Can we have multiple scheduled thread pools in java?

Question

So basically i'm very new to multithreading. i want to schedule 5 tasks at different intervals. So i found out about the executer services which provide scheduling.

Starting five tasks at different interval. i'm not sure can be done.

And it might be possible that one or tasks may start at the same time. So i thought about creating multiple thread pools for all tasks. will they still collide? and what performance issue i might face if i start multiple thread pools Please guide on this too..!

So please help!

public class NewScheduler {

public static final Logger logger = Logger.getLogger(NewScheduler.class.getName());
static ScheduledExecutorService scheduledExecutorService;
List<ExecuterSchedulerBean> list = new ArrayList<>();
FanMonitorDao fanMonitorDao;

public static void proceed(){
    logger.info("NewScheduler || proceed || :-START");
    List<Runnable> runnableList = new ArrayList<>();

    NewScheduler scheduler = new NewScheduler();

    runnableList.add(new ActiveLinkChecker());
    runnableList.add(new SecondScheduler());
    runnableList.add(new ThirdScheduler());
    runnableList.add(new FourthScheduler());
    runnableList.add(new FifthScheduler());

    for(Runnable check : runnableList){
        try {
            scheduledExecutorService = Executors.newScheduledThreadPool(1);
            if(check instanceof ActiveLinkChecker){
                scheduler.schedulerTasks("linkChecker", check);
                ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                bean.setServiceName("linkChecker");
                bean.setScheduledExecutorService(scheduledExecutorService);
            }else if(check instanceof SecondScheduler){
                scheduler.schedulerTasks("secondChecker", check);
                ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                bean.setServiceName("secondChecker");
                bean.setScheduledExecutorService(scheduledExecutorService);
            }else if(check instanceof ThirdScheduler){
                scheduler.schedulerTasks("thirdChecker", check);
                ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                bean.setServiceName("thirdChecker");
                bean.setScheduledExecutorService(scheduledExecutorService);
            }else if(check instanceof FourthScheduler){
                scheduler.schedulerTasks("fourthChecker", check);
                ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                bean.setServiceName("fourthChecker");
                bean.setScheduledExecutorService(scheduledExecutorService);
            }else if(check instanceof FifthScheduler){
                scheduler.schedulerTasks("fifthChecker", check);
                ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                bean.setServiceName("fifthChecker");
                bean.setScheduledExecutorService(scheduledExecutorService);
            }
        } catch (SocketException e) {
            logger.info("Error in SchedularTaskServlet in Scheduling batches :-" + e);
            try {
                scheduledExecutorService = Executors.newScheduledThreadPool(1);
                if(check instanceof ActiveLinkChecker){
                    scheduler.schedulerTasks("linkChecker", check);
                    ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                    bean.setServiceName("linkChecker");
                    bean.setScheduledExecutorService(scheduledExecutorService);
                }else if(check instanceof SecondScheduler){
                    scheduler.schedulerTasks("secondChecker", check);
                    ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                    bean.setServiceName("secondChecker");
                    bean.setScheduledExecutorService(scheduledExecutorService);
                }else if(check instanceof ThirdScheduler){
                    scheduler.schedulerTasks("thirdChecker", check);
                    ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                    bean.setServiceName("thirdChecker");
                    bean.setScheduledExecutorService(scheduledExecutorService);
                }else if(check instanceof FourthScheduler){
                    scheduler.schedulerTasks("fourthChecker", check);
                    ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                    bean.setServiceName("fourthChecker");
                    bean.setScheduledExecutorService(scheduledExecutorService);
                }else if(check instanceof FifthScheduler){
                    scheduler.schedulerTasks("fifthChecker", check);
                    ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                    bean.setServiceName("fifthChecker");
                    bean.setScheduledExecutorService(scheduledExecutorService);
                }
            } catch (Exception ex) {
                logger.info("Error in SchedularTaskServlet in Scheduling batches :-" + ex, new Throwable());
                e.printStackTrace();
            }
            e.printStackTrace();
        } catch (SQLException e) {
            logger.info("Error in SchedularTaskServlet in Scheduling batches :-" + e);
            try {
                scheduledExecutorService = Executors.newScheduledThreadPool(1);
                if(check instanceof ActiveLinkChecker){
                    scheduler.schedulerTasks("linkChecker", check);
                    ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                    bean.setServiceName("linkChecker");
                    bean.setScheduledExecutorService(scheduledExecutorService);
                }else if(check instanceof SecondScheduler){
                    scheduler.schedulerTasks("secondChecker", check);
                    ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                    bean.setServiceName("secondChecker");
                    bean.setScheduledExecutorService(scheduledExecutorService);
                }else if(check instanceof ThirdScheduler){
                    scheduler.schedulerTasks("thirdChecker", check);
                    ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                    bean.setServiceName("thirdChecker");
                    bean.setScheduledExecutorService(scheduledExecutorService);
                }else if(check instanceof FourthScheduler){
                    scheduler.schedulerTasks("fourthChecker", check);
                    ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                    bean.setServiceName("fourthChecker");
                    bean.setScheduledExecutorService(scheduledExecutorService);
                }else if(check instanceof FifthScheduler){
                    scheduler.schedulerTasks("fifthChecker", check);
                    ExecuterSchedulerBean bean = new ExecuterSchedulerBean();
                    bean.setServiceName("fifthChecker");
                    bean.setScheduledExecutorService(scheduledExecutorService);
                }
            } catch (Exception ex) {
                logger.info("Error in SchedularTaskServlet in Scheduling batches :-" + ex, new Throwable());
                e.printStackTrace();
            }
            e.printStackTrace();
        } catch (Exception e) {
            logger.info("Error in SchedularTaskServlet in Scheduling batches :-" + e, new Throwable());
            e.printStackTrace();
        }
    }

