分布式事务解决方案-Seata之AT（1）

静思笃行的蜗牛 2021-10-27

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Seata 是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。Seata 将为用户提供了 AT、TCC、SAGA 和 XA 事务模式，为用户打造一站式的分布式解决方案。

一、Seata各事务模式区别简介

个人总结：除了XA，其他模式AT，TCC，SAGA都是补偿型的事务

XA：业务无侵入、全局锁，完全自动提交和回滚（依靠如数据库的强事务）

AT：业务无侵入、全局锁，完全自动提交和回滚（seata依靠数据库回滚事务日志）

TCC：业务有侵入、无锁，需要手写提交和回滚业务

SATA：业务有侵入、无锁，需要手写回滚业务

二、Seata的AT模式简介

http://seata.io/zh-cn/docs/dev/mode/at-mode.html

两阶段提交协议的演变：

一阶段：业务数据和回滚日志记录在同一个本地事务中提交，释放本地锁和连接资源。
二阶段：

提交异步化，非常快速地完成。
回滚通过一阶段的回滚日志进行反向补偿。

三、Seata的官网sample运行

1）到官网下载seata

下载地址可以到官网，我这里开始选择了最新的版本结果没成功，但我用1.2.0版本就成功了，暂没研究具体原因，先下载1.2.0版本吧http://seata.io/zh-cn/index.html

下载解压后，

新建seata数据库，执行以下sql文件

/*
Navicat MySQL Data Transfer


Source Server         : Test3
Source Server Version : 50621
Source Host           : 172.17.17.13:3306
Source Database       : seata


Target Server Type    : MYSQL
Target Server Version : 50621
File Encoding         : 65001


Date: 2021-10-27 10:03:39
*/


SET FOREIGN_KEY_CHECKS=0;


-- ----------------------------
-- Table structure for branch_table
-- ----------------------------
DROP TABLE IF EXISTS `branch_table`;
CREATE TABLE `branch_table` (
  `branch_id` bigint(20) NOT NULL,
  `xid` varchar(128) NOT NULL,
  `transaction_id` bigint(20) DEFAULT NULL,
  `resource_group_id` varchar(32) DEFAULT NULL,
  `resource_id` varchar(256) DEFAULT NULL,
  `lock_key` varchar(128) DEFAULT NULL,
  `branch_type` varchar(8) DEFAULT NULL,
  `status` tinyint(4) DEFAULT NULL,
  `client_id` varchar(64) DEFAULT NULL,
  `application_data` varchar(2000) DEFAULT NULL,
  `gmt_create` datetime DEFAULT NULL,
  `gmt_modified` datetime DEFAULT NULL,
  PRIMARY KEY (`branch_id`) USING BTREE,
  KEY `idx_xid` (`xid`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC;


-- ----------------------------
-- Records of branch_table
-- ----------------------------


-- ----------------------------
-- Table structure for global_table
-- ----------------------------
DROP TABLE IF EXISTS `global_table`;
CREATE TABLE `global_table` (
  `xid` varchar(128) NOT NULL,
  `transaction_id` bigint(20) DEFAULT NULL,
  `status` tinyint(4) NOT NULL,
  `application_id` varchar(32) DEFAULT NULL,
  `transaction_service_group` varchar(32) DEFAULT NULL,
  `transaction_name` varchar(64) DEFAULT NULL,
  `timeout` int(11) DEFAULT NULL,
  `begin_time` bigint(20) DEFAULT NULL,
  `application_data` varchar(2000) DEFAULT NULL,
  `gmt_create` datetime DEFAULT NULL,
  `gmt_modified` datetime DEFAULT NULL,
  PRIMARY KEY (`xid`) USING BTREE,
  KEY `idx_gmt_modified_status` (`gmt_modified`,`status`) USING BTREE,
  KEY `idx_transaction_id` (`transaction_id`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC;


-- ----------------------------
-- Records of global_table
-- ----------------------------


