How to Create Your own Messenger Transport

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How to Create Your own Messenger Transport

Once you have written your transport's sender and receiver, you can register your transport factory to be able to use it via a DSN in the Symfony application.

Create your Transport Factory

You need to give FrameworkBundle the opportunity to create your transport from a DSN. You will need a transport factory:

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use Symfony\Component\Messenger\Transport\Receiver\ReceiverInterface;
use Symfony\Component\Messenger\Transport\Sender\SenderInterface;
use Symfony\Component\Messenger\Transport\Serialization\SerializerInterface;
use Symfony\Component\Messenger\Transport\TransportFactoryInterface;
use Symfony\Component\Messenger\Transport\TransportInterface;

class YourTransportFactory implements TransportFactoryInterface
{
    public function createTransport(string $dsn, array $options, SerializerInterface $serializer): TransportInterface
    {
        return new YourTransport(/* ... */);
    }

    public function supports(string $dsn, array $options): bool
    {
        return 0 === strpos($dsn, 'my-transport://');
    }
}

The transport object needs to implement the TransportInterface (which combines the SenderInterface and ReceiverInterface). Here is a simplified example of a database transport:

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use Symfony\Component\Messenger\Envelope;
use Symfony\Component\Messenger\Stamp\TransportMessageIdStamp;
use Symfony\Component\Messenger\Transport\Serialization\PhpSerializer;
use Symfony\Component\Messenger\Transport\Serialization\SerializerInterface;
use Symfony\Component\Messenger\Transport\TransportInterface;
use Symfony\Component\Uid\Uuid;

class YourTransport implements TransportInterface
{
    private $db;
    private $serializer;

    /**
     * @param FakeDatabase $db is used for demo purposes. It is not a real class.
     */
    public function __construct(FakeDatabase $db, SerializerInterface $serializer = null)
    {
        $this->db = $db;
        $this->serializer = $serializer ?? new PhpSerializer();
    }

    public function get(): iterable
    {
        // Get a message from "my_queue"
        $row = $this->db->createQuery(
                'SELECT *
                FROM my_queue
                WHERE (delivered_at IS NULL OR delivered_at < :redeliver_timeout)
                AND handled = FALSE'
            )
            ->setParameter('redeliver_timeout', new DateTimeImmutable('-5 minutes'))
            ->getOneOrNullResult();

        if (null === $row) {
            return [];
        }

        $envelope = $this->serializer->decode([
            'body' => $row['envelope'],
        ]);

        return [$envelope->with(new TransportMessageIdStamp($row['id']))];
    }

    public function ack(Envelope $envelope): void
    {
        $stamp = $envelope->last(TransportMessageIdStamp::class);
        if (!$stamp instanceof TransportMessageIdStamp) {
            throw new \LogicException('No TransportMessageIdStamp found on the Envelope.');
        }

        // Mark the message as "handled"
        $this->db->createQuery('UPDATE my_queue SET handled = TRUE WHERE id = :id')
            ->setParameter('id', $stamp->getId())
            ->execute();
    }

    public function reject(Envelope $envelope): void
    {
        $stamp = $envelope->last(TransportMessageIdStamp::class);
        if (!$stamp instanceof TransportMessageIdStamp) {
            throw new \LogicException('No TransportMessageIdStamp found on the Envelope.');
        }

        // Delete the message from the "my_queue" table
        $this->db->createQuery('DELETE FROM my_queue WHERE id = :id')
            ->setParameter('id', $stamp->getId())
            ->execute();
    }

    public function send(Envelope $envelope): Envelope
    {
        $encodedMessage = $this->serializer->encode($envelope);
        $uuid = (string) Uuid::v4();
        // Add a message to the "my_queue" table
        $this->db->createQuery(
                'INSERT INTO my_queue (id, envelope, delivered_at, handled)
                VALUES (:id, :envelope, NULL, FALSE)'
            )
            ->setParameters([
                'id' => $uuid,
                'envelope' => $encodedMessage['body'],
            ])
            ->execute();

        return $envelope->with(new TransportMessageIdStamp($uuid));
    }
}

The implementation above is not runnable code but illustrates how a TransportInterface could be implemented. For real implementations see InMemoryTransport and DoctrineReceiver.

Register your Factory

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# config/services.yaml
services:
    Your\Transport\YourTransportFactory:
        tags: [messenger.transport_factory]

Use your Transport

Within the framework.messenger.transports.* configuration, create your named transport using your own DSN:

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# config/packages/messenger.yaml
framework:
    messenger:
        transports:
            yours: 'my-transport://...'

In addition of being able to route your messages to the yours sender, this will give you access to the following services:

  1. messenger.sender.yours: the sender;
  2. messenger.receiver.yours: the receiver.
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
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