Code below -     
// Clients may take some time to receive an update from zookeeper that the node is still servicing requests.
    // We wait for a preconfigured time to make an effort before shutting down core search internals
    // to not disturb normal service operation
    if(_shutdownPauseMillis > 0) {
      logger.info("Waiting " + _shutdownPauseMillis + " milliseconds for all clients to stop sending requests to server");
      try {
        Thread.sleep(_shutdownPauseMillis);
      } catch (InterruptedException e) {
        logger.warn("Interrupted while waiting, continuing with shutdown ", e);
      }
    }