Symfony messenger and mailer : how to add a binding_key?

Question

I have a running Symfony 4.4 project with messenger and rabbitMQ. I have an async transport with 2 queues.

    transports:
        # https://symfony.com/doc/current/messenger.html#transport-configuration
      async:
        dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
        options:
          exchange:
            name: myexchange
            type: direct
          queues:
            email:
              binding_keys:
                - email
            extranet:
              binding_keys:
                  - extranet
        # failed: 'doctrine://default?queue_name=failed'
        # sync: 'sync://'

    routing:
        # Route your messages to the transports
        'App\Message\ExtranetMessage': async
        'Symfony\Component\Mailer\Messenger\SendEmailMessage': async

I need to send email with the symfony/mailer component to the email queue.

public function contact(Request $request, MailerInterface $mailer)
{
    if($request->isXmlHttpRequest())
    {
        //dd($request->request->all());
        $body =
            'Nouveau message depuis le front<br />
             Nom = '.$request->request->get('nom').'<br />
             Prénom = '.$request->request->get('prenom').'<br />
             Société = '.$request->request->get('societe').'<br />
             Email = '.$request->request->get('mail').'<br />';

        $email = (new Email())
            ->from('[email protected]')
            ->replyTo($request->request->get('mail'))
            ->to('$request->request->get('mail')')
            ->subject('test')
            ->html($body);

        $mailer->send($email);

        return new JsonResponse('OK', 200);
    }
}

How can I add the binding_key to the mailer in order to let rabbitMQ know how to handle the email ?

Answer 1

Allright, I found the answer while searching for the complete messenger configuration reference.

In order to process messages without binding key, a default_publish_routing_key entry has to be added. The configuration now looks like :

    transports:
        # https://symfony.com/doc/current/messenger.html#transport-configuration
      async:
        dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
        options:
          exchange:
            name: myexchange
            type: direct
            default_publish_routing_key: email
          queues:
            email:
              binding_keys:
                - email
            extranet:
              binding_keys:
                  - extranet
        # failed: 'doctrine://default?queue_name=failed'
        # sync: 'sync://'

    routing:
        # Route your messages to the transports
        'App\Message\ExtranetMessage': async
        'Symfony\Component\Mailer\Messenger\SendEmailMessage': async

This allows the messenger component to process messages event if they don't have any queue specified.

Answer 2

Routing keys can be specified via stamps. Unfortunately, the mailer integration doesn't expose a way to add them, it just dispatches the message to the default queue. But you can still dispatch the message manually:

$this->dispatchMessage(new SendEmailMessage($email), [new AmqpStamp('email')]);

This approach has some limitations: Since this is not using mailer code, MessageEvent won't be dispatched and the "E-mails" Pane in the profiler will be empty.

Another option is to add the stamp using a middleware:

1. Create the middleware

// src/Messenger/StampEmailMessageMiddleware.php
class StampEmailMessageMiddleware implements MiddlewareInterface
{
    const bindingKey = 'email';

    public function handle(Envelope $envelope, StackInterface $stack): Envelope
    {
        // Add the stamp. Since the middleware gets called both when dispatching and 
        // consuming the message, we make sure there's no stamp already added.
        if (
            $envelope->getMessage() instanceof SendEmailMessage && 
            null === $envelope->last(AmqpStamp::class)
        ) {
            $envelope = $envelope->with(new AmqpStamp(self::bindingKey));
        }

        return $stack->next()->handle($envelope, $stack);
    }
}

2. Add the middleware to the bus configuration:

# config/packages/messenger.yaml
messenger:
    buses:
        messenger.bus.default:
            middleware:
                - 'App\Messenger\StampEmailMessageMiddleware'

3. Send the message normally:

$mailer->send($email);

Answer 3

Alternatively you could define separate transports for each queue using different exchange names.

    transports:
      async_email:
        dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
        options:
          exchange:
            name: messages_email
          queues:
            email: ~
      async_extranet:
        dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
        options:
          exchange:
            name: messages_extranet
          queues:
            extranet: ~

    routing:
        'App\Message\ExtranetMessage': async_extranet
        'Symfony\Component\Mailer\Messenger\SendEmailMessage': async_email

In this case you don't need to specify binding key on every message dispatch or create custom middleware.