[Messenger] AMQP Transport creates a queue based on the exchange name if no queues are configured

[leroy0211]

Symfony version(s) affected: 4.4.*

Description
In \Symfony\Component\Messenger\Transport\AmqpExt\Connection.php when you don't configure any queue name, it uses the exchange name to create a queue.

Use Case (with RabbitMQ):

We have a microservice application that only needs to send out messages to an exchange. And let other microservice applications read those messages. Those other microservices can be symfony, but that doesn't matter.
Out consumer microservices create and manage their queue's. That means that the producer will send messages to some exchange and when no consumer is listening, those messages are gone. That's fine.

The problem is that when we run the producer microservice, it automatically creates a queue with the same name as the exchange. Because that's what that Connection.php class is doing.

We also don't want to use the auto_setup: false, because we believe that the producer is responsible to create the right exchange.

We have a workaround, where we have configured the queues property to be an empty array. Because then we can trick messenger to not create any queue's.

How to reproduce

#messenger.yaml
framework:
    messenger:
        transports:
            async:
                dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
                options:
                    # hack: We trick messenger here to not create queues
                    queues: []
            sync: 'sync://'

#.env.local
MESSENGER_TRANSPORT_DSN=amqp://guest:guest@localhost:5672/%2f/my_exchange_name

Additional context

This application does not have any handlers, it only produces messages which need to be distributed to other applications.

[melihovv]

I intentionally use the same hack in order to publish message into exchange instead of queue, although it is not documented anywhere. If this is a bug that should be fixed, what a proper way to publish messages into exchange instead of queue?

[carsonbot]

Hey, thanks for your report!
There has not been a lot of activity here for a while. Is this bug still relevant? Have you managed to find a workaround?

[dbu]

i was running into the same issue. looking at it a bit, i don't think there is a bug or that this is a hack. the default behaviour is to bind a queue to the exchange, but you can overwrite the configuration to make a different queue name, or to not create a queue at all.

having a separate option like 'do-not-create-queues' would be redundant to queues: [].

imho it would make sense to document this at https://symfony.com/doc/current/messenger.html#amqp-transport , maybe with a ..tip:: notation.

[carsonbot]

Hey, thanks for your report!
There has not been a lot of activity here for a while. Is this bug still relevant? Have you managed to find a workaround?

[dbu]

i created symfony/symfony-docs#16689 - i think we can now close this issue