public static int loadConfigNodeIdWhenRestarted() throws IOException {
    Properties systemProperties = systemPropertiesHandler.read();
    try {
      return Integer.parseInt(systemProperties.getProperty("config_node_id", null));
    } catch (NumberFormatException e) {
      throw new IOException(
          "The parameter config_node_id doesn't exist in "
              + "data/confignode/system/confignode-system.properties. "
              + "Please delete data dir data/confignode and restart again.",
          e);
    }
  }
Load the config_node_id in confignode-system.properties file. We only invoke this interface
when restarted.

@return The property of config_node_id in confignode-system.properties file
@throws IOException When load confignode-system.properties file failed
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/conf/SystemPropertiesUtils.java