《分布式事务系列教程-第五章-Seata分布式事务解决方案》

落日映苍穹つ 2022-09-04 13:49 252阅读 0赞

# 《分布式事务系列教程-第五章-Seata分布式事务解决方案》 #

# 一、seata解决方案 #

Seata是一个开源的分布式事务解决方案，是由阿里中间件团队研发的，原名Fescar，后更名为seata，seata致力于提供**高性能**和易于使用的分布式事务服务。Seata将为用户提供AT，TCC，SAGA和XA交易模型，以为用户创建一站式分布式解决方案。

>  *  seata官网：http://seata.io
>  *  github地址：https://github.com/seata/seata

**seata也是基于2PC的一种分布式解决方案，对传统的2PC基础上进行了一些优化**，通过引入事务协调器（TC）来监控各个分支事务的执行状态来判断全局事务是否提交或回滚，引入**日志表来替代锁表**问题。

*  阶段1：在同一本地事务中**提交**业务数据并且记录日志到undo表，然后释放本地锁和连接资源。
 *  阶段2：
    
     *  对于提交情况，异步快速地完成工作。
     *  对于回滚情况，请根据阶段1中创建的日志数据进行补偿。

## 1.1 seata执行流程： ##

1）当RM启动时，首先注册到TC中。

2）TM向TC申请开启全局事务，全局事务开启后生成用于标识此次全局事务的id（XID）。每个全局事务ID各不相同。

4）首先第一个RM向TC开启分支事务，当进行微服务调用时，XID也会随之传递下来，**此时的RM事务已经真正提交**

5）最终TM根据各分支事务执行情况，来请求TC提交或者回滚全局事务

6）TC根据XID对应的全局事务下的分支事务来提交或回滚。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JiMTUwNzAwNDc3NDg_size_16_color_FFFFFF_t_70_pic_center]

> TM和全局事务的发起方在一起；

## 1.2 搭建seata工程 ##

### 1.2.1 启动seata协调器 ###

启动事务协调器TC

seata-server.bat -p 10101 -m file

*  `-p`：指定启动的端口
 *  `-m`：指定启动的模式，file代表以文件方式存储信息

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JiMTUwNzAwNDc3NDg_size_16_color_FFFFFF_t_70_pic_center 1]

### 1.2.2 搭建父工程 ###

*  pom.xml：

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>com.lscl</groupId>
        <artifactId>seata_transaction</artifactId>
        <packaging>pom</packaging>
        <version>1.0-SNAPSHOT</version>
        <modules>
            <module>eureka_server</module>
            <module>store</module>
            <module>orders</module>
        </modules>
    
        <properties>
            <spring-cloud-alibaba.version>2.1.0.RELEASE</spring-cloud-alibaba.version>
        </properties>
    
        <dependencyManagement>
    
            <dependencies>
                <dependency>
                    <groupId>commons-lang</groupId>
                    <artifactId>commons-lang</artifactId>
                    <version>2.6</version>
                </dependency>
    
                <dependency>
                    <groupId>com.alibaba</groupId>
                    <artifactId>druid-spring-boot-starter</artifactId>
                    <version>1.1.16</version>
                </dependency>
    
                <dependency>
                    <groupId>com.alibaba.cloud</groupId>
                    <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                    <version>2.1.0.RELEASE</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
                <dependency>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-dependencies</artifactId>
                    <version>2.1.3.RELEASE</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
    
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>Greenwich.RELEASE</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
    </project>

### 1.2.3 搭建EurekaServer ###

*  1）pom.xml：

*  2）Application.yml

server:
      port: 10102
    eureka:
      client:
        register-with-eureka: false # 是否将该服务注册到eureka服务端
        fetch-registry: false       # 是否从eureka服务端获取其他服务实例
        service-url:                # eureka的注册地址
          defaultZone: http://127.0.0.1:${ server.port}/eureka

*  3）启动类

package com.lscl.eureka;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
    
    @SpringBootApplication
    @EnableEurekaServer         // 开启eureka服务器
    public class EurekaApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(EurekaApplication.class);
        }
    }

