code: @Override
      protected void subAppend(LoggingEvent event) {
  	super.subAppend(event);
  	if (res != null && qw != null) {
  	    long size = ((CountingQuietWriter) qw).getCount();
  	    if (size >= maxFileSize && size >= nextRollover) {
  		rollOver();
  	    }
  	}
      }
docs: This method differentiates RollingFileAppender from its super class.
  
  @since 0.9.0