Rabbitmq suggestion for implementing call back queue feature

Question

I came across call back queue feature in RMQ. And its pretty fancy too. The whole idea is I have created One Message queue (queue1), its callback queue(queue1_cb) and its dlq(queue1_dlq). I am implementing HA feature with 2 nodes.

The problem comes when I am deploying 2 instances of my application(I have one sender and one receiver app in Spring boot). Both are listening to same HA cluster. The scenario is as below.

1. Sender publishes a message to RMQ.
2. Receiver app consumes message. Receiver app has to call third party API which is socket based API and its asynchronous so i do not get response in same connection. SO i store object of Channel & Message which i need to ack the message. (Please note i am delaying the ack till i receive response from third party API.
3. When i deploy 2 instances of receiver app, any instance will get response from third party API. And both will not have object of Channel and Message to ack message and send message to callback queue.

Can any one suggest me a solution on proiority? Below is my code.

At Receiver side :

    @Override
public void onMessage(Message arg0, Channel arg1) throws Exception {

    String msg = new String (arg0.getBody());
    AppObject obj = mapper.readValue(msg, AppObject.class);

    Packet packet = new Packet();
    packet.setChannel(arg1);
    packet.setMessage(arg0);
    packet.setAppObject(obj);

    AppParam.objects.put(
    String.valueOf(key , packet);

    //Call third party API

}

At the time of acking and sending callback message:

public boolean pushMessageToCallBack(String key , AppObject packet, Channel channel, Message message){
    RabbitTemplate replyRabbitTemplate =  //Get the RabbitTemplate object. It is handled properly.
    replyRabbitTemplate.convertAndSend(packet);
    channel.basicAck(message.getMessageProperties().getDeliveryTag(), false);

}

Answer 1

You need a different callback queue for each instance or, more simply, just use Direct Reply-to where you don't need a queue at all.