分布式事务

随着互联网快速发展，微服务，SOA 等服务架构模式正在被大规模的使用，现在分布式系统一般由多个独立的子系统组成，多个子系统通过网络通信互相协作配合完成各个功能。

有很多用例会跨多个子系统才能完成，比较典型的是电子商务网站的下单支付流程，至少会涉及交易系统和支付系统。而且这个过程中会涉及到事务的概念，即保证交易系统和支付系统的数据一致性，此处我们称这种跨系统的事务为分布式事务。
具体一点而言，分布式事务是指事务的参与者、支持事务的服务器、资源服务器以及事务管理器分别位于不同的分布式系统的不同节点之上。

解决方案

1.两阶段提交(2PC)
2.补偿事务(TCC)
3.本地消息表(异步确保)
4.MQ 事务消息

实现步骤

1.上游服务像消息服务发送一条预提交消息
2.消息服务返回对应的曲剧唯一的消息ID
3.上游服务实现自身业务，执行本地逻辑，根据本地事务决定提交或者回滚
4.消息服务根据上游服务响应的结果提交或者回滚(删除消息)
5.如果上游消息响应提交则吧消息发送到MQ
6.发送消息到MQ后，需要把MQ的Confirm机制打开，针对消息发送的状态进行回调
7.消息服务监听MQ回调，根据业务逻辑判断是否需要回滚或者提交，走第4步
8.当上游消息执行某段业务逻辑可能会抛异常或者其他的错误，会导致消息一直都是待提交的状态，需要启动一个后台定时任务轮询消息表，把所有未提交的消息进行确定，根据结果提交或者回滚

流程图

image

实战代码

1.项目结构

源码会上传到github和csdn的资源，可以自行下载，就不提供像maven等相关依赖、配置文件相关的代码了，项目整体的架构是Springboot、注册和配置中心Nacos、Redis加上RabbitMQ。需要好哥哥们熟悉相关的技术点，后续有时间一个个来整吧

结构

image

2.sql语句

CREATE TABLE `message_record` (`id_` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键ID',`business_id` varchar(64) DEFAULT NULL COMMENT '业务数据ID',`business_type` tinyint(2) DEFAULT NULL COMMENT '业务类型：具体业务',`message_id` varchar(64) NOT NULL COMMENT '消息ID',`retries_number` tinyint(2) DEFAULT '0' COMMENT '重试次数',`status_` tinyint(2) DEFAULT '0' COMMENT '结果 1 成功  0 失败',`create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',PRIMARY KEY (`id_`),UNIQUE KEY `inx_message_id` (`message_id`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8 COMMENT='rabbit消息记录';

3.MQ配置

import com.xjw.config.constant.RabbitmqConstant;
import org.springframework.amqp.core.Binding;
import org.springframework.amqp.core.BindingBuilder;
import org.springframework.amqp.core.DirectExchange;
import org.springframework.amqp.core.Queue;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;/*** @author xiejianwei* @ClassName BusinessOrderRabbitMqConfig*/
@Configuration
public class OrderRabbitMqConfig {/*** 初始化队列** @return*/@Beanpublic Queue orderQueue() {return new Queue(RabbitmqConstant.ORDER_QUEUE, true);}/*** 初始化交换机** @return*/@Beanpublic DirectExchange orderExchange() {return new DirectExchange(RabbitmqConstant.ORDER_EXCHANGE, true, false);}/*** 队列通过路由键绑定到交换机** @return*/@Beanpublic Binding bind() {return BindingBuilder.bind(orderQueue()).to(orderExchange()).with(RabbitmqConstant.ORDER_ROUTING_KEY);}
}

3.实体类

import lombok.Getter;
import lombok.Setter;import java.util.Date;
import java.util.UUID;/*** @author xiejianwei*/
@Getter
@Setter
public class MessageRecord {/*** 主键ID*/private Long id;/*** 业务数据ID*/private String businessId;/*** 业务类型*/private int businessType;/*** 消息ID*/private String messageId;/*** 重试次数*/private int retriesNumber;/*** 消息状态 (0.失败，1成功)*/private int status;/*** 创建时间*/private Date createTime;public MessageRecord() {}public MessageRecord(String businessId, int businessType) {this.businessId = businessId;this.businessType = businessType;this.messageId = UUID.randomUUID().toString().replace("-", "").toLowerCase();this.retriesNumber = 0;this.createTime = new Date();this.status = 0;}
}

import java.math.BigDecimal;/*** @author xiejianwei*/
@Getter
@Setter
public class Order extends SerializableDto {/*** 订单编号*/private String orderId;/*** 订单金额*/private BigDecimal amount;/*** 做简单的例子就不关联业务ID了*/private String productName;
}

4.业务实现

import com.xjw.entity.pojo.MessageRecord;
import com.xjw.entity.pojo.Order;
import com.xjw.service.MessageRecordService;
import com.xjw.service.OrderService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;/*** @author xiejianwei*/
@Service
@Slf4j
public class OrderServiceImpl implements OrderService {@Autowiredpublic MessageRecordService messageRecordService;/*** 模拟发起一个简单的订单** @param order* @return*/@Override@Transactional(rollbackFor = Exception.class)public boolean start(Order order) {//触发保存本地消息表MessageRecord messageRecord = new MessageRecord(order.getOrderId(), 1);messageRecordService.preCommit(messageRecord);log.info("这里可以做本地业务操作");log.info("下单中，请稍等-----");log.info("恭喜您，下单成功，订单号：{}", order.getOrderId());// 操作本地事务成功则commit 消息，如果处理本地事务异常，则会有定时任务回调messageRecordService.commit(messageRecord.getMessageId(), true);return true;}
}

