// format "ss mm hh" meaning at hh:mm:ss time of the day, we roll forward for DAILY rolling
// if it is hourly rolling, it means at mm:ss time of the hour, we roll forward
// if it is MINUTELY, it means at ss seond of the minute, we roll forward.
ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(1);
HourGlassScheduler scheduler = new HourGlassScheduler(frequency, schedule, appendOnly, trimThreshold);
HourglassDirectoryManagerFactory dirmgr = new HourglassDirectoryManagerFactory(partDir, scheduler,_dirMode);
log.info("creating Hourglass for nodeId: " + nodeId + " partition: " + partitionId);
return new Hourglass<BoboIndexReader,T>(dirmgr, _interpreter, _indexReaderDecorator, _zoieConfig, hourglassListeners, executor);
}