RabbitMQ中的延迟消息

Question

是否有可能通过RabbitMQ发送消息有一些延迟？例如,我希望在30分钟后使客户端会话到期,并且我发送一条消息,该消息将在30分钟后处理.

Answer 1

您可以尝试两种方法:

旧方法:在每个消息/队列(策略)中设置TTL(生存时间)标头,然后引入DLQ来处理它.一旦ttl过期,您的消息将从DLQ移动到主队列,以便您的侦听器可以处理它.

最新方法:最近,RabbitMQ提出了RabbitMQ延迟消息插件,使用它可以实现相同的功能,并且自RabbitMQ-3.5.8起支持此插件支持.

您可以使用x-delayed-message类型声明交换,然后使用自定义标头x-delay发布消息,以毫秒为单位表示消息的延迟时间.消息将在x延迟毫秒后传递到相应的队列

byte[] messageBodyBytes = "delayed payload".getBytes("UTF-8");
Map<String, Object> headers = new HashMap<String, Object>();
headers.put("x-delay", 5000);
AMQP.BasicProperties.Builder props = new 
AMQP.BasicProperties.Builder().headers(headers);
channel.basicPublish("my-exchange", "", props.build(), messageBodyBytes);

更多这里:git

Answer 2

随着RabbitMQ v2.8的发布,预定的交付现在可用,但作为间接功能:http://www.javacodegeeks.com/2012/04/rabbitmq-scheduled-message-delivery.html

Answer 3

感谢Norman的回答,我可以在NodeJS中实现它.

从代码中可以清楚地看到一切.希望它能节省一些人的时间.

var ch = channel;
ch.assertExchange("my_intermediate_exchange", 'fanout', {durable: false});
ch.assertExchange("my_final_delayed_exchange", 'fanout', {durable: false});

// setup intermediate queue which will never be listened.
// all messages are TTLed so when they are "dead", they come to another exchange
ch.assertQueue("my_intermediate_queue", {
      deadLetterExchange: "my_final_delayed_exchange",
      messageTtl: 5000, // 5sec
}, function (err, q) {
      ch.bindQueue(q.queue, "my_intermediate_exchange", '');
});

ch.assertQueue("my_final_delayed_queue", {}, function (err, q) {
      ch.bindQueue(q.queue, "my_final_delayed_exchange", '');

      ch.consume(q.queue, function (msg) {
          console.log("delayed - [x] %s", msg.content.toString());
      }, {noAck: true});
});

Answer 4

因为我没有足够的声誉来添加评论,发布一个新的答案.这只是对http://www.javacodegeeks.com/2012/04/rabbitmq-scheduled-message-delivery.html上已经讨论过的内容的补充.

除了不在消息上设置ttl,您可以在队列级别设置它.此外,您可以避免仅为了将消息重定向到不同的队列而创建新的交换.这是示例java代码:

制片人:

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import java.util.HashMap;
import java.util.Map;

public class DelayedProducer {
    private final static String QUEUE_NAME = "ParkingQueue";
    private final static String DESTINATION_QUEUE_NAME = "DestinationQueue";

    public static void main(String[] args) throws Exception{
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("localhost");
        Connection connection = connectionFactory.newConnection();
        Channel channel = connection.createChannel();

        Map<String, Object> arguments = new HashMap<String, Object>();
        arguments.put("x-message-ttl", 10000);
        arguments.put("x-dead-letter-exchange", "");
        arguments.put("x-dead-letter-routing-key", DESTINATION_QUEUE_NAME );
        channel.queueDeclare(QUEUE_NAME, false, false, false, arguments);

        for (int i=0; i<5; i++) {
            String message = "This is a sample message " + i;
            channel.basicPublish("", QUEUE_NAME, null, message.getBytes());
            System.out.println("message "+i+" got published to the queue!");
            Thread.sleep(3000);
        }

        channel.close();
        connection.close();
    }
}

消费者:

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

public class Consumer {
   private final static String DESTINATION_QUEUE_NAME = "DestinationQueue";

    public static void main(String[] args) throws Exception{
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();

        channel.queueDeclare(QUEUE_NAME, false, false, false, null);
        System.out.println(" [*] Waiting for messages. To exit press CTRL+C");

        QueueingConsumer consumer = new QueueingConsumer(channel);
        boolean autoAck = false;
        channel.basicConsume(DESTINATION_QUEUE_NAME, autoAck, consumer);

        while (true) {
            QueueingConsumer.Delivery delivery = consumer.nextDelivery();
            String message = new String(delivery.getBody());
            System.out.println(" [x] Received '" + message + "'");
            channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
        }

    }
}

Answer 5

看起来这个博客文章描述了使用死信交换和消息ttl做类似的事情.

下面的代码使用CoffeeScript和Node.JS来访问Rabbit并实现类似的东西.

amqp   = require 'amqp'
events = require 'events'
em     = new events.EventEmitter()
conn   = amqp.createConnection()

key = "send.later.#{new Date().getTime()}"
conn.on 'ready', ->
  conn.queue key, {
    arguments:{
      "x-dead-letter-exchange":"immediate"
    , "x-message-ttl": 5000
    , "x-expires": 6000
    }
  }, ->
    conn.publish key, {v:1}, {contentType:'application/json'}

  conn.exchange 'immediate'

  conn.queue 'right.now.queue', {
      autoDelete: false
    , durable: true
  }, (q) ->
    q.bind('immediate', 'right.now.queue')
    q.subscribe (msg, headers, deliveryInfo) ->
      console.log msg
      console.log headers

Answer 6

这是目前不可能的.您必须将过期时间戳存储在数据库或类似的东西中,然后有一个帮助程序读取这些时间戳并对消息进行排队.

延迟消息是一种经常被请求的功能,因为它们在许多情况下都很有用.但是,如果您需要使客户端会话到期,我相信消息传递不是您理想的解决方案,而另一种方法可能会更好.