前言

阿里官方给出了seata-sample地址，官方自己也对Sample提供了很多类型，可以查看学习。 我这里选择演示SpringBoot+MyBatis。
Seata分布式事务框架Sample-小白菜博客
该聚合工程共包括5个module：

  • sbm-account-service
  • sbm-business-service
  • sbm-common-service
  • sbm-order-service
  • sbm-storage-service

不同Module之间的服务通信使用Rest方式通信。
​

准备工作

创建数据库

在sql/all_in_one_sql里是演示中需要的sql脚本，共创建了3个schema: db_account, db_order, db_storage， 分别演示三个不同的数据库，每个schema里都有一张undo_log表。
QQ截图20210608172250.png

启动Seata-Server

Seata-Server扮演TM的角色，在官网下载http://seata.io/zh-cn/blog/download.html，最新版本为1.4.2。
Seata分布式事务框架Sample-小白菜博客
/conf/registry.conf 中有两个大的节点registry - 注册中心配置选项，config - 配置中心配置选项。

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

  nacos {
    application = "seata-server"
    serverAddr = "127.0.0.1:8848"
    group = "SEATA_GROUP"
    namespace = ""
    cluster = "default"
    username = ""
    password = ""
  }
  eureka {
    serviceUrl = "http://localhost:8761/eureka"
    application = "default"
    weight = "1"
  }
  redis {
    serverAddr = "localhost:6379"
    db = 0
    password = ""
    cluster = "default"
    timeout = 0
  }
  zk {
    cluster = "default"
    serverAddr = "127.0.0.1:2181"
    sessionTimeout = 6000
    connectTimeout = 2000
    username = ""
    password = ""
  }
  consul {
    cluster = "default"
    serverAddr = "127.0.0.1:8500"
    aclToken = ""
  }
  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"
  }
}

# 配置中心配置
config {
  # file、nacos 、apollo、zk、consul、etcd3
  type = "file"

  nacos {
    serverAddr = "127.0.0.1:8848"
    namespace = ""
    group = "SEATA_GROUP"
    username = ""
    password = ""
    dataId = "seataServer.properties"
  }
  consul {
    serverAddr = "127.0.0.1:8500"
    aclToken = ""
  }
  apollo {
    appId = "seata-server"
    ## apolloConfigService will cover apolloMeta
    apolloMeta = "http://192.168.1.204:8801"
    apolloConfigService = "http://192.168.1.204:8080"
    namespace = "application"
    apolloAccesskeySecret = ""
    cluster = "seata"
  }
  zk {
    serverAddr = "127.0.0.1:2181"
    sessionTimeout = 6000
    connectTimeout = 2000
    username = ""
    password = ""
    nodePath = "/seata/seata.properties"
  }
  etcd3 {
    serverAddr = "http://localhost:2379"
  }
  file {
    name = "file.conf"
  }
}

/conf/file.conf - 只有当registry.conf下 config.type=file时才加载file.config中的参数。config.type等于其他值的话则不需要file.config。 seata-server也提供了file.conf.example， 详细的参数介绍也可以查看http://seata.io/zh-cn/docs/user/configurations.html。

## transaction log store, only used in seata-server
store {
  ## store mode: file、db、redis
  mode = "file"
  ## rsa decryption public key
  publicKey = ""
  ## 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)/HikariDataSource(hikari) etc.
    datasource = "druid"
    ## mysql/oracle/postgresql/h2/oceanbase etc.
    dbType = "mysql"
    driverClassName = "com.mysql.jdbc.Driver"
    ## if using mysql to store the data, recommend add rewriteBatchedStatements=true in jdbc connection param
    url = "jdbc:mysql://127.0.0.1:3306/seata?rewriteBatchedStatements=true"
    user = "mysql"
    password = "mysql"
    minConn = 5
    maxConn = 100
    globalTable = "global_table"
    branchTable = "branch_table"
    lockTable = "lock_table"
    queryLimit = 100
    maxWait = 5000
  }

