前言

本文使用工具版本如下：
seata-1.4.2
dubbo-3.0.5
mysql-8

1.概念

一個分佈式的全局事務，整體是兩階段提交的模型。全局事務是由若干分支事務組成的，分支事務要滿足兩階段提交的模型要求，即需要每個分支事務都具備自己的：

一階段 prepare 行爲
二階段 commit 或 rollback 行爲 TCC 模式，不依賴於底層數據資源的事務支持：
一階段 prepare 行爲：調用自定義的 prepare 邏輯。
二階段 commit 行爲：調用自定義的 commit 邏輯。
二階段 rollback 行爲：調用自定義的 rollback 邏輯。所謂 TCC 模式，是指支持把自定義的分支事務納入到全局事務的管理中。那TCC事務開發就需要完成prepare、commit、rollback三個方法邏輯。

2.開發

2.1 概覽圖

2.2 工程總體結構

2.3 訂單模塊

2.3.1 order-api模塊

2.3.1.1 工程結構

2.3.1.2 TccOrderService

import com.liuhangs.learning.seata.tcc.order.vo.TccOrderVO;

/**
 * 創建訂單 dubbo接口定義
 */
public interface TccOrderService {

    boolean createOrder(TccOrderVO tccOrderVO);
}

2.3.2 order模塊

2.3.2.1 工程結構

2.3.2.2 建表語句

CREATE TABLE test1.seata_tcc_order (
	`id` BIGINT(64) auto_increment NOT NULL COMMENT '自增ID' PRIMARY KEY,
	`order_id` varchar(64) NOT NULL COMMENT '訂單ID' ,
	`user_id` BIGINT NOT NULL COMMENT '用戶ID',
	`amount` INT NOT NULL COMMENT '訂單金額',
	`is_delete` INT DEFAULT 0 NOT null COMMENT '是否刪除，0-未刪除，1-已刪除',
	`create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '創建時間',
  	`update_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
	key(order_id),
	key(user_id)
)
ENGINE=InnoDB
COMMENT='訂單表';

CREATE TABLE test1.seata_tcc_order_tx (
	`id` BIGINT(64) auto_increment NOT NULL COMMENT '自增ID' PRIMARY KEY,
	`order_id` varchar(64) NOT NULL COMMENT '訂單ID' ,
	`xid` varchar(128) NOT NULL COMMENT '事務ID',
	`status` INT NOT NULL DEFAULT 0 COMMENT '事務狀態，0-初始狀態，1-已提交，9-已回滾',
	`create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '創建時間',
  	`update_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
	key(order_id),
	key(xid)
)
ENGINE=InnoDB
COMMENT='訂單事務表';

2.3.2.3 pom依賴

<dependencies>
    <dependency>
      <groupId>com.liuhangs.learning</groupId>
      <artifactId>seata-tcc-order-api</artifactId>
      <version>0.0.1-SNAPSHOT</version>
    </dependency>

    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <optional>true</optional>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>

    <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>3.2.0</version>
    </dependency>
    <dependency>
      <groupId>org.apache.dubbo</groupId>
      <artifactId>dubbo-spring-boot-starter</artifactId>
      <version>3.0.5</version>
    </dependency>
    <dependency>
      <groupId>org.apache.dubbo</groupId>
      <artifactId>dubbo-registry-nacos</artifactId>
      <version>3.0.5</version>
    </dependency>
    <dependency>
      <groupId>io.seata</groupId>
      <artifactId>seata-spring-boot-starter</artifactId>
      <version>1.4.2</version>
    </dependency>
    <dependency>
      <groupId>com.esotericsoftware.kryo</groupId>
      <artifactId>kryo</artifactId>
      <version>2.24.0</version>
    </dependency>
    <dependency>
      <groupId>com.esotericsoftware</groupId>
      <artifactId>kryo</artifactId>
      <version>4.0.2</version>
    </dependency>
    <dependency>
      <groupId>de.javakaffee</groupId>
      <artifactId>kryo-serializers</artifactId>
      <version>0.42</version>
    </dependency>
  </dependencies>

