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POScheduling tasks, making sure task is ever being executed
 

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    <p>I have an application that checks a resource on the internet for new mails. If there is are new mails it does some processing on them. This means that depending on the amount of mails it might take just a few seconds to hours of processing. </p> <p>Now the object/program that does the processing is already a singleton. So right now I already took care of there really only being 1 instance that's handling the checking and processing.</p> <p>However I only have it running once now and I'd like to have it continuously running, checking for new mails more or less every 10 minutes or so to handle them in a timely manner. </p> <p>I understand I can take care of this with Timer/Timertask or even better I found a resource here: <a href="http://www.ibm.com/developerworks/java/library/j-schedule/index.html" rel="nofollow">http://www.ibm.com/developerworks/java/library/j-schedule/index.html</a> that uses Scheduler/SchedulerTask. But what I am afraid of.. is if I set it to run every 10 minutes and a previous session is already processing data it will put the new task in a stack waiting to be executed once the previous one is done. So what I'm afraid of is for instance the first run running for 5 hours and then, because it was busy all the time, after that it will launch 5*6-1=29 runs immediately after each other checking for mails and/do some processing without giving the server a break.</p> <p>Does anyone know how I can solve this? </p> <p>P.S. the way I have my application set up right now is I'm using a Java Servlet on my tomcat server that's launched upon server start where it creates a Singleton instance of my main program, then calls some method to do the fetching/processing. And what I want is to repeat that fetching/processing every "x" amount of time (10 minutes or so), making sure that really only 1 instance is doing this and that really after each run 10 minutes or so are given to rest.</p>
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    1. USDelimitry
    1. USMaurits
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    1. COwhy don't you try event based approach; so your scheduler class launches a task which can take variable amount of time; while launching this task it also registers a listener on which it would listen to process completion event; now when the mail processing task of variable durable is complete, the scheduler would be notified. The scheduler can then enqueue another task to trigger after 10 minutes. This will also ensure that unnecessary tasks aren't queued on the task queue.
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      1. USScorpion
 

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