Symfony News

New in Symfony 4.1: Messenger component

Samuel Roze

Contributed by
Samuel Roze
in #24411.

In Symfony 4.1, we added a new Messenger component that helps applications send and receive messages to/from other applications or via message queues. It provides a message bus and some routing capabilities to send messages in any service where you need it, like in a controller:

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// src/Controller/DefaultController.php
namespace App\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\Messenger\MessageBusInterface;
use Symfony\Component\Routing\Annotation\Route;

class DefaultController extends Controller
{
    /**
     * @Route("/", name="homepage")
     */
    public function index(MessageBusInterface $bus)
    {
        // ...

        $bus->dispatch(new MyMessage());
    }
}

Sending messages is the first part of the process. Then you need to create a "message handler" and register it as a service with the messenger.message_handler tag to receive the message and do something with it:

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// src/MessageHandler/MyMessageHandler.php
namespace App\MessageHandler;

class MyMessageHandler
{
    public function __invoke(MyMessage $message)
    {
        // do something with the message
    }
}

Queues and AMQP adapters

The component includes an AMQP adapter ready to communicate with most of the popular AMQP brokers, such as RabbitMQ. The communication with queuing systems or third parties (Kafka, Amazon SQL, Google Pub/sub) is delegated to libraries like Enqueue's adapter:

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# config/packages/messenger.yaml
framework:
    messenger:
        adapters:
            default: "amqp://guest:guest@localhost:5672/%2f/messages"

This config allows to route messages to the messenger.default_adapter and also configures a messenger.default_sender and messenger.default_receiver to be used when routing and consuming messages.

Routing

Instead of calling a handler, you can also route your messages to one or multiple senders:

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# config/packages/messenger.yaml
framework:
    messenger:
        routing:
            # route this message to a singe sender
            'My\Message\Message':  messenger.default_sender

            # route this message to multiple senders
            'My\Message\ToBeSentToTwoSenders': [messenger.default_sender, messenger.audit_sender]

            # route the rest of messages to the default sender
            '*': messenger.default_sender

Once your messages have been routed, you can consume them with the messenger:consume-messages command:

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$ bin/console messenger:consume-messages messenger.default_receiver

The message bus defined by the Messenger component is based on middlewares. You can read more about them and the rest of features of Messenger in the latest draft of its documentation.

Be trained by Symfony experts - 2018-04-23 Lyon - 2018-04-23 Lyon - 2018-04-25 Clichy


Source: https://symfony.com/blog

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