Dubbo整合Seata，教你轻松实现TTC模式分布式事务！

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Seata

• AT模式： AT 模式的一阶段、二阶段提交和回滚（借助undo_log表来实现）均由 Seata 框架自动生成，用户只需编写“业务SQL”，便能轻松接入分布式事务，AT 模式是一种对业务无任何侵入的分布式事务解决方案。
• TTC模式： 相对于 AT 模式，TCC 模式对业务代码有一定的侵入性，但是 TCC 模式无 AT 模式的全局行锁，TCC 性能会比 AT模式高很多。（ 适用于核心系统等对性能有很高要求的场景。）
• SAGA模式：Sage 是长事务解决方案，事务驱动，使用那种存在流程审核的业务场景，如： 金融行业，需要层层审核。
• XA模式： XA模式是分布式强一致性的解决方案，但性能低而使用较少。

TCC模式

• Try：做业务检查和资源预留
• Confirm：确认提交
• Cancel：业务执行错误需要回滚的状态下执行分支事务的业务取消，预留资源释放

Seata Server安装

unzip  seata-server-1.1.0.zip 

• bin:存放各系统的启动脚本
• conf:存放seata server启动时所需要配置信息、数据库模式下所需要的建表语句
• lib:运行seata server所需要的的依赖包

• file.conf: 该文件用于配置存储方式、透传事务信息的NIO等信息，默认对应registry.conf中file配置方式
• registry.conf:seata server核心配置文件，可以通过该文件配置服务注册方式、配置读取方式。

• 注册中心使用Nacos
• 配置中心使用file进行配置

registry {
  # file 、nacos 、eureka、redis、zk、consul、etcd3、sofa
  type = "nacos"
  consul {
    cluster = "seata"
    serverAddr = "127.0.0.1:8848"
  }
}

config {
  # file、nacos 、apollo、zk、consul、etcd3
  type = "file"
  file {
    name = "file.conf"
  }
}

store {
  ## store mode: file?.b
  mode = "file"

  ## file store property
  file {
    ## store location dir
    dir = "sessionStore"
    # branch session size , if exceeded first try compress lockkey, still exceeded throws exceptions
    maxBranchSessionSize = 16384
    # globe session size , if exceeded throws exceptions
    maxGlobalSessionSize = 512
    # file buffer size , if exceeded allocate new buffer
    fileWriteBufferCacheSize = 16384
    # when recover batch read size
    sessionReloadReadSize = 100
    # async, sync
    flushDiskMode = async
  }

  ## database store property
  db {
    ## the implement of javax.sql.DataSource, such as DruidDataSource(druid)/BasicDataSource(dbcp) etc.
    datasource = "dbcp"
    ## mysql/oracle/h2/oceanbase etc.
    dbType = "mysql"
    driverClassName = "com.mysql.jdbc.Driver"
    url = "jdbc:mysql://127.0.0.1:3306/seata"
    registry.confuser = "mysql"
    password = "mysql"
    minConn = 1
    maxConn = 10
    globalTable = "global_table"
    branchTable = "branch_table"
    lockTable = "lock_table"
    queryLimit = 100
  }
}

• global_table: 存储全局事务session数据的表
• branch_table:存储分支事务session数据的表
• lockTable:存储分布式锁数据的表

  -- -------------------------------- The script used when storeMode is 'db' -------------------------------- -- the table to store GlobalSession data CREATE TABLE IF NOT EXISTS 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) ) ENGINE = InnoDB DEFAULT CHARSET = utf8; -- the table to store BranchSession data CREATE TABLE IF NOT EXISTS branch_table ( branch_id BIGINT NOT NULL, xid VARCHAR(128) NOT NULL, transaction_id BIGINT, resource_group_id VARCHAR(32), resource_id VARCHAR(256), 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) ) ENGINE = InnoDB DEFAULT CHARSET = utf8; -- the table to store lock data CREATE TABLE IF NOT EXISTS lock_table ( row_key VARCHAR(128) NOT NULL, xid VARCHAR(96), transaction_id BIGINT, branch_id BIGINT NOT NULL, resource_id VARCHAR(256), table_name VARCHAR(32), pk VARCHAR(36), gmt_create DATETIME, gmt_modified DATETIME, PRIMARY KEY (row_key), KEY idx_branch_id (branch_id) ) ENGINE = InnoDB DEFAULT CHARSET = utf8;

sh seata-server.sh -p 8091 -h 0.0.0.0 -m file 

Options: 

