今天继续给大家分享一下阿里的分布式事务中间件seata的使用，跟上篇文章《springboot多数据源整合分布式事务中间件seata》不一样的是，上篇文章是单服务绑定多数据源的分布式情况，而本文基于微服务下每个服务绑定一个数据源的场景，服务之间依靠eureka客户端feign进行通信。

注:seata有三种模式，AT模式、TCC模式和saga模式，上篇文章和本篇文章介绍的都是AT模式。感兴趣的同学可以参考官网进行了解这三种模式：

http://seata.io/en-us/docs/dev/mode/at-mode.html

环境搭建

还是先说一下本文使用的实验环境：

springboot：2.1.6.RELEASE

orm框架：mybatis

数据库：mysql

数据库连接池：HikariCP

seata server：1.3.0

springcloud:Greenwich.SR2

整个项目的架构如下：

可以看到，项目中有order-server,account-server，storage-server这3个服务，每个服务绑定自己的数据库。这3个服务都注册到eureka上面，同时也都注册TM到seata-server。seata-server也注册到了eureka上。

首先我们启动eureka，这里监听8889端口，yml文件配置如下：

server:  port: 8889spring:  application:    name: eureka-server#Eureka实例名，集群中根据这里相互识别eureka:  instance:    hostname: localhost#客户端  client:#是否开启注册服务，因为这里如果为true表示自己注册自己，而自己就是一个服务注册方，没必要自己注册自己    register-with-eureka: false#是否拉取服务列表，这里我只提供服务给别的服务。    fetch-registry: false#注册中心地址    service-url:      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/#服务端：  server:    enable-self-preservation: false

接着我们启动seata server，由于seata server也要注册到eureka上面，我们需要修改seata server，把registry.conf文件修改为如下：

registry {  # file 、nacos 、eureka、redis、zk、consul、etcd3、sofa  type = "eureka"  #省略无关的代码  eureka {    #我本地配置的eureka地址    serviceUrl = "http://192.168.59.1:8889/eureka"    application = "seata-server"    weight = "1"  }  #省略其他代码

执行如下命令启动seata server:

./seata-server.sh -p 8091 -h 127.0.0.1 -m file

配置3个微服务，这里我们以order-server为例，先看yml文件，核心配置就是eureka、feign、mybatis和数据源，代码如下：

#配置eurekaeureka:    instance:        hostname: localhost        prefer-ip-address: true    client:        serviceUrl:            defaultZone: http://${eureka.instance.hostname}:8889/eureka/feign:    hystrix:        enabled: false    client:        config:            default:                connectTimeout: 5000                readTimeout: 10000logging:    level:        io:            seata: info#配置mybatismybatis:    mapperLocations: classpath:mapper/*.xml    typeAliasesPackage: io.seata.sample.entityserver:    port: 8180spring:    application:        name: order-server    cloud:        alibaba:            seata:                tx-service-group: my_test_tx_group                #配置数据源    datasource:        driver-class-name: com.mysql.jdbc.Driver        password: 123456        jdbcUrl: jdbc:mysql://192.168.59.1:3306/seata_order?useAffectedRows=true&serverTimezone=UTC&characterEncoding=utf-8        username: root

registry.conf文件，最核心的就是type使用eureka，然后配置eureka地址和应用名称，部分代码如下：

registry {  # file 、nacos 、eureka、redis、zk、consul、etcd3、sofa  type = "eureka"#省略其他代码  eureka {    serviceUrl = "http://localhost:8889/eureka"    application = "order-server"    weight = "1"  }#省略其他代码file.conf文件只要改一下service就可以了，里面配置seata server地址，代码如下：service {  #transaction service group mapping  vgroupMapping.my_test_tx_group = "seata-server"  #only support when registry.type=file, please don't set multiple addresses  default.grouplist = "192.168.59.132:8091"  #degrade, current not support  enableDegrade = false  #disable seata  disableGlobalTransaction = false}

