@[toc](SpringCloud Alibaba Seata Dealing with distributed transactions )

Source code download address ：gitee Warehouse address

1、 Distributed transaction problems

Before distribution ：

   There is no such problem for single machine and single database .

After distribution :
   Single applications are split into microservice applications , The original three modules are split into three independent applications , Use three separate data sources , Business operations need to call three services to complete . At this time, the data consistency within each service is guaranteed by local transactions , But the global data consistency cannot be guaranteed .

  == namely ： A business operation needs to be called remotely across multiple data sources or systems , There will be distributed transaction problems .==

2、Seata brief introduction

2.1 Seata What is it? ？

  Seata Is an open source distributed transaction solution , Committed to providing high-performance and easy-to-use distributed transaction services .Seata Will provide users with AT、TCC、SAGA and XA Transaction mode , Create a one-stop distributed solution for users .

   Official website address ：https://seata.io/zh-cn/docs/overview/what-is-seata.html

2.2 Seata What can be done ？

   A typical distributed transaction process ： A part of distributed transaction processing ID+ Three component model

• Transaction ID XID： Globally unique transaction ID

• Transaction Coordinator (TC)： Transaction coordinator , Maintain the running state of the global transaction , Responsible for coordinating and driving global transaction commit or rollback ;

• Transaction Manager ： Transaction manager , Control the boundaries of global transactions , Responsible for opening a global transaction , And finally initiate a global commit or global rollback resolution ;

• Resource Manager (RM)： Explorer , Control branch transactions , Responsible for branch registration 、 Status report , And receive instructions from the transaction coordinator , Drive branch （ Local ） Transaction commit and rollback

Treatment process ：

  (1) TM towards TC Request to open a global transaction , The global transaction is created successfully and generates a globally unique XID;
   (2) XID Propagate in the context of the microservice call link ;
   (3) RM towards TC Register branch transactions , Be included in the XID Jurisdiction corresponding to global transaction ;
   (4) TM towards TC Launch against XID The global commit or rollback resolution for ;
   (5) TC Dispatch XID All branch transactions under the jurisdiction complete the commit or rollback request .

2.3 download

   Address ：https://github.com/seata/seata/releases

   I downloaded it 1.3.0 edition .

3、Seata-Server install

3.1 Seata-Server Of zip Extract the file and modify the configuration

   modify seata-server-1.3.0\seata\conf Under directory file.conf file

   Major changes ： Custom transaction group name + The transaction log storage mode is db+ Database connection information

   This 1.3.0 Why doesn't it default service 了 , We add it ourselves

service {  #transaction service group mapping  vgroupMapping.my_test_tx_group = "default"  #only support when registry.type=file, please don't set multiple addresses  default.grouplist = "127.0.0.1:8091"  #degrade, current not support  enableDegrade = false  #disable seata  disableGlobalTransaction = false}

   Modify the log storage mode to db

mode = "db"

   Modify database connection information ,Seata1.3.0 Version already supports mysql8.0 Database , Earlier versions are not supported .

 ## database store property  db {    ## the implement of javax.sql.DataSource, such as DruidDataSource(druid)/BasicDataSource(dbcp)/HikariDataSource(hikari) etc.    datasource = "druid"    ## mysql/oracle/postgresql/h2/oceanbase etc.    dbType = "mysql"    driverClassName = "com.mysql.cj.jdbc.Driver"    url = "jdbc:mysql://localhost:3306/seata?serverTimezone=GMT%2B8&characterEncoding=utf8&connectTimeout=10000&socketTimeout=30000&autoReconnect=true&useSSL=false"    user = "root"    password = "123456"    minConn = 5    maxConn = 30    globalTable = "global_table"    branchTable = "branch_table"    lockTable = "lock_table"    queryLimit = 100    maxWait = 5000  }

