原文

本文只介紹Seata的簡單使用,沒有涉及其原理.

1.在本地搭建一個TC服務(事務協調者).
1.1 下載seata的安裝包
官網(https://github.com/seata/seata/releases)

往下滑滑,找到你想要的版本和格式下載即可.我這里使用的是seata-server-1.1.0.zip,解壓即可使用.

1.2 配置
打開解壓目錄下的conf/registry.conf文件如下

registry {# file 、nacos 、eureka、redis、zk、consul、etcd3、sofa# 可以把seata-server理解為一個服務,它需要把自己注冊到某個注冊中心上去,方便使用seata的服務來找到自己#在這里就是指定注冊中心的類型,由于我們項目用的是eureka,所以這里我選擇eureka,即這一堆配置就下面一個eureka生效了#這里默認的是file,即文件,選了文件就可以不用搭注冊中心,直接從文件里讀取服務列表#復制之后一定要改一改type = "eureka" nacos {serverAddr = "localhost"namespace = ""cluster = "default"}eureka { #"只有我生效啦"serviceUrl = "http://localhost:10086/eureka" #eureka地址application = "seata_tc_server" #在eureka里顯示的名字weight = "1"}redis {serverAddr = "localhost:6379"db = "0"}zk {cluster = "default"serverAddr = "127.0.0.1:2181"session.timeout = 6000connect.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 {#在這里選擇配置中心,這里我們選擇file# file、nacos 、apollo、zk、consul、etcd3type = "file"nacos {serverAddr = "localhost"namespace = ""group = "SEATA_GROUP"}consul {serverAddr = "127.0.0.1:8500"}apollo {app.id = "seata-server"apollo.meta = "http://192.168.1.204:8801"namespace = "application"}zk {serverAddr = "127.0.0.1:2181"session.timeout = 6000connect.timeout = 2000}etcd3 {serverAddr = "http://localhost:2379"}file {#由于選擇了file,所以這里生效了name = "file.conf"} }

所以接下來看一下file.conf文件

## transaction log store, only used in seata-server store {## store mode: file、db#選擇配置中心的存儲模式,由于選擇file存到文件里(性能高)會變為二進制流不好觀察,所以選擇數據庫#復制之后一定要改一改mode = "db"## file store propertyfile {## store location dirdir = "sessionStore"# branch session size , if exceeded first try compress lockkey, still exceeded throws exceptionsmaxBranchSessionSize = 16384# globe session size , if exceeded throws exceptionsmaxGlobalSessionSize = 512# file buffer size , if exceeded allocate new bufferfileWriteBufferCacheSize = 16384# when recover batch read sizesessionReloadReadSize = 100# async, syncflushDiskMode = async}## database store propertydb {#選擇了數據庫必定要做出一些配置,數據庫里一定要有這3張表## the implement of javax.sql.DataSource, such as DruidDataSource(druid)/BasicDataSource(dbcp) etc.datasource = "dbcp"## mysql/oracle/h2/oceanbase etc.dbType = "mysql"driverClassName = "com.mysql.jdbc.Driver"url = "jdbc:mysql://192.168.206.99:3306/seata"user = "root"password = "root"minConn = 1maxConn = 10globalTable = "global_table"branchTable = "branch_table"lockTable = "lock_table"queryLimit = 100} }

建表SQL如下:

CREATE TABLE IF NOT EXISTS `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`) ) ENGINE = InnoDBDEFAULT CHARSET = utf8;-- the table to store BranchSession data CREATE TABLE IF NOT EXISTS `branch_table` (`branch_id` BIGINT NOT NULL,`xid` VARCHAR(128) NOT NULL,`transaction_id` BIGINT,`resource_group_id` VARCHAR(32),`resource_id` VARCHAR(256),`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`) ) ENGINE = InnoDBDEFAULT CHARSET = utf8;-- the table to store lock data CREATE TABLE IF NOT EXISTS `lock_table` (`row_key` VARCHAR(128) NOT NULL,`xid` VARCHAR(96),`transaction_id` BIGINT,`branch_id` BIGINT NOT NULL,`resource_id` VARCHAR(256),`table_name` VARCHAR(32),`pk` VARCHAR(36),`gmt_create` DATETIME,`gmt_modified` DATETIME,PRIMARY KEY (`row_key`),KEY `idx_branch_id` (`branch_id`) ) ENGINE = InnoDBDEFAULT CHARSET = utf8;

1.3 啟動
如果是linux環境（要有JRE），執行seata-server.sh

如果是windows環境，執行seata-server.bat

2 改造微服務
只要是需要用到seata(分布式事務)的服務,都要做類似的配置.

