seata分布式事务解决方案

客官°小女子只卖身不卖艺 2022-10-28 04:59 232阅读 0赞

> 整个项目请看gitee：[https://gitee.com/xwb1056481167/spring-cloud][https_gitee.com_xwb1056481167_spring-cloud]
> 
> nacos的配置安装请到：[https://blog.csdn.net/www1056481167/article/details/113612177][https_blog.csdn.net_www1056481167_article_details_113612177]查看

> seata官网：[https://seata.io/zh-cn][https_seata.io_zh-cn]

分布式事务的处理过程为

# **一ID+三组件模型** #

## 核心概念 ##

*  **一ID**  
           全局事务的id
 *  **三组件概念**
    
     *  1、TC(Transaction Coordinator)-事务协调者  
        维护全局和分支事务的状态，驱动全局事务提交或回滚
     *  2、TM(Transaction Manager)-事务管理者  
        定义全局事务的范围：开始全局事务、提交或回滚全局事务
     *  3、RM(Resource Manager)-资源管理器  
        管理分支事物处理的资源，与TC交谈以注册分支事务和报告分支事务的状态，并驱动分支事务提交或回滚

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70 1][]

## 处理流程图 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70 2][]

> 说明：  
> 1、TM向TC申请开启一个全局事务，全局事务创建成功并生成一个全局唯一的XID  
> 2、XID在微服务传播链路上下文中传播  
> 3、RM向TC注册分支事务，将其纳入XID对应全局事务的管辖  
> 4、TM向TC发起针对XID的全局提交或回滚决议  
> 5、TC调度XID下管辖的全部分支事务完成提交或或回滚请求

# seata的环境搭建配置 #

## 一、seata的下载 ##

下载地址：[https://github.com/seata/seata/releases][https_github.com_seata_seata_releases]  
版本 0.9： windows: [https://github.com/seata/seata/releases/download/v0.9.0/seata-server-0.9.0.zip][https_github.com_seata_seata_releases_download_v0.9.0_seata-server-0.9.0.zip]

## 二、seata的安装 ##

### 1、修改file.conf自定义事务组名称+事务日志模式为db+数据库连接 ###

**1、service的vgroup\_mapping.my\_test\_tx\_group属性**

service {
      #vgroup->rgroup
      vgroup_mapping.my_test_tx_group = "fsp_tx_group"
      #only support single node
      default.grouplist = "127.0.0.1:8091"
      #degrade current not support
      enableDegrade = false
      #disable
      disable = false
      #unit ms,s,m,h,d represents milliseconds, seconds, minutes, hours, days, default permanent
      max.commit.retry.timeout = "-1"
      max.rollback.retry.timeout = "-1"
    }

**2、指定存储方式为数据库**

store {
      ## store mode: file、db
      mode = "db"
    ...
    ## database store
      db {
        ## the implement of javax.sql.DataSource, such as DruidDataSource(druid)/BasicDataSource(dbcp) etc.
        datasource = "dbcp"
        ## mysql/oracle/h2/oceanbase etc.
        db-type = "mysql"
        driver-class-name = "com.mysql.jdbc.Driver"
        url = "jdbc:mysql://127.0.0.1:3306/seata"
        user = "root"
        password = "123456"
        min-conn = 1
        max-conn = 3
        global.table = "global_table"
        branch.table = "branch_table"
        lock-table = "lock_table"
        query-limit = 100
      }
    }

**3、创建数据库seata,并且创建表**

-- the table to store GlobalSession data
    drop table if exists `global_table`;
    create table `global_table` (
      `xid` varchar(128)  not null,
      `transaction_id` bigint,
      `status` tinyint not null,
      `application_id` varchar(32),
      `transaction_service_group` varchar(32),
      `transaction_name` varchar(128),
      `timeout` int,
      `begin_time` bigint,
      `application_data` varchar(2000),
      `gmt_create` datetime,
      `gmt_modified` datetime,
      primary key (`xid`),
      key `idx_gmt_modified_status` (`gmt_modified`, `status`),
      key `idx_transaction_id` (`transaction_id`)
    );
    
    -- the table to store BranchSession data
    drop table if exists `branch_table`;
    create table `branch_table` (
      `branch_id` bigint not null,
      `xid` varchar(128) not null,
      `transaction_id` bigint ,
      `resource_group_id` varchar(32),
      `resource_id` varchar(256) ,
      `lock_key` varchar(128) ,
      `branch_type` varchar(8) ,
      `status` tinyint,
      `client_id` varchar(64),
      `application_data` varchar(2000),
      `gmt_create` datetime,
      `gmt_modified` datetime,
      primary key (`branch_id`),
      key `idx_xid` (`xid`)
    );
    
