视频链接：2020最新版SpringCloud框架开发教程-周阳
文章源码：https://github.com/geyiwei-suzhou/cloud2020/

用户购买商品的业务逻辑。整个业务逻辑由3个微服务提供支持：

• 仓储服务：对给定的商品扣除仓储数量
• 订单服务：根据采购需求创建订单
• 账户服务：从用户账户中扣除余额

单体应用被拆分成微服务应用，原来的三个模块被拆分成三个独立应用，分别使用三个独立的数据源

业务操作需要调用三个服务完成。此时每个微服务内部的数据一致性由本地事务来保证，但是全局的数据一致性问题没法保证

一次业务操作需要跨多个数据源或需要跨多个系统进行远程调用，就会产生分布式事务问题

Seata简介

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下提供高性能和简单易用的分布式事务服务
分布式事务处理过程：一个ID + 三个组件模型

• XID (Transaction ID) - 全局唯一的事务ID
• 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
  
  
  分布式事务处理过程：

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

Seata下载安装

下载地址：https://github.com/seata/seata/releases/tag/v0.9.0

1. 下载压缩包，解压到指定目录

2. 修改目录中conf/file.conf：

   • 自定义事务组名称： vgroup_mapping.my_test_tx_group = “fsp_tx_group”
   • 事务日志存储模式为db：mode = “db”
   • 数据库连接信息：
     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”

   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->rgroup
     vgroup_mapping.my_test_tx_group = "fsp_tx_group"
     #only support single node
     default.grouplist = "127.0.0.1:8091"
     #degrade current not support
     enableDegrade = false
     #disable
     disable = false
     #unit ms,s,m,h,d represents milliseconds, seconds, minutes, hours, days, default permanent
     max.commit.retry.timeout = "-1"
     max.rollback.retry.timeout = "-1"
   }
   
   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
     }
   }
   

3. 修改目录中conf/registry.conf：

   • 注册类型： type = “nacos”
   • 修改nacos配置：serverAddr = “localhost:8848”

   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"
     }
   }
   

4. 在数据库中创建数据库：seata

   在seata数据库里导入SQL脚本conf/db_store.sql

5. 启动

   nohup sh ./bin/seata-server.sh & # 后台运行