    logger.info("NewScheduler || proceed || :-END");
}

private void schedulerTasks(String taskName, Runnable scheduler) throws SQLException, SocketException {
    logger.debug("NewScheduler || schedulerTasks || :-START");
    SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy kk:mm");
    Calendar cal = null;
    int weekDay = 0, weekMin = 0, weekHr = 0, runDay = 0, runHr = 0, runMin = 0, runDelay = 0;
    float runGap = 0;
    String flag = null;
    fanMonitorDao = new FanMonitorDaoImpl();
    try {
        SchedulerBean bean = fanMonitorDao.getScheduler(taskName);
        flag = (("A").equalsIgnoreCase(bean.getSchedulerStatus())?"Y":"N").trim();
        if (flag != null && flag.equalsIgnoreCase("Y")) {

            cal = Calendar.getInstance();
            weekDay = cal.get(Calendar.DAY_OF_WEEK);// get the Weekday , from 1 to 7
            weekHr = cal.get(Calendar.HOUR_OF_DAY);// get the Weekday , from 0 to 23
            weekMin = cal.get(Calendar.MINUTE);// get the Weekday , from 0 to 59
            System.out.println("Current Week Day is :->" + weekDay + ", Week Hrs:->" + weekHr + ", Week Min:->" + weekMin);
            runDay = (runDay=Integer.parseInt(bean.getSchedulerDay().trim())) == 0 ? weekDay : runDay;
            runHr = (runHr=Integer.parseInt(bean.getSchedulerHrs().trim()))== 0 ? weekHr : runHr;
            runMin = Integer.parseInt(bean.getSchedulerMin().trim());
            runGap = Float.parseFloat(bean.getSchedulerGap().trim());
            runDelay = Integer.parseInt(bean.getSchedulerDelay().trim());
            runDay = (runDay >= weekDay) ? (runDay - weekDay) : runDay + (7 - weekDay);
            runHr = (runHr >= weekHr) ? (runHr - weekHr) : runHr + (24 - weekHr);
            runMin = (runMin >= weekMin) ? (runMin - weekMin) : runMin - weekMin;
            System.out.println("Difference between current values and Property values are :-days:->" + runDay + " Hrs:->" + runHr + " Min:->" + runMin);
            cal.setTime(sdf.parse(sdf.format(new Date())));
            cal.add(Calendar.DATE, runDay);
            cal.add(Calendar.HOUR, runHr);
            cal.add(Calendar.MINUTE, runMin);
            runDay = Integer.parseInt(String.valueOf((cal.getTimeInMillis() - (sdf.parse(sdf.format(new Date()))).getTime())));
            System.out.println("Next First run time is :->" + runDay + "-->>" + runDelay * runGap * 60 * 60 * 1000);
            @SuppressWarnings("unused")
            ScheduledFuture<?> alarmFuture = scheduledExecutorService.scheduleWithFixedDelay(scheduler, (long) runDay, (long) ((long) runDelay * runGap * 60 * 60 * 1000), TimeUnit.MILLISECONDS);
        }
    } catch (Exception e) {
        logger.info("Error in SchedularTaskServlet in Scheduling batches :-" + e, new Throwable());
        e.printStackTrace();
    }
    logger.debug("NewScheduler || schedulerTasks || :-END");
}

