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问题

前面所讲的延迟队列有一个不足之处，比如现在有一个需求需要延迟半个小时的消息，那么就只有添加一个新的队列。那就意味着，每新增一个不同时间需求，就会新创建一个队列。

解决方案

应该讲消息的时间不要跟队列绑定，应该交给消息的生产者，由发送消息来指定延迟时间。这样就可以定义个通用的队列。

方案图

代码

配置类

package com.xkj.org.config;import org.springframework.amqp.core.*;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;import java.util.HashMap;
import java.util.Map;/*** TTL队列，配置文件代码*/
@Configuration
public class TtlQueueConfig {//普通交换机public static final String X_EXCHANGE = "X";//死信交换机public static final String Y_HEAD_LETTER_EXCHANGE = "Y";//普通队列public static final String QUEUE_A = "QA";public static final String QUEUE_B = "QB";public static final String QUEUE_C = "QC";//死信队列public static final String DEAD_LETTER_QUEUE = "QD";/*** 声明普通交换机X,bean的别名xExchange* @return*/@Bean("xExchange")public DirectExchange xExchange() {return new DirectExchange(X_EXCHANGE);}/*** 声明死信交换机Y,bean的别名yExchange* @return*/@Bean("yExchange")public DirectExchange yExchange() {return new DirectExchange(Y_HEAD_LETTER_EXCHANGE);}/*** 声明普通队列QA* @return*/@Bean("queueA")public Queue queueA() {Map<String, Object> arguments = new HashMap<>(3);//设置死信交换机arguments.put("x-dead-letter-exchange", Y_HEAD_LETTER_EXCHANGE);//声明死信的routingeyarguments.put("x-dead-letter-routing-key", "YD");//设置消息过期时间ttl为10sarguments.put("x-message-ttl", 10000);return QueueBuilder.durable(QUEUE_A).withArguments(arguments).build();}/*** 声明普通队列QB* @return*/@Bean("queueB")public Queue queueB() {Map<String, Object> arguments = new HashMap<>(3);//设置死信交换机arguments.put("x-dead-letter-exchange", Y_HEAD_LETTER_EXCHANGE);//声明死信的routingKeyarguments.put("x-dead-letter-routing-key", "YD");//设置消息过期时间ttl为40sarguments.put("x-message-ttl", 40000);return QueueBuilder.durable(QUEUE_B).withArguments(arguments).build();}/*** 声明普通队列QC* @return*/@Bean("queueC")public Queue queueC() {Map<String, Object> arguments = new HashMap<>(2);//设置死信交换机arguments.put("x-dead-letter-exchange", Y_HEAD_LETTER_EXCHANGE);//设置死信的routingKeyarguments.put("x-dead-letter-routing-key", "YD");//这里不要设置TTL时间return QueueBuilder.durable(QUEUE_C).withArguments(arguments).build();}/*** 声明死信队列QD* @return*/@Bean("queueD")public Queue queueD() {return QueueBuilder.durable(DEAD_LETTER_QUEUE).build();}/*** 将队列QA绑定到交换机X上，指定routingKey为XA* @param queueA* @param xExchange* @return*/@Beanpublic Binding queueABindingX(@Qualifier("queueA") Queue queueA, @Qualifier("xExchange")DirectExchange xExchange) {return BindingBuilder.bind(queueA).to(xExchange).with("XA");}/*** 将队列QB绑定到交换机X上，指定routingKey为XB* @param queueB* @param xExchange* @return*/@Beanpublic Binding queueBBindingX(@Qualifier("queueB") Queue queueB, @Qualifier("xExchange") DirectExchange xExchange) {return BindingBuilder.bind(queueB).to(xExchange).with("XB");}/*** 将队列QC绑定到交换机X上，指定routingKey为XC* @param queueC* @param xExchange* @return*/@Beanpublic Binding queueCBindingX(@Qualifier("queueC") Queue queueC, @Qualifier("xExchange") DirectExchange xExchange) {return BindingBuilder.bind(queueC).to(xExchange).with("XC");}/*** 将队列QD绑定到交换机Y上，指定routingKey为YD* @param queueD* @param yExchange* @return*/@Beanpublic Binding queueDBindingY(@Qualifier("queueD") Queue queueD, @Qualifier("yExchange") DirectExchange yExchange) {return BindingBuilder.bind(queueD).to(yExchange).with("YD");}}

生产者

package com.xkj.org.controller;import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import io.swagger.annotations.ApiParam;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.Date;/*** 消息生产者*/
@Slf4j
@RestController
@RequestMapping("/ttl")
@Api(tags = "消息生产者", description = "消息生产者控制器")
public class MessageController {@Autowiredprivate RabbitTemplate rabbitTemplate;@ApiOperation("消息发送测试")@GetMapping("/sendMsg/{msg}")public void sendMsg(@ApiParam(value = "发送的消息内容", required = true) @PathVariable("msg") String message) {log.info("当前时间{}，发送一条消息给两个队列：{}", new Date().toString(), message);rabbitTemplate.convertAndSend("X", "XA", "ttl=10s的消息：" + message);rabbitTemplate.convertAndSend("X", "XB", "ttl=40s的消息：" + message);}@ApiOperation("发送带过期时间的消息")@GetMapping("/sendExpiredMsg/{msg}/{ttl}")public void sendMsgExpired(@ApiParam(value = "消息内容", required = true)@PathVariable("msg") String message,@ApiParam(value = "ttl时间", required = true)@PathVariable("ttl") String ttlTime) {log.info("当前时间{}，发送一条消息给队列QC：{}，ttl={}", new Date().toString(), message, ttlTime);rabbitTemplate.convertAndSend("X", "XC", message, msg -> {msg.getMessageProperties().setExpiration(ttlTime);return msg;});}}

消费者

package com.xkj.org.listener;import com.rabbitmq.client.Channel;
import lombok.extern.slf4j.Slf4j;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.stereotype.Component;import java.util.Date;/*** 消费者*/
@Slf4j
@Componentpublic class DeadLetterQueueConsumer {@RabbitListener(queues = "QD")public void receiveD(Message message, Channel channel) throws Exception {String msg = new String(message.getBody(), "UTF-8");log.info("当前时间：{}，收到死信队列的消息：{}", new Date().toString(), msg);}
}

问题

改造代码后，发送两条消息，一条ttl为2s,另一条ttl为10s。ttl为2s的消息也要等到10s后才会收到。 

原因

因为队列是先进先出的，消息需要排队，第一条消息10s才会发出去，第二条消息2s发出去，但是由于10s的消息没有发出去，2s的消息就只有等待。

解决方案

使用rabbitmq插件来解决,请看后续博文。