分布式事务-Seata 控制分布式事务

一、Seata概念

Seata 是一款开源的分布式事务解决方案，致力于提供高性能和简单易用的分布式事务服务。Seata 将为用户提供了 AT、TCC、SAGA 和 XA 事务模式，为用户打造一站式的分布式解决方案。

Seata术语

• TC：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。
• TM：事务管理器。定义全局事务的范围：开始全局事务、提交或回滚全局事务
• RM：管理分支事务处理的资源，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。 RPC（Remote Procedure Call）远程过程调用，简单的理解是一个节点请求另一个节点提供的服务。 我们只需要使用一个 @GlobalTransactional注解在业务方法上:

@GlobalTransactional
public void purchase(String userId, String commodityCode, int orderCount) {
        ......
}

二、Seata使用

1、创建 UNDO_LOG 表

SEATA AT 模式需要 UNDO_LOG 表

-- 注意此处0.3.0+ 增加唯一索引 ux_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 AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

如果每一个微服务都想参与到全局事务中，则每个微服务都需要创建一个回滚日志表 UNDO_LOG。

给我们项目所涉及的微服务数据库都添加undo_log表：gulimall-oms,gulimall-pms, gulimall-ums,gulimall-wms 。

2、安装事务协调器

从 https://github.com/seata/seata/releases, 下载服务器软件包，将其解压缩。

3、整合

在 gulimall-common 服务导入seata依赖: gulimall-common/pom.xml

 <!-- 分布式事务seata -->
    <dependency>
      <groupId>com.alibaba.cloud</groupId>
      <artifactId>spring-cloud-starter-alibaba-seata</artifactId>
    </dependency>

• 可以看到导入的Seata版本为 seata-all-0.7.1 ，所以，seata服务版本也必须是 0.7.1。
• 注册中心配置： /seata-server-0.7.1/conf/registry.conf:修改 registry type=nacos

registry {
  # file 、nacos 、eureka、redis、zk、consul、etcd3、sofa  指定注册中心
  type = "nacos"

  # 如果类型为nacos，则需要配置nacos的服务addr
  nacos {
    serverAddr = "localhost:8848"  
    namespace = "public"
    cluster = "default"
  }
  eureka {
    serviceUrl = "http://localhost:1001/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  Seata的配置都在哪里，默认是在该文件 file.conf
  type = "file"

  nacos {
    serverAddr = "localhost"
    namespace = "public"
    cluster = "default"
  }
  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"
  }
}

• Seata服务器配置： /seata-server-0.7.1/conf/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->rgroup
  vgroup_mapping.my_test_tx_group = "default"
  #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"
}

client {
  async.commit.buffer.limit = 10000
  lock {
    retry.internal = 10
    retry.times = 30
  }
  report.retry.count = 5
}

## transaction log store，事务日志存储在哪里
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
  }

  ## 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"
    url = "jdbc:mysql://127.0.0.1:3306/seata"
    user = "mysql"
    password = "mysql"
    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 {
  committing-retry-delay = 30
  asyn-committing-retry-delay = 30
  rollbacking-retry-delay = 30
  timeout-retry-delay = 30
}

transaction {
  undo.data.validation = true
  undo.log.serialization = "jackson"
}

## metrics settings
metrics {
  enabled = false
  registry-type = "compact"
  # multi exporters use comma divided
  exporter-list = "prometheus"
  exporter-prometheus-port = 9898
}

• 启动Seata服务： cd /seata-server-0.7.1/bin

sh seata-server.sh -p 8091 -h 127.0.0.1 -m file

chmod +x seata-server.sh sh seata-server.sh -p 8091 -h 127.0.0.1

然后再进入到Nacos中心，可以看到Seata服务已经成功注册到Nacos服务中心了。

• 其他微服务也需要引入这两个文件,其他微服务引入的时候，要记得file.conf文件修改 application.name名字

4、数据源代理

• 所有想要用到分布式事务的微服务使用 seata DataSourceProxy 代理自己的数据源。 创建Seata数据源配置文件： MySeataConfig

@Configuration
public class MySeataConfig {


    @Bean(name = "sqlSessionFactory")
    public SqlSessionFactory sqlSessionFactoryBean(DataSource dataSourceProxy) throws Exception {
        MybatisSqlSessionFactoryBean bean = new MybatisSqlSessionFactoryBean();
        bean.setDataSource(dataSourceProxy);
        ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        bean.setMapperLocations(resolver.getResources("classpath*:mapper/**/*.xml"));

        SqlSessionFactory factory = null;
        try {
            factory = bean.getObject();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
        return factory;
    }
    @Bean
    public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

然后将该配置文件放到需要使用seata服务的配置目录下

5、微服务导入配置文件#

每个微服务，都必须导入 registry.conf , file.conf，并且修改file.conf配置应用名为我们微服务名 vgroup_mapping.{application.name}-fescar-server-group = "default" ，否则会找不到。 代码略

6、启动测试分布式事务

给分布式大事务的入口标注@GlobalTransactional 每一个远程的小事务用@Trabsactional

  @GlobalTransactional
  @Transactional
  @Override
  public SubmitOrderResponseVo submitOrder(OrderSubmitVo vo) {}