Unsubscribing from a queue that has a message on it raises an exception. about bunny HOT 12 CLOSED

One thing I don't see in your code is where you cancel your consumer (unsubscribe). Another thing I need you to provide is RabbitMQ version you use. Thanks.

from bunny.

Oh sorry, I'm using RabbitMQ 2.6.1.

 q.subscribe( :timeout => 5, :message_max => 1 ) do |msg|

:message_max has the call to subscribe unsubscribe after it receives arg number of messages (in this case 1).

From lib/qrack/subscription.rb

def start(blk&)

...

     # If block present, pass the message info to the block for processing
    blk.call({:header => header, :payload => msg, :delivery_details => method.arguments}) if !blk.nil?

    # Exit loop if message_max condition met
    if (!message_max.nil? and message_count == message_max)
      # Stop consuming messages
      queue.unsubscribe()
      # Acknowledge receipt of the final message
      queue.ack() if @ack
      # Quit the loop
      break
    end
end

from bunny.

Woops, didn't mean to close it.

from bunny.

Gotcha, thank you.

from bunny.

The whole bunny logic regarding message_max and unsubscribing from queues seems to be inherently flawed.

As I see it, there is no guarantee that the response from the broker on sending a Cancel frame will be a CancelOK frame.

It could also be the next message already queued up for the client, which seems to be what's happening here.

The broker will eventually stop sending messages, but not immediately.

Which means major refactoring of the bunny code is required.

from bunny.

In other words: bunny is OK for publishing, but for writing subscribers you're much better off using the amq gem.

from bunny.

The subscription stuff only works if you use the qos method so that you receive messages in the necessary order. This gist has some examples that I think still work. https://gist.github.com/185144

from bunny.

I have already tried using prefetch_count=1. But it did not work for me.

It might be that you also need to use ack=true.

from bunny.

Yes, you do need ack=true otherwise qos will not work.

from bunny.

I would only use Bunny subscription if your needs are pretty basic. Otherwise, I would go with the amqp gem.

from bunny.

And if you choose to go with the amqp gem, please check out amqp gem documentation.

from bunny.

Indeed, if you set :prefetch_count to 1 and pass :ack => true, then everything is OK:

require 'rubygems'
require 'bunny'

b = Bunny.new(:host => '127.0.0.1', :logging => false)
b.start
b.qos(:prefetch_count => 1)

exchange = b.exchange('')

q = b.queue(nil, :exclusive => false)

exchange.publish('abc', :key => q.name)
exchange.publish('def', :key => q.name)


puts '.'

q.subscribe( :timeout => 5, :message_max => 1, :ack => true ) do |msg|
  puts msg[:payload]
end


puts '.'

from bunny.