Symfony Messenger & Async Processing

You are an expert in async message processing with Symfony Messenger within hexagonal architecture.

When to Activate

• User needs async processing or background jobs
• User asks about message queues or retry strategies
• User mentions cron jobs (redirect to Scheduler)
• User needs idempotency or failure handling
• User asks about Symfony Scheduler

Core Principle: No Cron Jobs

Never use raw cron. Always use:

• Symfony Messenger for async message processing
• Symfony Scheduler for recurring tasks

Async Command Pattern

// The command is the same — async is a routing concern, not a code concern
namespace App\Application\Report\Command;

final readonly class GenerateReport
{
    public function __construct(
        public string $reportId,
        public string $userId,
        public string $type,
    ) {
    }
}

// Handler is identical to sync — the bus handles async dispatch
#[AsMessageHandler(bus: 'command.bus')]
final readonly class GenerateReportHandler
{
    public function __invoke(GenerateReport $command): void
    {
        // Long-running operation
    }
}

# Route to async transport
framework:
    messenger:
        routing:
            'App\Application\Report\Command\GenerateReport': async

Idempotency

Every async handler MUST be idempotent — safe to retry:

#[AsMessageHandler(bus: 'command.bus')]
final readonly class ProcessPaymentHandler
{
    public function __construct(
        private PaymentRepositoryInterface $paymentRepository,
        private PaymentGatewayInterface $paymentGateway,
    ) {
    }

    public function __invoke(ProcessPayment $command): void
    {
        // Check if already processed (idempotency)
        $existing = $this->paymentRepository->findByIdempotencyKey($command->idempotencyKey);
        if ($existing !== null) {
            return; // Already processed, skip
        }

        // Process payment
        $result = $this->paymentGateway->charge($command->customerId, $command->amount);
        $this->paymentRepository->save($result);
    }
}

References

See references/ for detailed guides:

• messenger-config.md — Full Messenger YAML configuration
• idempotency-patterns.md — Idempotency key strategies
• scheduler-patterns.md — Symfony Scheduler setup and patterns