Need to restart timer with different time

[aanshu gupta]

Hi,
I have a requirement where in we need to create a timer which runs every 5 mins(default). This works fine and our operation runs fine every 5 mins.
The problem is we need to change this time duration based on user choice and this is what creates the problem.
We have tried stopping the timer by timer.cancel() and restarting it with the new passed time interval but this does not work.

Anyone having worked on similar requirements/ knows the workaround?
Please help.
Thanks

[aanshu gupta]

sorry forgot to mention this but we are using EJB 3.0 and Jboss 4.2

[Davide Crudo]

aanshu gupta wrote:Hi,
I have a requirement where in we need to create a timer which runs every 5 mins(default). This works fine and our operation runs fine every 5 mins.
The problem is we need to change this time duration based on user choice and this is what creates the problem.
We have tried stopping the timer by timer.cancel() and restarting it with the new passed time interval but this does not work.

Anyone having worked on similar requirements/ knows the workaround?
Please help.
Thanks

Remember that timers will survive the server restart...are you sure you didn't schedule multiple timers? It sounds like you cancelled one timer
but probably all other timers are still active.

How do you cancel the timer? do you assign a different name to each one of them?

[aanshu gupta]

We are creating only one instance of the timer. For this we use
@PoolClass(value = org.jboss.ejb3.StrictMaxPool.class, maxSize = 1)
This ensures we have only one timer object in the object pool.
For canceling timer am using :
for (Object timerObj : this.timerService.getTimers()) {
if (timerObj != null) {
Timer timer = (Timer) timerObj;
timer.cancel();
}
}
This cancels the timer.
What I am doing is on @Timeout method checking for a particular condition and based on that stoping and again restarting the timer with new time interval.
But the timer is not getting restarted. It waits till the next timeout method and then stops if the time interval has changed.
Thanks for your response.

[Davide Crudo]

Hi,

As a general rule, i don't think is a good idea to control the Pool size of the timers. The pool size is automatically managed
by the container.

From your code, i can see you cancel the timer but where do you re-create it?

could you post the complete @Timeout method?

Dave

[aanshu gupta]

@Timeout
public void timeout(Timer timer) throws Exception{
//Some code to retrieve a value from DB using JPA
int timeoutInterval ;//Some code to retrieve a value from DB using JPA
if(timeoutInterval != DEFAULT_TIMEOUT_VALUE){
stopTimer();
startTimer(timeoutInterval);
}
else
//Using the existing timeout interval and do the job.
}

public void startTimer(long timeperiod) {

int timerNum = this.timerService.getTimers().size();
if ( timerNum == 1)
return;
else if (timerNum > 1) {
stopTimer(); //stop all the old timers before launch new.
}
Timer timer = timerService.createTimer(new Date(), timeperiod, null);
}

public void stopTimer() {
for (Object timerObj : this.timerService.getTimers()) {
if (timerObj != null) {
Timer timer = (Timer) timerObj;
timer.cancel();
}
}
}

Thanks

[Davide Crudo]

I have the feeling that your timers overlap and autocancel, more specifically:

Timer timer = timerService.createTimer(new Date(), timeperiod, null); 

i would try to change it into:

Timer timer = timerService.createTimer(new Date(System.currentTimeMillis()+timeperiod), timeperiod, null); 

I think the timer is Scheduled for "now" then it runs and finds another timer running and it will cancel it.

As mentioned earlier, is better you name your timers so that you know which one you are cancelling, otherwise
with your code you are cancelling All timers and it will prevent you from using other timers efficiently. (to name
a timer, just change the 'null' field into a string or something)

I've prepared an example you can try out. This will cancel the current timer and re-create a new one each time:

package com.test.scheduler;

import java.io.Serializable;
import java.util.Date;

import javax.annotation.Resource;
import javax.ejb.SessionContext;
import javax.ejb.Stateless;
import javax.ejb.Timeout;
import javax.ejb.TimerService;

import org.jboss.seam.annotations.Name;

@Stateless
@Name("pingImpl")
public class PingImpl
                implements PingLocal, PingRemote, Serializable {

        private static final long serialVersionUID = 1105969164226368956L;
   
        @Resource
        SessionContext sessionContext;
        private static final String name = "Ping";

        public void doAction() {
                Long schedule = new Long(5000); //new timeout...
                TimerService timerService = sessionContext.getTimerService();
                System.out.println("++++ Initialize: AppTimers");
                removeTimer();
                System.out.println("Re-initialize Timers: Setting new timer : " + name);
                timerService.createTimer(new Date(System.currentTimeMillis()+schedule), schedule, name);
                System.out.println("++++ Initialize: Completed");
        }

        public void removeTimer() {
                TimerService timerService = sessionContext.getTimerService();
                for (Object obj : timerService.getTimers()) {
                        javax.ejb.Timer timer = (javax.ejb.Timer) obj;
                        String scheduled = (String) timer.getInfo();
                        System.out.println("-> Timer Found : " + scheduled);
                        if (scheduled.equals(name)) {
                                System.out.println("-> Removing old timer : " + scheduled);
                                timer.cancel();
                        }
                }
        }

        @Timeout
        public void timeout(javax.ejb.Timer timer) {
                System.out.println("Timed event called: " + name);
                doAction();
        }
}

[aanshu gupta]

Thanks a lot Davide.. It solved the problem.

[mani palani]

Hi,

requied to set future date in server. In my application, createTimer have keep on created timer in some fixed interval. say example, interval is 10000 milisencods, after 10 sec is ready to execute some business logic. but in intermeditate changing server time from future time to current time. so timer waits to further date, the timer is not running in as per the scheduled time period. if any idea to resolve this issue..... actually i wnat to reset the remaining if more than some fixed interval time, but i could not reset the remaining time value in timer. could you please help any one. Thansk in advance.