---
title: "Configuration"
description: "Configuration — point a Symfony Messenger transport at the BabelQueue serializer and map URNs to message classes."
source: https://babelqueue.com/docs/symfony/1.x/configuration/
updated: 2026-06-07T00:00:00.000Z
---

# Configuration

Two pieces: point a Messenger transport at the BabelQueue serializer, and map
inbound URNs to your message classes.

## Messenger transport

Set the transport's `serializer` to `babelqueue.messenger.serializer`. Routing and
retry stay exactly as Messenger defines them.

```yaml
# config/packages/messenger.yaml
framework:
    messenger:
        transports:
            babel:
                dsn: '%env(MESSENGER_TRANSPORT_DSN)%'   # e.g. amqp:// or redis://
                serializer: 'babelqueue.messenger.serializer'
        routing:
            'App\Message\OrderCreated': babel
        buses:
            messenger.bus.default:
                middleware:
                    # Forward trace_id from a handled message to any it dispatches,
                    # so a chain of work stays in one trace.
                    - 'babelqueue.messenger.trace_middleware'
```

## URN ↔ message-class map

To **consume**, the adapter needs to turn an inbound URN back into one of your
message classes. Declare the mapping, plus the default `queue` written to the
envelope's `meta.queue`:

```yaml
# config/packages/babelqueue.yaml
babelqueue:
    queue: 'orders'            # written to the envelope meta.queue
    messages:                  # urn => message class (needed to consume)
        'urn:babel:orders:created': 'App\Message\OrderCreated'
```

> Producing only needs the message to declare its own URN (see
> [Producing messages](/docs/symfony/1.x/producing-messages/)); the registry is what
> lets a consumer route an inbound envelope back to a class.

## The trace middleware

`babelqueue.messenger.trace_middleware` (added to the bus above) attaches the
inbound `trace_id` to the message as a `BabelTraceStamp` and ensures any message a
handler dispatches **inherits** that `trace_id` — so end-to-end tracing needs no
manual plumbing. It is optional but recommended.

Next: [Producing messages](/docs/symfony/1.x/producing-messages/).