import com.alibaba.fastjson.JSON;
import com.xjw.config.constant.RabbitmqConstant;
import com.xjw.entity.pojo.MessageRecord;
import com.xjw.mapper.MessageRecordMapper;
import com.xjw.service.MessageRecordService;
import com.xjw.service.RabbitmqService;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.util.List;/*** @author xiejianwei*/
@Service
public class MessageRecordServiceImpl implements MessageRecordService {@Autowiredpublic MessageRecordMapper messageRecordMapper;@Autowiredpublic RabbitmqService rabbitmqService;@Overridepublic boolean preCommit(MessageRecord messageRecord) {return messageRecordMapper.insert(messageRecord);}@Overridepublic boolean commit(String messageId, boolean commitFlag) {/*** 不提交则代表回滚*/if (!commitFlag) {messageRecordMapper.delete(messageId);return true;}// 提交消息到MQMessageRecord messageRecord = messageRecordMapper.find(messageId);/*** 发送MQ消息* 将唯一消息ID设置给CorrelationData* 回调时可以用这个ID查找到数据对应的消息记录*/rabbitmqService.sendMessage(RabbitmqConstant.ORDER_EXCHANGE, RabbitmqConstant.ORDER_ROUTING_KEY, JSON.toJSONString(messageRecord), new CorrelationData(messageRecord.getMessageId()));return true;}@Overridepublic void update(String messageId) {messageRecordMapper.update(messageId);}@Overridepublic MessageRecord find(String messageId) {return messageRecordMapper.find(messageId);}@Overridepublic List<MessageRecord> findAll(int status) {return messageRecordMapper.findAll(status);}
}

import com.xjw.callback.RabbitMqConfirmCallback;
import com.xjw.service.RabbitmqService;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;/*** @author xiejianwei* @ClassName RabbitmqServiceImpl* @Description 发送mq消息*/
@Service
public class RabbitmqServiceImpl implements RabbitmqService {@Autowiredprivate RabbitTemplate rabbitTemplate;@Autowiredprivate RabbitMqConfirmCallback rabbitMqConfirmCallback;/*** 发送消息到mq(单个)** @param exchange   交换机的名称* @param routingKey 路由key值* @param messages   消息的附件消息*/@Overridepublic void sendMessage(String exchange, String routingKey, String messages, CorrelationData correlationData) {/*** 设置回调*/rabbitTemplate.setConfirmCallback(rabbitMqConfirmCallback);rabbitTemplate.convertAndSend(exchange, routingKey, messages, correlationData);}
}

5.接口管理

import com.xjw.entity.pojo.Order;
import com.xjw.entity.vo.R;
import com.xjw.service.OrderService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.math.BigDecimal;
import java.util.UUID;/*** 订单接口管理** @author xiejianwei*/
@RestController
@RequestMapping("/order")
@Validated
public class OrderController {@Autowiredpublic OrderService orderService;@PostMapping("/start")public R page(@RequestBody String productName) {Order order = new Order();order.setAmount(BigDecimal.valueOf(5000));order.setProductName(productName);order.setOrderId(UUID.randomUUID().toString().replace("-", "").toLowerCase());orderService.start(order);return R.success();}
}

6.mq/本地消息回调

import com.alibaba.fastjson.JSON;
import com.xjw.config.constant.RabbitmqConstant;
import com.xjw.entity.pojo.MessageRecord;
import com.xjw.service.MessageRecordService;
import com.xjw.service.RabbitmqService;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;/*** @author xiejianwei*/
@Component
public class RabbitMqConfirmCallback implements RabbitTemplate.ConfirmCallback {@Autowiredprivate MessageRecordService messageRecordService;@Autowiredpublic RabbitmqService rabbitmqService;/*** @param correlationData 相关配置信息* @param ack             交换机是否成功收到消息* @param cause           错误信息*/@Overridepublic void confirm(CorrelationData correlationData, boolean ack, String cause) {/*** 这个就是我们发送消息设置的messageId*/String messageId = correlationData.getId();// 未发送成功if (!ack) {MessageRecord messageRecord = messageRecordService.find(messageId);if (null != messageRecord) {// 重发rabbitmqService.sendMessage(RabbitmqConstant.ORDER_EXCHANGE, RabbitmqConstant.ORDER_ROUTING_KEY, JSON.toJSONString(messageRecord), new CorrelationData(messageRecord.getMessageId()));}} else {// 修改消息状态为成功messageRecordService.update(messageId);}}
}

/*** 根据具体的业务，判断是否需要提交或者回滚消息** @author xiejianwei*/
@Component
public class OrderMessageRecordConfirm implements MessageRecordCallback {@Overridepublic boolean confirm(MessageRecord messageRecord) {String messageId = messageRecord.getMessageId();/*** 根据具体的业务，判断是否需要提交或者回滚消息*/if ("1212321".equals(messageId)) {return true;}return false;}
}

7.定时任务

import com.xjw.callback.MessageRecordCallback;
import com.xjw.entity.pojo.MessageRecord;
import com.xjw.service.MessageRecordService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;import java.util.List;/*** @author xiejianwei*/
@Component
@EnableScheduling
public class MessageRecordConfirmTask {@Autowiredpublic MessageRecordService messageRecordService;@Autowiredpublic MessageRecordCallback messageRecordCallback;/*** 每隔5分钟轮询消息表*/@Scheduled(cron = "0 0/5 * * * ?")public void confirm() {// 查询所有状态等于0(未提交的状态)List<MessageRecord> all = messageRecordService.findAll(0);if (null != all && all.size() > 0) {all.forEach(messageRecord -> {boolean confirm = messageRecordCallback.confirm(messageRecord);// 根据回调结果执行提交或者回滚messageRecordService.commit(messageRecord.getMessageId(), confirm);});}}
}