RabbitMQ——死信隊(duì)列

死信隊(duì)列（Dead Letter Queue，DLQ）是 RabbitMQ 中的一種重要特性，用于處理無(wú)法被消費(fèi)的消息，防止消息丟失。

死信的來(lái)源

在消息隊(duì)列中，當(dāng)消息滿足一定條件而無(wú)法被正常消費(fèi)時(shí)，這些消息會(huì)被發(fā)送到死信隊(duì)列。滿足條件的情況包括但不限于：

• 消息被拒絕（basic.reject 或 basic.nack）且不重新入隊(duì)（requeue 參數(shù)為 false）。
• 消息過(guò)期（TTL，Time-To-Live）。
• 隊(duì)列長(zhǎng)度超過(guò)限制，無(wú)法再添加數(shù)據(jù)到mq中。

生產(chǎn)者

package com.weipch.rabbitmq.dlq;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.GetResponse;
import com.weipch.util.RabbitMqUtils;

/**
 * @Author 方唐鏡
 * @Create 2024-03-03 14:08
 * @Description
 */
public class Produce {


	private static final String NORMAL_EXCHANGE = "normal_exchange";


	public static void main(String[] args) throws Exception {
		Channel channel = RabbitMqUtils.getChannel();
        //模擬消息過(guò)期 10s
		//AMQP.BasicProperties properties = new AMQP.BasicProperties().builder().expiration("10000").build();
		for (int i = 0; i < 10; i++) {
			String message = "hello world" + i;
			channel.basicPublish(NORMAL_EXCHANGE, "normal-routing-key", null, message.getBytes());
		}
	}
}

消費(fèi)者

正常隊(duì)列：

package com.weipch.rabbitmq.dlq;

import com.rabbitmq.client.BuiltinExchangeType;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.DeliverCallback;
import com.weipch.util.RabbitMqUtils;

import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

/**
 * @Author 方唐鏡
 * @Create 2024-03-03 13:50
 * @Description
 */
public class Consumer01 {


	private static final String NORMAL_EXCHANGE = "normal_exchange";
	private static final String DEAD_EXCHANGE = "dead_exchange";

	private static final String NORMAL_QUEUE = "normal_queue";
	private static final String DEAD_QUEUE = "dead_queue";


	public static void main(String[] args) throws Exception {
		Channel channel = RabbitMqUtils.getChannel();
		//聲明死信交換機(jī)和隊(duì)列
		channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
		channel.queueDeclare(DEAD_QUEUE, false, false, false, null);
		//綁定
		channel.queueBind(DEAD_QUEUE, DEAD_EXCHANGE, "dead-routing-key");


		//聲明普通交換機(jī)和隊(duì)列
		channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
		//在正常隊(duì)列中設(shè)置死信參數(shù) 指定死信交換機(jī)和死信路由鍵
		Map<String, Object> map = new HashMap<>();
		map.put("x-dead-letter-exchange", DEAD_EXCHANGE);
		map.put("x-dead-letter-routing-key", "dead-routing-key");
		//最大長(zhǎng)度
		//map.put("x-max-length", 6);
		channel.queueDeclare(NORMAL_QUEUE, false, false, false, map);
		channel.queueBind(NORMAL_QUEUE, NORMAL_EXCHANGE, "normal-routing-key");
		DeliverCallback deliverCallback = (consumerTag, delivery) -> {
			String message = new String(delivery.getBody(), StandardCharsets.UTF_8);
			if (message.contains("5")){
				System.out.println("Consumer01接收消息：" + message + "，此消息被拒絕");
				//拒絕消息并把消息丟入死信隊(duì)列
				channel.basicReject(delivery.getEnvelope().getDeliveryTag(), false);
			}else {
				System.out.println("Consumer01接收消息：" + message);
				channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
			}
		};
		channel.basicConsume(NORMAL_QUEUE, false, deliverCallback, (consumerTag, e) -> {});
	}
}

死信隊(duì)列：

package com.weipch.rabbitmq.dlq;

import com.rabbitmq.client.BuiltinExchangeType;
import com.rabbitmq.client.Channel;
import com.weipch.util.RabbitMqUtils;

import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

/**
 * @Author 方唐鏡
 * @Create 2024-03-03 13:50
 * @Description
 */
public class Consumer02 {
	
	private static final String DEAD_QUEUE = "dead_queue";

	public static void main(String[] args) throws Exception {
		Channel channel = RabbitMqUtils.getChannel();
		channel.basicConsume(DEAD_QUEUE, true,
			(consumerTag, delivery) -> System.out.println("Consumer02:" + new String(delivery.getBody(), StandardCharsets.UTF_8)),
			(consumerTag, e) -> {});
	}
}

生產(chǎn)者發(fā)送消息到正常隊(duì)列，而消費(fèi)者負(fù)責(zé)消費(fèi)正常隊(duì)列的消息。當(dāng)消息被消費(fèi)者拒絕并不再重新投遞時(shí)，消息會(huì)被發(fā)送到死信隊(duì)列。文章來(lái)源地址http://www.zghlxwxcb.cn/news/detail-839926.html

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