java B2B2C 仿淘宝电子商城系统-基于Rabbitmq实现延迟消息

墨蓝 2022-05-01 12:54 137阅读 0赞

1.  预备知识

1.1 消息传递

首先我们知道消费者是从队列中获取消息的，那么消息是如何到达队列的？

当我们发送一条消息时，首先会发给交换器（exchange），交换器根据规则（路由键：routing key）将会确定消息投递到那个队列（queue）。

需要JAVA Spring Cloud大型企业分布式微服务云构建的B2B2C电子商务平台源码 一零三八七七四六二六

带着这几个关键字：交换器、路由键和队列。

1.2 交换器类型

如之前所说，交换器根据规则决定消息的路由方向。因此，rabbitmq的消息投递分类便是从交换器开始的，不同的交换器实现不同的路由算法便实现了不同的消息投递方式。

direct交换器

direct -> routingKey -> queue，相当一种点对点的消息投递，如果路由键匹配，就直接投递到相应的队列

fanout交换器

fanout交换器相当于实现了一（交换器）对多（队列）的广播投递方式

topic交换器

提供一种模式匹配的投递方式，我们可以根据主题来决定消息投递到哪个队列。

1.3 消息延迟

本文想要实现一个可延迟发送的消息机制。消息如何延迟？

ttl (time to live) 消息存活时间

ttl是指一个消息的存活时间。

Per-Queue Message TTL in Queues

引用官方的一句话：

TTL can be set for a given queue by setting the x-message-ttl argument to queue.declare, or by setting the message-ttl policy. A message that has been in the queue for longer than the configured TTL is said to be dead. 我们可以通过x-message-ttl设置一个队列中消息的过期时间，消息一旦过期，将会变成死信（dead-letter），可以选择重新路由。

Per-Message TTL in Publishers

引用官方的一句话：

A TTL can be specified on a per-message basis, by setting the expiration field in the basic AMQP class when sending a basic.publish.

The value of the expiration field describes the TTL period in milliseconds. The same constraints as for x-message-ttl apply. Since the expiration field must be a string, the broker will (only) accept the string representation of the number.

我们可以通过设置每一条消息的属性expiration，指定单条消息有效期。消息一旦过期，将会变成死信（dead-letter），可以选择重新路由。

重新路由-死信交换机(Dead Letter Exchanges) 引用官方一句话：

Dead Letter Exchanges

Messages from a queue can be ‘dead-lettered’; that is, republished to another exchange when any of the following events occur:

The message is rejected (basic.reject or basic.nack) with requeue=false, The TTL for the message expires; or The queue length limit is exceeded. Dead letter exchanges (DLXs) are normal exchanges. They can be any of the usual types and are declared as usual. To set the dead letter exchange for a queue, set the x-dead-letter-exchange argument to the name of the exchange.

我们可以通过设置死信交换器（x-dead-letter-exchange）来重新发送消息到另外一个队列，而这个队列将是最终的消费队列。

1.  具体实现

rabbitmq配置

属性文件-rabbitmq.properties

交换、路由等配置按照以上策略，其中，添加了prefetch参数来根据服务器能力控制消费数量。

连接用户名

mq.user =sms\_user

密码

mq.password =123456

主机

mq.host =192.168.99.100

端口

mq.port =5672

默认virtual-host

mq.vhost =/

the default cache size for channels is 25

mq.channelCacheSize =50

发送消息路由

sms.route.key =sms\_route\_key

延迟消息队列

sms.delay.queue =sms\_delay\_queue

延迟消息交换器

sms.delay.exchange =sms\_delay\_exchange

消息的消费队列

sms.queue =sms\_queue

消息交换器

sms.exchange =sms\_exchange

每秒消费消息数量

sms.prefetch =30

配置rabbitmq.xml

<?xml version="1.0" encoding="UTF-8"?>
 <beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:rabbit="http://www.springframework.org/schema/rabbit"
 xmlns:context="http://www.springframework.org/schema/context"
 xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/rabbit http://www.springframework.org/schema/rabbit/spring-rabbit-1.7.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
 <context:property-placeholder location="rabbitmq.properties"/>
 
 <rabbit:connection-factory id="connectionFactory"
 username="${mq.user}" password="${mq.password}"
 host="${mq.host}" port="${mq.port}" virtual-host="${mq.vhost}" />
 
 
 <rabbit:template id="amqpTemplate" connection-factory="connectionFactory" />
 
 
 <rabbit:admin connection-factory="connectionFactory" />
 
 
 <rabbit:queue name="${sms.queue}" durable="true" auto-delete="false" exclusive="false" />
 
