public int getCacheSize() {
    return CACHE.size();
  }
Returns the {@link FileArchiverNotifier} instance for the given {@link TableName}.
@param tn The table to obtain a notifier for
@return The notifier for the given {@code tablename}.
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/FileArchiverNotifierFactoryImpl.java