code: public void recoverFromStartSync(AlluxioURI uri, long mountId) {
      // if the init sync has been launched, we need to stop it
      if (mSyncPathStatus.containsKey(uri)) {
        Future<?> syncFuture = mSyncPathStatus.remove(uri);
        if (syncFuture != null) {
          syncFuture.cancel(true);
        }
      }
  
      // if the polling thread has been launched, we need to stop it
      mFilterMap.remove(mountId);
      Future<?> future = mPollerMap.remove(mountId);
      if (future != null) {
        future.cancel(true);
      }
    }
docs: Recover from start sync operation.
  
  @param uri uri to start sync
  @param mountId mount id of the uri