def process_response_queue_message(metadata, payload)
      response_queue = @transactions.delete metadata.correlation_id
      response_queue << payload if response_queue
    end
def process_response_queue_message(metadata, payload)
      response_queue = @transactions.delete metadata.correlation_id
      response_queue << payload if response_queue
    end
process a response message

 If a message is put on this services response queue
 its response will be pushed onto the blocking queue