public function getConsumer($instanceId, $topicName, $consumer, $messageTag = NULL)
    {
        if ($topicName == NULL || $topicName == "") {
            throw new InvalidArgumentException(400, "TopicName is null or empty");
        }
        if ($consumer == NULL || $consumer == "" ) {
            throw new InvalidArgumentException(400, "Consumer is null or empty");
        }
        return new MQConsumer($this->client, $instanceId, $topicName, $consumer, $messageTag);
    }