### 1.2.4 搭建库存微服 ###

#### 1）pom.xml： ####

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <parent>
            <artifactId>seata_transaction</artifactId>
            <groupId>com.lscl</groupId>
            <version>1.0-SNAPSHOT</version>
        </parent>
        <modelVersion>4.0.0</modelVersion>
    
        <artifactId>store</artifactId>
        <dependencies>
    
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-alibaba-seata</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-openfeign</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.47</version>
            </dependency>
    
        </dependencies>
    
    </project>

#### 2）registry.conf： ####

registry {
      # file 、redis、zookeeper、eureka、nacos 、consul、etcd3、sofa
      type = "file"
    
      file {
        name = "file.conf"
      }
    }
    
    config {
      # file、nacos 、apollo、zk
      type = "file"
    
      file {
        name = "file.conf"
      }
    }

#### 3）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
      }
    }
    ## transaction log store
    store {
      ## store mode: file、db
      mode = "file"
    
      ## 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
      }
    
    }
    
    service {
      #vgroup->rgroup
      vgroup_mapping.orders-fescar-service-group = "default"		# 微服名称
      #only support single node
      default.grouplist = "127.0.0.1:10101"			# seata
      #degrade current not support
      enableDegrade = false
      #disable
      disable = false
    }
    client {
      async.commit.buffer.limit = 10000
      lock {
        retry.internal = 10
        retry.times = 30
      }
    }

#### 4）application.xml： ####

server:
      port: 10104
      servlet:
        context-path: /store
    spring:
      application:
        name: store #指定服务名
      datasource:
        driverClassName: com.mysql.jdbc.Driver
        url: jdbc:mysql://localhost:3306/store?serverTimezone=GMT%2b8
        username: root
        password: admin
      jpa:
        properties:
          hibernate:
            format_sql: true	# 格式化sql
            show_sql: true		# 显示sql
    eureka:
      client:
        service-url:
          defaultZone: http://127.0.0.1:10102/eureka

#### 5）启动类： ####

package com.lscl.store;
    
    import com.alibaba.druid.pool.DruidDataSource;
    import io.seata.rm.datasource.DataSourceProxy;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.context.properties.ConfigurationProperties;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Primary;
    
    import javax.sql.DataSource;
    
    @EnableEurekaClient
    @SpringBootApplication
    public class StoreApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(StoreApplication.class);
        }
    
        private final ApplicationContext applicationContext;
    
        public StoreApplication(ApplicationContext applicationContext) { 
            this.applicationContext = applicationContext;
        }
    
    
        @Bean
        @ConfigurationProperties(prefix = "spring.datasource")
        public DruidDataSource druidDataSource() { 
            DruidDataSource druidDataSource = new DruidDataSource();
            return druidDataSource;
        }
    
    
        @Primary
        @Bean               // 代理数据源
        public DataSource dataSource(DruidDataSource dataSource)  { 
            DataSourceProxy proxyDS = new DataSourceProxy(dataSource);
            return proxyDS;
        }
    }

#### 6）entity.java： ####

package com.lscl.store.entity;
    
    import javax.persistence.Entity;
    import javax.persistence.Id;
    import javax.persistence.Table;
    import java.io.Serializable;
    
    @Entity
    @Table(name = "t_store")
    public class Store implements Serializable { 
        @Id
        private String id;
    
        private Integer count;
    
        public String getId() { 
            return id;
        }
    
        public void setId(String id) { 
            this.id = id;
        }
    
        public Integer getCount() { 
            return count;
        }
    
        public void setCount(Integer count) { 
            this.count = count;
        }
    }

#### 7）dao.java： ####

package com.lscl.store.dao;
    
    import com.lscl.store.entity.Store;
    import org.springframework.data.jpa.repository.JpaRepository;
    import org.springframework.data.jpa.repository.Modifying;
    import org.springframework.data.jpa.repository.Query;
    import org.springframework.stereotype.Repository;
    
    @Repository
    public interface StoreDao extends JpaRepository<Store,String> { 
        @Query("update Store s set s.count=s.count-1")
        @Modifying
        void updateCount();
    
    }

#### 8）service.java： ####

package com.lscl.store.service;
    
    import com.lscl.store.dao.StoreDao;
    import io.seata.core.context.RootContext;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    import org.springframework.transaction.annotation.Transactional;
    
    @Service
    public class StoreService { 
        @Autowired
        private StoreDao storeDao;
    