 <rabbit:queue name="${sms.delay.queue}" durable="true" auto-delete="false">
 <rabbit:queue-arguments>
 <entry key="x-message-ttl">
 
 <value type="java.lang.Long">3600000</value>
 </entry>
 
 <entry key="x-dead-letter-exchange" value="${sms.exchange}"/>
 </rabbit:queue-arguments>
 </rabbit:queue>
 
 
 <rabbit:direct-exchange name="${sms.exchange}" durable="true" auto-delete="false">
 <rabbit:bindings>
 <rabbit:binding queue="${sms.queue}" key="${sms.route.key}"/>
 </rabbit:bindings>
 </rabbit:direct-exchange>
 
 <rabbit:direct-exchange name="${sms.delay.exchange}" durable="true" auto-delete="false">
 <rabbit:bindings>
 <rabbit:binding queue="${sms.delay.queue}" key="${sms.route.key}"/>
 </rabbit:bindings>
 </rabbit:direct-exchange>
 
 
 <bean id="messageReceiver" class="git.yampery.consumer.MsgConsumer"/>
 
 <rabbit:listener-container connection-factory="connectionFactory" prefetch="${sms.prefetch}">
 <rabbit:listener queues="${sms.queue}" ref="messageReceiver"/>
 </rabbit:listener-container>
 </beans>
 
 复制代码

消息发布者

package git.yampery.producer;
 
 import org.springframework.amqp.core.AmqpTemplate;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Component;
 
 import javax.annotation.Resource;
 
 /**
 * @decription MsgProducer
 * 生产者
 * @author Yampery
 * @date 2018/2/11 11:44
 */
 @Component
 public class MsgProducer {
 
 @Resource
 private AmqpTemplate amqpTemplate;
 @Value("${sms.delay.exchange}") private String SMS_DELAY_EXCHANGE;
 @Value("${sms.exchange}") private String SMS_EXCHANGE;
 @Value("${sms.route.key}") private String SMS_ROUTE_KEY;
 
 /**
 * 延迟消息放入延迟队列中
 * @param msg
 * @param expiration
 */
 public void publish(String msg, String expiration) {
 amqpTemplate.convertAndSend(SMS_DELAY_EXCHANGE, SMS_ROUTE_KEY, msg, message -> {
 // 设置消息属性-过期时间
 message.getMessageProperties().setExpiration(expiration);
 return message;
 });
 }
 
 /**
 * 非延迟消息放入待消费队列
 * @param msg
 */
 public void publish(String msg) {
 amqpTemplate.convertAndSend(SMS_EXCHANGE, SMS_ROUTE_KEY, msg);
 }
 }
 
 复制代码

消费者

package git.yampery.consumer;
 
 import org.springframework.amqp.core.Message;
 import org.springframework.amqp.core.MessageListener;
 
 /**
 * @decription MsgConsumer
 * 消费者
 * @author Yampery
 * @date 2018/2/11 11:43
 */
 public class MsgConsumer implements MessageListener {
 @Override
 public void onMessage(Message message) {
 String msg;
 try {
 // 线程每秒消费一次
 Thread.sleep(1000);
 msg = new String(message.getBody(), "utf-8");
 System.out.println(msg);
 
 } catch (Exception e) {
 // 这里并没有对服务异常等失败的消息做处理，直接丢弃了
 // 防止因业务异常导致消息失败造成unack阻塞再队列里
 // 可以选择路由到另外一个专门处理消费失败的队列
 return;
 }
 }
 }
 
 复制代码

测试

package git.yampery.mq;
 
 import com.alibaba.fastjson.JSONObject;
 import git.yampery.producer.MsgProducer;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.test.context.junit4.SpringRunner;
 
 import javax.annotation.Resource;
 
 /**
 * @decription TestMq
 * 测试
 * @author Yampery
 * @date 2018/2/11 15:03
 */
 @RunWith(SpringRunner.class)
 @SpringBootTest
 public class TestMq {
 
 @Resource
 private MsgProducer producer;
 
 @Test
 public void testMq() {
 JSONObject jObj = new JSONObject();
 jObj.put("msg", "这是一条短信");
 producer.publish(jObj.toJSONString(), String.valueOf(10 * 1000));
 }
 }
 
 复制代码

[java B2B2C 仿淘宝电子商城系统][java B2B2C]

转载于:https://juejin.im/post/5ca304c06fb9a05e2f23c258

[java B2B2C]: https://link.juejin.im?target=https%3A%2F%2F2147775633.iteye.com%2Fblog%2F2434341