电商项目-分布式事务(四)基于消息队列实现分布式事务

基于消息队列实现分布式事务，实现消息最终一致性

如何基于消息队列实现分布式事务？

通过消息队列实现分布式事务的话，可以保证当前数据的最终一致性。实现思路：将大的分布式事务，进行拆分，拆分成若干个小的本地事务，只要每一个小的本地事务是执行成功的，那就代表当前的分布式事务是执行成功的。下面以用户下单增加积分，来进行消息队列实现分布式事务的操作。

功能实现流程图如下：

主要包含三个角色：订单服务，消息队列和用户服务。
步骤（1-4）：订单服务
1.首先，在订单服务中，会生成订单相关数据，并添加到数据库中。
2.接着会在订单数据库中，创建任务表 ，会向任务表添加数据，（Username，orderID，point积分）

3.设置定时任务，扫描任务表，获取相关数据，如每隔7S扫描一次
4.发送任务数据到MQ

步骤（5-12）：用户服务
5.6.7.用户服务会接收消息，保证消息的不可重复消费，判断在Redis和 在数据库中是否存在。防止重复处理，不要重复添加积分。
用户服务正在执行消息
如果不存在，继续业务功能。
添加本地事务
12.通知订单服务

步骤（13）：订单服务
13.删除任务表数据。

一、 准备工作

1.1 shangcheng_order库新增数据表

任务表：

DROP TABLE IF EXISTS `tb_task`;
CREATE TABLE `tb_task` (`id` bigint(32) NOT NULL AUTO_INCREMENT COMMENT '任务id',`create_time` datetime DEFAULT NULL,`update_time` datetime DEFAULT NULL,`delete_time` datetime DEFAULT NULL,`task_type` varchar(32) DEFAULT NULL COMMENT '任务类型',`mq_exchange` varchar(64) DEFAULT NULL COMMENT '交换机名称',`mq_routingkey` varchar(64) DEFAULT NULL COMMENT 'routingkey',`request_body` varchar(512) DEFAULT NULL COMMENT '任务请求的内容',`status` varchar(32) DEFAULT NULL COMMENT '任务状态',`errormsg` varchar(512) DEFAULT NULL COMMENT '任务错误信息',PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

历史任务表：

DROP TABLE IF EXISTS `tb_task_his`;
CREATE TABLE `tb_task_his` (`id` bigint(32) NOT NULL AUTO_INCREMENT COMMENT '任务id',`create_time` datetime DEFAULT NULL,`update_time` datetime DEFAULT NULL,`delete_time` datetime DEFAULT NULL,`task_type` varchar(32) DEFAULT NULL COMMENT '任务类型',`mq_exchange` varchar(64) DEFAULT NULL COMMENT '交换机名称',`mq_routingkey` varchar(64) DEFAULT NULL COMMENT 'routingkey',`request_body` varchar(512) DEFAULT NULL COMMENT '任务请求的内容',`status` varchar(32) DEFAULT NULL COMMENT '任务状态',`errormsg` varchar(512) DEFAULT NULL,PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8;

1.2 shangcheng_service_order_api添加相关实体类

@Table(name="tb_task")
public class Task {
​@Idprivate Long id;
​@Column(name = "create_time")private Date createTime;
​@Column(name = "update_time")private Date updateTime;
​@Column(name = "delete_time")private Date deleteTime;
​@Column(name = "task_type")private String taskType;
​@Column(name = "mq_exchange")private String mqExchange;
​@Column(name = "mq_routingkey")private String mqRoutingkey;
​@Column(name = "request_body")private String requestBody;
​@Column(name = "status")private String status;
​@Column(name = "errormsg")private String errormsg;//getter，setter略
}

