Symfony Messenger Transport

Symfony Messenger CQRS DDD

Symfony Messenger Transport Integration

Ecotone comes with Symfony Messenger Transport integration. We may use Transports as our Message Channels. This way we can work with familiar environment and reuse already set up Symfony Serializer.

Asynchronous Message Handler

Suppose we have "async" transport:

framework:
  messenger:
    transports:
      async: 'doctrine://default?queue_name=async'

Then we can register it using Service Context in Ecotone:

final class MessagingConfiguration
{
    #[ServiceContext]
    public function asyncChannel()
    {
        return SymfonyMessengerMessageChannelBuilder::create("async");
    }
}

After that we can start using it as any other asynchronous channel.

#[Asynchronous('async')]
#[CommandHandler(endpointId:"place_order_endpoint")]
public function placeOrder(PlaceOrder $command): void
{
    // place the order
}

Trigger Command/Event/Query via Ecotone Bus

In order to trigger Command Event or Query Handler, we will be sending the Message via given Ecotone's Bus, sending Messages via Symfony Bus will have no effect due to lack of information what kind of message it's.

Ecotone provide Command/Event/Query buses, Symfony contains general Message Bus. It's important to distinguish between Message types as Queries are handled synchronously, Commands are point to point and target single Handler, Events on other hand are publish-subscribe which means multiple Handlers can subscribe to it.

In order to trigger given Bus, inject CommandBus, EventBus or QueryBus (they are automatically available after installing Ecotone) and make use of them to send a Message.

final class OrderController
{
    public function __construct(private CommandBus $commandBus) {}

    public function placeOrder(Request $request): Response
    {
        $command = $this->prepareCommand($request);

        $this->commandBus->send($command);

        return new Response();
    }
    
    (...)

Running Message Consumer (Worker)

We will be running Message Consumer using "ecotone:run" command:

bin/console ecotone:run async -vvv

Sending messages via routing

When sending command and events via routing, it's possible to use non-class types. In case of Symfony however, Messenger Transports require to Classes. To solve that Ecotone wraps simple types in a class and unwrap it on deserialization. Thanks to that we can Symfony Transport like any other Ecotone's Message Channel.

• Command Handler with command having array payload

$this->commandBus->sendWithRouting('order.place', ["products" => [1,2,3]]);

#[Asynchronous('async')]
#[CommandHandler('order.place', 'place_order_endpoint')]
public function placeOrder(array $payload): void
{
    // do something with 
}

• Command Handler inside Aggregate with command having no payload at all

$this->commandBus->sendWithRouting('order.place', metadata: ["aggregate.id" => 123]);

#[Aggregate]
class Order
{
    #[Asynchronous('async')]
    #[CommandHandler('cancel', 'cancel_order_endpoint')]
    public function cancel(): void
    {
        $this->isCancelled = true;
    }
(...)    

Asynchronous Event Handlers

In case of sending events, we will be using Event Bus.

• EventBus is available out of the box in Dependency Container. Therefore all we need to do, is to inject it and publish an Event

$this->eventBus->publish(new OrderWasPlaced($orderId));

• Subscribe to Event

#[Asynchronous('async')]
#[EventHandler('order_was_placed_endpoint')]
public function notifyAbout(OrderWasPlaced $event): void
{
    // send notification
}

Dead Letter (Failed Transport)

Failed transport is configured on Ecotone side using Error Channel. Read more in related section.