2.3.2.4 application.yml

server:
  port: 7001
  servlet:
    context-path: /

spring:
  application:
    name: seata-tcc-order
  datasource:
    type: com.zaxxer.hikari.HikariDataSource
    url: jdbc:mysql://127.0.0.1:3306/test1?serverTimezone=UTC&useSSL=false&useUnicode=true&characterEncoding=UTF-8
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: root
    password: root


mybatis-plus:
  configuration:
    map-underscore-to-camel-case: true
    auto-mapping-behavior: full
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  mapper-locations: classpath*:mapper/**/*Mapper.xml

dubbo:
  application:
    name: seata-tcc-order
  registry:
    address: nacos://127.0.0.1:8848
  protocol:
    port: 20883
    name: dubbo

seata:
  enabled: true
  tx-service-group: seata_learning_tx_group #事務分組，需要和seata服務器一致
  #這裏很關鍵，使用XA模式時，需要關掉seata的數據源代理，否則會出現無法回滾或者部分回滾的問題
  #enable-auto-data-source-proxy: false
  registry:
    type: nacos
    nacos:
      server-addr: localhost:8848
      namespace: edc58481-b3b7-4596-8cfb-de304633c6d2
      group: SEATA_GROUP
  config:
    type: nacos
    nacos:
      server-addr: localhost:8848
      namespace: edc58481-b3b7-4596-8cfb-de304633c6d2
      group: SEATA_GROUP

2.3.2.5 配置類SeataTccOrderConfig

import org.apache.dubbo.config.spring.context.annotation.EnableDubbo;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Configuration;

@EnableDubbo(scanBasePackages = "com.liuhangs.learning.seata.tcc.order.service")
@MapperScan("com.liuhangs.learning.seata.tcc.order.mapper")
@Configuration
public class SeataTccOrderConfig {

}

2.3.2.6 TccOrderMapper

import org.apache.ibatis.annotations.Mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.liuhangs.learning.seata.tcc.order.mapper.po.TccOrderPO;

@Mapper
public interface TccOrderMapper extends BaseMapper<TccOrderPO> {

}

2.3.2.7 TccOrderTxMapper

import org.apache.ibatis.annotations.Mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.liuhangs.learning.seata.tcc.order.mapper.po.TccOrderPO;
import com.liuhangs.learning.seata.tcc.order.mapper.po.TccOrderTxPO;

@Mapper
public interface TccOrderTxMapper extends BaseMapper<TccOrderTxPO> {

}

2.3.2.8 dubbo接口實現TccOrderServiceImpl

import org.apache.dubbo.config.annotation.DubboService;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.liuhangs.learning.seata.tcc.order.vo.TccOrderVO;

import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;

/**
 * 創建訂單 dubbo接口實現類
 */
@DubboService
@Service
@RequiredArgsConstructor
@Slf4j
public class TccOrderServiceImpl implements TccOrderService {

    private final TccOrderTxService tccOrderTxService;

    @Override
    @Transactional(rollbackFor = Exception.class)
    public boolean createOrder(TccOrderVO tccOrderVO) {
        return tccOrderTxService.prepare(null, tccOrderVO.getOrderId(), tccOrderVO.getUserId(), tccOrderVO.getAmount());
    }
}

2.3.2.9 TCC分支事務定義TccOrderTxService

import io.seata.rm.tcc.api.BusinessActionContext;
import io.seata.rm.tcc.api.BusinessActionContextParameter;
import io.seata.rm.tcc.api.LocalTCC;
import io.seata.rm.tcc.api.TwoPhaseBusinessAction;

/**
 * TCC分支事務定義
 */
@LocalTCC
public interface TccOrderTxService {

    /**
     * OrderTcc爲分支事務名稱，全局唯一
     * commitMethod爲提交方法名稱
     * rollbackMethod爲回滾方法名稱
     * @BusinessActionContextParameter註解表示將參數傳給commit和rollback方法，
     * 在commit和rollback方法可以通過actionContext.getActionContext("orderId")方式獲取參數
     */
    @TwoPhaseBusinessAction(name = "OrderTcc", commitMethod = "commit", rollbackMethod = "rollback")
    boolean prepare(BusinessActionContext actionContext, @BusinessActionContextParameter(paramName = "orderId") String orderId,
        @BusinessActionContextParameter(paramName = "userId") Long userId,
        @BusinessActionContextParameter(paramName = "amount") Long amount);

    /**
     * Commit boolean.
     *
     * @param actionContext the action context
     * @return the boolean
     */
    boolean commit(BusinessActionContext actionContext);

    /**
     * Rollback boolean.
     *
     * @param actionContext the action context
     * @return the boolean
     */
    boolean rollback(BusinessActionContext actionContext);
}

2.3.2.10 TCC分支事務實現

import java.util.Objects;

import org.apache.dubbo.config.annotation.DubboService;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.update.LambdaUpdateWrapper;
import com.liuhangs.learning.seata.tcc.order.mapper.TccOrderMapper;
import com.liuhangs.learning.seata.tcc.order.mapper.TccOrderTxMapper;
import com.liuhangs.learning.seata.tcc.order.mapper.po.TccOrderPO;
import com.liuhangs.learning.seata.tcc.order.mapper.po.TccOrderTxPO;

import io.seata.rm.tcc.api.BusinessActionContext;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;