3.2 mysql8.0 Database new database seata

3.3 stay seata Build a table in the library

   Table creation in earlier versions sql Will be directly in conf The contents are given below , But the new version is not given , I'll find it here sql Put it underneath. ：

db_store.sql

-- -------------------------------- The script used when storeMode is 'db' ---------------------------------- the table to store GlobalSession dataCREATE 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 = InnoDB  DEFAULT CHARSET = utf8;-- the table to store BranchSession dataCREATE 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(6),    `gmt_modified`      DATETIME(6),    PRIMARY KEY (`branch_id`),    KEY `idx_xid` (`xid`)) ENGINE = InnoDB  DEFAULT CHARSET = utf8;-- the table to store lock dataCREATE 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 = InnoDB  DEFAULT CHARSET = utf8;

3.4 modify conf Under directory registry.conf The configuration file

   Configure registry connection information , Here it is modified as Nacos

registry {  # file 、nacos 、eureka、redis、zk、consul、etcd3、sofa  type = "nacos"  nacos {    application = "seata-server"    serverAddr = "127.0.0.1:8848"    group = "SEATA_GROUP"    namespace = ""    cluster = "default"    username = "nacos"    password = "nacos"  } ...}

3.5 Start the test

   Start... First nacos

startup.cmd -m standalone

   Restart seata-server

   perform bin Under directory seata-server.bat

   see seata Is registration successful

4、 Order / stock / Account business database preparation

   The following tests need to be started first Nacos Restart Seata, Make sure both are OK .

4.1 Distributed transaction business description

   Here we will create three services , An order service , An inventory service , An account service .

   When the user places an order , An order will be created in the order service , Then the inventory service is called remotely to deduct the inventory of the ordered goods , Then the balance in the user account can be deducted by calling the account service remotely , Finally, modify the order status to completed in the order service .

   This operation spans three databases , There are two remote calls , There's obviously a problem with distributed transactions .

   summary ： Place the order —> Inventory deduction —> Less account ( balance )

4.2 Create a business database

seata_order： Database to store orders ;

seata_storage： A database for storing inventory ;

seata_account： A database for storing account information .

CREATE DATABASE seata_order; CREATE DATABASE seata_storage; CREATE DATABASE seata_account;

4.3 Right up there 3 Create corresponding business tables for each library

  seata_order Construction under reservoir t_order surface

 CREATE TABLE t_order (  `id` BIGINT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,  `user_id` BIGINT(11) DEFAULT NULL COMMENT ' user id',  `product_id` BIGINT(11) DEFAULT NULL COMMENT ' product id',  `count` INT(11) DEFAULT NULL COMMENT ' Number ',  `money` DECIMAL(11,0) DEFAULT NULL COMMENT ' amount of money ',  `status` INT(1) DEFAULT NULL COMMENT ' The order status ：0： In the create ;1： It's over ' ) ENGINE=INNODB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8; SELECT * FROM t_order;

  seata_storage Construction under reservoir t_storage surface

 CREATE TABLE t_storage ( `id` BIGINT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY, `product_id` BIGINT(11) DEFAULT NULL COMMENT ' product id', `total` INT(11) DEFAULT NULL COMMENT ' Total inventory ', `used` INT(11) DEFAULT NULL COMMENT ' Used stock ', `residue` INT(11) DEFAULT NULL COMMENT ' Surplus stock ') ENGINE=INNODB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;  INSERT INTO seata_storage.t_storage(`id`, `product_id`, `total`, `used`, `residue`)VALUES ('1', '1', '100', '0', '100'); SELECT * FROM t_storage;

  seata_account Construction under reservoir t_account surface

 CREATE TABLE t_account (  `id` BIGINT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY COMMENT 'id',  `user_id` BIGINT(11) DEFAULT NULL COMMENT ' user id',  `total` DECIMAL(10,0) DEFAULT NULL COMMENT ' Total amount ',  `used` DECIMAL(10,0) DEFAULT NULL COMMENT ' Used balance ',  `residue` DECIMAL(10,0) DEFAULT '0' COMMENT ' The remaining amount available ') ENGINE=INNODB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8; INSERT INTO seata_account.t_account(`id`, `user_id`, `total`, `used`, `residue`)  VALUES ('1', '1', '1000', '0', '1000'); SELECT * FROM t_account;

