前言

一次业务操作需要跨多个数据源或需要跨多个系统进行远程调用，就会产生分布式事务问题

Seata是一款开源的分布式事务解决方案，致力于在微服务架构下提供高性能和简单易用的分布式事务服务。

Seata官网下载

分布式事务过程：

分布式事务处理过程的一ID+三组件模型

Transaction ID XID：全局唯一的事务ID

3组件概念

Transaction Coordinator (TC)：事务协调器，维护全局事务的运行状态，负责协调并驱动全局事务的提交或回滚；

Transaction Manager ™：控制全局事务的边界，负责开启一个全局事务，并最终发起全局提交或全局回滚的决议；

Resource Manager (RM)：控制分支事务，负责分支注册、状态汇报，并接收事务协调器的指令，驱动分支（本地）事务的提交和回滚

处理过程：

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；

XID 在微服务调用链路的上下文中传播；

RM 向 TC 注册分支事务，将其纳入 XID 对应全局事务的管辖；

TM 向 TC 发起针对 XID 的全局提交或回滚决议；

TC 调度 XID 下管辖的全部分支事务完成提交或回滚请求。

使用：

在业务入口方法上开启 @GlobalTransactional(name = "fsp-create-order",rollbackFor = Exception.class)

Seata-Server安装

修改conf目录下的seata\conf\file.conf配置文件

主要修改：自定义事务组名称+事务日志存储模式为db+数据库连接信息

mysql5.7数据库新建库seata

在seata库，执行 \seata-server-0.9.0\seata\conf\db_store.sql

修改seata-server-0.9.0\seata\conf目录下的registry.conf配置文件

启动nacos，启动 seata

实际应用

这里我们会创建三个服务，一个订单服务，一个库存服务，一个账户服务。

当用户下单时，会在订单服务中创建一个订单，然后通过远程调用库存服务来扣减下单商品的库存，

再通过远程调用账户服务来扣减用户账户里面的余额，

最后在订单服务中修改订单状态为已完成。

该操作跨越三个数据库，有两次远程调用，很明显会有分布式事务问题。

业务流程：下订单->减库存->扣余额->改(订单)状态

seata_order：存储订单的数据库；

seata_storage：存储库存的数据库；

seata_account：存储账户信息的数据库。

seata_order库下建t_order订单表

seata_storage库下建t_storage库存表

seata_account库下建t_account 账户表

订单-库存-账户3个库下都需要建各自的回滚日志表，\seata-server-0.9.0\seata\conf目录下的db_undo_log.sql

这里只列举创建订单微服务，代码太多，已上传 gitee

新建Module：seata-order-service2001

pom

<dependencies>
        <!--nacos-->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
        <!--seata-->
        <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>
        <!--feign-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <!--web-actuator-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <!--mysql-druid-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.37</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.10</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.0.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>

yml

server:
  port: 2001
spring:
  application:
    name: seata-order-service
  cloud:
    alibaba:
      seata:
        #自定义事务组名称需要与seata-server中的对应
        tx-service-group: fsp_tx_group
    nacos:
      discovery:
        server-addr: localhost:8848
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/seata_order
    username: root
    password: 123456
feign:
  hystrix:
    enabled: false
logging:
  level:
    io:
      seata: info
mybatis:
  mapperLocations: classpath:mapper/*.xml

resources/file.conf

transport {
  # tcp udt unix-domain-socket
  type = "TCP"
  #NIO NATIVE
  server = "NIO"
  #enable heartbeat
  heartbeat = true
  #thread factory for netty
  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"
    # netty boss thread size,will not be used for UDT
    boss-thread-size = 1
    #auto default pin or 8
    worker-thread-size = 8
  }
  shutdown {
    # when destroy server, wait seconds
    wait = 3
  }
  serialization = "seata"
  compressor = "none"
}
service {
  vgroup_mapping.fsp_tx_group = "default" #修改自定义事务组名称
  default.grouplist = "127.0.0.1:8091"
  enableDegrade = false
  disable = false
  max.commit.retry.timeout = "-1"
  max.rollback.retry.timeout = "-1"
  disableGlobalTransaction = false
}
client {
  async.commit.buffer.limit = 10000
  lock {
    retry.internal = 10
    retry.times = 30
  }
  report.retry.count = 5
  tm.commit.retry.count = 1
  tm.rollback.retry.count = 1
}
## transaction log store
store {
  ## store mode: file、db
  mode = "db"
  ## file store
  file {
    dir = "sessionStore"
    # branch session size , if exceeded first try compress lockkey, still exceeded throws exceptions
    max-branch-session-size = 16384
    # globe session size , if exceeded throws exceptions
    max-global-session-size = 512
    # file buffer size , if exceeded allocate new buffer
    file-write-buffer-cache-size = 16384
    # when recover batch read size
    session.reload.read_size = 100
    # async, sync
    flush-disk-mode = async
  }
  ## 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" #seata的数据库
    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
  }
}
lock {
  ## the lock store mode: local、remote
  mode = "remote"
  local {
    ## store locks in user's database
  }
  remote {
    ## store locks in the seata's server
  }
}
recovery {
  #schedule committing retry period in milliseconds
  committing-retry-period = 1000
  #schedule asyn committing retry period in milliseconds
  asyn-committing-retry-period = 1000
  #schedule rollbacking retry period in milliseconds
  rollbacking-retry-period = 1000
  #schedule timeout retry period in milliseconds
  timeout-retry-period = 1000
}
transaction {
  undo.data.validation = true
  undo.log.serialization = "jackson"
  undo.log.save.days = 7
  #schedule delete expired undo_log in milliseconds
  undo.log.delete.period = 86400000
  undo.log.table = "undo_log"
}
## metrics settings
metrics {
  enabled = false
  registry-type = "compact"
  # multi exporters use comma divided
  exporter-list = "prometheus"
  exporter-prometheus-port = 9898
}
support {
  ## spring
  spring {
    # auto proxy the DataSource bean
    datasource.autoproxy = false
  }
}

