什么是分布式事务

单体应用被拆分成微服务应用，原来的三个模块被拆成三个独立的应用，分别使用三个独立的数据源
业务操作需要调用三个服务来完成，此时每个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。

一句话：

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 是什么

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。

官网地址

https://seata.io/zh-cn/

Seata能干吗

一个典型的分布式事务过程：

  1. 分布式事务处理过程的一ID+三组件模型

    1. Transaction ID XID 全局事务id
    2. 3组件概念
      1. Transaction Coordinator(TC) 事务协调器：维护全局事务的运行状态，负责协调并驱动全局事务的提交或回滚。
      2. Transaction Manager(TM) 事务管理器：控制全局事务的边界，负责开启一个全局事务，并最终发起全局提交或全局回滚的决议；
      3. Resource Manager(RM) 资源管理器：控制分支事务，负责分支注册，状态汇报，并接收事务协调器的指令，驱动分支（本地）事务的提交和回滚

        Seata 的执行流程

  2. 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；

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

    Seata去哪下

    发布说明： https://github.com/seata/seata/releases

    Seata 怎么玩

    在单机事务： @Transactional
    在分布式事务： @GlobalTransactional

    SEATA的分布式交易解决方案

Seata的安装

下载地址

https://seata.io/zh-cn/blog/download.html

修改 file.conf 配置文件

1. 备份原文件

  1. cp file.conf file.conf.bak

2. 主要修改： 自定义事务组名称 + 事务日志存储模式为db + 数据库连接信息

  2. ## transaction log store, only used in seata-server
  3. store {
  4.   ## store mode: file、db、redis
  5.   mode = "db"
  7.   ## file store property
  8.   file {
  9.     ## store location dir
  10.     dir = "sessionStore"
  11.     # branch session size , if exceeded first try compress lockkey, still exceeded throws exceptions
  12.     maxBranchSessionSize = 16384
  13.     # globe session size , if exceeded throws exceptions
  14.     maxGlobalSessionSize = 512
  15.     # file buffer size , if exceeded allocate new buffer
  16.     fileWriteBufferCacheSize = 16384
  17.     # when recover batch read size
  18.     sessionReloadReadSize = 100
  19.     # async, sync
  20.     flushDiskMode = async
  21.   }
  23.   ## database store property
  24.   db {
  25.     ## the implement of javax.sql.DataSource, such as DruidDataSource(druid)/BasicDataSource(dbcp)/HikariDataSource(hikari) etc.
  26.     datasource = "druid"
  27.     ## mysql/oracle/postgresql/h2/oceanbase etc.
  28.     dbType = "mysql"
  29.     driverClassName = "com.mysql.jdbc.Driver"
  30.     url = "jdbc:mysql://127.0.0.1:3306/seata"
  31.     user = "root"
  32.     password = "123456"
  33.     minConn = 5
  34.     maxConn = 30
  35.     globalTable = "global_table"
  36.     branchTable = "branch_table"
  37.     lockTable = "lock_table"
  38.     queryLimit = 100
  39.     maxWait = 5000
  40.   }
  42.   ## redis store property
  43.   redis {
  44.     host = "127.0.0.1"
  45.     port = "6379"
  46.     password = ""
  47.     database = "0"
  48.     minConn = 1
  49.     maxConn = 10
  50.     queryLimit = 100
  51.   }
  53. }

