code: private static String lookupScheme(Properties props) {
          String scheme = null;
  
          // 1. lookup system property 'td.logger.api.server.scheme'
          if (props.containsKey(Config.TD_LOGGER_API_SERVER_SCHEME)) {
              scheme = props.getProperty(Config.TD_LOGGER_API_SERVER_SCHEME);
          }
  
          // if not exists, set default value
          if (scheme == null) {
              scheme = Config.TD_LOGGER_API_SERVER_SCHEME_DEFAULT;
          }
  
          // write/overwrite it to 'td.api.server.port'
          props.setProperty(Config.TD_CK_API_SERVER_SCHEME, scheme);
          return scheme;
      }
docs: Define order for scheme lookup.
  1. lookup props's td.logger.api.server.scheme