public synchronized void loadHotModifiedProps() throws QueryProcessException {
    URL url = getPropsUrl(CommonConfig.SYSTEM_CONFIG_NAME);
    if (url == null) {
      LOGGER.warn("Couldn't load the configuration from any of the known sources.");
      return;
    }

    TrimProperties commonProperties = new TrimProperties();
    try (InputStream inputStream = url.openStream()) {
      LOGGER.info("Start to reload config file {}", url);
      commonProperties.load(new InputStreamReader(inputStream, StandardCharsets.UTF_8));
      ConfigurationFileUtils.loadConfigurationDefaultValueFromTemplate();
      loadHotModifiedProps(commonProperties);
    } catch (Exception e) {
      LOGGER.warn("Fail to reload config file {}", url, e);
      throw new QueryProcessException(
          String.format("Fail to reload config file %s because %s", url, e.getMessage()));
    } finally {
      ConfigurationFileUtils.releaseDefault();
    }
    reloadMetricProperties(commonProperties);
  }
load a property file and set TsfileDBConfig variables.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/conf/IoTDBDescriptor.java