用这种方式配置account-server和storage-server，之后把3个服务都起来，启动成功后，访问eureka页面，地址如下：

http://localhost:8889/

这时我们能看到加上seata server一共4个服务都已经启动成功了，见下图：

下面我贴一下整个项目的sql语句：

#########################seata_order库use database seata_order;CREATE TABLE `orders` (  `id` mediumint(11) NOT NULL AUTO_INCREMENT,  `user_id` int(11) DEFAULT NULL,  `product_id` int(11) DEFAULT NULL,  `COUNT` int(11) DEFAULT NULL COMMENT '数量',  `pay_amount` decimal(10,2) DEFAULT NULL,  `status` varchar(100) DEFAULT NULL,  `add_time` datetime DEFAULT CURRENT_TIMESTAMP,  `last_update_time` datetime DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,  PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8#########################seata_pay库use database seata_pay;DROP TABLE account;CREATE TABLE `account` (  `id` BIGINT(11) NOT NULL AUTO_INCREMENT COMMENT 'id',  `user_id` BIGINT(11) DEFAULT NULL COMMENT '用户id',  `total` DECIMAL(10,0) DEFAULT NULL COMMENT '总额度',  `used` DECIMAL(10,0) DEFAULT NULL COMMENT '已用余额',  `balance` DECIMAL(10,0) DEFAULT '0' COMMENT '剩余可用额度',  `last_update_time` DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,  PRIMARY KEY (`id`)) ENGINE=INNODB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;INSERT INTO `seata_pay`.`account` (`id`, `user_id`, `total`, `used`, `balance`) VALUES ('1', '1', '1000', '0', '100');#########################seata_storage库use database seata_storage;CREATE TABLE `storage` (  `id` BIGINT(11) NOT NULL AUTO_INCREMENT,  `product_id` BIGINT(11) DEFAULT NULL COMMENT '产品id',  `total` INT(11) DEFAULT NULL COMMENT '总库存',  `used` INT(11) DEFAULT NULL COMMENT '已用库存',  `residue` INT(11) DEFAULT NULL COMMENT '剩余库存',  PRIMARY KEY (`id`)) ENGINE=INNODB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;INSERT INTO `seata_storage`.`storage` (`id`, `product_id`, `total`, `used`, `residue`) VALUES ('1', '1', '100', '0', '100');#########################下面的undo_log表前面三个库都需要创建CREATE TABLE `undo_log` (  `id` bigint(20) NOT NULL AUTO_INCREMENT,  `branch_id` bigint(20) NOT NULL,  `xid` varchar(100) NOT NULL,  `context` varchar(128) NOT NULL,  `rollback_info` longblob NOT NULL,  `log_status` int(11) NOT NULL,  `log_created` datetime NOT NULL,  `log_modified` datetime NOT NULL,  PRIMARY KEY (`id`),  UNIQUE KEY `ux_undo_log` (`xid`,`branch_id`)) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=utf8

至此，整个环境就搭建完成了，接着我们进行测试。我们先看下account和storage两张表的数据，其他表都是空，如下图：

account

storage表

测试

现在我们开始进行测试，有2个场景，正常commit和场景和异常rollback场景。我们向order-server发一个post请求，content如下：

{  "userId":1,  "productId":1,  "count":1,  "money":1,  "payAmount":50}

这时order-server执行成功，日志如下:

2020-08-15 16:31:53.704  INFO 57868 --- [nio-8181-exec-1] i.s.sample.service.AccountServiceImpl    : ------->扣减账户开始account中2020-08-15 16:31:54.141  INFO 57868 --- [nio-8181-exec-1] i.s.sample.service.AccountServiceImpl    : ------->扣减账户结束account中2020-08-15 16:31:54.141  INFO 57868 --- [nio-8181-exec-1] i.s.sample.service.AccountServiceImpl    : 修改订单状态开始2020-08-15 16:31:54.309  INFO 57868 --- [nio-8181-exec-1] c.netflix.config.ChainedDynamicProperty  : Flipping property: order-server.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 21474836472020-08-15 16:31:54.344  INFO 57868 --- [nio-8181-exec-1] c.n.u.concurrent.ShutdownEnabledTimer    : Shutdown hook installed for: NFLoadBalancer-PingTimer-order-server2020-08-15 16:31:54.345  INFO 57868 --- [nio-8181-exec-1] c.netflix.loadbalancer.BaseLoadBalancer  : Client: order-server instantiated a LoadBalancer: DynamicServerListLoadBalancer:{NFLoadBalancer:name=order-server,current list of Servers=[],Load balancer stats=Zone stats: {},Server stats: []}ServerList:null2020-08-15 16:31:54.352  INFO 57868 --- [nio-8181-exec-1] c.n.l.DynamicServerListLoadBalancer      : Using serverListUpdater PollingServerListUpdater2020-08-15 16:31:54.385  INFO 57868 --- [nio-8181-exec-1] c.netflix.config.ChainedDynamicProperty  : Flipping property: order-server.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 21474836472020-08-15 16:31:54.386  INFO 57868 --- [nio-8181-exec-1] c.n.l.DynamicServerListLoadBalancer      : DynamicServerListLoadBalancer for client order-server initialized: DynamicServerListLoadBalancer:{NFLoadBalancer:name=order-server,current list of Servers=[10.192.86.60:8180],Load balancer stats=Zone stats: {defaultzone=[Zone:defaultzone;  Instance count:1;  Active connections count: 0;  Circuit breaker tripped count: 0;  Active connections per server: 0.0;]},Server stats: [[Server:10.192.86.60:8180;  Zone:defaultZone;  Total Requests:0;  Successive connection failure:0;  Total blackout seconds:0;  Last connection made:Thu Jan 01 08:00:00 CST 1970;  First connection made: Thu Jan 01 08:00:00 CST 1970;  Active Connections:0;  total failure count in last (1000) msecs:0;  average resp time:0.0;  90 percentile resp time:0.0;  95 percentile resp time:0.0;  min resp time:0.0;  max resp time:0.0;  stddev resp time:0.0]]}ServerList:org.springframework.cloud.netflix.ribbon.eureka.DomainExtractingServerList@5fa120e12020-08-15 16:31:54.562  INFO 57868 --- [nio-8181-exec-1] i.s.sample.service.AccountServiceImpl    : 修改订单状态结束：订单状态修改成功2020-08-15 16:31:54.578  WARN 57868 --- [nio-8181-exec-1] c.a.c.seata.web.SeataHandlerInterceptor  : xid in change during RPC from 192.168.59.132:8091:37575557075451904 to null2020-08-15 16:31:55.166  INFO 57868 --- [ch_RMROLE_1_1_8] i.s.c.r.p.c.RmBranchCommitProcessor      : rm client handle branch commit process:xid=192.168.59.132:8091:37575557075451904,branchId=37575566823014400,branchType=AT,resourceId=jdbc:mysql://192.168.59.1:3306/seata_pay,applicationData=null2020-08-15 16:31:55.169  INFO 57868 --- [ch_RMROLE_1_1_8] io.seata.rm.AbstractRMHandler            : Branch committing: 192.168.59.132:8091:37575557075451904 37575566823014400 jdbc:mysql://192.168.59.1:3306/seata_pay null2020-08-15 16:31:55.170  INFO 57868 --- [ch_RMROLE_1_1_8] io.seata.rm.AbstractRMHandler            : Branch commit result: PhaseTwo_Committed2020-08-15 16:31:55.356  INFO 57868 --- [erListUpdater-0] c.netflix.config.ChainedDynamicProperty  : Flipping property: order-server.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647

这时我们再看下数据库的数据，如下图：

order表

account表

storage表

容易迷惑我们的是，order表的pay_amount值是45.5，而不是50，这时因为account-server执行完成后，又调用了order-server，执行了更新操作，代码如下：

public void decrease(Long userId, BigDecimal payAmount) {    LOGGER.info("------->扣减账户开始account中");    //模拟超时异常，全局事务回滚    //try {    //    Thread.sleep(30*1000);    //} catch (InterruptedException e) {    //    e.printStackTrace();    //}    accountDao.decrease(userId,payAmount);    LOGGER.info("------->扣减账户结束account中");    //修改订单状态，此调用会导致调用成环    LOGGER.info("修改订单状态开始");    String mes = orderApi.update(userId, payAmount.multiply(new BigDecimal("0.09")),0);    LOGGER.info("修改订单状态结束：{}",mes);}

第二个场景的测试，我们把上面的代码模拟超时异常这段放开，用debug模式进行，继续发送前面一样的请求，可以看到seata_order库中的undo_log，如下图：

undo_log

等超时后，事务进行了回滚。

总结

可以看到，本篇文章介绍的场景跟上篇差不多，本质都是基于undo_log的交易补偿，这也是AT模式的特点。但是本文的环境比上节复杂很多，这并不是seata本身造成的，而是微服务的拆分带来的系统架构的复杂性。

源码地址：

https://github.com/jinjunzhu/springcloud-eureka-feign-mybatis-seata.githttps://github.com/jinjunzhu/eurekaserver.git