4.4 above 3 Create corresponding rollback log tables for each library

   Order - stock - Account 3 Each database needs to build its own rollback log table

  -- the table to store seata xid data-- 0.7.0+ add context-- you must to init this sql for you business databese. the seata server not need it.--  This script must be initialized in your current business database , be used for AT  Pattern XID Record . And server End independent （ notes ： Business database ）--  Notice here 0.3.0+  Add unique index  ux_undo_logDROP TABLE `undo_log`; 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;

5、 Order / stock / Account business micro service preparation

   Business needs ： Place the order -> Reduce inventory -> Deduct the balance -> Change ( Order ) state

5.1 New order Order-Module

5.1.1 newly build Module:seata-order-service2001

5.1.2 pom.xml

 <dependencies>        <!--nacos-->        <dependency>            <groupId>com.alibaba.cloud</groupId>            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>        </dependency>        <!--seata-->        <dependency>            <groupId>com.alibaba.cloud</groupId>            <artifactId>spring-cloud-starter-alibaba-seata</artifactId>            <!--  Exclude built-in Seata -->            <exclusions>                <exclusion>                    <artifactId>seata-all</artifactId>                    <groupId>io.seata</groupId>                </exclusion>            </exclusions>        </dependency>        <dependency>            <groupId>io.seata</groupId>            <artifactId>seata-all</artifactId>            <!--  According to your Seata Select the version of the service  -->            <version>1.3.0</version>        </dependency>        <!--feign-->        <dependency>            <groupId>org.springframework.cloud</groupId>            <artifactId>spring-cloud-starter-openfeign</artifactId>        </dependency>        <!--web-actuator-->        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-web</artifactId>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-actuator</artifactId>        </dependency>        <!--mysql-druid-->        <dependency>            <groupId>mysql</groupId>            <artifactId>mysql-connector-java</artifactId>            <version>8.0.19</version>        </dependency>        <dependency>            <groupId>com.alibaba</groupId>            <artifactId>druid-spring-boot-starter</artifactId>            <version>1.1.10</version>        </dependency>        <dependency>            <groupId>org.mybatis.spring.boot</groupId>            <artifactId>mybatis-spring-boot-starter</artifactId>            <version>2.0.0</version>        </dependency>        <dependency>            <groupId>org.springframework.boot</groupId>            <artifactId>spring-boot-starter-test</artifactId>            <scope>test</scope>        </dependency>        <dependency>            <groupId>org.projectlombok</groupId>            <artifactId>lombok</artifactId>            <optional>true</optional>        </dependency>    </dependencies>

5.1.3 application.yml

server:  port: 2001spring:  application:    name: seata-order-service  cloud:    alibaba:      seata:        enabled: true        application-id: ${spring.application.name}        tx-service-group: my_test_tx_group    nacos:      discovery:        server-addr: localhost:8848  datasource:    driver-class-name: com.mysql.cj.jdbc.Driver    url: jdbc:mysql://localhost:3306/seata_order?serverTimezone=GMT%2B8&characterEncoding=utf8&connectTimeout=10000&socketTimeout=30000&autoReconnect=true&useSSL=false    username: root    password: 123456feign:  hystrix:    enabled: falselogging:  level:    io:      seata: infomybatis:  mapperLocations: classpath:mapper/*.xml

5.1.4 file.conf and registry.conf

   We will configure the above file.conf Document and registry.conf Copy to project's resources Below directory

5.1.5 domain

  OrderDao:

@Mapperpublic interface OrderDao {    /** *  Create order  */    void create(Order order);    /** *  Modify order amount  */    void update(@Param("userId") Long userId, @Param("status") Integer status);}

resources New under folder mapper Add... After folder OrderMapper.xml:

 <?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" ><mapper namespace="com.atguigu.springcloud.alibaba.dao.OrderDao">    <resultMap id="BaseResultMap" type="com.atguigu.springcloud.alibaba.domain.Order">        <id column="id" property="id" jdbcType="BIGINT"/>        <result column="user_id" property="userId" jdbcType="BIGINT"/>        <result column="product_id" property="productId" jdbcType="BIGINT"/>        <result column="count" property="count" jdbcType="INTEGER"/>        <result column="money" property="money" jdbcType="DECIMAL"/>        <result column="status" property="status" jdbcType="INTEGER"/>    </resultMap>    <insert id="create">        INSERT INTO `t_order` (`id`, `user_id`, `product_id`, `count`, `money`, `status`)        VALUES (NULL, #{userId}, #{productId}, #{count}, #{money}, 0);    </insert>    <update id="update">        UPDATE `t_order`        SET status = 1        WHERE user_id = #{userId} AND status = #{status};    </update></mapper>

5.1.6 Service Interface and its implementation

  OrderService:

public interface OrderService {    /** *  Create order  */    void create(Order order);}

OrderServiceImpl:

@Service@Slf4jpublic class OrderServiceImpl implements OrderService{    @Resource    private OrderDao orderDao;    @Resource    private StorageService storageService;    @Resource    private AccountService accountService;    /** *  Create order -> Call inventory service to deduct inventory -> Call the account service to deduct the account balance -> Modify order status  *  In short ： *  Place the order -> Reduce inventory -> Less balance -> Change state  */    @Override    //@GlobalTransactional(name = "fsp-create-order",rollbackFor = Exception.class)    public void create(Order order) {        log.info("-------> Order start ");        // This application creates orders         orderDao.create(order);        // Call inventory service remotely to deduct inventory         log.info("------->order-service The deduction of inventory starts ");        storageService.decrease(order.getProductId(),order.getCount());        log.info("------->order-service After deducting the inventory from the inventory, the end ");        // Remote call account service deduction balance         log.info("------->order-service The deduction balance starts ");        accountService.decrease(order.getUserId(),order.getMoney());        log.info("------->order-service End of deduction balance in ");        // Change order status to completed         log.info("------->order-service Start by modifying the order status in ");        orderDao.update(order.getUserId(),0);        log.info("------->order-service End of modifying order status in ");        log.info("-------> End of order ");    }}

For the time being @GlobalTransactional Comment out , Let's demonstrate distributed transactions .

  StorageService：

@FeignClient(value = "seata-storage-service")public interface StorageService {    /** *  Deducting the inventory  */    @PostMapping(value = "/storage/decrease")    CommonResult decrease(@RequestParam("productId") Long productId, @RequestParam("count") Integer count);}

  AccountService

@FeignClient(value = "seata-account-service")public interface AccountService {    /** *  Deduct account balance  */    //@RequestMapping(value = "/account/decrease", method = RequestMethod.POST, produces = "application/json; charset=UTF-8")    @PostMapping("/account/decrease")    CommonResult decrease(@RequestParam("userId") Long userId, @RequestParam("money") BigDecimal money);}

  StorageService and AccountService The definition is to invoke the micro service of repository business and account business in order business. .

5.1.6 Controller

@RestControllerpublic class OrderController {    @Autowired    private OrderService orderService;    /** *  Create order  */    @GetMapping("/order/create")    public CommonResult create( Order order) {        orderService.create(order);        return new CommonResult(200, " Order created successfully !");    }}

5.1.7 Config To configure

  MybatisConfig:

@Configuration@MapperScan({"com.atguigu.springcloud.alibaba.dao"})public class MyBatisConfig {}

   DataSourceProxyConfig:

// Use Seata Proxy data sources @Configurationpublic class DataSourceProxyConfig {    @Value("${mybatis.mapperLocations}")    private String mapperLocations;    @Bean    @ConfigurationProperties(prefix = "spring.datasource")    public DataSource druidDataSource(){        return new DruidDataSource();    }    @Bean    public DataSourceProxy dataSourceProxy(DataSource dataSource) {        return new DataSourceProxy(dataSource);    }    @Bean    public SqlSessionFactory sqlSessionFactoryBean(DataSourceProxy dataSourceProxy) throws Exception {        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();        sqlSessionFactoryBean.setDataSource(dataSourceProxy);        sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(mapperLocations));        sqlSessionFactoryBean.setTransactionFactory(new SpringManagedTransactionFactory());        return sqlSessionFactoryBean.getObject();    }}

5.1.8 Main startup class

@EnableDiscoveryClient@EnableFeignClients@SpringBootApplication(exclude = DataSourceAutoConfiguration.class)// Cancel automatic creation of data source public class SeataOrderMainApp2001{    public static void main(String[] args)    {        SpringApplication.run(SeataOrderMainApp2001.class, args);    }}

5.2 New inventory Storage-Module

   The code will not be repeated , Go to the link address at the top of the article to download .

   gitee Warehouse address

5.3 New account Account-Module

   The code will not be repeated , Go to the link address at the top of the article to download .

  gitee Warehouse address

6、 Distributed transaction testing

   Place the order -> Reduce inventory -> Deduct the balance -> Change ( Order ) state

   Initial status of the database

6.1 Simulate normal order

   Start three microservices

   Order normally ：http://localhost:2001/order/create?userId=1&productId=1&count=10&money=100

   Database situation ：

SELECT *  FROM  `seata_order`.`t_order`

SELECT * FROM `seata_storage`.`t_storage`

SELECT *  FROM  `seata_account`.`t_account`;

   You can see , There is no problem placing an order normally , Inventory decrease 10, Monthly decrease of account 100, The order status changes to 1.

6.2 Simulation timeout exception , No addition @GlobalTransactional annotation

  AccountServiceImpl Add timeout

because 30 Seconds have passed OpenFeign Timeout for , So it will fail .

Revisit ：http://localhost:2001/order/create?userId=1&productId=1&count=10&money=100

Database situation ：

Oh my god , Failed to place an order, and even reduced the inventory and the user's account balance , That's good .

6.3 Timeout exception , add to @GlobalTransactional

  AccountServiceImpl Add timeout

  OrderServiceImpl add to @GlobalTransactional annotation , The function of this annotation is to roll back whenever an exception occurs .

   Visit at this time ：http://localhost:2001/order/create?userId=1&productId=1&count=10&money=100

   At this time, the database is in good condition ：

)

   You can see , There is no change in the database data after placing the order , No data was added , The distributed transaction rollback test was successful .

7、 Knowledge points supplement

   Our default above is AT Transaction mode .

7.1 AT How to make the model non intrusive to the business

AT The premise of the pattern ：

• Based on support for local ACID Relational database of transactions
• Java application , adopt JDBC Access database

The whole mechanism ：

The evolution of the two-stage submission agreement ：

• A stage ： Business data and rollback logging are committed in the same local transaction , Release local locks and connection resources .
• Two stages ：
  • Submit asynchronized , Complete... Very quickly .
  • Rollback is compensated by a phase of rollback log

7.2 Three components of distributed transaction

Execute the process ：

• TM Open distributed transaction （TM towards TC Register global transaction records ）;

• By business scenario , Arrange the database 、 Services and other internal resources （RM towards TC Report resource readiness ）;

• TM End distributed transaction , The end of the first phase of the business （TM notice TC Submit / Roll back distributed transactions ）;

• TC Summarize transaction information , Decide whether a distributed transaction is committed or rolled back ;

• TC Inform all RM Submit / Roll back resources , The second phase of business is over .

   What I use here is Seata1.3.0 Version of , Many pits were also stepped on during the operation . This is just a simple tutorial , The real distributed transaction mechanism is very complex , More in-depth research is needed .