@Table(name="tb_task_his")
public class TaskHis {
​@Idprivate Long id;
​@Column(name = "create_time")private Date createTime;
​@Column(name = "update_time")private Date updateTime;
​@Column(name = "delete_time")private Date deleteTime;
​@Column(name = "task_type")private String taskType;
​@Column(name = "mq_exchange")private String mqExchange;
​@Column(name = "mq_routingkey")private String mqRoutingkey;
​@Column(name = "request_body")private String requestBody;
​@Column(name = "status")private String status;
​@Column(name = "errormsg")private String errormsg;
​//getter，setter略
}

1.3 shangcheng_user新增积分日志表

DROP TABLE IF EXISTS `tb_point_log`;
CREATE TABLE `tb_point_log` (`order_id` varchar(200) NOT NULL,`user_id` varchar(200) NOT NULL,`point` int(11) NOT NULL,PRIMARY KEY (`order_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

1.4 shangcheng_service_user_api添加实体类 PointLog

@Table(name="tb_point_log")
public class PointLog {
​private String orderId;private String userId;private Integer point;//getter，setter略
}

1.5 shangcheng_service_order添加rabbitMQ配置类

@Configuration
public class RabbitMQConfig {//添加积分任务交换机public static final String EX_BUYING_ADDPOINTUSER = "ex_buying_addpointuser";
​//添加积分消息队列public static final String CG_BUYING_ADDPOINT = "cg_buying_addpoint";
​//完成添加积分消息队列public static final String CG_BUYING_FINISHADDPOINT = "cg_buying_finishaddpoint";
​//添加积分路由keypublic static final String CG_BUYING_ADDPOINT_KEY = "addpoint";
​//完成添加积分路由keypublic static final String CG_BUYING_FINISHADDPOINT_KEY = "finishaddpoint";
​/*** 交换机配置* @return the exchange*/@Bean(EX_BUYING_ADDPOINTUSER)public Exchange EX_BUYING_ADDPOINTUSER() {return ExchangeBuilder.directExchange(EX_BUYING_ADDPOINTUSER).durable(true).build();}//声明队列@Bean(CG_BUYING_FINISHADDPOINT)public Queue QUEUE_CG_BUYING_FINISHADDPOINT() {Queue queue = new Queue(CG_BUYING_FINISHADDPOINT);return queue;}//声明队列@Bean(CG_BUYING_ADDPOINT)public Queue QUEUE_CG_BUYING_ADDPOINT() {Queue queue = new Queue(CG_BUYING_ADDPOINT);return queue;}/*** 绑定队列到交换机 .* @param queue    the queue* @param exchange the exchange* @return the binding*/@Beanpublic Binding BINDING_QUEUE_FINISHADDPOINT(@Qualifier(CG_BUYING_FINISHADDPOINT) Queue queue, @Qualifier(EX_BUYING_ADDPOINTUSER) Exchange exchange) {return BindingBuilder.bind(queue).to(exchange).with(CG_BUYING_FINISHADDPOINT_KEY).noargs();}@Beanpublic Binding BINDING_QUEUE_ADDPOINT(@Qualifier(CG_BUYING_ADDPOINT) Queue queue, @Qualifier(EX_BUYING_ADDPOINTUSER) Exchange exchange) {return BindingBuilder.bind(queue).to(exchange).with(CG_BUYING_ADDPOINT_KEY).noargs();}
}

二、 订单服务添加任务并发送

步骤1： 修改添加订单方法
当添加订单的时候，添加任务表中相关数据, 代码如下：

//增加任务表记录
Task task = new Task();
task.setCreateTime(new Date());
task.setUpdateTime(new Date());
task.setMqExchange(RabbitMQConfig.EX_BUYING_ADDPOINTURSE);
task.setMqRoutingkey(RabbitMQConfig.CG_BUYING_ADDPOINT_KEY);
​
Map map = new HashMap();
map.put("userName",order.getUsername());
map.put("orderId",order.getId());
map.put("point",order.getPayMoney());
task.setRequestBody(JSON.toJSONString(map));
taskMapper.insertSelective(task);

