code: static void initSelectTimeout() {
          String currentTimeout = System.getProperty(PROPERTY_NETTY_SELECT_TIMEOUT);
          if (currentTimeout == null || "".equals(currentTimeout)) {
              try {
                  System.setProperty(PROPERTY_NETTY_SELECT_TIMEOUT, Long.toString(DEFAULT_SELECT_TIMEOUT_MILLIS));
              }
              catch (SecurityException e) {
                  if (logger.isWarnEnabled()) {
                      logger.warn(String.format(
                              "Unable to set System property \"%s\" to %d due to %s, Gateway performance may be reduced",
                              PROPERTY_NETTY_SELECT_TIMEOUT, DEFAULT_SELECT_TIMEOUT_MILLIS, e));
                  }
              }
          }
      }
docs: but also allow explicit setting of the Netty property (for internal testing purposes)