2.1 引入依賴
我這里是springboot項目,所以我先在父pom中聲明了.如下

<properties> <alibaba.seata.version>2.1.0.RELEASE</alibaba.seata.version><seata.version>1.1.0</seata.version></properties><dependencyManagement><dependencies><!--seata--><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-seata</artifactId><version>${alibaba.seata.version}</version><exclusions><exclusion><artifactId>seata-all</artifactId><groupId>io.seata</groupId></exclusion></exclusions></dependency><dependency><artifactId>seata-all</artifactId><groupId>io.seata</groupId><version>${seata.version}</version></dependency></dependencies></dependencyManagement>

接下來只要在需要seata的微服務里添加依賴就好了.

<dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-seata</artifactId> </dependency> <dependency><groupId>io.seata</groupId><artifactId>seata-all</artifactId> </dependency>

2.2 添加配置

spring:cloud:alibaba:seata:tx-service-group: test_tx_group # 定義事務組的名稱

2.3 在resources目錄下添加2個文件file.conf和registry.conf
registry.conf和前面的一樣,直接復制過來就好.

file.conf里的內容不同了,新的內容如下:

transport {# tcp udt unix-domain-sockettype = "TCP"#NIO NATIVEserver = "NIO"#enable heartbeatheartbeat = true# the client batch send request enableenableClientBatchSendRequest = true#thread factory for nettythreadFactory {bossThreadPrefix = "NettyBoss"workerThreadPrefix = "NettyServerNIOWorker"serverExecutorThread-prefix = "NettyServerBizHandler"shareBossWorker = falseclientSelectorThreadPrefix = "NettyClientSelector"clientSelectorThreadSize = 1clientWorkerThreadPrefix = "NettyClientWorkerThread"# netty boss thread size,will not be used for UDTbossThreadSize = 1#auto default pin or 8workerThreadSize = "default"}shutdown {# when destroy server, wait secondswait = 3}serialization = "seata"compressor = "none" } service { #這里注意,等號前后都是配置,前面是yml里配置的事務組,后面是register.conf里定義的seata-servervgroupMapping.test_tx_group = "seata_tc_server"#only support when registry.type=file, please don't set multiple addressesseata_tc_server.grouplist = "127.0.0.1:8091"#degrade, current not supportenableDegrade = false#disable seatadisableGlobalTransaction = false }client {rm {asyncCommitBufferLimit = 10000lock {retryInterval = 10retryTimes = 30retryPolicyBranchRollbackOnConflict = true}reportRetryCount = 5tableMetaCheckEnable = falsereportSuccessEnable = false}tm {commitRetryCount = 5rollbackRetryCount = 5}undo {dataValidation = truelogSerialization = "jackson"logTable = "undo_log"}log {exceptionRate = 100} }

