SpringCloudAlibaba使⽤Seata处理分布式事务的技巧Seata简介在传统的单体项⽬中，我们使⽤@Transactional注解就能实现基本的ACID事务了。
但是前提是：1）数据库⽀持事务（如：MySQL的innoDB引擎）2）所有业务都在同⼀个数据库中执⾏随着微服务架构的引⼊，需要对数据库进⾏分库分表，每个服务拥有⾃⼰的数据库，这样传统的事务就不起作⽤了，那么我们如何保证多个服务中数据的⼀致性呢？这样就出现了分布式事务，⽽Seata就是为微服务架构⽽⽣的⼀种⾼性能、易于使⽤的分布式事务解决⽅案。
Seata 中有三个基础组件：1. Transaction Coordinator(TC协调者)：维护全局和分⽀事务的状态，驱动全局提交或回滚。
2. Transaction Manager(TM事务管理)：定义全局事务的范围，开启、提交或回滚⼀个全局事务。
3. Resource Manager(RM资源管理)：管理分⽀事务资源，与 TC 通讯并报告分⽀事务状态，管理本地事务的提交与回滚。
可以这么说⼀个分布式事务就是全局事务GlobalTransaction，⽽全局事务是由⼀个个的分⽀事务组成的，每个分⽀事务就是⼀个本地事务。
Seata的⽣命周期1. TM 要求 TC ⽣成⼀个全局事务，并由 TC ⽣成⼀个全局事务XID 返回。
2. XID 通过微服务调⽤链传播。
3. RM 向 TC 注册本地事务，将其注册到 ID 为 XID 的全局事务中。
4. TM 要求 TC 提交或回滚XID 对应的全局事务。
5. TC 驱动 XID 对应的全局事务对应的所有的分⽀事务提交或回滚。
Seata安装和配置startup -m standalone安装和配置Seatafile.conf主要是数据库的配置，配置如下registry.conf 是注册中⼼的配置另外conf⽬录中还需要⼀个脚本⽂件：nacos-config.sh ⽤于对nacos进⾏初始化配置在seata1.4.0中是没有的，需要⾃⾏创建，内容如下：#!/usr/bin/env bash# Copyright 1999-2019 Seata.io Group.## Licensed under the Apache License, Version 2.0 (the "License");# you may not use this file except in compliance with the License.# You may obtain a copy of the License at、## /licenses/LICENSE-2.0## Unless required by applicable law or agreed to in writing, software# distributed under the License is distributed on an "AS IS" BASIS,# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.# See the License for the specific language governing permissions and# limitations under the License.while getopts ":h:p:g:t:u:w:" optdocase $opt inh)host=$OPTARG;;p)port=$OPTARG;;g)group=$OPTARG;;t)tenant=$OPTARG;;u)username=$OPTARG;;w)password=$OPTARG;;)echo " USAGE OPTION: $0 [-h host] [-p port] [-g group] [-t tenant] [-u username] [-w password] " exit 1;;esacdoneurlencode() {for ((i=0; i < ${#1}; i++))dochar="${1:$i:1}"case $char in[a-zA-Z0-9.~_-]) printf $char ;;*) printf '%%%02X' "'$char" ;;esacdone}if [[ -z ${host} ]]; thenhost=localhostfiif [[ -z ${port} ]]; thenport=8848fiif [[ -z ${group} ]]; thengroup="SEATA_GROUP"fiif [[ -z ${tenant} ]]; thentenant=""fiif [[ -z ${username} ]]; thenusername=""fiif [[ -z ${password} ]]; thenpassword=""finacosAddr=$host:$portcontentType="content-type:application/json;charset=UTF-8"echo "set nacosAddr=$nacosAddr"echo "set group=$group"failCount=0tempLog=$(mktemp -u)function addConfig() {curl -X POST -H "${contentType}" "http://$nacosAddr/nacos/v1/cs/configs?dataId=$(urlencode $1)&group=$group&content=$(urlencode $2)&tenant=$tenant&username=$username&password=$password" >"${tempLog}" 2>/dev/null if [[ -z $(cat "${tempLog}") ]]; thenecho " Please check the cluster status. "exit 1fiif [[ $(cat "${tempLog}") =~ "true" ]]; thenecho "Set $1=$2 successfully "elseecho "Set $1=$2 failure "(( failCount++ ))fi}count=0for line in $(cat $(dirname "$PWD")/config.txt | sed s/[[:space:]]//g); do(( count++ ))key=${line%%=*}value=${line#*=}addConfig "${key}" "${value}"doneecho "========================================================================="echo " Complete initialization parameters, total-count:$count , failure-count:$failCount "echo "========================================================================="if [[ ${failCount} -eq 0 ]]; thenecho " Init nacos config finished, please start seata-server. "elseecho " init nacos config fail. "fi在seata的根⽬录，与conf同级的⽬录下，还需要config.txt 配置⽂件，默认也是没有的只需要对mysql的配置进⾏修改完整⽂件：transport.type=TCPtransport.server=NIOtransport.heartbeat=truetransport.enableClientBatchSendRequest=truetransport.threadFactory.bossThreadPrefix=NettyBosstransport.threadFactory.workerThreadPrefix=NettyServerNIOWorkertransport.threadFactory.serverExecutorThreadPrefix=NettyServerBizHandlertransport.threadFactory.shareBossWorker=falsetransport.threadFactory.clientSelectorThreadPrefix=NettyClientSelectortransport.threadFactory.clientSelectorThreadSize=1transport.threadFactory.clientWorkerThreadPrefix=NettyClientWorkerThreadtransport.threadFactory.bossThreadSize=1transport.threadFactory.workerThreadSize=defaulttransport.shutdown.wait=3service.vgroupMapping.my_test_tx_group=defaultservice.default.grouplist=127.0.0.1:8091service.enableDegrade=falseservice.disableGlobalTransaction=falseclient.rm.asyncCommitBufferLimit=10000client.rm.lock.retryInterval=10client.rm.lock.retryTimes=30client.rm.lock.retryPolicyBranchRollbackOnConflict=trueclient.rm.reportRetryCount=5client.rm.tableMetaCheckEnable=falseclient.rm.tableMetaCheckerInterval=60000client.rm.sqlParserType=druidclient.rm.reportSuccessEnable=falseclient.rm.sagaBranchRegisterEnable=falseclient.rm.tccActionInterceptorOrder=-2147482648mitRetryCount=5client.tm.rollbackRetryCount=5client.tm.defaultGlobalTransactionTimeout=60000client.tm.degradeCheck=falseclient.tm.degradeCheckAllowTimes=10client.tm.degradeCheckPeriod=2000client.tm.interceptorOrder=-2147482648store.mode=filestore.lock.mode=filestore.session.mode=filestore.publicKey=xxstore.file.dir=file_store/datastore.file.maxBranchSessionSize=16384store.file.maxGlobalSessionSize=512store.file.fileWriteBufferCacheSize=16384store.file.flushDiskMode=asyncstore.file.sessionReloadReadSize=100store.db.datasource=druidstore.db.dbType=mysqlstore.db.driverClassName=com.mysql.jdbc.Driverstore.db.url=jdbc:mysql://127.0.0.1:3306/seata?useUnicode=true&rewriteBatchedStatements=true er=rootstore.db.password=123456store.db.minConn=5store.db.maxConn=30store.db.globalTable=global_tablestore.db.branchTable=branch_tablestore.db.queryLimit=100store.db.lockTable=lock_tablestore.db.maxWait=5000store.redis.mode=singlestore.redis.single.host=127.0.0.1store.redis.single.port=6379store.redis.sentinel.masterName=xxstore.redis.sentinel.sentinelHosts=xxstore.redis.maxConn=10store.redis.minConn=1store.redis.maxTotal=100store.redis.database=0store.redis.password=xxstore.redis.queryLimit=100mittingRetryPeriod=1000server.recovery.asynCommittingRetryPeriod=1000server.recovery.rollbackingRetryPeriod=1000server.recovery.timeoutRetryPeriod=1000server.maxCommitRetryTimeout=-1server.maxRollbackRetryTimeout=-1server.rollbackRetryTimeoutUnlockEnable=falseserver.distributedLockExpireTime=10000client.undo.dataValidation=trueclient.undo.logSerialization=jacksonclient.undo.onlyCareUpdateColumns=trueserver.undo.logSaveDays=7server.undo.logDeletePeriod=86400000client.undo.logTable=undo_logpress.enable=truepress.type=zippress.threshold=64klog.exceptionRate=100transport.serialization=seatapressor=nonemetrics.enabled=falsemetrics.registryType=compactmetrics.exporterList=prometheusmetrics.exporterPrometheusPort=9898在conf⽬录中，使⽤Git Bash进⼊命令⾏，输⼊sh nacos-config.sh 127.0.0.1这是对Seata进⾏初始化配置，上图表⽰所有配置都成功设置了在nacos中可以看到出现了seata相关的配置接下来在seata数据库中，新建三个表drop table if exists `global_table`;create table `global_table` (`xid` varchar(128) not null,`transaction_id` bigint,`status` tinyint not null,`application_id` varchar(32),`transaction_service_group` varchar(32),`transaction_name` varchar(128),`timeout` int,`begin_time` bigint,`application_data` varchar(2000),`gmt_create` datetime,`gmt_modified` datetime,primary key (`xid`),key `idx_gmt_modified_status` (`gmt_modified`, `status`),key `idx_transaction_id` (`transaction_id`));drop table if exists `branch_table`;create table `branch_table` (`branch_id` bigint not null,`xid` varchar(128) not null,`transaction_id` bigint ,`resource_group_id` varchar(32),`resource_id` varchar(256) ,`lock_key` varchar(128) ,`branch_type` varchar(8) ,`status` tinyint,`client_id` varchar(64),`application_data` varchar(2000),`gmt_create` datetime,`gmt_modified` datetime,primary key (`branch_id`),key `idx_xid` (`xid`));drop table if exists `lock_table`;create table `lock_table` (`row_key` varchar(128) not null,`xid` varchar(96),`transaction_id` long ,`branch_id` long,`resource_id` varchar(256) ,`table_name` varchar(32) ,`pk` varchar(36) ,`gmt_create` datetime ,`gmt_modified` datetime,primary key(`row_key`));在项⽬相关的数据库中，新建表undo_log ⽤于记录撤销⽇志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,`ext` varchar(100) DEFAULT NULL,PRIMARY KEY (`id`),UNIQUE KEY `ux_undo_log` (`xid`,`branch_id`)) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;最后在bin⽬录中，启动命令⾏，执⾏seata-server.bat 启动Seata服务项⽬应⽤SeataSpringCloud项⽬中有两个服务：订单服务和库存服务，基本业务是：购买商品插⼊订单减少库存订单详情表DROP TABLE IF EXISTS `tb_order_detail`;CREATE TABLE `tb_order_detail` (`id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '订单详情id ',`order_id` bigint(20) NOT NULL COMMENT '订单id',`sku_id` bigint(20) NOT NULL COMMENT 'sku商品id',`num` int(11) NOT NULL COMMENT '购买数量',`title` varchar(256) NOT NULL COMMENT '商品标题',`own_spec` varchar(1024) DEFAULT '' COMMENT '商品动态属性键值集',`price` bigint(20) NOT NULL COMMENT '价格,单位：分',`image` varchar(128) DEFAULT '' COMMENT '商品图⽚',PRIMARY KEY (`id`),KEY `key_order_id` (`order_id`) USING BTREE) ENGINE=MyISAM AUTO_INCREMENT=131 DEFAULT CHARSET=utf8 COMMENT='订单详情表';库存表DROP TABLE IF EXISTS `tb_stock`;CREATE TABLE `tb_stock` (`sku_id` bigint(20) NOT NULL COMMENT '库存对应的商品sku id',`seckill_stock` int(9) DEFAULT '0' COMMENT '可秒杀库存',`seckill_total` int(9) DEFAULT '0' COMMENT '秒杀总数量',`stock` int(9) NOT NULL COMMENT '库存数量',PRIMARY KEY (`sku_id`)) ENGINE=MyISAM DEFAULT CHARSET=utf8 COMMENT='库存表，代表库存，秒杀库存等信息';⽗项⽬定义了springboot、springcloud、springcloud-alibaba的版本<parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.3.10.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-alibaba-dependencies</artifactId><version>0.9.0.RELEASE</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-dependencies</artifactId><version>2.2.1.RELEASE</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>Hoxton.SR8</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement>⼦项⽬的依赖定义了nacos和seata客户端<dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId><version>3.3.2</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-seata</artifactId><exclusions><exclusion><groupId>io.seata</groupId><artifactId>seata-spring-boot-starter</artifactId></exclusion></exclusions></dependency><dependency><groupId>io.seata</groupId><artifactId>seata-spring-boot-starter</artifactId><version>1.2.0</version></dependency>⼦项⽬配置⽂件完整配置server:port: 8001spring:application:name: stock-servicecloud:nacos:discovery:server-addr: localhost:8848alibaba:seata:enabled: trueenable-auto-data-source-proxy: truetx-service-group: my_test_tx_groupregistry:type: nacosnacos:application: seata-serverserver-addr: 127.0.0.1:8848username: nacospassword: nacosconfig:type: nacosnacos:server-addr: 127.0.0.1:8848group: SEATA_GROUPusername: nacospassword: nacosservice:vgroup-mapping:my_test_tx_group: defaultdisable-global-transaction: falseclient:rm:report-success-enable: falsedatasource:driver-class-name: com.mysql.cj.jdbc.Driverurl: jdbc:mysql://localhost:3306/eshop?serverTimezone=UTC&useUnicode=true&useSSL=false&characterEncoding=utf8 username: rootpassword: 123456库存服务定义了减库存的⽅法@RestControllerpublic class StockController {@Autowiredprivate IStockService stockService;@PutMapping("/stock")public ResponseEntity<Stock> reduceSkuStock(@RequestParam("skuId")Long skuId,@RequestParam("number")Integer number){Stock stock = stockService.getById(skuId);if(stock.getStock() < number){throw new RuntimeException("库存不⾜,SkuId:" + skuId);}stock.setStock(stock.getStock() - number);stockService.updateById(stock);return ResponseEntity.ok(stock);}}订单服务在插⼊订单后，使⽤Feign调⽤了减库存的服务@Servicepublic class OrderDetailServiceImpl extends ServiceImpl<OrderDetailMapper, OrderDetail> implements IOrderDetailService {//库存服务Feign@Autowiredprivate StockFeignClient stockFeignClient;// @Transactional@GlobalTransactional(rollbackFor = {Exception.class})@Overridepublic void makeOrder(OrderDetail orderDetail) {this.save(orderDetail); //保存订单int x = 11 / 0; //抛出异常//减库存stockFeignClient.reduceSkuStock(orderDetail.getSkuId(),orderDetail.getNum());}}插订单和减库存属于两个服务，传统的@Transactional已经不能保证它们的原⼦性了这⾥使⽤了Seata提供的@GlobalTransactional全局事务注解，出现任何异常后都能实现业务回滚。