@Service
@RequiredArgsConstructor
@Slf4j
public class TccOrderTxServiceImpl implements TccOrderTxService {

    private final TccOrderMapper tccOrderMapper;

    private final TccOrderTxMapper tccOrderTxMapper;

    @Override
    public boolean prepare(BusinessActionContext actionContext, String orderId, Long userId, Long amount) {
        log.info("準備事務開始，xid={}, orderId={}", actionContext.getXid(), orderId);
        // 冪等
        LambdaQueryWrapper<TccOrderTxPO> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(TccOrderTxPO::getXid, actionContext.getXid());
        TccOrderTxPO alreadyExistsTx = tccOrderTxMapper.selectOne(queryWrapper);
        // 如果已經存在事務，並且狀態是已提交或者已回滾，表示事務已經執行完成，直接返回
        // 結合rollback方法的防止空回滾插入的事務數據，可以解決懸掛問題
        if(Objects.nonNull(alreadyExistsTx)) {
            log.info("觸發冪等，xid={}, orderId={}", actionContext.getXid(), orderId);
            return true;
        }

        // 插入訂單
        TccOrderPO tccOrderPO = new TccOrderPO();
        tccOrderPO.setOrderId(orderId);
        tccOrderPO.setUserId(userId);
        tccOrderPO.setAmount(amount);
        tccOrderMapper.insert(tccOrderPO);

        // 插入訂單事務
        TccOrderTxPO tccOrderTxPO = new TccOrderTxPO();
        tccOrderTxPO.setOrderId(orderId);
        tccOrderTxPO.setXid(actionContext.getXid());
        // 初始狀態
        tccOrderTxPO.setStatus(0);
        tccOrderTxMapper.insert(tccOrderTxPO);
        log.info("準備事務結束，xid={}, orderId={}", actionContext.getXid(), orderId);
        return true;
    }

    @Override
    public boolean commit(BusinessActionContext actionContext) {
        log.info("提交事務開始，xid={}", actionContext.getXid());
        // 冪等
        LambdaQueryWrapper<TccOrderTxPO> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(TccOrderTxPO::getXid, actionContext.getXid());
        TccOrderTxPO alreadyExistsTx = tccOrderTxMapper.selectOne(queryWrapper);
        // 如果已經存在事務，並且狀態是已提交或者已回滾，表示事務已經執行完成，直接返回
        if(Objects.nonNull(alreadyExistsTx) && !Objects.equals(alreadyExistsTx.getStatus(), 0)) {
            log.info("觸發冪等，xid={}", actionContext.getXid());
            return true;
        }

        TccOrderTxPO tccOrderTxPO = new TccOrderTxPO();
        tccOrderTxPO.setXid(actionContext.getXid());
        // 提交狀態
        tccOrderTxPO.setStatus(1);

        LambdaUpdateWrapper<TccOrderTxPO> wapper = new LambdaUpdateWrapper<>();
        wapper.eq(TccOrderTxPO::getXid, actionContext.getXid());
        tccOrderTxMapper.update(tccOrderTxPO, wapper);
        log.info("提交事務結束，xid={}", actionContext.getXid());
        return true;
    }

    @Override
    public boolean rollback(BusinessActionContext actionContext) {
        String orderId = (String) actionContext.getActionContext("orderId");
        log.info("回滾事務開始，xid={}, orderId={}", actionContext.getXid(), orderId);
        // 冪等
        LambdaQueryWrapper<TccOrderTxPO> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(TccOrderTxPO::getXid, actionContext.getXid());
        TccOrderTxPO alreadyExistsTx = tccOrderTxMapper.selectOne(queryWrapper);
        // 如果已經存在事務，並且狀態是已提交或者已回滾，表示事務已經執行完成，直接返回
        if(Objects.nonNull(alreadyExistsTx) && !Objects.equals(alreadyExistsTx.getStatus(), 0)) {
            log.info("觸發冪等，xid={}, orderId={}", actionContext.getXid(), orderId);
            return true;
        }

        // 空回滾，沒有事務初始記錄，就開始回滾，就表示空回滾
        if(Objects.isNull(alreadyExistsTx)) {
            log.info("觸發空回滾，xid={}, orderId={}", actionContext.getXid(), orderId);
            // 插入訂單事務
            TccOrderTxPO tccOrderTxPO = new TccOrderTxPO();
            tccOrderTxPO.setOrderId(orderId);
            tccOrderTxPO.setXid(actionContext.getXid());
            // 回滾狀態
            tccOrderTxPO.setStatus(9);
            tccOrderTxMapper.insert(tccOrderTxPO);
            return true;
        }

