Spring with AMQP and RabbitMQ, queue with optional x-dead-letter-exchange

Question

I have an existing queue created in RabbitMQ. It can be created with or without x-dead-letter-exchange parameter. I am creating a consumer of this queue in Spring using the RabbitTemplate. When I declare the queue, I don't want to specify the x-dead-letter-exchange parameter. I would like the template to somehow figure it itself or not care. I am throwing AmqpRejectAndDontRequeueException from my consumer to indicate bad messages, but I want the creator of the queue to be responsible for the decision whether or not to create an exchange and queue for the rejected messages.

Here is my bean that declares the queue in Spring:

@Bean
Queue queue() {
    Map<String, Object> args = new HashMap<>();
    // set the queue with a dead letter feature
    args.put("x-dead-letter-exchange", REJECTED_EXCHANGE);
    args.put("x-dead-letter-routing-key", REJECTED_ROUTING_KEY);
    Queue queue = new Queue(Constants.QUEUE_NAME, false, false, false, args);
    return queue;
}

This works fine, but when the creator of the queue decides not to use the dead letter feature, I see the following error:

Channel shutdown: channel error; protocol method: #method<channel.close>
(reply-code=406, reply-text=PRECONDITION_FAILED - 
inequivalent arg 'x-dead-letter-exchange' for queue 'queueName'

The message is a bit longer, it continues telling me which side has which x-dead-letter-exchange (none or a name of the exchange). I've tried different combinations (e.g. creating the queue with exchange and not specifying it in the Spring or creating the queue without the exchange and specifying it in the Spring), only to see different variants of this message.

How do I declare the queue so it simply accepts whatever parameters are already set in the queue?

Solution 1

As you can see in the spring docs: The RabbitMQ broker will not allow declaration of a queue with mismatched arguments., so you can't do it.
In the RabbitMQ Java API there is a method to check whether a queue already exists: queueDeclarePassive.

If the Spring AMQP API provides a similar functionality you can use it before trying to declare the queue.

Solution 2

Yes, The possible cause is - if you declare some queues manually and later your program (client in code) tries to create one (based on the settings you had in code) then you get this error. The reason behind it is when your code (client application) tries to access one queue. It gets a signal from the server that the connection is not available for this.

To solve this problem

• Delete all the queues that you have created manually, and let the client program create them by itself.
• If you got problems in deleting the queues, because of some data is there in it, or for some reason, you want to maintain it, create one queue manually, and move all the queue data to be deleted in it through "Move" tab of the queue.

Comments

[manasouza]

Deleting queues and let them being created on application startup solved for me