    -- the table to store lock data
    drop table if exists `lock_table`;
    create table `lock_table` (
      `row_key` varchar(128) not null,
      `xid` varchar(96),
      `transaction_id` long ,
      `branch_id` long,
      `resource_id` varchar(256) ,
      `table_name` varchar(32) ,
      `pk` varchar(36) ,
      `gmt_create` datetime ,
      `gmt_modified` datetime,
      primary key(`row_key`)
    );

### 2、修改registry.conf注册信息 ###

修改注册类型为nacos，并且指定nacos的注册地址为localhost:8848(根据自己的nacos配置)

有关nacos的安装配置请到[https://blog.csdn.net/www1056481167/article/details/113612177][https_blog.csdn.net_www1056481167_article_details_113612177]查看

registry {
      # file 、nacos 、eureka、redis、zk、consul、etcd3、sofa
      type = "nacos"
    
      nacos {
        serverAddr = "localhost:8848"
        namespace = ""
        cluster = "default"
      }
      ...

### 启动验证是否成功配置 ###

1、启动nacos  
2、启动seata(双击seata-server.bat找到注册进nacos的注册语句即可)

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70 3][]

### 三、准备业务表结构 ###

DROP TABLE IF EXISTS `t_account`;
    CREATE TABLE `t_account`  (
      `id` bigint(11) NOT NULL AUTO_INCREMENT,
      `user_id` bigint(11) NULL DEFAULT NULL COMMENT '用户id',
      `total` decimal(10, 0) NULL DEFAULT NULL COMMENT '总额度',
      `used` decimal(10, 0) NULL DEFAULT NULL COMMENT '已用额度',
      `residue` decimal(10, 0) NULL DEFAULT NULL COMMENT '剩余可用额度',
      PRIMARY KEY (`id`) USING BTREE
    ) ENGINE = InnoDB AUTO_INCREMENT = 2 CHARACTER SET = utf8mb4;
    
    DROP TABLE IF EXISTS `seata_storage`;
    CREATE TABLE `t_storage`  (
      `id` bigint(11) NOT NULL AUTO_INCREMENT,
      `product_id` bigint(11) NULL DEFAULT NULL COMMENT '产品id',
      `total` int(11) NULL DEFAULT NULL COMMENT '库存',
      `used` int(11) NULL DEFAULT NULL COMMENT '已用库存',
      `residue` int(11) NULL DEFAULT NULL COMMENT '剩余库存',
      PRIMARY KEY (`id`) USING BTREE
    ) ENGINE = InnoDB AUTO_INCREMENT = 2 CHARACTER SET = utf8mb4 ;
    
    DROP TABLE IF EXISTS `t_order`;
    CREATE TABLE `t_order`  (
      `id` bigint(11) NOT NULL AUTO_INCREMENT,
      `user_id` bigint(11) NULL DEFAULT NULL COMMENT '用户id',
      `product_id` bigint(11) NULL DEFAULT NULL COMMENT '产品id',
      `count` int(11) NULL DEFAULT NULL COMMENT '数量',
      `money` decimal(11, 0) NULL DEFAULT NULL COMMENT '金额',
      `status` int(1) NULL DEFAULT NULL COMMENT '订单状态：0：创建中；1：已完结',
      PRIMARY KEY (`id`) USING BTREE
    ) ENGINE = InnoDB AUTO_INCREMENT = 7 CHARACTER SET = utf8mb4;
    
    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 AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

最终表结构

![20210205171644759.png][]

# 新建订单、库存、余额模块 #

> 业务需求：下订单->减库存->扣余额->改(订单)状态
> 
> 以下只列举了核心代码，全部代码请到gitee上查看

## 新建订单模块seata-order-service2001 ##

1、pom.xml(部分省略)

<dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
    </dependency>
    <dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-starter-alibaba-seata</artifactId>
        <exclusions>
            
            <exclusion>
                <artifactId>seata-all</artifactId>
                <groupId>io.seata</groupId>
            </exclusion>
        </exclusions>
    </dependency>
    
    <dependency>
        <groupId>io.seata</groupId>
        <artifactId>seata-all</artifactId>
        <version>0.9.0</version>
    </dependency>
    
