RabbitMQ 消费端的ack与重回队列

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博客介绍了RabbitMQ中消费端如何处理消息确认（ACK）和否定确认（NACK）。在遇到业务异常时，消费端会记录日志并可能进行补偿操作。对于服务器宕机等严重问题，需要手动ACK确保消息已被消费。同时，示例展示了生产者和消费者的Java代码，消费者在处理消息时，如果消息编号为3，则会NACK并重回队列，否则ACK。

消费端的ACK与NACK

ack：成功处理
nack：处理失败

消费端因为业务异常，我们可以进行日志的记录，然后进行补偿。
由于服务器宕机等严重问题，那我们就需要手工ACK，保障消费端消费成功。

消费端重回队列：
对没有处理成功的消息，会把消息重新递给Broker。
一般不使用重回队列。

生产者代码：

package com.example.rabbitmq.limit.ack;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

import java.io.IOException;
import java.util.concurrent.TimeoutException;

/**
 * 生产者
 */
public class producer {

    public static void main(String[] args) throws IOException, TimeoutException {

        //1,创建工厂
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("127.0.0.1");
        connectionFactory.setPort(5672);
        connectionFactory.setUsername("guest");
        connectionFactory.setPassword("guest");
        //2, 获取连接
        Connection connection = connectionFactory.newConnection();
        //3, 通过connection创建一个channel
        Channel channel = connection.createChannel();

        String exchangeName = "test_ack_exchange";
        String routingKey = "ack.save";

        //5, 发送消息
        for (int i = 0; i < 10; i++) {
            Map<String, Object> headers = new HashMap<>();
            headers.put("num", i);
            String msg = "hello rabbitmq send retuen message! - " + i;
            AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()
                    .deliveryMode(2)
                    .contentEncoding("utf-8")
                    .headers(headers)
                    .build();
            channel.basicPublish(exchangeName, routingKey, true,properties, msg.getBytes());
        }
//        channel.close();
//        connection.close();

    }
}

消费者代码：

package com.example.rabbitmq.limit.ack;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

import java.io.IOException;
import java.util.concurrent.TimeoutException;

/**
 * 消费者
 */
public class Consumer {

    public static void main(String[] args) throws IOException, TimeoutException, InterruptedException {
        //1,创建工厂
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("127.0.0.1");
        connectionFactory.setPort(5672);
        connectionFactory.setUsername("guest");
        connectionFactory.setPassword("guest");
        //2,获取连接
        Connection connection = connectionFactory.newConnection();
        //3,通过connection创建一个channel
        Channel channel = connection.createChannel();
        //4,exchange, routingkey, queue, 并将queue和交换机绑定
        //设置交换机
        String exchangeName = "test_ack_exchange";
        String routingKey = "ack.#";
        String queueName = "test_ack_queue";

        //声明一个交换机
        channel.exchangeDeclare(exchangeName, "topic", true, false, null);
        //声明一个队列
        channel.queueDeclare(queueName, true, false, false, null);
        //建立关系
        channel.queueBind(queueName, exchangeName, routingKey);

        //5,创建消费者
        //限流方式, autoAck 必须为fale
        //prefetchSize, prefetchCount, global
        channel.basicQos(0, 3, false);
        channel.basicConsume(queueName, false, new MyConsumer(channel));
    }
}

自定义消费者类：

package com.example.rabbitmq.limit.ack;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.Envelope;

import java.io.IOException;

/**
 * 自定义消费者
 */
public class MyConsumer extends DefaultConsumer {

    private Channel channel;

    public MyConsumer(Channel channel) {
        super(channel);
        this.channel = channel;
    }

    @Override
    public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties basicProperties,  byte[] body) throws IOException {
        System.out.println("----- consumer message -----");
        System.out.println("body = " + new String(body));

        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        //channel.basicAck(envelope.getDeliveryTag(), false);
        if((Integer)basicProperties.getHeaders().get("num") == 3){
            //multiple 是否批量,  requeue 是否重回队列
            channel.basicNack(envelope.getDeliveryTag(), false,true);
        }else{
            //手动签收
            channel.basicAck(envelope.getDeliveryTag(), false);
        }
    }
}