  ## redis store property
  redis {
    ## redis mode: single、sentinel
    mode = "single"
    ## single mode property
    single {
      host = "127.0.0.1"
      port = "6379"
    }
    ## sentinel mode property
    sentinel {
      masterName = ""
      ## such as "10.28.235.65:26379,10.28.235.65:26380,10.28.235.65:26381"
      sentinelHosts = ""
    }
    password = ""
    database = "0"
    minConn = 1
    maxConn = 10
    maxTotal = 100
    queryLimit = 100
  }
}

启动服务./bin/seata-server.bat ，默认打开了8091端口。
QQ截图20210608173152.png

启动Sample服务

依此启动account-service，business-service，order-service，storage-service。business-service作为业务逻辑的入口分别调用order-service和storage-service。这里就看到了关键注解GlobalTransactional。
4个服务的默认端口分别是8081，8082， 8083，8084。
Seata分布式事务框架Sample-小白菜博客
​

BusinessService

@Service
public class BusinessService {

    private static final Logger LOGGER = LoggerFactory.getLogger(BusinessService.class);

    @Autowired
    private StorageClient storageClient;
    @Autowired
    private OrderClient orderClient;

    /**
     * 减库存，下订单
     *
     * @param userId
     * @param commodityCode
     * @param orderCount
     */
    @GlobalTransactional
    public void purchase(String userId, String commodityCode, int orderCount) {
        LOGGER.info("purchase begin ... xid: " + RootContext.getXID());
        storageClient.deduct(commodityCode, orderCount);
        orderClient.create(userId, commodityCode, orderCount);
    }
}

OrderClient

@Slf4j
@Component
public class OrderClient {

    @Autowired
    private RestTemplate restTemplate;

    public void create(String userId, String commodityCode, int orderCount) {
        String url = "http://127.0.0.1:8082/api/order/debit?userId=" + userId + "&commodityCode=" + commodityCode + "&count=" + orderCount;
        try {
            restTemplate.getForEntity(url, Void.class);
        } catch (Exception e) {
            log.error("create url {} ,error:", url);
            throw new RuntimeException();
        }
    }
}

StorageClient

@Slf4j
@Component
public class StorageClient {

    @Autowired
    private RestTemplate restTemplate;

    public void deduct(String commodityCode, int orderCount) {
        System.out.println("business to storage " + RootContext.getXID());
        String url = "http://127.0.0.1:8081/api/storage/deduct?commodityCode=" + commodityCode + "&count=" + orderCount;
        try {
            restTemplate.getForEntity(url, Void.class);
        } catch (Exception e) {
            log.error("deduct url {} ,error:", url, e);
            throw new RuntimeException();
        }
    }
}

​

运行Sample

模拟正常事务提交

运行Sample前，我们先查看下当前三个服务数据库的数据。
db_account.account_tbl
Seata分布式事务框架Sample-小白菜博客
db_storage.storage_tbl
Seata分布式事务框架Sample-小白菜博客
业务接口在business-service/BusinessController里，我们先来执行下购买下单正常的提交流程。
Seata分布式事务框架Sample-小白菜博客
执行接口http://localhost:8094/api/business/purchase/commit/, 执行后，seata-server控制台上会显示全局事务执行的具体日志和执行成功的日志。
Seata分布式事务框架Sample-小白菜博客
执行后我们再查看下数据库。
db_account.account_tbl。 user_id对应1001的账户减去了5元（9995）。
Seata分布式事务框架Sample-小白菜博客
db_storage.storage_tbl
Seata分布式事务框架Sample-小白菜博客
db_order.order_tbl
QQ截图20210609111421.png

模拟全局事务回滚

执行接口http://localhost:8084/api/business/purchase/rollback， 这里我们想查看undo_log表的数据，则在BusinessSerivce#purchase断点。
Seata分布式事务框架Sample-小白菜博客
db_storage.undo_log
Seata分布式事务框架Sample-小白菜博客
QQ截图20210609112112.png

undo_log里最重要的是关注beforeImage和afterImage节点。

全局事务回滚后，undo_log表会清空数据。
​