        // 刪除訂單數據
        TccOrderPO tccOrderPO = new TccOrderPO();
        tccOrderPO.setIsDelete(1);
        LambdaUpdateWrapper<TccOrderPO> orderWrapper = new LambdaUpdateWrapper<>();
        orderWrapper.eq(TccOrderPO::getOrderId, orderId);
        tccOrderMapper.update(tccOrderPO, orderWrapper);

        // 更新事務表狀態
        TccOrderTxPO tccOrderTxPO = new TccOrderTxPO();
        tccOrderTxPO.setXid(actionContext.getXid());
        // 提交狀態
        tccOrderTxPO.setStatus(9);

        LambdaUpdateWrapper<TccOrderTxPO> wapper = new LambdaUpdateWrapper<>();
        wapper.eq(TccOrderTxPO::getXid, actionContext.getXid());
        tccOrderTxMapper.update(tccOrderTxPO, wapper);
        log.info("回滾事務結束，xid={}, orderId={}", actionContext.getXid(), orderId);
        return true;
    }
}

2.4 錢包模塊

2.4.1 wallet-api模塊

2.4.1.1 工程結構

2.4.1.2 TccWalletService

import com.liuhangs.learning.seata.tcc.wallat.vo.TccUserBalanceVO;

/**
 * 錢包扣款 dubbo接口定義
 */
public interface TccWalletService {

    boolean deductionBalance(TccUserBalanceVO tccUserBalanceVO);
}

2.4.2 wallet模塊

2.4.2.1 工程結構

2.4.2.2 建表語句init.sql

CREATE TABLE test2.seata_tcc_wallet_balance (
	id BIGINT(64) auto_increment NOT NULL PRIMARY key COMMENT '自增ID',
	user_id BIGINT NOT NULL COMMENT '用戶ID',
	user_name varchar(32) NOT NULL COMMENT '用戶名稱',
	balance BIGINT(64) NOT NULL COMMENT '用戶餘額',
	freeze_balance BIGINT(64) NOT NULL DEFAULT 0 COMMENT '用戶凍結餘額',
	`create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '創建時間',
  	`update_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
	is_delete INT DEFAULT 0 NOT null,
	key(user_id)
)
ENGINE=InnoDB
COMMENT='錢包餘額表';

INSERT INTO test2.seata_tcc_wallet_balance (user_id,user_name,balance,create_time,update_time,is_delete) VALUES
	 (1,'tom',3000000,'2022-01-29 10:33:16','2022-02-09 09:27:50',0);

CREATE TABLE test2.seata_tcc_wallet_bill (
	id BIGINT(64) auto_increment NOT NULL PRIMARY key COMMENT '自增ID',
	user_id BIGINT NOT NULL COMMENT '用戶ID',
	user_name varchar(32) NOT NULL COMMENT '用戶名稱',
	order_id varchar(64) NOT NULL COMMENT '訂單ID' ,
	amount BIGINT(64) NOT NULL COMMENT '消費金額',
	remark varchar(64) default NULL COMMENT '備註' ,
	`create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '創建時間',
  	`update_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
	is_delete INT DEFAULT 0 NOT null,
	key(user_id)
)
ENGINE=InnoDB
COMMENT='錢包賬單表';

CREATE TABLE test1.seata_tcc_wallet_tx (
	`id` BIGINT(64) auto_increment NOT NULL COMMENT '自增ID' PRIMARY KEY,
	`xid` varchar(128) NOT NULL COMMENT '事務ID',
	`status` INT NOT NULL DEFAULT 0 COMMENT '事務狀態，0-初始狀態，1-已提交，9-已回滾',
	`create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '創建時間',
  	`update_time` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
	key(xid)
)
ENGINE=InnoDB
COMMENT='錢包事務表';

2.4.2.3 pom依賴

<dependencies>
    <dependency>
      <groupId>com.liuhangs.learning</groupId>
      <artifactId>seata-tcc-wallet-api</artifactId>
      <version>1.0.0-SNAPSHOT</version>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <optional>true</optional>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
    </dependency>
    <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>3.2.0</version>
    </dependency>
    <dependency>
      <groupId>org.apache.dubbo</groupId>
      <artifactId>dubbo-spring-boot-starter</artifactId>
      <version>3.0.5</version>
    </dependency>
    <dependency>
      <groupId>org.apache.dubbo</groupId>
      <artifactId>dubbo-registry-nacos</artifactId>
      <version>3.0.5</version>
    </dependency>
    <dependency>
      <groupId>io.seata</groupId>
      <artifactId>seata-spring-boot-starter</artifactId>
      <version>1.4.2</version>
    </dependency>
    <dependency>
      <groupId>com.esotericsoftware.kryo</groupId>
      <artifactId>kryo</artifactId>
      <version>2.24.0</version>
    </dependency>
    <dependency>
      <groupId>com.esotericsoftware</groupId>
      <artifactId>kryo</artifactId>
      <version>4.0.2</version>
    </dependency>
    <dependency>
      <groupId>de.javakaffee</groupId>
      <artifactId>kryo-serializers</artifactId>
      <version>0.42</version>
    </dependency>
  </dependencies>

