How to run certain task every day at a particular time using ScheduledExecutorService?
As with the present java SE 8 release with it's excellent date time API with java.time these kind of calculation can be done more easily instead of using java.util.Calendar and java.util.Date.
- Use date time class's i.e. LocalDateTime of this new API
- Use ZonedDateTime class to handle Time Zone specific calculation including Daylight Saving issues. You will find tutorial and example here.
Now as a sample example for scheduling a task with your use case:
ZonedDateTime now = ZonedDateTime.now(ZoneId.of("America/Los_Angeles"));
ZonedDateTime nextRun = now.withHour(5).withMinute(0).withSecond(0);
if(now.compareTo(nextRun) > 0)
nextRun = nextRun.plusDays(1);
Duration duration = Duration.between(now, nextRun);
long initalDelay = duration.getSeconds();
ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
scheduler.scheduleAtFixedRate(new MyRunnableTask(),
initalDelay,
TimeUnit.DAYS.toSeconds(1),
TimeUnit.SECONDS);
The initalDelay is computed to ask the scheduler to delay the execution in TimeUnit.SECONDS. Time difference issues with unit milliseconds and below seems to be negligible for this use case. But you can still make use of duration.toMillis() and TimeUnit.MILLISECONDS for handling the scheduling computaions in milliseconds.
And also TimerTask is better for this or ScheduledExecutorService?
NO: ScheduledExecutorService seemingly better than TimerTask. StackOverflow has already an answer for you.
From @PaddyD,
You still have the issue whereby you need to restart this twice a year if you want it to run at the right local time. scheduleAtFixedRate won't cut it unless you are happy with the same UTC time all year.
As it is true and @PaddyD already has given a workaround(+1 to him), I am providing a working example with Java8 date time API with ScheduledExecutorService. Using daemon thread is dangerous
class MyTaskExecutor
{
ScheduledExecutorService executorService = Executors.newScheduledThreadPool(1);
MyTask myTask;
volatile boolean isStopIssued;
public MyTaskExecutor(MyTask myTask$)
{
myTask = myTask$;
}
public void startExecutionAt(int targetHour, int targetMin, int targetSec)
{
Runnable taskWrapper = new Runnable(){
@Override
public void run()
{
myTask.execute();
startExecutionAt(targetHour, targetMin, targetSec);
}
};
long delay = computeNextDelay(targetHour, targetMin, targetSec);
executorService.schedule(taskWrapper, delay, TimeUnit.SECONDS);
}
private long computeNextDelay(int targetHour, int targetMin, int targetSec)
{
LocalDateTime localNow = LocalDateTime.now();
ZoneId currentZone = ZoneId.systemDefault();
ZonedDateTime zonedNow = ZonedDateTime.of(localNow, currentZone);
ZonedDateTime zonedNextTarget = zonedNow.withHour(targetHour).withMinute(targetMin).withSecond(targetSec);
if(zonedNow.compareTo(zonedNextTarget) > 0)
zonedNextTarget = zonedNextTarget.plusDays(1);
Duration duration = Duration.between(zonedNow, zonedNextTarget);
return duration.getSeconds();
}
public void stop()
{
executorService.shutdown();
try {
executorService.awaitTermination(1, TimeUnit.DAYS);
} catch (InterruptedException ex) {
Logger.getLogger(MyTaskExecutor.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
Note:
-
MyTaskis an interface with functionexecute. - While stopping
ScheduledExecutorService, Always useawaitTerminationafter invokingshutdownon it: There's always a likelihood your task is stuck / deadlocking and the user would wait forever.
The previous example I gave with Calender was just an idea which I did mention, I avoided exact time calculation and Daylight saving issues. Updated the solution on per the complain of @PaddyD
In Java 8:
scheduler = Executors.newScheduledThreadPool(1);
//Change here for the hour you want ----------------------------------.at()
Long midnight=LocalDateTime.now().until(LocalDate.now().plusDays(1).atStartOfDay(), ChronoUnit.MINUTES);
scheduler.scheduleAtFixedRate(this, midnight, 1440, TimeUnit.MINUTES);
If you don't have the luxury of being able to use Java 8, the following will do what you need:
public class DailyRunnerDaemon
{
private final Runnable dailyTask;
private final int hour;
private final int minute;
private final int second;
private final String runThreadName;
public DailyRunnerDaemon(Calendar timeOfDay, Runnable dailyTask, String runThreadName)
{
this.dailyTask = dailyTask;
this.hour = timeOfDay.get(Calendar.HOUR_OF_DAY);
this.minute = timeOfDay.get(Calendar.MINUTE);
this.second = timeOfDay.get(Calendar.SECOND);
this.runThreadName = runThreadName;
}
public void start()
{
startTimer();
}
private void startTimer();
{
new Timer(runThreadName, true).schedule(new TimerTask()
{
@Override
public void run()
{
dailyTask.run();
startTimer();
}
}, getNextRunTime());
}
private Date getNextRunTime()
{
Calendar startTime = Calendar.getInstance();
Calendar now = Calendar.getInstance();
startTime.set(Calendar.HOUR_OF_DAY, hour);
startTime.set(Calendar.MINUTE, minute);
startTime.set(Calendar.SECOND, second);
startTime.set(Calendar.MILLISECOND, 0);
if(startTime.before(now) || startTime.equals(now))
{
startTime.add(Calendar.DATE, 1);
}
return startTime.getTime();
}
}
It doesn't require any external libs, and will account for daylight savings. Simply pass in the time of day you want to run the task as a Calendar object, and the task as a Runnable. For example:
Calendar timeOfDay = Calendar.getInstance();
timeOfDay.set(Calendar.HOUR_OF_DAY, 5);
timeOfDay.set(Calendar.MINUTE, 0);
timeOfDay.set(Calendar.SECOND, 0);
new DailyRunnerDaemon(timeOfDay, new Runnable()
{
@Override
public void run()
{
try
{
// call whatever your daily task is here
doHousekeeping();
}
catch(Exception e)
{
logger.error("An error occurred performing daily housekeeping", e);
}
}
}, "daily-housekeeping");
N.B. the timer task runs in a Daemon thread which is not recommended for doing any IO. If you need to use a User thread, you will need to add another method which cancels the timer.
