.vgroup-mapping.my_test_tx_group=default seata.service.disable-global-transaction=false seata.data-source-proxy-mode=AT
积分服务
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SQL脚本
CREATE DATABASE IF NOT EXISTS seata_points DEFAULT CHARSET utf8mb4 COLLATE utf8mb4_bin; DROP TABLE IF EXISTS `t_points`; CREATE TABLE `t_points` ( `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT COMMENT '主键', `user_id` varchar(50) COLLATE utf8mb4_bin NOT NULL COMMENT '用户唯一标识', `num` bigint(20) NOT NULL COMMENT '积分', `create_time` datetime NOT NULL COMMENT '创建时间', `update_time` datetime NOT NULL COMMENT '更新时间', PRIMARY KEY (`id`), UNIQUE KEY `uniq_userid` (`user_id`) USING BTREE ) ENGINE=InnoDB AUTO_INCREMENT=13 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin COMMENT='积分'; DROP TABLE IF EXISTS `undo_log`; 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, `ext` varchar(100) DEFAULT NULL, PRIMARY KEY (`id`), UNIQUE KEY `ux_undo_log` (`xid`,`branch_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4; -
接口
public interface PointsFacadeService { public void increasePoints(PointsRequestDTO pointsRequestDTO); } @DubboService(version = "1.0.0") @Slf4j public class PointsFacadeServiceImpl implements PointsFacadeService { @Autowired private PointsService pointsService; @Override public void increasePoints(PointsRequestDTO pointsRequestDTO) { log.info("全局事务id:{}", RootContext.getXID()); Points points = new Points(); BeanUtils.copyProperties(pointsRequestDTO, points); pointsService.increasePoints(points); } } -
配置代理数据源
@Configuration @Slf4j public class DataSourceProxyConfig { @Bean public SqlSessionFactory sqlSessionFactoryBean(DataSource dataSource) throws Exception { log.info("代理的原始数据源类:{}", dataSource.getClass().getName()); //seata数据源代理类代理原始的DataSource DataSourceProxy dataSourceProxy = new DataSourceProxy(dataSource); SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean(); sqlSessionFactoryBean.setDataSource(dataSourceProxy); sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver() .getResources("classpath*:/mapper/*Mapper.xml")); sqlSessionFactoryBean.setTransactionFactory(new SpringManagedTransactionFactory()); return sqlSessionFactoryBean.getObject(); } } -
seata配置
seata.enabled=true #写成这样不生效 #seata.enable-auto-data-source-proxy=true #seata.enableAutoDataSourceProxy=true seata.application-id=points-provider-seata seata.registry.type=nacos # Server和Client端的值需一致，默认seata-server seata.registry.nacos.application=seata-server seata.registry.nacos.server-addr=192.168.101.8:8848 seata.registry.nacos.group=DEFAULT_GROUP seata.registry.nacos.cluster=default seata.registry.nacos.username=root seata.registry.nacos.password=root seata.registry.nacos.namespace=e489e0de-8001-41b8-83a6-3241d426a9f7 seata.config.type=nacos seata.config.nacos.data-id=seataServer.properties seata.config.nacos.server-addr=192.168.101.8:8848 seata.config.nacos.group=DEFAULT_GROUP seata.config.nacos.username=root seata.config.nacos.password=root seata.config.nacos.namespace=e489e0de-8001-41b8-83a6-3241d426a9f7 # nacos server默认值是my_test_tx_group seata.tx-service-group=my_test_tx_group seata.service.vgroup-mapping.my_test_tx_group=default seata.service.disable-global-transaction=false seata.data-source-proxy-mode=AT
聚合服务
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代码