创建Seata所需数据库，并创建表结构

  1. -- the table to store GlobalSession data
  2. drop table if exists `global_table`;
  3. create table `global_table` (
  4.   `xid` varchar(128)  not null,
  5.   `transaction_id` bigint,
  6.   `status` tinyint not null,
  7.   `application_id` varchar(32),
  8.   `transaction_service_group` varchar(32),
  9.   `transaction_name` varchar(128),
  10.   `timeout` int,
  11.   `begin_time` bigint,
  12.   `application_data` varchar(2000),
  13.   `gmt_create` datetime,
  14.   `gmt_modified` datetime,
  15.   primary key (`xid`),
  16.   key `idx_gmt_modified_status` (`gmt_modified`, `status`),
  17.   key `idx_transaction_id` (`transaction_id`)
  18. );
  20. -- the table to store BranchSession data
  21. drop table if exists `branch_table`;
  22. create table `branch_table` (
  23.   `branch_id` bigint not null,
  24.   `xid` varchar(128) not null,
  25.   `transaction_id` bigint ,
  26.   `resource_group_id` varchar(32),
  27.   `resource_id` varchar(256) ,
  28.   `lock_key` varchar(128) ,
  29.   `branch_type` varchar(8) ,
  30.   `status` tinyint,
  31.   `client_id` varchar(64),
  32.   `application_data` varchar(2000),
  33.   `gmt_create` datetime,
  34.   `gmt_modified` datetime,
  35.   primary key (`branch_id`),
  36.   key `idx_xid` (`xid`)
  37. );
  39. -- the table to store lock data
  40. drop table if exists `lock_table`;
  41. create table `lock_table` (
  42.   `row_key` varchar(128) not null,
  43.   `xid` varchar(96),
  44.   `transaction_id` long ,
  45.   `branch_id` long,
  46.   `resource_id` varchar(256) ,
  47.   `table_name` varchar(32) ,
  48.   `pk` varchar(36) ,
  49.   `gmt_create` datetime ,
  50.   `gmt_modified` datetime,
  51.   primary key(`row_key`)
  52. );

修改registry.conf

  1. registry {
  2.   # file 、nacos 、eureka、redis、zk、consul、etcd3、sofa
  3.   type = "nacos"
  5.   nacos {
  6.     application = "seata-server"
  7.     serverAddr = "127.0.0.1:8848"
  8.     group = "SEATA_GROUP"
  9.     namespace = ""
  10.     cluster = "default"
  11.     username = ""
  12.     password = ""
  13.   }
  14.   eureka {
  15.     serviceUrl = "http://localhost:8761/eureka"
  16.     application = "default"
  17.     weight = "1"
  18.   }
  19.   redis {
  20.     serverAddr = "localhost:6379"
  21.     db = 0
  22.     password = ""
  23.     cluster = "default"
  24.     timeout = 0
  25.   }
  26.   zk {
  27.     cluster = "default"
  28.     serverAddr = "127.0.0.1:2181"
  29.     sessionTimeout = 6000
  30.     connectTimeout = 2000
  31.     username = ""
  32.     password = ""
  33.   }
  34.   consul {
  35.     cluster = "default"
  36.     serverAddr = "127.0.0.1:8500"
  37.   }
  38.   etcd3 {
  39.     cluster = "default"
  40.     serverAddr = "http://localhost:2379"
  41.   }
  42.   sofa {
  43.     serverAddr = "127.0.0.1:9603"
  44.     application = "default"
  45.     region = "DEFAULT_ZONE"
  46.     datacenter = "DefaultDataCenter"
  47.     cluster = "default"
  48.     group = "SEATA_GROUP"
  49.     addressWaitTime = "3000"
  50.   }
  51.   file {
  52.     name = "file.conf"
  53.   }
  54. }
  56. config {
  57.   # file、nacos 、apollo、zk、consul、etcd3
  58.   type = "file"
  60.   nacos {
  61.     serverAddr = "127.0.0.1:8848"
  62.     namespace = ""
  63.     group = "SEATA_GROUP"
  64.     username = ""
  65.     password = ""
  66.   }
  67.   consul {
  68.     serverAddr = "127.0.0.1:8500"
  69.   }
  70.   apollo {
  71.     appId = "seata-server"
  72.     apolloMeta = "http://192.168.1.204:8801"
  73.     namespace = "application"
  74.   }
  75.   zk {
  76.     serverAddr = "127.0.0.1:2181"
  77.     sessionTimeout = 6000
  78.     connectTimeout = 2000
  79.     username = ""
  80.     password = ""
  81.   }
  82.   etcd3 {
  83.     serverAddr = "http://localhost:2379"
  84.   }
  85.   file {
  86.     name = "file.conf"
  87.   }
  88. }

启动测试

如果看到如下的输出，则Seata服务端启动成功!
image.png