resources/registry.conf

registry {
  # file 、nacos 、eureka、redis、zk、consul、etcd3、sofa
  type = "nacos"  ##注册类型
  nacos {
    serverAddr = "localhost:8848"
    namespace = ""
    cluster = "default"
  }
  eureka {
    serviceUrl = "http://localhost:8761/eureka"
    application = "default"
    weight = "1"
  }
  redis {
    serverAddr = "localhost:6379"
    db = "0"
  }
  zk {
    cluster = "default"
    serverAddr = "127.0.0.1:2181"
    session.timeout = 6000
    connect.timeout = 2000
  }
  consul {
    cluster = "default"
    serverAddr = "127.0.0.1:8500"
  }
  etcd3 {
    cluster = "default"
    serverAddr = "http://localhost:2379"
  }
  sofa {
    serverAddr = "127.0.0.1:9603"
    application = "default"
    region = "DEFAULT_ZONE"
    datacenter = "DefaultDataCenter"
    cluster = "default"
    group = "SEATA_GROUP"
    addressWaitTime = "3000"
  }
  file {
    name = "file.conf"
  }
}
config {
  # file、nacos 、apollo、zk、consul、etcd3
  type = "file"
  nacos {
    serverAddr = "localhost"
    namespace = ""
  }
  consul {
    serverAddr = "127.0.0.1:8500"
  }
  apollo {
    app.id = "seata-server"
    apollo.meta = "http://192.168.1.204:8801"
  }
  zk {
    serverAddr = "127.0.0.1:2181"
    session.timeout = 6000
    connect.timeout = 2000
  }
  etcd3 {
    serverAddr = "http://localhost:2379"
  }
  file {
    name = "file.conf"
  }
}

OrderDao

@Mapper
public interface OrderDao {
    /**
     * 创建订单
     */
    void create(Order order);
    /**
     * 修改订单金额
     */
    void update(@Param("userId") Long userId, @Param("status") Integer status);
}

resources/mapper/OrderMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.atguigu.springcloud.dao.OrderDao">
    <resultMap id="BaseResultMap" type="com.atguigu.springcloud.alibaba.domain.Order">
        <id column="id" property="id" jdbcType="BIGINT"/>
        <result column="user_id" property="userId" jdbcType="BIGINT"/>
        <result column="product_id" property="productId" jdbcType="BIGINT"/>
        <result column="count" property="count" jdbcType="INTEGER"/>
        <result column="money" property="money" jdbcType="DECIMAL"/>
        <result column="status" property="status" jdbcType="INTEGER"/>
    </resultMap>
    <insert id="create">
        INSERT INTO `t_order` (`id`, `user_id`, `product_id`, `count`, `money`, `status`)
        VALUES (NULL, #{userId}, #{productId}, #{count}, #{money}, 0);
    </insert>
    <update id="update">
        UPDATE `t_order`
        SET status = 1
        WHERE user_id = #{userId} AND status = #{status};
    </update>
</mapper>

OrderService

public interface OrderService {
    /**
     * 创建订单
     */
    void create(Order order);
}

