Spring Cloud Alibaba Seata

一、简介

官网地址:http://seata.io/zh-cn/

1，概念

　　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在提供高性能和简单一样的分布式事务服务。

2，处理过程

　　Transaction ID XID:全局唯一的事务ID

　　Transaction Coordinator(TC) :维护全局和分支事务的状态，驱动全局事务提交或回滚。

　　Transaction  Manager(TM) :定义全局事务的范围：开始全局事务、提交或回滚全局事务。

　　Resource Manager(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。

                   

1. 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
2. XID在微服务调用链路的上下文中传播
3. RM向TC注册分支事务，将其纳入XID对应全局事务的管辖
4. TM向TC发起针对XID的全局提交或回滚决议
5. TC调度XID下管辖的全部分支事务完成提交或回滚请求

二、Seata-Server的安装

1，下载

　　http://seata.io/zh-cn/blog/download.html 选择指定版本下载(我这里用的是0.9.0)

2，修改配置文件

　　修改seata/conf/file.conf

#将service中修改group
vgroup_mapping.my_test_tx_group = "my_group"
#将store模块修改为db并修改数据连接，将conf目录下的db_store.sql文件导入到数据库中
mode = "db"
db {
    datasource = "dbcp"
    db-type = "mysql"
    driver-class-name = "com.mysql.jdbc.Driver"
    url = "jdbc:mysql://127.0.0.1:3306/seata"
    user = "root"
    password = "123456"
}

 　　修改seata/conf/registry.conf

registry {
  type = "nacos"
  nacos {
    serverAddr = "localhost:8848"
    namespace = ""
    cluster = "default"
 }

三、Seata的应用

1，订单服务

源码:seata-order-service2001

a，配置pom

<!--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>

b，配置yaml

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: my_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

c，添加file.conf(与seata-server配置相同)

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.my_group = "default"

  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"
    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
  }
}

d，添加registry.conf(与seata-server的配置相同)

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

  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"
  }
}

e，fegin调用(这里以其中一个account为例)

@FeignClient(value = "seata-account-service")
public interface AccountService {

    @RequestMapping("/account/decrease")
    public CommonResult decrease(@RequestParam("userId") Long userId, @RequestParam("money") BigDecimal money);

}

f，事务service

@Slf4j
@Service
public class OrderServiceImpl implements OrderService {

    @Autowired
    OrderDao orderDao;
    @Autowired
    AccountService accountService;
    @Autowired
    StorageService storageService;

    @Override
    @GlobalTransactional(name = "my-order-test",rollbackFor = Exception.class) //加注解使用全局的事务，name 为事务名称不重复就行
    public Long create(Order order) {
        log.info("=========================下订单，开始");
        orderDao.create(order);
        log.info("=========================下订单，完成");

        log.info("=========================减库存，开始");
        storageService.decrease(order.getProductId(), order.getCount());
        log.info("=========================减库存，完成");

        log.info("=========================减积分，开始");
        accountService.decrease(order.getUserId(), order.getMoney());
        log.info("=========================减积分，完成");

        log.info("=========================订单状态修改，开始");
        orderDao.update(order.getId(),1);
        log.info("=========================订单状态修改，完成");

        return order.getId();
    }
}

g，启动类

2，库存服务

源码：seata-storage-service2002

　　与订单服务中的a，b，c，d，g配置步骤相同

3，账户服务

源码:seata-account-service2003

　　与库存服务的配置步骤相同

四、Seata的原理解析

参考文档：http://seata.io/zh-cn/docs/overview/what-is-seata.html

1，AT模式

一阶段

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，在业务数更新之后
3，将其保存成"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。

                 

二阶段提交

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。

回滚的方式便是用"before image"还原业务数据；但在还原前要首先校验脏写，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。