I'd like to send a message to a RabbitMQ server and then wait for a reply message (on a "reply-to" queue). Of course, I don't want to wait forever in case the application processing these messages is down - there needs to be a timeout. It sounds like a very basic task, yet I can't find a way to do this. I've now run into this problem with both py-amqplib and the RabbitMQ .NET client.
The best solution I've got so far is to poll using basic_get with sleep in-between, but this is pretty ugly:
def _wait_for_message_with_timeout(channel, queue_name, timeout):
slept = 0
sleep_interval = 0.1
while slept < timeout:
reply = channel.basic_get(queue_name)
if reply is not None:
return reply
time.sleep(sleep_interval)
slept += sleep_interval
raise Exception('Timeout (%g seconds) expired while waiting for an MQ response.' % timeout)
Surely there is some better way?
I just added timeout support for amqplib in carrot.
This is a subclass of amqplib.client0_8.Connection:
http://github.com/ask/carrot/blob/master/carrot/backends/pyamqplib.py#L19-97
wait_multi is a version of channel.wait able to receive on an arbitrary number
of channels.
I guess this could be merged upstream at some point.