步骤2： 定时扫描任务表最新数据
订单服务新增定时任务类，获取小于系统当前时间的所有任务数据

（1） 修改订单服务启动类，添加开启定时任务注解

@EnableScheduling

（2） 定义定时任务类
查询最新数据
更新taskMapper新增方法，查询所有小于系统当前时间的数据

public interface TaskMapper extends Mapper<Task> {
​@Select("SELECT * from tb_task WHERE update_time<#{currentTime}")@Results({@Result(column = "create_time",property = "createTime"),@Result(column = "update_time",property = "updateTime"),@Result(column = "delete_time",property = "deleteTime"),@Result(column = "task_type",property = "taskType"),@Result(column = "mq_exchange",property = "mqExchange"),@Result(column = "mq_routingkey",property = "mqRoutingkey"),@Result(column = "request_body",property = "requestBody"),@Result(column = "status",property = "status"),@Result(column = "errormsg",property = "errormsg")})List<Task> findTaskLessTanCurrentTime(Date currentTime);
}

任务类实现

@Component
public class QueryPointTask {
​@Autowiredprivate RabbitTemplate rabbitTemplate;
​@Autowiredprivate TaskMapper taskMapper;
​@Scheduled(cron = "0 0/2 * * * ?")public void queryTask(){
​//1.获取小于系统当前时间数据List<Task> taskList = taskMapper.findTaskLessTanCurrentTime(new Date());
​if (taskList!=null && taskList.size()>0){//将任务数据发送到消息队列for (Task task : taskList) {rabbitTemplate.convertAndSend(RabbitMQConfig.EX_BUYING_ADDPOINTURSE,RabbitMQConfig.CG_BUYING_ADDPOINT_KEY, JSON.toJSONString(task));}}}
}

三、 用户服务更改积分

步骤1： 添加rabbitmq配置类(与订单服务相同)

@Configuration
public class RabbitMQConfig {//添加积分任务交换机public static final String EX_BUYING_ADDPOINTURSE = "ex_buying_addpointurse";
​//添加积分消息队列public static final String CG_BUYING_ADDPOINT = "cg_buying_addpoint";
​//完成添加积分消息队列public static final String CG_BUYING_FINISHADDPOINT = "cg_buying_finishaddpoint";
​//添加积分路由keypublic static final String CG_BUYING_ADDPOINT_KEY = "addpoint";
​//完成添加积分路由keypublic static final String CG_BUYING_FINISHADDPOINT_KEY = "finishaddpoint";
​/*** 交换机配置* @return the exchange*/@Bean(EX_BUYING_ADDPOINTURSE)public Exchange EX_DECLARE() {return ExchangeBuilder.directExchange(EX_BUYING_ADDPOINTURSE).durable(true).build();}//声明队列@Bean(CG_BUYING_FINISHADDPOINT)public Queue QUEUE_CG_BUYING_FINISHADDPOINT() {Queue queue = new Queue(CG_BUYING_FINISHADDPOINT);return queue;}//声明队列@Bean(CG_BUYING_ADDPOINT)public Queue QUEUE_CG_BUYING_ADDPOINT() {Queue queue = new Queue(CG_BUYING_ADDPOINT);return queue;}/*** 绑定队列到交换机 .* @param queue    the queue* @param exchange the exchange* @return the binding*/@Beanpublic Binding BINDING_QUEUE_FINISHADDPOINT(@Qualifier(CG_BUYING_FINISHADDPOINT) Queue queue, @Qualifier(EX_BUYING_ADDPOINTURSE) Exchange exchange) {return BindingBuilder.bind(queue).to(exchange).with(CG_BUYING_FINISHADDPOINT_KEY).noargs();}@Beanpublic Binding BINDING_QUEUE_ADDPOINT(@Qualifier(CG_BUYING_ADDPOINT) Queue queue, @Qualifier(EX_BUYING_ADDPOINTURSE) Exchange exchange) {return BindingBuilder.bind(queue).to(exchange).with(CG_BUYING_ADDPOINT_KEY).noargs();}
}

