public String getConnectorProtocol() {
        return getString(POLARIS_SERVER_CONNECTOR_PROTOCOL_KEY, POLARIS_SERVER_CONNECTOR_PROTOCOL);
    }
the properties of polaris registry

@author <a href=mailto:bner666@gmail.com>ZhangLibin</a>
registry/registry-polaris/src/main/java/com/alipay/sofa/rpc/registry/polaris/PolarisRegistryProperties.java