def all_existing_queues
      known_queues    = Backburner::Worker.known_queue_classes.map(&:queue)
      existing_tubes  = self.connection.tubes.all.map(&:name).select { |tube| tube =~ /^#{queue_config.tube_namespace}/ }
      existing_tubes + known_queues + [queue_config.primary_queue]
    end
Returns a list of all tubes known within the system
Filtered for tubes that match the known prefix