步骤2： 定义消息监听类：

@Component
public class AddPointListener {
​@Autowiredprivate UserService userService;
​@Autowiredprivate RedisTemplate redisTemplate;
​@Autowiredprivate RabbitTemplate rabbitTemplate;
​@RabbitListener(queues = RabbitMQConfig.CG_BUYING_ADDPOINT)public void receiveMessage(String message){
​Task task = JSON.parseObject(message, Task.class);
​if (task == null || StringUtils.isEmpty(task.getRequestBody())){return;}
​//判断redis中是否存在内容Object value = redisTemplate.boundValueOps(task.getId()).get();if (value != null){return;}
​//更新用户积分int result = userService.updateUserPoints(task);
​if (result<=0){return;}
​//返回通知
rabbitTemplate.convertAndSend(RabbitMQConfig.EX_BUYING_ADDPOINTURSE,RabbitMQConfig.CG_BUYING_FINISHADDPOINT_KEY,JSON.toJSONString(task));
​}
}

步骤3： 定义修改用户积分实现
实现思路：

1）判断当前订单是否操作过

2）将任务存入redis

3）修改用户积分

4）添加积分日志表记录

5）删除redis中记录

@Autowired
private PointLogMapper pointLogMapper;
​/*** 修改用户积分* @param task* @return*/@Override@Transactionalpublic int updateUserPoints(Task task) {Map info = JSON.parseObject(task.getRequestBody(), Map.class);String userName = info.get("userName").toString();String orderId = info.get("orderId").toString();int point = (int) info.get("point");
​//判断当前订单是否操作过PointLog pointLog = pointLogMapper.findLogInfoByOrderId(orderId);if (pointLog != null){return 0;}
​//将任务存入redisredisTemplate.boundValueOps(task.getId()).set("exist",1,TimeUnit.MINUTES);
​//修改用户积分int result = userMapper.updateUserPoint(userName, point);if (result<=0){return result;}
​//添加积分日志表记录pointLog = new PointLog();pointLog.setOrderId(orderId);pointLog.setPoint(point);pointLog.setUserId(userName);result = pointLogMapper.insertSelective(pointLog);if (result<=0){return result;}
​//删除redis中的记录redisTemplate.delete(task.getId());
​return 1;}

步骤4： 定义根据订单id查询积分日志表
定义PointLogMapper，实现根据订单id查询：

public interface PointLogMapper extends Mapper<PointLog> {
​@Select("select * from tb_point_log where order_id=#{orderId}")PointLog findLogInfoByOrderId(@Param("orderId") String orderId);
}

四、 订单服务删除原任务

步骤1： 定义监听类
在订单服务中定义监听类，用于监听队列，如果队列中有消息，则删除原任务防止消息重复发送，并对任务信息进行记录

@Component
public class DelTaskListener {
​@Autowiredprivate TaskService taskService;
​@RabbitListener(queues = RabbitMQConfig.CG_BUYING_FINISHADDPOINT)public void receiveMessage(String message){
​Task task = JSON.parseObject(message, Task.class);
​taskService.delTask(task);}
}

步骤： 定义任务service

public interface TaskService {
​void delTask(Task task);
}

@Service
@Transactional
public class TaskServiceImpl implements TaskService {
​@Autowiredprivate TaskMapper taskMapper;
​@Autowiredprivate TaskHisMapper taskHisMapper;
​
​@Overridepublic void delTask(Task task) {//1. 设置删除时间task.setDeleteTime(new Date());Long id = task.getId();task.setId(null);
​//bean复制TaskHis taskHis = new TaskHis();BeanUtils.copyProperties(task,taskHis);
​//记录任务信息taskHisMapper.insertSelective(taskHis);
​//删除原任务task.setId(id);taskMapper.deleteByPrimaryKey(task);}
}