2.4.2.4 application.yml

server:
  port: 7002
  servlet:
    context-path: /

spring:
  application:
    name: seata-tcc-wallet
  datasource:
    type: com.zaxxer.hikari.HikariDataSource
    url: jdbc:mysql://127.0.0.1:3306/test2?serverTimezone=UTC&useSSL=false&useUnicode=true&characterEncoding=UTF-8
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: root
    password: root

mybatis-plus:
  configuration:
    map-underscore-to-camel-case: true
    auto-mapping-behavior: full
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
  mapper-locations: classpath*:mapper/**/*Mapper.xml

dubbo:
  application:
    name: seata-tcc-wallet
  registry:
    address: nacos://127.0.0.1:8848
  protocol:
    port: 20884
    name: dubbo

seata:
  enabled: true
  tx-service-group: seata_learning_tx_group
  #這裏很關鍵，使用XA模式時，需要關掉seata的數據源代理，否則會出現無法回滾或者部分回滾的問題
  #enable-auto-data-source-proxy: false
  registry:
    type: nacos
    nacos:
      server-addr: localhost:8848
      namespace: edc58481-b3b7-4596-8cfb-de304633c6d2
      group: SEATA_GROUP
  config:
    type: nacos
    nacos:
      server-addr: localhost:8848
      namespace: edc58481-b3b7-4596-8cfb-de304633c6d2
      group: SEATA_GROUP

2.4.2.5 配置類TccWalletConfig

import org.apache.dubbo.config.spring.context.annotation.EnableDubbo;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Configuration;

@EnableDubbo(scanBasePackages = "com.liuhangs.learning.seata.tcc.wallet.service")
@MapperScan("com.liuhangs.learning.seata.tcc.wallet.mapper")
@Configuration
public class TccWalletConfig {

}

2.4.2.6 TccWalletBalanceMapper

import org.apache.ibatis.annotations.Mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.liuhangs.learning.seata.tcc.wallet.mapper.po.TccWalletBalancePO;

/**
 * 錢包餘額mapper
 */
@Mapper
public interface TccWalletBalanceMapper extends BaseMapper<TccWalletBalancePO> {

}

2.4.2.7 TccWalletBillMapper

import org.apache.ibatis.annotations.Mapper;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.liuhangs.learning.seata.tcc.wallet.mapper.po.TccWalletBillPO;

/**
 * 錢包賬單mapper
 */
@Mapper
public interface TccWalletBillMapper extends BaseMapper<TccWalletBillPO> {

}

2.4.2.8 TccWalletTxMapper

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.liuhangs.learning.seata.tcc.wallet.mapper.po.TccWalletTxPO;

/**
 * 錢包事務mapper
 */
@Mapper
public interface TccWalletTxMapper extends BaseMapper<TccWalletTxPO> {

    /**
     * 此方法爲了解決懸掛問題。以下是問題過程（涉及到mysql mvcc的原理）：
     * 當prepare方法調用超時，開始調用rollback回滾方法，
     * rollback方法查詢seata_tcc_wallet_tx表沒有事務，插入一條已回滾（9）的數據，
     * prepare方法此時也正在調用，查詢seata_tcc_wallet_tx表，由於rollback方法沒有提交，prepare方法本地事務不可見已回滾（9）的數據，
     * 此時就會再插入一條初始化（0）的數據，
     * 爲了解決這個問題，使用for update語句將此事務xid的數據加一個間隙鎖，在prepare方法或者rollback方法事務提交以前，數據加上間隙鎖，另一個事務會被阻塞，直到任意一個事務提交。
     * 其實這裏有三種情況：
     * 1.prepare方法先執行到此sql，獲得間隙鎖，繼續執行完成prepare方法中insert語句，此時才執行rollback方法，執行此sql會阻塞，等待prepare方法提交。
     * 2.rollback方法先執行到此sql，獲得間隙鎖，繼續執行完成rollback方法中insert語句，此時才執行到prepare方法的此sql，prepare方法會阻塞，等待rollback方法提交。
     * 3.rollback方法先執行到此sql，獲得間隙鎖，此時prepare方法也執行到此sql，同時也獲得間隙鎖，
     * 然後rollback方法執行到insert語句，獲取排他鎖X失敗，轉爲得到共享鎖S，等待排他鎖X，
     * 此時prepare方法也執行到insert語句，獲取排他鎖X失敗，轉爲得到共享鎖S，等待排他鎖X，
     * 產生死鎖，會報錯：Deadlock found when trying to get lock; try restarting transaction
     * 然後自動釋放rollback方法事務，prepare方法執行完成，rollback方法再次嘗試回滾。
     * 在prepare方法或者rollback方法事務提交後，mvcc生成的readview視圖就將已提交的事務當成可見的，另一個事務就可以查詢出來了，
     * 這樣保證prepare方法和rollback方法併發時，插入seata_tcc_wallet_tx表的數據只有一條。
     * @param xid
     * @return
     */
    @Select("select id, xid, status from seata_tcc_wallet_tx where xid = #{xid} for update")
    TccWalletTxPO selectByXidForUpdate(@Param("xid") String xid);

