Catching NO_ROUTE from AMQP.Basic.publish

You can use return to register a handler to deal with returned messages.

If you get this message: {:basic_return, payload, meta}, send it again.

Hi, thank you.

Unfortunately this does not work because I receive a message only in case there was an error. So when everything goes right i’ll have to add a timeout to the receive, which is only slightly better than the sleep.

Edit: It seems that if I also add the following:

    AMQP.Confirm.select(chan)
    AMQP.Confirm.register_handler(chan, self())

the :basic_ack message is always delivered after the :basic_return message, so it may be safe to consider that receiving basic_ack without basic_return means that the message was routed.

Would something like this work?

Def ensure_routed_publish(chan, exchange, routing_key, payload) do
AMQP.Basic.return(chan, self())
AMQP.Confirm.select(chan)
AMQP.Confirm.register_handler(chan, self())
:ok = AMQP.Basic.publish(chan, exchange, routing_key, payload, mandatory: true)

receive do
{:basic_ack, _, _} →
:ok
{:basic_return, returned_payload, _} →
{:error, returned_payload}
after
timeout →
{:error, :timeout}
end
end

Yes this is more or less what I did:

  defp ensure_routed_publish(chan, exchange, key, payload) do
    AMQP.Confirm.select(chan)
    AMQP.Confirm.register_handler(chan, self())
    AMQP.Basic.return(chan, self())
    publish_loop(chan, exchange, key, payload)
  end

  defp publish_loop(chan, exchange, key, payload) do
    :ok = AMQP.Basic.publish(chan, exchange, key, payload, mandatory: true)

    receive do
      {:basic_return, _, %{reply_text: "NO_ROUTE"}} ->
        receive do
          {:basic_ack, _, _} ->
            Process.sleep(50)
            publish_loop(chan, exchange, key, payload)
        end

      {:basic_ack, _, _} ->
        :ok
    after
      5000 -> flunk("could not deliver message to RabbitMQ")
    end
  end

(It is in a test so we know the queue will exist at some point.)

Hi!

Do you know if there is a way to catch when an exchange does not exist?

operation basic.publish caused a channel exception not_found: no exchange ‘does_not_exist’ in vhost ‘/’

I have the following code:

    :ok = AMQP.Confirm.select(chan)
    :ok = AMQP.Confirm.register_handler(chan, self())

And was expecting to receive a basic nack.

I also have this code AMQP.Basic.return(chan, self()) but it does not seem to handle that.
Thank you!