Unsubscribe from rabbit queue when machine is shut down - ruby

Question

I am running rabbitmq through AMQP gem on 3 worker machines. When the machines are rebooted, my queue shows that workers are only added, not unsubscribed. For example, say each machine runs 5 workers:
When I boot 3 machines, I have 15 workers subscribed to the queue
When I shut down all 3 machines, I still have 15 workers subscribed to the queue
When I reboot the 3 machines, I now have 30 workers subscribed to the queue
In reality, I should only have 15 workers.
How can I ensure that my connection to my task queue closes when the machine reboots/shuts down? I have tried:
Signal.trap("INT") do #handles the ctrl c case
connection.close do
EM.stop { exit }
end
end
Signal.trap("TERM") do #handles the reboot and shut down case
connection.close do
EM.stop { exit }
end
end
This does NOT work.

Answer 1

I think what you are looking for is a Consumer cancellation Notification extension.
In your case, the clients has not been notified of the machines rebooting (in other words they have not received a 'basic.cancel' notification from the rabbitmq broker when the machines rebooted).
See the excerpts taken from the link above:
an extension in which the broker will send to the client a basic.cancel in the case of such unexpected consumer cancellations. This is not sent in the case of the broker receiving a basic.cancel from the client. AMQP 0-9-1 clients don't by default expect to receive basic.cancel methods from the broker asynchronously, and so in order to enable this behaviour, the client must present a capabilities table in its client-properties in which there is a key consumer_cancel_notify and a boolean value true
I'm not a ruby programmer, but I reckon the java example in the link above should give you the full picture.