}

2.4.2.9 dubbo接口實現TccWalletServiceImpl

import org.apache.dubbo.config.annotation.DubboService;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.liuhangs.learning.seata.tcc.wallat.service.TccWalletService;
import com.liuhangs.learning.seata.tcc.wallat.vo.TccUserBalanceVO;

import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;

/**
 * 錢包扣款和記賬單dubbo接口
 */
@DubboService  //dubbo服務提供類
@Service
@RequiredArgsConstructor
@Slf4j
public class TccWalletServiceImpl implements TccWalletService {

    private final TccWalletTxService tccWalletTxService;

    @Override
    //@Transactional(rollbackFor = Exception.class) //這裏加上事務不能解決懸掛問題，涉及到mvcc的原理
    public boolean deductionBalance(TccUserBalanceVO tccUserBalanceVO) {
        return tccWalletTxService.prepare(null, tccUserBalanceVO.getOrderId(), tccUserBalanceVO.getUserId(),
            tccUserBalanceVO.getUserName(), tccUserBalanceVO.getAmount());
    }
}

2.4.2.10 TCC分支事務定義TccWalletTxService

import io.seata.rm.tcc.api.BusinessActionContext;
import io.seata.rm.tcc.api.BusinessActionContextParameter;
import io.seata.rm.tcc.api.LocalTCC;
import io.seata.rm.tcc.api.TwoPhaseBusinessAction;

/**
 * 錢包TCC事務定義
 * @author hang.liu6
 * @version 1.0
 * @date 2022/2/9 14:31
 */
@LocalTCC
public interface TccWalletTxService {

    /**
     * WalletTcc爲分支事務名稱
     * commitMethod提交方法名稱
     * rollbackMethod回滾方法名稱
     * @BusinessActionContextParameter註解表示將參數傳給commit和rollback方法，
     * 在commit和rollback方法可以通過actionContext.getActionContext("orderId")方式獲取參數
     */
    @TwoPhaseBusinessAction(name = "WalletTcc", commitMethod = "commit", rollbackMethod = "rollback")
    boolean prepare(BusinessActionContext actionContext, @BusinessActionContextParameter(paramName = "orderId") String orderId,
        @BusinessActionContextParameter(paramName = "userId") Long userId,
        String userName,
        @BusinessActionContextParameter(paramName = "amount") Long amount);

    /**
     * Commit boolean.
     *
     * @param actionContext the action context
     * @return the boolean
     */
    boolean commit(BusinessActionContext actionContext);

    /**
     * Rollback boolean.
     *
     * @param actionContext the action context
     * @return the boolean
     */
    boolean rollback(BusinessActionContext actionContext);
}

2.4.2.11 TCC分支事務實現

import java.util.Objects;
import java.util.concurrent.TimeUnit;

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.update.LambdaUpdateWrapper;
import com.liuhangs.learning.seata.tcc.wallet.mapper.TccWalletBalanceMapper;
import com.liuhangs.learning.seata.tcc.wallet.mapper.TccWalletBillMapper;
import com.liuhangs.learning.seata.tcc.wallet.mapper.TccWalletTxMapper;
import com.liuhangs.learning.seata.tcc.wallet.mapper.po.TccWalletBalancePO;
import com.liuhangs.learning.seata.tcc.wallet.mapper.po.TccWalletBillPO;
import com.liuhangs.learning.seata.tcc.wallet.mapper.po.TccWalletTxPO;

import io.seata.rm.tcc.api.BusinessActionContext;
import io.seata.spring.annotation.GlobalLock;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;

