This issue is related to this one: #35449

I found this issue which explains the reason the failed message does not get sent into the failure transport once it fails again without being retried: #33685

Can someone clarify why we do not want retried messages which are failing again being sent to the failure transport again? For example I have remote API which is down, the message gets retried for a number of times, then fails. I try it again, lets say a day later, it gets retried once, then I lose the message entirely. Would be really thankful for someone giving me feedback on that.

The UnrecoverableMessageHandlingException implements UnrecoverableExceptionInterface. Reading from that interface's description:

Marker interface for exceptions to indicate that handling a message will continue to fail.
If something goes wrong while handling a message that's received from a transport and the message should not be retried, a handler can throw such an exception.

So the definition of using this exception is that they should not be retired because it is impossible to recover.

For your example with the remote API, that does not seam to be a "Unrecoverable Message Handling Exception", we just need to wait a while until the API comes back up. So make sure you dont throw a UnrecoverableMessageHandlingException.

@Nyholm Thanks for answering. Currently, when a message is handled the first time and a UnrecoverableMessageHandlingException occurs, the message is still sent to the failure transport. Reading your explanation, I understand that the message should never reach the failure transport, as it can be retried from there. Shouldn't that be changed then?

Currently, when a message is handled the first time and a UnrecoverableMessageHandlingException occurs, the message is still sent to the failure transport.

Are you sure about that?

Yes, I am.
The message does not get retried, that's true, as the mechanism in the SendFailedMessageForRetryListener prevents that.

private function shouldRetry(\Throwable $e, Envelope $envelope, RetryStrategyInterface $retryStrategy): bool
    {
        // if ALL nested Exceptions are an instance of UnrecoverableExceptionInterface we should not retry
        if ($e instanceof HandlerFailedException) {
            $shouldNotRetry = true;
            foreach ($e->getNestedExceptions() as $nestedException) {
                if (!$nestedException instanceof UnrecoverableExceptionInterface) {
                    $shouldNotRetry = false;
                    break;
                }
            }
            if ($shouldNotRetry) {
                return false;
            }
        }

        if ($e instanceof UnrecoverableExceptionInterface) {
            return false;
        }

        return $retryStrategy->isRetryable($envelope);
    }

But the SendFailedMessageToFailureTransportListener still acts on it, as it is currently not interested in the type of the exception.