配置解讀：

transport：與TC交互的一些配置

heartbeat：client和server通信心跳檢測開關

enableClientBatchSendRequest：客戶端事務消息請求是否批量合并發送

service：TC的地址配置，用于獲取TC的地址

vgroupMapping.test_tx_group = “seata_tc_server”：

test_tx_group：是事務組名稱，要與application.yml中配置一致，

seata_tc_server：是TC服務端集群的名稱，將來通過注冊中心獲取TC地址

enableDegrade：服務降級開關，默認關閉。如果開啟，當業務重試多次失敗后會放棄全局事務

disableGlobalTransaction：全局事務開關，默認false。false為開啟，true為關閉

default.grouplist：這個當注冊中心為file的時候，才用到

client：客戶端配置

rm：資源管理器配

asynCommitBufferLimit：二階段提交默認是異步執行，這里指定異步隊列的大小

lock：全局鎖配置

retryInterval：校驗或占用全局鎖重試間隔，默認10，單位毫秒

retryTimes：校驗或占用全局鎖重試次數，默認30次

retryPolicyBranchRollbackOnConflict：分支事務與其它全局回滾事務沖突時鎖策略，默認true，優先釋放本地鎖讓回滾成功

reportRetryCount：一階段結果上報TC失敗后重試次數，默認5次

tm：事務管理器配置

commitRetryCount：一階段全局提交結果上報TC重試次數，默認1

rollbackRetryCount：一階段全局回滾結果上報TC重試次數，默認1

undo：undo_log的配置

dataValidation：是否開啟二階段回滾鏡像校驗，默認true

logSerialization：undo序列化方式，默認Jackson

logTable：自定義undo表名，默認是undo_log

log：日志配置

exceptionRate：出現回滾異常時的日志記錄頻率，默認100，百分之一概率。回滾失敗基本是臟數據，無需輸出堆棧占用硬盤空間

2.4 代理DataSource
由于在一階段是通過攔截sql分析語義來生成回滾策略,原來的數據源已經不夠用了,得換個牛逼的.在服務里新建一個配置類.

如果是使用的是mybatis

import io.seata.rm.datasource.DataSourceProxy; import org.apache.ibatis.session.SqlSessionFactory; import org.mybatis.spring.SqlSessionFactoryBean; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration;import javax.sql.DataSource;@Configuration public class DataSourceProxyConfig {@Beanpublic SqlSessionFactory sqlSessionFactoryBean(DataSource dataSource) throws Exception {// 因為使用的是mybatis，這里定義SqlSessionFactoryBeanSqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();// 配置數據源代理sqlSessionFactoryBean.setDataSource(new DataSourceProxy(dataSource));return sqlSessionFactoryBean.getObject();} }

如果使用的是mybatis-plus

import com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean; import io.seata.rm.datasource.DataSourceProxy; import org.apache.ibatis.session.SqlSessionFactory; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration;import javax.sql.DataSource;@Configuration public class DataSourceProxyConfig {@Beanpublic SqlSessionFactory sqlSessionFactoryBean(DataSource dataSource) throws Exception {// 訂單服務中引入了mybatis-plus，所以要使用特殊的SqlSessionFactoryBeanMybatisSqlSessionFactoryBean sqlSessionFactoryBean = new MybatisSqlSessionFactoryBean();// 代理數據源sqlSessionFactoryBean.setDataSource(new DataSourceProxy(dataSource));// 生成SqlSessionFactoryreturn sqlSessionFactoryBean.getObject();} }

2.5 加上注解
給事務發起者的方法上加上@GlobalTransactional即可,其它的參與者只要加@Transactional就好了.

3.踩坑記錄
1.由于更換了數據源,不知道為什么我在yml里給mybatis配置的駝峰映射失效了,導致我查到的數據缺少了某些字段.不知道這個問題在mybatis-plus中會不會出現.

解決辦法:單獨給數據源配置映射規則就好了.所以我把上面的配置類加了一個設置,修改后的代碼如下.

import io.seata.rm.datasource.DataSourceProxy; import org.apache.ibatis.session.SqlSessionFactory; import org.mybatis.spring.SqlSessionFactoryBean; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration;import javax.sql.DataSource;@Configuration public class DataSourceProxyConfig {@Beanpublic SqlSessionFactory sqlSessionFactoryBean(DataSource dataSource) throws Exception {// 因為使用的是mybatis，這里定義SqlSessionFactoryBeanSqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();// 配置數據源代理sqlSessionFactoryBean.setDataSource(new DataSourceProxy(dataSource));SqlSessionFactory object = sqlSessionFactoryBean.getObject();assert object != null;// 單獨給數據源設置駝峰映射object.getConfiguration().setMapUnderscoreToCamelCase(true);return object;} }

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