Duplicate Timers in JBOSS

[Stu Quinn]

Good day,

I have used Quartz with no real problems in Tomcat. Now I am using EJB3 over JBOSS 4.2.2 and it looks straight-forward, however I have run into an issue. I seem to end up with multiple instances of the timer. After I have deployed / restarted several times I end up with my job executing repeatedly. Obviously I am not approaching this correctly as the JBOSS is persisting the timer (which is nice), but I am somehow generating duplicates.

First I am creating my timed job the first time my session bean is initialized. Below is my code:

    
			// Run the cron job starting 1 hour after startup and 1 hour thereafter
			TimerService timer=ctx.getTimerService();
			Date now = new Date();
			Long oneHour = 60L*60L*1000L;
			// First execution time should be now plus one hour
			Date firstTimeToExecute = new Date(now.getTime() + oneHour);
			timer.createTimer(firstTimeToExecute,oneHour,null);

So far, so good, or so I thought. After multiple redeploys and restarts when working on my code I found that the job was running repeatedly with multiple different timer IDs. Following is the log:


16:25:51,566 INFO [PromisPartSpecBean] scheduledJob(Timer timer=[id=1251501729393,target=[target=jboss.j2ee:service=EJB3,ear=OnPromisPartSpecEAR.ear,jar=OnPromisPartSpec.jar,name=PromisPartSpecBean],remaining=17546,periode=60000,canceled_in_tx]) - end
16:25:51,597 INFO [PromisPartSpecBean] updateFwPlans() - end
16:25:51,597 INFO [PromisPartSpecBean] scheduledJob(Timer timer=[id=1251501729637,target=[target=jboss.j2ee:service=EJB3,ear=OnPromisPartSpecEAR.ear,jar=OnPromisPartSpec.jar,name=PromisPartSpecBean],remaining=34179,periode=60000,canceled_in_tx]) - end
16:25:51,644 INFO [OnFwPartSpecBean] init() - start
16:25:51,644 INFO [OnFwPartSpecBean] init() - end
16:25:51,644 INFO [OnFwPartSpecBean] findFwPlans() - start
16:25:51,644 INFO [FwPartSpecDataDelegate] findFwPlans() - start
16:25:51,644 INFO [PromisPartSpecBean] updateFwPlans() - end
16:25:51,644 INFO [PromisPartSpecBean] scheduledJob(Timer timer=[id=1251501729709,target=[target=jboss.j2ee:service=EJB3,ear=OnPromisPartSpecEAR.ear,jar=OnPromisPartSpec.jar,name=PromisPartSpecBean],remaining=34382,periode=60000,canceled_in_tx]) - end
16:25:51,706 INFO [PromisPartSpecBean] updateFwPlans() - end
16:25:51,722 INFO [PromisPartSpecBean] scheduledJob(Timer timer=[id=1251501729407,target=[target=jboss.j2ee:service=EJB3,ear=OnPromisPartSpecEAR.ear,jar=OnPromisPartSpec.jar,name=PromisPartSpecBean],remaining=33210,periode=60000,canceled_in_tx]) - end
16:25:52,175 INFO [FwPartSpecDataDelegate] findFwPlans() - end
16:25:52,175 INFO [OnFwPartSpecBean] findFwPlans() - end
16:25:52,285 INFO [PromisPartSpecBean] updateFwPlans() - end
16:25:52,285 INFO [PromisPartSpecBean] scheduledJob(Timer timer=[id=1251501729560,target=[target=jboss.j2ee:service=EJB3,ear=OnPromisPartSpecEAR.ear,jar=OnPromisPartSpec.jar,name=PromisPartSpecBean],remaining=-1384392,periode=60000,canceled_in_tx]) - end

I am obviously missing some basic aspect about creating and managing timers. I would sure appreciate a little help here.

Thanks,
Stu

[Ankit Garg]

I think you are starting the timer each time your application starts. Obviously jBoss is persisting your timers (which you know). So basically do you want to turn of timer persistence or you can get a list of all timers, and then check if your timer is already running??

[Stu Quinn]

Ankit,

I would like to retain persistence of the timers within the app serve, so yes what I am looking for is how to query the timer service to determine if my timer already exists. I would then check the persisted timer to see if the interval was the same. If it is the same then I will not create it again. If I had changed the interval I would delete the prior instance of the timer and create it again.

Thank you for taking time to help. Life is good at the ranch.
Stu

[Ankit Garg]

In your bean try using TimerService.getTimers(), that will return a list of timers, then you can check the next timeout of the timers using Timer.getNextTimeout(). I've never tried this but I had read it so should work I think...

[Stu Quinn]

This was just what I needed. From the JavaDoc:

getTimers()
Get all the active timers associated with this bean.

I had expected the Timer to include the interval, but no such luck. However, when you create the timer you can pass an object so I just passed in the interval in for the 'info' parameter and now I am able check to see if the interval has changed. If so I clear the timer and re-create it, otherwise I take no action. Here is the code.

		// Prep criteria for the cron job
		boolean timerExists = false;
		Date now = new Date();
		// Execute every hour
		Long oneHour = 60*60L*1000L;
		// Explicitly set interval which affects time of first and subsequent executions.
		Long interval = oneHour;
		// The first execution should be 1 hour after startup the session is activated
		Date firstTimeToExecute = new Date(now.getTime() + interval);
		
		// When the timer is created the interval is passed in. If the interval has 
		// changed then clear the timer and we will re-create. Also, utilize a flag just
		// in case we had for some reason ended up with duplicates of the timer.
		for (Object obj : timerSvc.getTimers()) {
			Timer timer = (Timer) obj;
			if ( timer.getInfo() != null && timer.getInfo().toString().equals(interval.toString())) {
				timerExists = true;

				logger.info("Timer already exists. Executes every " + interval / (60 * 1000) + " minute(s).");
			} else {
				logger.info("Canceled a timer that was a duplicate or the interval was changed.");
				timer.cancel();
			}
		}

		if ( ! timerExists) {
			// Pass in the interval as info we can reference when querying timers (see above)
			timerSvc.createTimer(firstTimeToExecute,interval, interval);
			logger.info("Created timer to execute every " + interval / (60 * 1000) + " minute(s).");
		}

Lastly, the use of the TimerService is not supported in an @PostConstruct method. It might work some of the time, but may also throw some unexpected errors.

All is well.