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:

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 :class:`Symfony\\Component\\Messenger\\Transport\\TransportInterface` (which combines the :class:`Symfony\\Component\\Messenger\\Transport\\Sender\\SenderInterface` and :class:`Symfony\\Component\\Messenger\\Transport\\Receiver\\ReceiverInterface`). Here is a simplified example of a database transport:

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 :class:`Symfony\\Component\\Messenger\\Transport\\TransportInterface` could be implemented. For real implementations see :class:`Symfony\\Component\\Messenger\\Transport\\InMemoryTransport` and :class:`Symfony\\Component\\Messenger\\Bridge\\Doctrine\\Transport\\DoctrineReceiver`.

Register your Factory

Before using your factory, you must register it. If you're using the :ref:`default services.yaml configuration <service-container-services-load-example>`, this is already done for you, thanks to :ref:`autoconfiguration <services-autoconfigure>`. Otherwise, add the following:

.. configuration-block::

    .. code-block:: yaml

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

    .. code-block:: xml

        <!-- config/services.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <container xmlns="http://symfony.com/schema/dic/services"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://symfony.com/schema/dic/services
                https://symfony.com/schema/dic/services/services-1.0.xsd">

            <services>
                <service id="Your\Transport\YourTransportFactory">
                   <tag name="messenger.transport_factory"/>
                </service>
            </services>
        </container>

    .. code-block:: php

        // config/services.php
        use Your\Transport\YourTransportFactory;

        $container->register(YourTransportFactory::class)
            ->setTags(['messenger.transport_factory']);

Use your Transport

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

.. configuration-block::

    .. code-block:: yaml

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

    .. code-block:: xml

        <!-- config/packages/messenger.xml -->
        <?xml version="1.0" encoding="UTF-8" ?>
        <container xmlns="http://symfony.com/schema/dic/services"
            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xmlns:framework="http://symfony.com/schema/dic/symfony"
            xsi:schemaLocation="http://symfony.com/schema/dic/services
                https://symfony.com/schema/dic/services/services-1.0.xsd
                http://symfony.com/schema/dic/symfony
                https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">

            <framework:config>
                <framework:messenger>
                    <framework:transport name="yours" dsn="my-transport://..."/>
                </framework:messenger>
            </framework:config>
        </container>

    .. code-block:: php

        // config/packages/messenger.php
        use Symfony\Config\FrameworkConfig;

        return static function (FrameworkConfig $framework) {
            $framework->messenger()
                ->transport('yours')
                    ->dsn('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.