微服务-分布式事务seata

什么是分布式事务

指一次大的操作由不同的小操作组成的，这些小的操作分布在不同的服务器上，分布式事务需要保证这些小操作要么全部成功，要么全部失败。从本质上来说，分布式事务就是为了保证不同数据库的数据一致性。

为什么要使用分布式事务

在微服务独立数据源的思想，每一个微服务都有一个或者多个数据源，虽然单机单库事务已经非常成熟，但是由于网路延迟和不可靠的客观因素，分布式事务到现在也还没有成熟的方案，对于中大型网站，特别是涉及到交易的网站，一旦将服务拆分微服务，分布式事务一定是绕不开的一个组件，通常解决分布式事务问题。

seata 分布式事务

Seata是阿里开源的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。

TC (Transaction Coordinator) - 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 (Transaction Manager) - 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 (Resource Manager) - 资源管理器

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。

seata下载

http://seata.io/zh-cn/blog/download.html
或者
链接：https://pan.baidu.com/s/1E2oJcuiC0jZdDYKRReL6_A
提取码：mq18

seata安装

1.修改conf/file.conf配置文件

mode 改成db

db的连接地址改成本机的

## transaction log store, only used in seata-server
store {
  ## store mode: file、db、redis
  mode = "db"

  ## 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"
    url = "jdbc:mysql://127.0.0.1:3306/seata"
    user = "root"
    password = "root"
    minConn = 5
    maxConn = 100
    globalTable = "global_table"
    branchTable = "branch_table"
    lockTable = "lock_table"
    queryLimit = 100
    maxWait = 5000
  }

  ## redis store property
  redis {
    host = "127.0.0.1"
    port = "6379"
    password = ""
    database = "0"
    minConn = 1
    maxConn = 10
    maxTotal = 100
    queryLimit = 100
  }

}

2.registry.conf

注册中心改成nacos

type = “nacos”

registry {
  # file 、nacos 、eureka、redis、zk、consul、etcd3、sofa
  type = "nacos"
  loadBalance = "RandomLoadBalance"
  loadBalanceVirtualNodes = 10

  nacos {
    application = "seata-server"
    serverAddr = "127.0.0.1:8848"
    group = "SEATA_GROUP"
    namespace = ""
    cluster = "default"
    username = "nacos"
    password = "nacos"
  }
  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"
  }
  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 = "127.0.0.1:8848"
    namespace = ""
    group = "SEATA_GROUP"
    username = ""
    password = ""
  }
  consul {
    serverAddr = "127.0.0.1:8500"
  }
  apollo {
    appId = "seata-server"
    apolloMeta = "http://192.168.1.204:8801"
    namespace = "application"
    apolloAccesskeySecret = ""
  }
  zk {
    serverAddr = "127.0.0.1:2181"
    sessionTimeout = 6000
    connectTimeout = 2000
    username = ""
    password = ""
  }
  etcd3 {
    serverAddr = "http://localhost:2379"
  }
  file {
    name = "file.conf"
  }
}

3.执行seata的数据库脚本
链接：https://pan.baidu.com/s/1HEy27tx46vgiDyf2xGXorQ
提取码：chpm

4.启动seata

执行bin目录的seata-server.bat

5.引入pom

 <dependency>
     <groupId>com.alibaba.cloudgroupId>
     <artifactId>spring-cloud-starter-alibaba-seataartifactId>
     <exclusions>
         <exclusion>
             <artifactId>seata-allartifactId>
             <groupId>io.seatagroupId>
         exclusion>
     exclusions>
 dependency>
 <dependency>
     <groupId>io.seatagroupId>
     <artifactId>seata-allartifactId>
     <version>1.3.0version>
 dependency>

6.修改yml

server:
  port: 2001
spring:
  application:
    name: seata-order-service
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848 #配置nacos地址
    alibaba:
      seata:
        tx-service-group: SEATA_GROUP
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/seata_order
    username: root
    password: root
##消费者访问微服务服务端名称
#service-url:
#  nacos-user-service: http://nacos-payment-provider
##激活sentinel对feign的支持
feign:
  hystrix:
    enabled: false
logging:
  level:
    io:
      seata: info
mybatis:
  # 搜索指定包别名
  mapper-locations: classpath:mapper/*.xml

7.加载配置

把刚才修改后的file.conf和registry.conf移动到项目的resource目录

8.代码演示
在最开始的业务实现类加入@GlobalTransactional注解，其余的业务模块方法添加
@Transactional(propagation = Propagation.REQUIRES_NEW)

Transactional详解
如果A.f1()调用B.f2()，那么事务X被挂起，重新创建一个事务Y，B.f2()在事务Y中执行，Y执行完毕再继续X事务。接受，给的不收，用自己的

	@Override
    @GlobalTransactional // 重点 第一个开启事务的需要添加seata全局事务注解
    public void create(TOrder order) {
        log.info("----------->创建订单");
        //1.新建订单
        tOrderMapper.create(order);
        //2.扣减库存
        log.info("----------->订单微服务开始调用库存，做扣减count");
        storageService.decrease(order.getProductId(),order.getCount());
        log.info("----------->订单微服务开始调用库存，做扣减end");
        //3.扣减账户
        log.info("----------->订单微服务开始调用账户，做扣减Money");
        accountService.decrease(order.getUserId(),order.getMoney());
        log.info("----------->订单微服务开始调用账户，做扣减end");
        //4.修改订单的状态，从0到1，1代表已经完成。
        log.info("----------->修改订单状态开始");
        tOrderMapper.update(order.getUserId(),0);
        log.info("----------->修改订单状态开始end");
        log.info("----------->创建订单成功");
    }