private void createSubDir(String propertyName, Path parent, String subDirName) {
    Path newPath = new Path(parent, subDirName);
    File newDir = new File(newPath.toString()).getAbsoluteFile();

    if (deleteOnExit()) {
      newDir.deleteOnExit();
    }

    conf.set(propertyName, newDir.getAbsolutePath());
  }
@return A dir with a random (uuid) name under the test dir
@see #getBaseTestDir()
hbase-diagnostics/src/main/java/org/apache/hadoop/hbase/util/WALPerformanceEvaluationUtil.java