Sync / Async event handlers

request.php

<?php

// In requests:

final class SomeSubscriber {
  public function applyDomainEvent(DomainEvent $xyz) {
    // Maybe fire another event to get some consistency.
  }
}

final class SyncSubscriberNotifier implements EventSubscriberNotifier {}

$notifier = new SyncSubscriberNotifier(new LaravelContainerResolver);
$notifier->register(SomeSubscriber::class);

// Handle some message synchronous, others asynchronous.
$bus = new MiddlewareBus([
  new FinishBeforeHandlingOthers,
  $notifier,
  new PublishAsync, // terminates the pipeline (maybe conditionally), and puts a serialized event in an envelope with some metadata
]);

$bus->dispatch(new DomainMessage());

worker.php

<?php

// In workers:

final class SomeProjector {
  public function applyDomainEvent(DomainEvent $xyz) {
    // Do some heavy database stuff that can be eventually consistent, or some networking
  }
}

final class DelayedSubscribersNotifier implements EventSubscriberNotifier {}

$notifier = new DelayedSubscribersNotifier(new LaravelContainerResolver);
$notifier->register(SomeProjector::class);

// Handle some message synchronous, other asynchronous.
$bus = new MiddlewareBus([
  new FinishBeforeHandlingOthers,
  $notifier,
  // No need to publish async things.
]);

$deserializer = ...;

$loop->listen('DomainMessageReceived', function(MessageEnvelope $envelope) use ($deserializer, $bus) {
  $message = $envelope->deserialize($deserializer);
  $bus->dispatch($message);
});