code: @Override
    protected void serviceStop() {
      try {
        if (shuffleServer != null) {
          shuffleServer.close();
        }
        if (transportContext != null) {
          transportContext.close();
        }
        if (blockHandler != null) {
          blockHandler.close();
        }
        if (db != null) {
          db.close();
        }
      } catch (Exception e) {
        logger.error("Exception when stopping service", e);
      }
    }
docs: Close the shuffle server to clean up any associated state.