OrderServiceImpl

import com.atguigu.springcloud.alibaba.dao.OrderDao;
import com.atguigu.springcloud.alibaba.domain.Order;
import com.atguigu.springcloud.alibaba.service.AccountService;
import com.atguigu.springcloud.alibaba.service.OrderService;
import com.atguigu.springcloud.alibaba.service.StorageService;
import io.seata.spring.annotation.GlobalTransactional;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.annotation.Resource;
@Service
@Slf4j
public class OrderServiceImpl implements OrderService
{
    @Resource
    private OrderDao orderDao;
    @Resource
    private StorageService storageService;
    @Resource
    private AccountService accountService;
    /**
     * 创建订单->调用库存服务扣减库存->调用账户服务扣减账户余额->修改订单状态
     * 简单说：
     * 下订单->减库存->减余额->改状态
     */
    @Override
    @GlobalTransactional(name = "fsp-create-order",rollbackFor = Exception.class)
    public void create(Order order) {
        log.info("------->下单开始");
        //本应用创建订单
        orderDao.create(order);
        //远程调用库存服务扣减库存
        log.info("------->order-service中扣减库存开始");
        storageService.decrease(order.getProductId(),order.getCount());
        log.info("------->order-service中扣减库存结束");
        //远程调用账户服务扣减余额
        log.info("------->order-service中扣减余额开始");
        accountService.decrease(order.getUserId(),order.getMoney());
        log.info("------->order-service中扣减余额结束");
        //修改订单状态为已完成
        log.info("------->order-service中修改订单状态开始");
        orderDao.update(order.getUserId(),0);
        log.info("------->order-service中修改订单状态结束");
        log.info("------->下单结束");
    }
}

StorageService

@FeignClient(value = "seata-storage-service")
public interface StorageService {
    /**
     * 扣减库存
     */
    @PostMapping(value = "/storage/decrease")
    CommonResult decrease(@RequestParam("productId") Long productId, @RequestParam("count") Integer count);
}

AccountService

@FeignClient(value = "seata-account-service")
public interface AccountService {
    /**
     * 扣减账户余额
     */
    //@RequestMapping(value = "/account/decrease", method = RequestMethod.POST, produces = "application/json; charset=UTF-8")
    @PostMapping("/account/decrease")
    CommonResult decrease(@RequestParam("userId") Long userId, @RequestParam("money") BigDecimal money);
}

controller

@RestController
public class OrderController {
    @Autowired
    private OrderService orderService;
    /**
     * 创建订单
     */
    @GetMapping("/order/create")
    public CommonResult create( Order order) {
        orderService.create(order);
        return new CommonResult(200, "订单创建成功!");
    }
}

config.MyBatisConfig.java

@Configuration
@MapperScan({"com.atguigu.springcloud.alibaba.dao"})
public class MyBatisConfig {
}

config.DataSourceProxyConfig.java

import com.alibaba.druid.pool.DruidDataSource;
import io.seata.rm.datasource.DataSourceProxy;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.transaction.SpringManagedTransactionFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import javax.sql.DataSource;
/**
 * @auther zzyy
 * @create 2019-12-11 16:58
 * 使用Seata对数据源进行代理
 */
@Configuration
public class DataSourceProxyConfig {
    @Value("${mybatis.mapperLocations}")
    private String mapperLocations;
    @Bean
    @ConfigurationProperties(prefix = "spring.datasource")
    public DataSource druidDataSource(){
        return new DruidDataSource();
    }
    @Bean
    public DataSourceProxy dataSourceProxy(DataSource dataSource) {
        return new DataSourceProxy(dataSource);
    }
    @Bean
    public SqlSessionFactory sqlSessionFactoryBean(DataSourceProxy dataSourceProxy) throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(dataSourceProxy);
        sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(mapperLocations));
        sqlSessionFactoryBean.setTransactionFactory(new SpringManagedTransactionFactory());
        return sqlSessionFactoryBean.getObject();
    }
}

主启动：

@EnableDiscoveryClient
@EnableFeignClients
@SpringBootApplication(exclude = DataSourceAutoConfiguration.class)//取消数据源的自动创建
public class SeataOrderMainApp2001
{
    public static void main(String[] args)
    {
        SpringApplication.run(SeataOrderMainApp2001.class, args);
    }
}

库存、账户服务类似。

下订单入口添加了@GlobalTransactional，要么全执行，要么回滚，事务没啥可说的，下边主要看看实现的原理

补充

Simple Extensible Autonomous Transaction Architecture，简单可扩展自治事务框架

分布式事务的执行流程：

TM 开启分布式事务（TM 向 TC 注册全局事务记录）；

按业务场景，编排数据库、服务等事务内资源（RM 向 TC 汇报资源准备状态）；

TM 结束分布式事务，事务一阶段结束（TM 通知 TC 提交/回滚分布式事务）；

TC 汇总事务信息，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。

Seata有四大模式，默认AT模式

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，将其保存成“before image”，

2 执行“业务 SQL”更新业务数据，在业务数据更新之后，

3 其保存成“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。

二阶段如是顺利提交的话，

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锁删掉，完成数据清理即可。

二阶段回滚：

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，出现脏写就需要转人工处理。

在下订单的方法打断点，此时去数据库看undo_log表，可以看到操作数据前后，seata都做了前置快照（before image）后置快照（after image），当正常提交或回滚后数据都会被删除，遇到脏写就需要人工处理

展开 rows，可以看到每个表执行事务前、执行事务后字段的值

当正常提交，回滚后这些记录都会被删除。

处理分布式事务(SpringCloud Alibaba Seata)

前言

Seata-Server安装

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处理分布式事务(SpringCloud Alibaba Seata)

前言

Seata-Server安装

实际应用

补充

热门文章

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相关电子书

相关实验场景