如何使用RabbitMQ中的死信交换器(dead letter exchange)

RabbitMQ中的死信交换器(dead letter exchange)可以接收下面三种场景中的消息:

• 消费者对消息使用了basicReject或者basicNack回复,并且requeue参数设置为false,即不再将该消息重新在消费者间进行投递.
• 消息在队列中超时. RabbitMQ可以在单个消息或者队列中设置TTL属性.
• 队列中的消息已经超过其设置的最大消息个数.

死信交换器可以在程序中设置,也可以使用rabbitmqctl工具进行设置.关于死信交换器的介绍请参考RabbitMQ官网https://www.rabbitmq.com/dlx.html.

死信交换器可以统计或者监控错误消息, 下面使用RabbitMQ的Java客户端库给出一个完整的例子, 结合第一种消息来源说明死信交换器的使用.

示例代码

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;

import com.rabbitmq.client.AMQP.BasicProperties;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.DeliverCallback;
import com.rabbitmq.client.Envelope;

public class DeadLetterExchange {
    private static final String NORMAL_EXCHANGE = "normal_exchange";
    private static final String DEAD_LETTER_EXCHANGE = "dead_letter_exchange";    
    private static final String DEFAULT_WORKER_QUEUE = "queue_to_normal_exchange";
    private static final String DLX_WORKER_QUEUE = "queue_to_deadletter_exchange";
    private static final String NORMAL_ROUTE_KEY = "normal_route_key";
    private static final String DLX_ROUTE_KEY = "dlx_route_key";
        
    private Connection connection;
    // For consumer and producer schedule.
    private final ExecutorService executorService;
    
    private static class SimpleThreadFactory implements ThreadFactory {
        private final AtomicInteger idx = new AtomicInteger(0);
                
        public Thread newThread(Runnable r) {
            return new Thread(r, "Thread#" + idx.getAndIncrement());            
        }        
    }
    
    private static class WorkerConsumer implements Runnable {        
        private final Connection connection;
        private Channel channel;
        private String queue;
        
        private final DeliverCallback deliverCallback = (consumerTag, delivery) -> {            
            final String message = new String(delivery.getBody(), "UTF-8");
            final Envelope envelope = delivery.getEnvelope();
            final long deliveryTag = envelope.getDeliveryTag();
            final boolean redelivery = envelope.isRedeliver();
            final BasicProperties props = delivery.getProperties();
            final String msgId = props.getMessageId();
            
            /