    
        @Transactional
        public void updateCount(Integer flag) { 
            System.out.println("orders_xid: "+ RootContext.getXID());
    
            // 库存-1
            storeDao.updateCount();
    
            if(flag==200){ 			// 模拟异常
                throw new RuntimeException("store...error");
            }
    
        }
    }

#### 9）controller.java： ####

package com.lscl.store.controller;
    
    import com.lscl.store.service.StoreService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class StoreController { 
    
        @Autowired
        private StoreService storeService;
    
        @RequestMapping("/updateCount/{flag}")
        public String updateCount(@PathVariable Integer flag){ 
            storeService.updateCount(flag);
    
            return "store...success";
        }
    }

### 1.2.5 搭建订单微服 ###

#### 1）pom.xml： ####

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
        <parent>
            <artifactId>seata_transaction</artifactId>
            <groupId>com.lscl</groupId>
            <version>1.0-SNAPSHOT</version>
        </parent>
        <modelVersion>4.0.0</modelVersion>
    
        <artifactId>orders</artifactId>
    
        <dependencies>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
    
            <dependency>
                <groupId>com.alibaba.cloud</groupId>
                <artifactId>spring-cloud-alibaba-seata</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-openfeign</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.47</version>
            </dependency>
    
        </dependencies>
    </project>

#### 2）registry.conf： ####

#### 3）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
      }
    }
    ## transaction log store
    store {
      ## store mode: file、db
      mode = "file"
    
      ## 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
      }
    
    }
    
    service {
      #vgroup->rgroup
      vgroup_mapping.store-fescar-service-group = "default"
      #only support single node
      default.grouplist = "127.0.0.1:10101"
      #degrade current not support
      enableDegrade = false
      #disable
      disable = false
    }
    client {
      async.commit.buffer.limit = 10000
      lock {
        retry.internal = 10
        retry.times = 30
      }
    }

#### 4）application.yml： ####

server:
      port: 10103
      servlet:
        context-path: /orders
    spring:
      application:
        name: orders #指定服务名
      datasource:
        driverClassName: com.mysql.jdbc.Driver
        url: jdbc:mysql://localhost:3306/orders?serverTimezone=GMT%2b8
        username: root
        password: admin
      jpa:
        properties:
          hibernate:
            format_sql: true	# 格式化sql
            show_sql: true		# 显示sql
    eureka:
      client:
        service-url:
          defaultZone: http://127.0.0.1:10102/eureka
    feign:   # 开启熔断器
      hystrix:
        enabled: true

#### 5）启动类： ####

package com.lscl.orders;
    
    import com.alibaba.druid.pool.DruidDataSource;
    import io.seata.rm.datasource.DataSourceProxy;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.context.properties.ConfigurationProperties;
    import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
    import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
    import org.springframework.cloud.openfeign.EnableFeignClients;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Primary;
    
    @EnableEurekaClient
    @EnableDiscoveryClient
    @EnableFeignClients
    @SpringBootApplication
    public class OrdersApplication { 
    
        public static void main(String[] args) { 
            SpringApplication.run(OrdersApplication.class);
        }
    
        private final ApplicationContext applicationContext;
    
        public OrdersApplication(ApplicationContext applicationContext) { 
            this.applicationContext = applicationContext;
        }
    
        @Bean
        @ConfigurationProperties(prefix = "spring.datasource")
        public DruidDataSource druidDataSource() { 
            DruidDataSource druidDataSource = new DruidDataSource();
            return druidDataSource;
        }
    
        @Primary
        @Bean       // 代理数据源
        public DataSourceProxy dataSource(DruidDataSource dataSource)  { 
            DataSourceProxy proxyDS = new DataSourceProxy(dataSource);
            return proxyDS;
        }
    
    }

#### 6）Client： ####

package com.lscl.orders.client;
    
    import com.lscl.orders.client.impl.StoreClientImpl;
    import org.springframework.cloud.openfeign.FeignClient;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    @FeignClient(value = "store",fallback = StoreClientImpl.class)
    public interface StoreClient { 
    
        @RequestMapping("/store/updateCount/{flag}")
        public String updateCount(@PathVariable("flag") Integer flag);
    
