And here I go ... Linux is Debian v3, with kernel 2.4.20, and jdk is 1.4.1_01 I don't have any native calls in my classes using
> Runtime (btw. I found some zombie problems on the web using > that class).
And symptoms of my problem if anyone is interested : This zombie behaviour don't disrupt my app or OS since it
> occures just few times per day in following fashion - all of > my app's threads function properly, but one zombie thread > keeps appearing and dissapearing ?! It didn't impose any > problems, but nonetheless I would like to get rid of it ..
I believe that's indeed the JVMs garbage collector. Nothing you can do about that in your code (or in avalon code), except watch for it and restart when you find one. I think. Not sure. Just guessing. Maybe running a testcase which creates and destroys lots of objects and calls System.gc() will get you some more info, ie, something like
testGC()
{
int num = 10000;
long pause = 10000; // millisSystem.out.println( "Creating " + num + " integer classes" );
Object[] list = new Object[num];
for( int i = 0; i < num; i++ )
{
list[i] = new Integer( i );
}System.out.println( "now sleeping for " + pause + "milliseconds" ); Thread.sleep( pause );
System.out.println( "dereferencing " + num + " integer classes" );
for( int i = 0; i < num; i++ )
{
list[i] = null;
}
list = null;System.out.println( "Now calling System.gc()" ); System.gc();
System.out.println( "now sleeping for " + pause + "milliseconds" ); Thread.sleep( pause );
System.out.println( "end of testGC()" ); }
(untested code). You could also try adding code like this somewhere in your actual application. If you get more zombie processes, you can assume it is the garbage collector :D
I found several reports on the web related to this, but nothing very informative.
For example, Costin (one of the tomcat hackers) writes @ http://www.webweavertech.com/costin/archives/cat_java.html:
"To recap: under load I got java "defunct processes" ( zombies ). I suspect this is related with the garbage collection and memory management, and of course a certain combination of libraries. I did try different kernels and glibc - including the exact same combination that works without problem on my other computer. Right now the only thing I can do is get the sources ( I remember they were available under scsl ) and see what's happening. A "clean" system works just fine, it is something I did or installed that created the problem - and no amount of reinstalling or checking libraries solved that."
my crappy advice: if it doesn't cause any problems, live with it.
- Leo
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