If you have to use a ScheduledExecutorService, simply change the startTimer method to the following:
private void startTimer()
{
Executors.newSingleThreadExecutor().schedule(new Runnable()
{
Thread.currentThread().setName(runThreadName);
dailyTask.run();
startTimer();
}, getNextRunTime().getTime() - System.currentTimeMillis(),
TimeUnit.MILLISECONDS);
}
I am not sure of the behaviour but you may need a stop method which calls shutdownNow if you go down the ScheduledExecutorService route, otherwise your application may hang when you try to stop it.
Java8:
My upgrage version from top answer:
- Fixed situation when Web Application Server doens't want to stop, because of threadpool with idle thread
- Without recursion
- Run task with your custom local time, in my case, it's Belarus, Minsk
/**
* Execute {@link AppWork} once per day.
* <p>
* Created by aalexeenka on 29.12.2016.
*/
public class OncePerDayAppWorkExecutor {
private static final Logger LOG = AppLoggerFactory.getScheduleLog(OncePerDayAppWorkExecutor.class);
private ScheduledExecutorService executorService = Executors.newScheduledThreadPool(1);
private final String name;
private final AppWork appWork;
private final int targetHour;
private final int targetMin;
private final int targetSec;
private volatile boolean isBusy = false;
private volatile ScheduledFuture<?> scheduledTask = null;
private AtomicInteger completedTasks = new AtomicInteger(0);
public OncePerDayAppWorkExecutor(
String name,
AppWork appWork,
int targetHour,
int targetMin,
int targetSec
) {
this.name = "Executor [" + name + "]";
this.appWork = appWork;
this.targetHour = targetHour;
this.targetMin = targetMin;
this.targetSec = targetSec;
}
public void start() {
scheduleNextTask(doTaskWork());
}
private Runnable doTaskWork() {
return () -> {
LOG.info(name + " [" + completedTasks.get() + "] start: " + minskDateTime());
try {
isBusy = true;
appWork.doWork();
LOG.info(name + " finish work in " + minskDateTime());
} catch (Exception ex) {
LOG.error(name + " throw exception in " + minskDateTime(), ex);
} finally {
isBusy = false;
}
scheduleNextTask(doTaskWork());
LOG.info(name + " [" + completedTasks.get() + "] finish: " + minskDateTime());
LOG.info(name + " completed tasks: " + completedTasks.incrementAndGet());
};
}
private void scheduleNextTask(Runnable task) {
LOG.info(name + " make schedule in " + minskDateTime());
long delay = computeNextDelay(targetHour, targetMin, targetSec);
LOG.info(name + " has delay in " + delay);
scheduledTask = executorService.schedule(task, delay, TimeUnit.SECONDS);
}
private static long computeNextDelay(int targetHour, int targetMin, int targetSec) {
ZonedDateTime zonedNow = minskDateTime();
ZonedDateTime zonedNextTarget = zonedNow.withHour(targetHour).withMinute(targetMin).withSecond(targetSec).withNano(0);
if (zonedNow.compareTo(zonedNextTarget) > 0) {
zonedNextTarget = zonedNextTarget.plusDays(1);
}
Duration duration = Duration.between(zonedNow, zonedNextTarget);
return duration.getSeconds();
}
public static ZonedDateTime minskDateTime() {
return ZonedDateTime.now(ZoneId.of("Europe/Minsk"));
}
public void stop() {
LOG.info(name + " is stopping.");
if (scheduledTask != null) {
scheduledTask.cancel(false);
}
executorService.shutdown();
LOG.info(name + " stopped.");
try {
LOG.info(name + " awaitTermination, start: isBusy [ " + isBusy + "]");
// wait one minute to termination if busy
if (isBusy) {
executorService.awaitTermination(1, TimeUnit.MINUTES);
}
} catch (InterruptedException ex) {
LOG.error(name + " awaitTermination exception", ex);
} finally {
LOG.info(name + " awaitTermination, finish");
}
}
}