protected function _rpcPreProcess($argument)
    {
        $this->affinity_key = null;
        if ($this->_affinity) {
            $command = $this->_affinity['command'];
            if ($command == self::BOUND || $command == self::UNBIND) {
                $this->affinity_key = $this->getAffinityKeyFromProto($argument);
            }
        }
        $this->channel_ref = $this->gcp_channel->getChannelRef($this->affinity_key);
        $this->channel_ref->activeStreamRefIncr();
        return $this->channel_ref;
    }