question: public synchronized void initTaskSchedulerIfNot ( ) { if ( scheduler == null ) { scheduler = Executors . newSingleThreadScheduledExecutor ( DaemonThreadFactory . getInstance ( ) ) ; CapacityAwareTaskScheduler runner = new CapacityAwareTaskScheduler ( ) ; scheduler . scheduleAtFixedRate ( runner , ParallecGlobalConfig . schedulerInitDelay , ParallecGlobalConfig . schedulerCheckInterval , TimeUnit . MILLISECONDS ) ; logger . info ( "initialized daemon task scheduler to evaluate waitQ tasks." ) ; } }
target:  as it is daemon thread TODO when release external resources should shutdown the scheduler.