code: public static long getTimestamp(Configuration conf, URI cache)
      throws IOException {
      FileSystem fileSystem = FileSystem.get(cache, conf);
      Path filePath = new Path(cache.getPath());
  
      return fileSystem.getFileStatus(filePath).getModificationTime();
    }
docs: Returns mtime of a given cache file on hdfs.
  @param conf configuration
  @param cache cache file
  @return mtime of a given cache file on hdfs
  @throws IOException