--host, -h 
The host to bind. 
Default: 0.0.0.0 

--port, -p 
The port to listen. 
Default: 8091 

--storeMode, -m log store mode : file、db 
Default: file 

--help

• 外网访问：如果需要外网访问 需要将0.0.0.0转成外网IP
• 后台启动： nohup sh seata-server.sh -p 8091 -h 127.0.0.1 -m file > catalina.out 2>&1 &

Dubbo整合Seata实现AT模式

<!--seata-->
<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-alibaba-seata</artifactId>
    <version>2.1.0.RELEASE</version>
    <exclusions>
        <exclusion>
            <artifactId>seata-all</artifactId>
            <groupId>io.seata</groupId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>io.seata</groupId>
    <artifactId>seata-all</artifactId>
    <version>1.1.0</version>
</dependency>

#mysql
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.driverClassName=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/dubbodemo
spring.datasource.username=mysql
spring.datasource.password=mysql

spring.cloud.alibaba.seata.tx-service-group=springcloud-alibaba-producer-test

transport {
  # tcp udt unix-domain-socket
  type = "TCP"
  #NIO NATIVE
  server = "NIO"
  #enable heartbeat
  heartbeat = true
  # the client batch send request enable
  enableClientBatchSendRequest = false
  #thread factory for netty
  threadFactory {
    bossThreadPrefix = "NettyBoss"
    workerThreadPrefix = "NettyServerNIOWorker"
    serverExecutorThreadPrefix = "NettyServerBizHandler"
    shareBossWorker = false
    clientSelectorThreadPrefix = "NettyClientSelector"
    clientSelectorThreadSize = 1
    clientWorkerThreadPrefix = "NettyClientWorkerThread"
    # netty boss thread size,will not be used for UDT
    bossThreadSize = 1
    #auto default pin or 8
    workerThreadSize = "default"
  }
  shutdown {
    # when destroy server, wait seconds
    wait = 3
  }
  serialization = "seata"
  compressor = "none"
}
# service configuration, only used in client side
service {
  #transaction service group mapping
  vgroupMapping.springcloud-alibaba-producer-test = "seata"
  seata.grouplist = "127.0.0.1:8091"
  #degrade, current not support
  enableDegrade = false
  #disable seata
  disableGlobalTransaction = false
}
#client transaction configuration, only used in client side
client {
  rm {
    asyncCommitBufferLimit = 10000
    lock {
      retryInterval = 10
      retryTimes = 30
      retryPolicyBranchRollbackOnConflict = true
    }
    reportRetryCount = 5
    tableMetaCheckEnable = false
    reportSuccessEnable = false
    sqlParserType = druid
  }
  tm {
    commitRetryCount = 5
    rollbackRetryCount = 5
  }
  undo {
    dataValidation = true
    logSerialization = "jackson"
    logTable = "undo_log"
  }
  log {
    exceptionRate = 100
  }
}

registry {
  # file 、nacos 、eureka、redis、zk、consul、etcd3、sofa
  type = "nacos"

  nacos {
    serverAddr = "127.0.0.1:8848"
    namespace = ""
    cluster = "seata"
  }
  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 = ""
    group = "SEATA_GROUP"
  }
  consul {
    serverAddr = "127.0.0.1:8500"
  }
  apollo {
    app.id = "seata-server"
    apollo.meta = "http://192.168.1.204:8801"
    namespace = "application"
  }
  zk {
    serverAddr = "127.0.0.1:2181"
    session.timeout = 6000
    connect.timeout = 2000
  }
  etcd3 {
    serverAddr = "http://localhost:2379"
  }
  file {
    name = "file.conf"
  }
}

• SEATA是基于数据源拦截来实现的分布式事务， 需要排除掉SpringBoot默认自动注入DataSourceAutoConfigurationBean，自定义配置数据源。

@Configuration
public class DataSourceProxyConfig {

    @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("classpath*:/mapper/*Mapper.xml"));
        sqlSessionFactoryBean.setTransactionFactory(new SpringManagedTransactionFactory());
        return sqlSessionFactoryBean.getObject();
    }