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
    </dependency>

2、application.yml

server:
      port: 2001
    spring:
      application:
        name: seata-order-service
      cloud:
        nacos:
          discovery: #Nacos注册中心地址
            server-addr: localhost:8848
        alibaba:
          seata:
            tx-service-group: fsp_tx_group
      datasource:
        driver-class-name: com.mysql.jdbc.Driver
        url: jdbc:mysql://localhost:3306/seata_order?useUnicode=true&characterEncoding=UTF-8&useSSL=false
        username: root
        password: 123456
    #    type: com.alibaba.druid.pool.DruidDataSource
    feign:
      hystrix:
        enabled: true
    
    logging:
      level:
        io:
          seata: info
    mybatis:
      mapper-locations: classpath:mapper/*.xml

3、备份seata的配置文件**file.conf** **registry.conf**  
4、提供dao,domain,mapper\*.xml,controller。  
5、service **特别注意的是调用的其他微服务的方法，需要@FeignClient(value="xx")标明调用的方法接口，本身的service提供的方法，不用该注解**

6、config的配置

//1、mybatis扫描的包
    @Configuration
    @MapperScan("org.xwb.springcloud.dao.*")
    public class MyBatisConfig {
    }
    //2、druid数据源  
    @Configuration
    public class DataSourceProxyConfig {
        @Value("${mybatis.mapper-locations}")
        private String mapperLocations;
        @Bean
        @ConfigurationProperties(prefix = "spring.datasource")
        public DataSource druidDataSource() {
            return new DruidDataSource();
        }
        @Primary
        @Bean("dataSource")
        public DataSourceProxy dataSourceProxy(DataSource druidDataSource) {
            return new DataSourceProxy(druidDataSource);
        }
        @Bean(name = "sqlSessionFactory")
        public SqlSessionFactory sqlSessionFactoryBean(DataSourceProxy dataSourceProxy) throws Exception {
            SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
            bean.setDataSource(dataSourceProxy);
            ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
            bean.setMapperLocations(resolver.getResources(mapperLocations));
            SqlSessionFactory factory;
            try {
                factory = bean.getObject();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
            return factory;
        }
    }

7、主启动类

@SpringBootApplication(exclude = DataSourceAutoConfiguration.class)
    @EnableDiscoveryClient
    @EnableFeignClients
    public class SeataOrderMainApp2001 {
        public static void main(String[] args) {
            SpringApplication.run(SeataOrderMainApp2001.class, args);
        }
    }

> 特别注意的是 **@SpringBootApplication(exclude = DataSourceAutoConfiguration.class)**  
> 排除自身的数据源，使用自己定义的数据源

## 新建库存模块seata-storage-service2002 ##

同以上2001相同，以下只说明不同之处  
1、application.xml

server:
      port: 2002
    spring:
      application:
        name: seata-storage-service
      cloud:
        nacos:
          discovery: #Nacos注册中心地址
            server-addr: localhost:8848
        alibaba:
          seata:
            tx-service-group: fsp_tx_group
      datasource:
        driver-class-name: com.mysql.jdbc.Driver
        url: jdbc:mysql://localhost:3306/seata_storage?useUnicode=true&characterEncoding=UTF-8&useSSL=false
        username: root
        password: 123456
    #    type: com.alibaba.druid.pool.DruidDataSource
    feign:
      hystrix:
        enabled: true
    
    logging:
      level:
        io:
          seata: info
    mybatis:
      mapper-locations: classpath:mapper/*.xml

其他业务可直接查看项目

## 新建账户模块seata-account-service2003 ##

同2003相同 ，以下只列出不同之处

server:
      port: 2003
    
    spring:
      application:
        name: seata-account-service
      cloud:
        alibaba:
          seata:
            tx-service-group: fsp_tx_group
        nacos:
          discovery:
            server-addr: localhost:8848
      datasource:
    #    type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.jdbc.Driver
        url: jdbc:mysql://localhost:3306/seata_account?useUnicode=true&characterEncoding=UTF-8&useSSL=false
        username: root
        password: 123456
    feign:
      hystrix:
        enabled: true
    logging:
      level:
        io:
          seata: info
    mybatis:
      mapper-locations: classpath*:mapper/*.xml

其他业务参照代码原始项目请到gitee上查看

# 测试(正常测试、GlobalTransactional) #

## 正常测试(不加GlobalTransactional统一事务进行测试) ##

1、启动nacos、seata、2001、2002、2003

2、浏览器输入 [http://localhost2001/order/create?userId=1&productId=1&count=1&money=100][http_localhost2001_order_create_userId_1_productId_1_count_1_money_100]查看库存是正确的  
3、此时需要将对seata-account-service2003账户付款进行改动(修改为超时，账户扣款失败)

@Service
    @Slf4j
    public class AccountServiceImpl implements AccountService {
        @Resource
        private AccountDao accountDao;
        @Override
        public void decrease(Long userId, BigDecimal money) {
            log.info("********->account-service中扣减账户余额开始");
            //此处故意超时
            try {
                TimeUnit.SECONDS.sleep(20);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            accountDao.decrease(userId, money);
            log.info("********->account-service中扣减账户余额结束");
        }
    }

