public static int conn_threshold() {
        return getInt(Configs.CONN_THRESHOLD, Configs.CONN_THRESHOLD_DEFAULT);
    }
get configs through system properties prior to default value

@author tsui
@version $Id: ConfigManager.java, v 0.1 2017-08-03 19:21 tsui Exp $
src/main/java/com/alipay/remoting/config/ConfigManager.java