See #32357. don't think there is a good solution that works in every case.

@Tobion I've spent all my day investigating the issue, and I think there is a real bug at line https://github.com/symfony/symfony/blob/5.4/src/Symfony/Component/Messenger/Bridge/Amqp/Transport/Connection.php#L555

A small test script shows that in case of using AmqpTransport as a sender on the environment with more than one Transport (whatever kind it is) for pulling but the AmqpTransport INSTANCE only occasionally publishing may cause a connection to be dropped silently by a broker which on above-mentioned line gives false positive.
A solution might be to call the AMQPConnection::(p)?reconnect method and instead of checking isConnect on a channel (which still gives a false positive after reconnecting) check the isConnect on the channel's connection!! (IMPORTANT) which should then give false.

This affects many Symfony versions I guess. Please ping me for more details if you have any doubts.

Ofc executing AMQPConnection::(p)?reconnect is an additional cost but I guess this has to be concerned when the transport is used only occasionally in senders mode. There could be a calculation of heartbeat considered or ask for help the maintainers of php-amqp as there are also some issues similar php-amqp/php-amqp#305

Hope I'm on the right track.

For me this worked in Connection class:

    private function clearWhenDisconnected(): void
    {
        $connection = $this->channel()->getConnection();
        if ($this->amqpChannel) {
            if ($connection->isPersistent()) {
                $connection->preconnect();
            } else {
                $connection->reconnect();
            }
            $this->amqpChannel = null;
            $this->amqpQueues = [];
            $this->amqpExchange = null;
            $this->amqpDelayExchange = null;

            return;
        }

        if (!($connection->isConnected())) {
            $this->amqpChannel = null;
            $this->amqpQueues = [];
            $this->amqpExchange = null;
            $this->amqpDelayExchange = null;
        }
    }

Note! I'm aware this is an ugly hack, presenting it here only to show that it might work to reconnect especially when only the sender is used.

nice to see this fix
on our side we've fixed by forcing the connection to disconnect when a TransportException occurs in AMQPTransport

    public function send(Envelope $envelope): Envelope
    {
        try {
            return $this->decorated->send($envelope);
        } catch (TransportException $e) {
            /** @var RetryAfterAMQPExceptionStamp|null $stamp */
            $stamp = $envelope->last(RetryAfterAMQPExceptionStamp::class);

            if (null === $stamp) {
                $stamp = new RetryAfterAMQPExceptionStamp();
                $envelope = $envelope->with($stamp);
            } else {
                $stamp->increaseRetryAttempts();
            }

            if ($stamp->getRetryAttempts() < 3) {
                /*
                 * We only disconnect: the Connection object will be cleaned and AmqpConnection reconnected afterwards
                 * @see \Symfony\Component\Messenger\Bridge\Amqp\Transport\Connection::clearWhenDisconnected()
                 */
                $this->connection->channel()->getConnection()->disconnect();

                return $this->send($envelope);
            }

            throw $e;
        }
    }

but I think @brzuchal is cleaner

For me this worked in Connection class:

    private function clearWhenDisconnected(): void
    {
        $connection = $this->channel()->getConnection();
        if ($this->amqpChannel) {
            if ($connection->isPersistent()) {
                $connection->preconnect();
            } else {
                $connection->reconnect();
            }
            $this->amqpChannel = null;
            $this->amqpQueues = [];
            $this->amqpExchange = null;
            $this->amqpDelayExchange = null;

            return;
        }

        if (!($connection->isConnected())) {
            $this->amqpChannel = null;
            $this->amqpQueues = [];
            $this->amqpExchange = null;
            $this->amqpDelayExchange = null;
        }
    }

Note! I'm aware this is an ugly hack, presenting it here only to show that it might work to reconnect especially when only the sender is used.

@brzuchal for me, your code works on symfony 5.4 too. Can you do a pull request for this code?

For me this worked in Connection class:

    private function clearWhenDisconnected(): void
    {
        $connection = $this->channel()->getConnection();
        if ($this->amqpChannel) {
            if ($connection->isPersistent()) {
                $connection->preconnect();
            } else {
                $connection->reconnect();
            }
            $this->amqpChannel = null;
            $this->amqpQueues = [];
            $this->amqpExchange = null;
            $this->amqpDelayExchange = null;

            return;
        }

        if (!($connection->isConnected())) {
            $this->amqpChannel = null;
            $this->amqpQueues = [];
            $this->amqpExchange = null;
            $this->amqpDelayExchange = null;
        }
    }

Note! I'm aware this is an ugly hack, presenting it here only to show that it might work to reconnect especially when only the sender is used.

@brzuchal for me, your code works on symfony 5.4 too. Can you do a pull request for this code?

I'll see if I find the time to od so next week.

Any updates on issue? I got the same bug