@Service
@RequiredArgsConstructor
@Slf4j
public class TccWalletTxServiceImpl implements TccWalletTxService {

    private final TccWalletBalanceMapper tccWalletBalanceMapper;

    private final TccWalletBillMapper tccWalletBillMapper;

    private final TccWalletTxMapper tccWalletTxMapper;

    private static final Object lock = new Object();

    @Override
    @Transactional(rollbackFor = Exception.class) //這裏加上事務不能解決懸掛問題，涉及到mvcc的原理
    public boolean prepare(BusinessActionContext actionContext, String orderId, Long userId, String userName, Long amount) {
        log.info("準備事務開始，xid={}, orderId={}", actionContext.getXid(), orderId);
        // 凍結餘額
        LambdaUpdateWrapper<TccWalletBalancePO> updateBalanceWrapper = new LambdaUpdateWrapper<>();
        updateBalanceWrapper.setSql("balance = balance - " + amount);
        updateBalanceWrapper.setSql("freeze_balance = freeze_balance + " + amount);
        updateBalanceWrapper.eq(TccWalletBalancePO::getUserId, userId);
        tccWalletBalanceMapper.update(null, updateBalanceWrapper);

        // 插入賬單
        TccWalletBillPO tccWalletBillPO = new TccWalletBillPO();
        tccWalletBillPO.setUserId(userId);
        tccWalletBillPO.setUserName(userName);
        tccWalletBillPO.setOrderId(orderId);
        tccWalletBillPO.setAmount(amount);
        tccWalletBillMapper.insert(tccWalletBillPO);

        // 插入訂單事務
        TccWalletTxPO tccWalletTxPO = new TccWalletTxPO();
        tccWalletTxPO.setXid(actionContext.getXid());
        // 初始狀態
        tccWalletTxPO.setStatus(0);

        // 冪等
        log.info("準備階段查詢是否存在事務");
        TccWalletTxPO alreadyExistsTx = tccWalletTxMapper.selectByXidForUpdate(actionContext.getXid());
        // 如果已經存在事務，並且狀態是已提交或者已回滾，表示事務已經執行完成，直接返回
        // 結合rollback方法的防止空回滾插入的事務數據，可以解決懸掛問題
        if (Objects.nonNull(alreadyExistsTx)) {
            log.info("觸發冪等，xid={}, orderId={}", actionContext.getXid(), orderId);
            throw new RuntimeException("事務數據已經存在");
        }
        tccWalletTxMapper.insert(tccWalletTxPO);
        log.info("準備事務結束，xid={}, orderId={}", actionContext.getXid(), orderId);
        return true;
    }

    @Override
    @Transactional(rollbackFor = Exception.class)
    public boolean commit(BusinessActionContext actionContext) {
        log.info("提交事務開始，xid={}", actionContext.getXid());
        // 冪等
        LambdaQueryWrapper<TccWalletTxPO> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.eq(TccWalletTxPO::getXid, actionContext.getXid());
        TccWalletTxPO alreadyExistsTx = tccWalletTxMapper.selectOne(queryWrapper);
        // 如果已經存在事務，並且狀態是已提交或者已回滾，表示事務已經執行完成，直接返回
        if(Objects.nonNull(alreadyExistsTx) && !Objects.equals(alreadyExistsTx.getStatus(), 0)) {
            log.info("觸發冪等，xid={}", actionContext.getXid());
            return true;
        }

        Long amount = Long.valueOf(actionContext.getActionContext("amount").toString());
        Long userId = Long.valueOf(actionContext.getActionContext("userId").toString());
        // 凍結金額扣除
        LambdaUpdateWrapper<TccWalletBalancePO> updateBalanceWrapper = new LambdaUpdateWrapper<>();
        updateBalanceWrapper.setSql("freeze_balance = freeze_balance - " + amount);
        updateBalanceWrapper.eq(TccWalletBalancePO::getUserId, userId);
        tccWalletBalanceMapper.update(null, updateBalanceWrapper);

        TccWalletTxPO tccWalletTxPO = new TccWalletTxPO();
        tccWalletTxPO.setXid(actionContext.getXid());
        // 提交狀態
        tccWalletTxPO.setStatus(1);

        LambdaUpdateWrapper<TccWalletTxPO> wapper = new LambdaUpdateWrapper<>();
        wapper.eq(TccWalletTxPO::getXid, actionContext.getXid());
        tccWalletTxMapper.update(tccWalletTxPO, wapper);
        log.info("提交事務結束，xid={}", actionContext.getXid());
        return true;
    }