    @Bean public GlobalTransactionScanner globalTransactionScanner(){ return new GlobalTransactionScanner("account-gts-seata-example", "account-service-seata-service-group"); }

}

# 业务数据表
CREATE TABLE `sys_user` (
  `id` varchar(36) NOT NULL,
  `name` varchar(100) NOT NULL,
  `msg` varchar(500) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `sys_user` (`id`, `name`, `msg`) VALUES ('1', '小王', '初始化数据');

public interface IUserTccService {

    @TwoPhaseBusinessAction(name = "IUserTccService",commitMethod = "commit",rollbackMethod = "rollback")
    boolean prepare(BusinessActionContext actionContext, @BusinessActionContextParameter(paramName = "userPojo") UserPojo userPojo);

    boolean commit(BusinessActionContext actionContext);

    boolean rollback(BusinessActionContext actionContext);
}

public interface IUserService {
    public String ceshi(String input);
}

• 初步操作 Try：完成所有业务检查，预留必须的业务资源，本身也有数据操作。（支付场景：冻结预扣款30元）
• 确认操作 Confirm：真正执行的业务逻辑，不做任何业务检查，只使用 Try 阶段预留的业务资源。因此，只要 Try操作成功，Confirm 必须能成功。另外，Confirm 操作需满足幂等性，保证一笔分布式事务能且只能成功一次。（支付场景：扣除预付款）
• 取消操作 Cancel：释放 Try 阶段预留的业务资源，来回滚Try的数据操作。同样的，Cancel操作也需要满足幂等性。（支付场景：释放预付款）

  @Service public class UserTccServiceImpl implements IUserTccService {

  @Autowired
  UserPojoMapper userPojoMapper;
  
  @Override
  public boolean prepare(BusinessActionContext actionContext, UserPojo userPojo) {
      System.out.println("actionContext获取Xid commit>>> "+ RootContext.getXID());
      int storage =userPojoMapper.updateByPrimaryKey(userPojo);
      if (storage > 0){
          return true;
      }
      return false;
  }
  
  @Override
  public boolean commit(BusinessActionContext actionContext) {
      System.out.println("actionContext获取Xid commit>>> "+actionContext.getXid());
      return true;
  }
  
  @Override
  public boolean rollback(BusinessActionContext actionContext) {
      System.out.println("actionContext获取Xid rollback>>> "+actionContext.getXid());
      UserPojo userPojo = JSONObject.toJavaObject((JSONObject)actionContext.getActionContext("userPojo"),UserPojo.class);
      userPojo.setName("姓名被回滾了");
      int storage = userPojoMapper.updateByPrimaryKey(userPojo);
      if (storage > 0){
          return true;
      }
      return false;
  }
  

  }

• 没有涉及RPC调用的话只是一个分支事务，并不会触发rollback，并且分支事务共享同一个全局事务ID（即XID）。分支事务本身也具有原子性，可以确保本地事务的原子性（可以理解为prepare、commit方法虽然执行了，但是事务还是没执行，会在RM和TC协调下顺序执行 ）
• TC（事务协调者）：会使得全部try执行成功后，才开始执行confirm，如果存在一个try执行失败（或者网络问题RPC调用失败），会开启回滚分布式事务，这一点满足了分布式事务的原子性。
• GlobalTransactionScanner 会同时启动 RM 和 TM client。

  @Service public class UserServiceImpl implements IUserService{

  @Autowired
  UserPojoMapper userPojoMapper;
  
  @Autowired
  UserTccServiceImpl userTccService;
  
  private static Logger logger = LogManager.getLogger(LogManager.ROOT_LOGGER_NAME);
  
  @Override
  @GlobalTransactional
  public String ceshi(String input) {
      logger.info("全局XID：{}", RootContext.getXID());
      UserPojo userPojo = userPojoMapper.selectByPrimaryKey("1");
     // userPojo.setId("11111111");
      userPojo.setName("正常提交");
      if (userTccService.prepare(null,userPojo)){
          return "Hello World,"+input+"! ,I am "+ userPojo.getName();
      }
      return "失敗";
  }
  

  }

调用服务，进行验证