docs: private String swapStore(String storeName, String directory) throws VoldemortException {
  
          ReadOnlyStorageEngine store = getReadOnlyStorageEngine(metadataStore,
                                                                 storeRepository,
                                                                 storeName);
  
          if(!Utils.isReadableDir(directory))
              throw new VoldemortException("Store directory '" + directory
                                           + "' is not a readable directory.");
  
          String currentDirPath = store.getCurrentDirPath();
  
          logger.info("Swapping RO store '" + storeName + "' to version directory '" + directory
                      + "'");
          store.swapFiles(directory);
          logger.info("Swapping swapped RO store '" + storeName + "' to version directory '"
                      + directory + "'");
  
          return currentDirPath;
      }