**测试结果**

> 会发现,成功创建了订单，但是订单的状态却不对。
> 
> 分析得知：
> 
> 整个事物分为4部分1、新建订单2、扣减库存3、扣减账户4、修改订单状态
> 
> 前面3部分都执行成功，但是最后需要修改订单的状态确失败，由于我们设置了超时，故意让等待超时处理，此时由于没有添加全局事务的控制，导致中途失败的无法执行成功，但是在他之前
> 
> 执行成功的无法回滚，就导致了整个事物不正确。订单下了，扣款，修改订单状态却不对。此时就需要全局事务来解决事物不统一的问题。

## 使用GlobalTransactional ##

通过以上测试会发现事物处理不统一接下来使用seata的全局事务进行控制

1、添加注解**@GlobalTransactional(name = "fsp-create-order", rollbackFor = Exception.class)name自定义即可**

@Override
    @GlobalTransactional(name = "fsp-create-order", rollbackFor = Exception.class)
    public void create(Order order) {
        log.info("--------->开始新建订单");
        //1 新建订单
        orderDao.create(order);
        //2 扣减库存
        log.info("------------->订单微服务开始调用库存,做扣减Count");
        storageService.decrease(order.getProductId(), order.getCount());
        log.info("------------->订单微服务开始调用库存,做扣减end");
        //3 扣减账户
        log.info("------------->订单微服务开始调用账户,做扣减Money");
        accountService.decrease(order.getUserId(), order.getMoney());
        log.info("------------->订单微服务开始调用账户,做扣减end");
        //4 修改订单状态
        log.info("------------->修改订单状态开始");
        orderDao.update(order.getUserId(), 0);
        log.info("------------->修改订单状态结束");
        log.info("------------->下订单结束了");
    }

重启应用，再次请求订单，会发现订单整个订单都添加不进来,全部回滚

原理解析

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70 4][]

> **TM开启分布式事务(TM向TC注册全局事务记录)  
> 按照业务场景，编排数据库、服务器等事务内资源(RM向TC汇报资源准备状态  
> TM结束分布式事务，事务一阶段准备结束(TM通知TC提交、回滚分布式事务)  
> TC汇报事务信息，决定分布式事务是提交还是回滚  
> TC通知所有RM提交回滚资源，事务二阶段结束**

# 核心原理分析 #

## 一阶段加载 ##

**在一阶段，Seata会拦截"业务SQL"**

> 1、解析sql语义，找到"业务SQL"要更新的业务数据，在业务数据被更新前，将其保存到"before image",  
> 2、执行"业务SQL"更新业务数据，在业务数据更新之后。  
> 3、将其保存城"after image",最后生成行锁。

**以上操作全部在一个数据库事务内完成，这样保证了一阶段操作的原子性。**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70 5][]

## 二阶段(成功、失败) ##

**1、二阶段如果顺利提交的话。**  
因为"业务SQL"在一阶段已经提交至数据库，所以Seata框架只需将**一阶段保存的快照数据和行级锁，完成数据清理即可。**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70 6][]

**2、二阶段失败(回滚)**

> 二阶段如果是回滚的话，Seata就需要回滚一阶段已经执行的"业务SQL"还原业务数据  
> 回滚方式便是用"before image" 还原业务数据；但在还原前要首先要校验脏写，对比"数据库当前业务数据"和"after image", 如果两份数据完全一致就说明没有脏写，可以还原业务数据，如果不一致就说明有脏写，出现脏写**需要转人工处理**。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70 7][]

[https_gitee.com_xwb1056481167_spring-cloud]: https://gitee.com/xwb1056481167/spring-cloud
[https_blog.csdn.net_www1056481167_article_details_113612177]: https://blog.csdn.net/www1056481167/article/details/113612177
[https_seata.io_zh-cn]: https://seata.io/zh-cn
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70]: /images/20221024/fa5ff32d1abd4df3965edc685abcaa0e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70 1]: /images/20221024/dad6fcccb5f94b4986e2c75764f24e72.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3d3dzEwNTY0ODExNjc_size_16_color_FFFFFF_t_70 2]: /images/20221024/27dc40e0da784db1aca247108666812b.png
[https_github.com_seata_seata_releases]: https://github.com/seata/seata/releases
[https_github.com_seata_seata_releases_download_v0.9.0_seata-server-0.9.0.zip]: https://github.com/seata/seata/releases/download/v0.9.0/seata-server-0.9.0.zip
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