}

this question should be helpful http://stackoverflow.com/questions/20387881/how-to-run-certain-task-every-day-at-a-particular-time-using-scheduledexecutorse — Praveen Kumar, Apr 06 '16 at 06:40
tushar try updating the question with code that you have tried also.. — Praveen Kumar, Apr 06 '16 at 07:17
k..give me a minute..the code is not complete but should be enough to understand the situation.! — tushar garg, Apr 06 '16 at 07:23
Multiple tasks with a single thread pool would be a good design and effective. — Praveen Kumar, Apr 06 '16 at 07:40
but then how will i schedule each task at different interval? @praveen — tushar garg, Apr 06 '16 at 07:44

Jens Schauder · Answer 1 · 2016-04-06T07:45:47.713

There is no problem in principle with using one ScheduledExecutorService. Also tasks starting at the same point in time shouldn't be a problem.

Depending on the number of tasks, and how resource intensive they are you might end up running out of threads (or CPU or IO ..), at which point tasks might get delayed. But you won't be able to fix that by creating a new ScheduledExecutorService.

Creating multiple such services makes only sense if you want isolate Tasks from each other. For example you have one Task which is really important, so you create a service with a thread pool size of 1 for this task. If you now take care that your application (including a ScheduledExecutorService for all other tasks), that Task should always be able to execute at the scheduled time. Please note that actually the overall utilization of threads decreases by this, so the overall timeliness and throughput will take a hit, because one thread is basically reserved for the high priority task.

@tushargarg I updated my answer to clarify the only reason I can come up with to create more then one service. — Jens Schauder, Apr 06 '16 at 07:46
So basically if i create more than one service. it might affect my TAT. — tushar garg, Apr 06 '16 at 07:48

Praveen Kumar · Answer 2 · 2016-04-06T06:44:07.293

0

You can use ScheduledThreadPoolExecutor

An ExecutorService that can schedule commands to run after a given delay, or to execute periodically.

ScheduledExecutorService

edited Apr 06 '16 at 06:44

answered Apr 06 '16 at 06:36

Praveen Kumar

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Had previously suggested using a Timer & TimerTask but then found that the ScheduledThredPoolExecutor has several advantages over the previous http://stackoverflow.com/questions/409932/java-timer-vs-executorservice?lq=1 – Praveen Kumar Apr 06 '16 at 06:46
i'm using the same only what i am asking is that can i create multiple instances of the same and hope that none of them collides and if they do what will happen..? – tushar garg Apr 06 '16 at 06:59
It should not be an issue the tasks wont collide. – Praveen Kumar Apr 06 '16 at 07:01
And is there any way to schedule a thread without using thread pool? – tushar garg Apr 06 '16 at 07:07
Timer and TimerTask would be the answer for that. – Praveen Kumar Apr 06 '16 at 07:16

Can we have multiple scheduled thread pools in java?

2 Answers2