-- ----------------------------
-- Table structure for lock_table
-- ----------------------------
DROP TABLE IF EXISTS `lock_table`;
CREATE TABLE `lock_table` (
  `row_key` varchar(128) NOT NULL,
  `xid` varchar(96) DEFAULT NULL,
  `transaction_id` mediumtext,
  `branch_id` mediumtext,
  `resource_id` varchar(256) DEFAULT NULL,
  `table_name` varchar(32) DEFAULT NULL,
  `pk` varchar(32) DEFAULT NULL,
  `gmt_create` datetime DEFAULT NULL,
  `gmt_modified` datetime DEFAULT NULL,
  PRIMARY KEY (`row_key`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC;


-- ----------------------------
-- Records of lock_table
-- ----------------------------

再修改file.config配置文件如下，主要的地方应该是

vgroup_mapping.fsp_tx_group = "default"

和数据库连接字符串的地方

整个配置文件完整配置如下

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.fsp_tx_group = "default"
  #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 = 75
    retry.times = 40
  }
  report.retry.count = 5
}


## transaction log store, only used in seata-server
store {
  ## store mode: file、db
  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) etc.
 datasource = "druid"
 ## mysql/oracle/postgresql/h2/oceanbase etc.
 dbType = "mysql"
 driverClassName = "com.mysql.cj.jdbc.Driver"
 url = "jdbc:mysql://127.0.0.1:3306/seata?useUnicode=true&characterEncoding=utf8&useSSL=false&&serverTimezone=UTC"
 user = "root"
 password = "123456"
 minConn = 5
 maxConn = 30
 globalTable = "global_table"
 branchTable = "branch_table"
 lockTable = "lock_table"
 queryLimit = 100
 }
}

registry.conf完整配置如下

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


  nacos {
    application = "seata-server"
    serverAddr = "localhost"
    namespace = ""
    cluster = "default"
    username = ""
    password = ""
  }
  eureka {
    serviceUrl = "http://localhost:8761/eureka"
    # application = "default"
    application = "fsp_tx_group"
    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 = "localhost"
    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"
  }
  zk {
    serverAddr = "127.0.0.1:2181"
    sessionTimeout = 6000
    connectTimeout = 2000
    username = ""
    password = ""
  }
  etcd3 {
    serverAddr = "http://localhost:2379"
  }
  file {
    name = "file.conf"
  }
}

进入目录seata-server-1.2.0\seata\bin双击seata-server.bat启动seata

2）请到如下地址下载案例代码

https://github.com/seata/seata-samples

我们需要的是代码中的如下项目

https://github.com/seata/seata-samples/tree/master/springcloud-eureka-seata

3）用Intellij Idea打开项目

4）修改数据库连接和初始化数据库

我们可以看到每个的项目都是连接的fescar数据库，所以这里我们就把业务数据表放到一个数据库里面（其实按道理应该是放到不同数据库里面更能体现分布式的性质）。

3.1-新建fescar数据库，执行项目里面sql文件，修改每个项目里面配置文件application.properties的数据库连接和用户名密码，有的可能数据库版本不同，连接数据库的字符串会稍有点区别。

3.1-修改application.properties里面的spring.cloud.alibaba.seata.tx-service-group配置为如下

spring.cloud.alibaba.seata.tx-service-group=fsp_tx_group

3.3-修改file.config文件里面的

为

vgroupMapping.fsp_tx_group = "fsp_tx_group"

即

5）修改storage项目的端口，因为我本地的8081端口被占用了

到storage项目项目的application.properties修改如下

server.port=8069

因为其他地方调用了该服务，所以调用方也要修改端口

6）这里为了能用接口api直接测试，我们来修改下business项目的controller,

之前是RequestMapping，修改成如下

先启动代码中的Eureka项目，再启动其他几个项目如account，storage，order，business

7）访问http://localhost:8084/business/purchase/commit

开始会返回成功

之后会返回

如果想看unlog表里面的临时数据，可以在代码中的业务代码步骤中的中途加一个断点，运行到此处时再查看unlog表就能看到数据，比如断点如下地方，但断点所到之处表示该处代码是还没运行但是打算运行，这时查看unlog表

参考地址：

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

https://seata.io/zh-cn/blog/seata-xa-introduce.html

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分布式事务解决方案-Seata之AT（1）

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