@Override
  public void onConfigurationChange(Configuration conf) {
    int newSize = conf.getInt(OLD_WALS_CLEANER_THREAD_SIZE, DEFAULT_OLD_WALS_CLEANER_THREAD_SIZE);
    if (newSize == oldWALsCleaner.size()) {
      LOG.debug(
        "Size from configuration is the same as previous which " + "is {}, no need to update.",
        newSize);
      return;
    }
    interruptOldWALsCleaner();
    oldWALsCleaner = createOldWalsCleaner(newSize);
    cleanerThreadTimeoutMsec = conf.getLong(OLD_WALS_CLEANER_THREAD_TIMEOUT_MSEC,
      DEFAULT_OLD_WALS_CLEANER_THREAD_TIMEOUT_MSEC);
  }
@param period    the period of time to sleep between each run
@param stopper   the stopper
@param conf      configuration to use
@param fs        handle to the FS
@param oldLogDir the path to the archived logs
@param pool      the thread pool used to scan directories
hbase-server/src/main/java/org/apache/hadoop/hbase/master/cleaner/LogCleaner.java