    @Override
    @Transactional(rollbackFor = Exception.class) //這裏加上事務不能解決懸掛問題，涉及到mvcc的原理
    public boolean rollback(BusinessActionContext actionContext) {
        String orderId = (String) actionContext.getActionContext("orderId");
        log.info("回滾事務開始，xid={}, orderId={}", actionContext.getXid(), orderId);
        // 冪等
        log.info("回滾階段查詢是否存在事務");
        TccWalletTxPO alreadyExistsTx = tccWalletTxMapper.selectByXidForUpdate(actionContext.getXid());
        // 如果已經存在事務，並且狀態是已提交或者已回滾，表示事務已經執行完成，直接返回
        if (Objects.nonNull(alreadyExistsTx) && !Objects.equals(alreadyExistsTx.getStatus(), 0)) {
            log.info("觸發冪等，xid={}, orderId={}", actionContext.getXid(), orderId);
            return true;
        }

        // 空回滾，沒有事務初始記錄，就開始回滾，就表示空回滾
        // 空回滾只是記錄下已經回滾，防止空回滾後懸掛的問題
        if (Objects.isNull(alreadyExistsTx)) {
            log.info("觸發空回滾，xid={}, orderId={}", actionContext.getXid(), orderId);
            // 插入訂單事務
            TccWalletTxPO tccWalletTxPO = new TccWalletTxPO();
            tccWalletTxPO.setXid(actionContext.getXid());
            // 回滾狀態
            tccWalletTxPO.setStatus(9);
            tccWalletTxMapper.insert(tccWalletTxPO);
            log.info("空回滾事務結束，xid={}, orderId={}", actionContext.getXid(), orderId);
            return true;
        }

        // 更新事務表狀態
        TccWalletTxPO tccWalletTxPO = new TccWalletTxPO();
        tccWalletTxPO.setXid(actionContext.getXid());
        // 提交狀態
        tccWalletTxPO.setStatus(9);

        LambdaUpdateWrapper<TccWalletTxPO> wapper = new LambdaUpdateWrapper<>();
        wapper.eq(TccWalletTxPO::getXid, actionContext.getXid());
        tccWalletTxMapper.update(tccWalletTxPO, wapper);

        Long amount = Long.valueOf(actionContext.getActionContext("amount").toString());
        Long userId = Long.valueOf(actionContext.getActionContext("userId").toString());
        // 還原凍結金額
        LambdaUpdateWrapper<TccWalletBalancePO> updateBalanceWrapper = new LambdaUpdateWrapper<>();
        updateBalanceWrapper.setSql("balance = balance + " + amount);
        updateBalanceWrapper.setSql("freeze_balance = freeze_balance - " + amount);
        updateBalanceWrapper.eq(TccWalletBalancePO::getUserId, userId);
        tccWalletBalanceMapper.update(null, updateBalanceWrapper);

        // 刪除錢包賬單
        LambdaUpdateWrapper<TccWalletBillPO> updateBillWrapper = new LambdaUpdateWrapper<>();
        updateBillWrapper.setSql("is_delete = 1");
        updateBillWrapper.eq(TccWalletBillPO::getOrderId, orderId);
        tccWalletBillMapper.update(null, updateBillWrapper);
        log.info("回滾事務結束，xid={}, orderId={}", actionContext.getXid(), orderId);
        return true;
    }
}

seata tcc使用1-RM工程搭建

前言

1.概念

2.開發

2.1 概覽圖

2.2 工程總體結構

2.3 訂單模塊

2.3.1 order-api模塊

2.3.1.1 工程結構

2.3.1.2 TccOrderService

2.3.2 order模塊

2.3.2.1 工程結構

2.3.2.2 建表語句

2.3.2.3 pom依賴

2.3.2.4 application.yml

2.3.2.5 配置類SeataTccOrderConfig

2.3.2.6 TccOrderMapper

2.3.2.7 TccOrderTxMapper

2.3.2.8 dubbo接口實現TccOrderServiceImpl

2.3.2.9 TCC分支事務定義TccOrderTxService

2.3.2.10 TCC分支事務實現

2.4 錢包模塊

2.4.1 wallet-api模塊

2.4.1.1 工程結構

2.4.1.2 TccWalletService

2.4.2 wallet模塊

2.4.2.1 工程結構

2.4.2.2 建表語句init.sql

2.4.2.3 pom依賴

2.4.2.4 application.yml

2.4.2.5 配置類TccWalletConfig

2.4.2.6 TccWalletBalanceMapper

2.4.2.7 TccWalletBillMapper

2.4.2.8 TccWalletTxMapper

2.4.2.9 dubbo接口實現TccWalletServiceImpl

2.4.2.10 TCC分支事務定義TccWalletTxService

2.4.2.11 TCC分支事務實現