• 分布式事务之Seata AT

    文章目录

    AT简介

    1. 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

    2. 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。

    3. 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

    1. AT模式工作流程分为两个阶段

      • 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

      • 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

      • 二阶段（回滚）：生成反向SQL，删除Undo log

    AT项目实战

    1. 项目源码：https://github.com/jannal/transaction/tree/master/seata-at

    2. 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

    1. 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;

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    2. 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);
    }
}

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    3. 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();
    }

}

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    4. 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

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    积分服务

    1. 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;

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    2. 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);
    }
}

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    3. 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();
    }

}

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    4. 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

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    聚合服务

    1. 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);

    }
}

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    2. 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

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    查看回滚日志

    1. 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

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    2. 在AbstractUndoLogManager#batchDeleteUndoLog出打断点

    3. 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
      在这里插入图片描述

    4. 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
                                                ]
                                            ]
                                        }
                                    ]
                                ]
                            }
                        ]
                    ]
                }
            }
        ]
    ]
}

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  • 原文地址：https://blog.csdn.net/usagoole/article/details/126162735