@Override
  public void onConfigChange(ConfigChangeEvent changeEvent) throws MetaException {
    if (changeEvent.getKey().equals(MetastoreConf.ConfVars.CLIENT_SOCKET_TIMEOUT.getVarname()) ||
        changeEvent.getKey().equals(MetastoreConf.ConfVars.CLIENT_SOCKET_TIMEOUT.getHiveName())) {
      // TODO: this only applies to current thread, so it's not useful at all.
      Deadline.resetTimeout(MetastoreConf.convertTimeStr(changeEvent.getNewValue(), TimeUnit.SECONDS,
          TimeUnit.MILLISECONDS));
    }
  }
It handles the changed properties in the change event.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/SessionPropertiesListener.java