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问题

前面谈到基于死信的延迟队列，存在的问题：如果第一个消息延时时间很长，而第二个消息延时时间很短，第二个消息并不会优先得到执行。

下载插件

地址：https://github.com/rabbitmq/rabbitmq-delayed-message-exchange/releases

rabbitmq_delayed_message_exchange-3.8.0.ez

说明：rabbitmq安装后，会生成这个目录

/usr/lib/rabbitmq/lib/rabbitmq_server-3.8.8/plugins/

拷贝插件到上面这个目录

安装插件

需要重启rabbitmq

监测插件是否安装成功

可以看出不再使用延迟队列，而是使用延迟交换机。

代码

配置代码

package com.xkj.org.config;import org.springframework.amqp.core.Binding;
import org.springframework.amqp.core.BindingBuilder;
import org.springframework.amqp.core.CustomExchange;
import org.springframework.amqp.core.Queue;
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;@Configuration
public class DelayExchangeConfig {//队列public static final String DELAYED_QUEUE_NAME = "delayed.queue";//交换机public static final String DELAYED_EXCHANGE_NAME = "delayed.exchange";//RoutingKeypublic static final String DELYAED_ROUTING_KEY = "delayed.routingkey";@Beanpublic CustomExchange delayedExchange() {Map<String, Object> arguments = new HashMap<>();arguments.put("x-delayed-type", "direct");//第一个参数交换机的名称//第二个参数交换机的类型//第三个参数是否持久化//第四个参数是否删除//第五个参数其他参数return new CustomExchange(DELAYED_EXCHANGE_NAME, "x-delayed-message", true, false,arguments);}@Beanpublic Queue delayedQueue() {return new Queue(DELAYED_QUEUE_NAME);}@Beanpublic Binding delayedQueueBindingDelayedExchange(@Qualifier("delayedExchange")CustomExchange delayedExchange,@Qualifier("delayedQueue")Queue delayedQueue) {return BindingBuilder.bind(delayedQueue).to(delayedExchange).with(DELYAED_ROUTING_KEY).noargs();}}

生产者

@ApiOperation("基于插件的延迟消息")@GetMapping("/sendDelayedMsg/{msg}/{delayedTime}")public void sendDelayedMsg(@ApiParam(value = "消息内容", required = true)@PathVariable("msg") String message,@ApiParam(value = "延迟时间", required = true)@PathVariable("delayedTime")Integer delayedTime) {log.info("当前时间{}，发送一条消息给延迟交换机：{}，delayedTime={}", new Date().toString(), message, delayedTime);rabbitTemplate.convertAndSend("delayed.exchange", "delayed.routingkey", message, msg -> {msg.getMessageProperties().setDelay(delayedTime);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.io.UnsupportedEncodingException;
import java.util.Date;/*** 基于插件的延迟消息队列监听*/
@Slf4j
@Component
public class DelayedQueueConsumer {@RabbitListener(queues = "delayed.queue")public void receiver(Message message, Channel channel) throws UnsupportedEncodingException {String msg = new String(message.getBody(), "UTF-8");log.info("当前时间：{}，收到延迟队列的消息：{}", new Date().toString(), msg);}}

 总结

延迟队列可以保证消息可靠发送，消息可靠投递，死信队列保证消息至少被消费一次，已经未被处理的消息不会被丢弃。