apollo-client/src/main/java/com/ctrip/framework/apollo/util/ConfigUtil.java/ConfigUtil/initLongPollingInitialDelayInMills
class ConfigUtil:  private void initLongPollingInitialDelayInMills() {
    String customizedLongPollingInitialDelay = System
        .getProperty("apollo.longPollingInitialDelayInMills");
    if (!Strings.isNullOrEmpty(customizedLongPollingInitialDelay)) {
      try {
        longPollingInitialDelayInMills = Long.parseLong(customizedLongPollingInitialDelay);
      } catch (Throwable ex) {
        logger.error("Config for apollo.longPollingInitialDelayInMills is invalid: {}",
            customizedLongPollingInitialDelay);
      }
    }
  }