@Service @Slf4j public class RegisterAggregationService { @DubboReference(version = "1.0.0") private AccountFacadeService accountFacadeService; @DubboReference(version = "1.0.0") private PointsFacadeService pointsFacadeService; /** * 注册用户，增加积分 */ @GlobalTransactional(rollbackFor = Exception.class, timeoutMills = 200000) public void register(UserRequestDTO userRequestDTO, PointsRequestDTO pointsRequestDTO) { log.info("全局事务id:{}", RootContext.getXID()); // 为了模拟注册失败，将增加积分放在前面。测试注册失败，积分是否会增加 pointsFacadeService.increasePoints(pointsRequestDTO); accountFacadeService.registerUser(userRequestDTO); } } -
seata配置
seata.enabled=true seata.enable-auto-data-source-proxy=true seata.application-id=${spring.application.name}-seata seata.registry.type=nacos # Server和Client端的值需一致，默认seata-server seata.registry.nacos.application=seata-server seata.registry.nacos.server-addr=192.168.101.8:8848 seata.registry.nacos.group=DEFAULT_GROUP seata.registry.nacos.cluster=default seata.registry.nacos.username=root seata.registry.nacos.password=root seata.registry.nacos.namespace=e489e0de-8001-41b8-83a6-3241d426a9f7 seata.config.type=nacos seata.config.nacos.data-id=seataServer.properties seata.config.nacos.server-addr=192.168.101.8:8848 seata.config.nacos.group=DEFAULT_GROUP seata.config.nacos.username=root seata.config.nacos.password=root seata.config.nacos.namespace=e489e0de-8001-41b8-83a6-3241d426a9f7 # nacos server默认值是my_test_tx_group seata.tx-service-group=my_test_tx_group seata.service.vgroup-mapping.my_test_tx_group=default seata.service.disable-global-transaction=false seata.data-source-proxy-mode=AT
查看回滚日志
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发送请求
curl -H "Content-Type: application/json" -X POST \ -d '{"username": "tom","password": "123456"}' \ http://127.0.0.1:9000/api/v1/register -
在
AbstractUndoLogManager#batchDeleteUndoLog出打断点 -
查看account回滚日志，回滚日志记录了业务操作前后的数据，当要执行全局事务回滚时，根据回滚日志进行补偿即可
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查看回滚日志JSON内容：
{ "@class": "io.seata.rm.datasource.undo.BranchUndoLog", "xid": "172.26.0.2:8091:18275457457209345", "branchId": 18275457457209351, "sqlUndoLogs": [ "java.util.ArrayList", [ { "@class": "io.seata.rm.datasource.undo.SQLUndoLog", "sqlType": "INSERT", "tableName": "t_user", "beforeImage": { "@class": "io.seata.rm.datasource.sql.struct.TableRecords$EmptyTableRecords", "tableName": "t_user", "rows": [ "java.util.ArrayList", [] ] }, "afterImage": { "@class": "io.seata.rm.datasource.sql.struct.TableRecords", "tableName": "t_user", "rows": [ "java.util.ArrayList", [ { "@class": "io.seata.rm.datasource.sql.struct.Row", "fields": [ "java.util.ArrayList", [ { "@class": "io.seata.rm.datasource.sql.struct.Field", "name": "id", "keyType": "PRIMARY_KEY", "type": -5, "value": [ "java.math.BigInteger", 24 ] }, { "@class": "io.seata.rm.datasource.sql.struct.Field", "name": "user_id", "keyType": "NULL", "type": 12, "value": "d131c0c4-c415-4f3b-9efd-ce6aa39be439" }, { "@class": "io.seata.rm.datasource.sql.struct.Field", "name": "username", "keyType": "NULL", "type": 12, "value": "tom" }, { "@class": "io.seata.rm.datasource.sql.struct.Field", "name": "password", "keyType": "NULL", "type": 12, "value": "123456" }, { "@class": "io.seata.rm.datasource.sql.struct.Field", "name": "create_time", "keyType": "NULL", "type": 93, "value": [ "java.sql.Timestamp", [ 1652170374000, 0 ] ] }, { "@class": "io.seata.rm.datasource.sql.struct.Field", "name": "update_time", "keyType": "NULL", "type": 93, "value": [ "java.sql.Timestamp", [ 1652170374000, 0 ] ] } ] ] } ] ] } } ] ] }