    }

#### 7）ClientImpl： ####

package com.lscl.orders.client.impl;
    
    import com.lscl.orders.client.StoreClient;
    import org.springframework.stereotype.Component;
    
    @Component
    public class StoreClientImpl implements StoreClient { 
        @Override
        public String updateCount(Integer flag) { 
            return "no";
        }
    }

#### 8）entity： ####

package com.lscl.orders.entity;
    
    import javax.persistence.Entity;
    import javax.persistence.Id;
    import javax.persistence.Table;
    import java.io.Serializable;
    
    @Entity
    @Table(name = "t_orders")
    public class Orders implements Serializable { 
        @Id
        private String id;
    
        private Integer count;
    
        public String getId() { 
            return id;
        }
    
        public void setId(String id) { 
            this.id = id;
        }
    
        public Integer getCount() { 
            return count;
        }
    
        public void setCount(Integer count) { 
            this.count = count;
        }
    }

#### 9）dao： ####

package com.lscl.orders.dao;
    
    import com.lscl.orders.entity.Orders;
    import org.springframework.data.jpa.repository.JpaRepository;
    import org.springframework.data.jpa.repository.Modifying;
    import org.springframework.data.jpa.repository.Query;
    import org.springframework.stereotype.Repository;
    
    @Repository
    public interface OrdersDao extends JpaRepository<Orders,String> { 
        @Query("update Orders o set o.count=o.count+1")
        @Modifying
        void updateCount();
    
    }

#### 10）service： ####

package com.lscl.orders.service;
    
    import com.lscl.orders.client.StoreClient;
    import com.lscl.orders.dao.OrdersDao;
    import io.seata.core.context.RootContext;
    import io.seata.spring.annotation.GlobalTransactional;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    import org.springframework.transaction.annotation.Transactional;
    
    @Service
    public class OrdersService { 
        @Autowired
        private OrdersDao ordersDao;
    
        @Autowired
        private StoreClient storeClient;
    
        @Transactional
        @GlobalTransactional            // 开启全局事务
        public void updateCount(Integer flag) { 
            System.out.println("orders_xid: "+RootContext.getXID());
            // 订单+1
            ordersDao.updateCount();
    
            // 库存-1
            String msg = storeClient.updateCount(flag);
    
            if("no".equals(msg)){ 
                throw new RuntimeException("store...error");
            }
    
            System.out.println(msg);
    
            if (flag == 100) { 
                throw new RuntimeException("orders...error");
            }
        }
    }

#### 11）controller： ####

package com.lscl.orders.controller;
    
    import com.lscl.orders.service.OrdersService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.PathVariable;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class OrdersController { 
        @Autowired
        private OrdersService ordersService;
    
        @RequestMapping("/updateCount/{flag}")
        public String updateCount(@PathVariable Integer flag){ 
    
            ordersService.updateCount(flag);
    
            return "orders...success";
        }
    }

### 1.2.5 创建undo\_log表 ###

根据2PC协议，我们知道在第一阶段时，执行完业务sql之后，会把前后镜像数据以及业务 SQL 相关的信息组成一条回滚日志记录，插入到 `UNDO_LOG` 表中

在第二阶段时如果是回滚则根据 UNDO LOG 中的前镜像和业务 SQL 的相关信息生成并执行回滚的语句

如果是提交则分支提交请求将异步和批量地删除相应 UNDO LOG 记录。

在订单、库存两个数据库中分别创建对应的undo\_log日志表。

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,
      PRIMARY KEY (`id`),
      UNIQUE KEY `ux_undo_log` (`xid`,`branch_id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

#### 全部RM执行成功流程： ####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JiMTUwNzAwNDc3NDg_size_16_color_FFFFFF_t_70_pic_center 2]

#### 某个RM执行失败流程： ####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0JiMTUwNzAwNDc3NDg_size_16_color_FFFFFF_t_70_pic_center 3]

## 1.3 总结 ##

seata也是基于2PC的一种分布式解决方案。seata方案解决了XA方案在准备阶段时，RM锁的问题。在高并发情况下，应当避免XA方案。

xa方案依赖于数据库对XA协议的支持，seata则是通过业务逻辑的处理（记录undo\_log表），来达到数据的回滚，底层不依赖于数据库。

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