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    <p>(I'm assuming that the idle threads you are talking about are application threads. If you are talking about Tomcat's worker threads, then they should not cause permgen problems when idle.)</p> <blockquote> <p>I tried to create a bug about this, but the NetBeans developer rejected it ... I am very surprise ...</p> </blockquote> <p>I'm very unsurprised. This is not really a NetBeans problem. It is not even really a Tomcat or JBoss problem. </p> <p>The problem with idle / orphaned application threads is that you cannot safely kill threads in a running JVM. And without the ability to do this you cannot stop leakages of (in this case) permgen space. This is essentially a Java platform problem. It can only be solved when JVMs support the Isolate mechanisms defined by JSR 121.</p> <p>But assuming that your problem is related to doing hot deployment, it is not just the idle application threads that you have to worry about. If there is <em>any</em> reachable instance of <em>any</em> class that you are redeploying, that will cause the original old class loader and all classes it loaded to remain reachable.</p> <blockquote> <p>... this is a big stopper to use NetBeans to develop web app. </p> </blockquote> <p>The solution is to restart your web container every now and then. This will clean out the idle threads and other cruft and release the leaked permgen space. You can ameliorate it by running with a larger heap and more permgen, but you cannot make it go away, especially if some of the orphaned threads are not idle ...</p> <p>Oh yea, and don't be a big baby! This ain't a show stopper, its just a small inconvenience :-) </p>
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    1. POWhat is wrong with runing app in tomcat server?
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    1. USStephen C
    1. USStephen C
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    1. COWhile I generally agree with your lack of surprise, it really has little to do with idle threads. Rather, it has to do with classes not, by default, being garbage collected. You can enable garbage collection of classes, if you really want to pay the price of the extra GC work. Generally, you won't want to do that in a production server, and personally, I'd rather just restart Tomcat from time to time (and set the max permgen space high enough that "from time to time" is not too frequent.
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    2. COThreads only enter into it, if they're actually running the user's code, and thus protecting it from GC, even if you enable GC of classes. And if THAT is the case, the user has a bad application; that's not how J2EE applications are supposed to work.
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    3. COIn a production server, you will only need enough permgen space for the code and associated data you actually use. It does not keep growing. What you are seeing is the impact of either deploying vast amounts of demo code, or repeatedly deploying. Raising your PermGen space will help you either way.
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