SpringCloud Alibaba Seata (收藏版)

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™ :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。

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
XID在微服务调用链路的上下文中传播
RM向TC注册分支事务，将其纳入XID对应全局事务的管辖
TM向TC发起针对XID的全局提交或回滚决议
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。

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