protected String buildProxySelectorKey(final String listenerNode) {
        return StringUtils.isNotBlank(listenerNode) ? listenerNode : DEFAULT_LISTENER_NODE;
    }
buildProxySelectorKey.

@param listenerNode listenerNode
@return key
shenyu-admin/src/main/java/org/apache/shenyu/admin/discovery/AbstractDiscoveryProcessor.java