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null LEAKING ClassLoader [message #748138] Mon, 24 October 2011 14:09 Go to next message
stefano zanchin is currently offline stefano zanchin
Messages: 2
Registered: October 2011
Junior Member
Hi guys,
during memory analizer of our application deployed in IBM WAS 6.1.
I found end fix same memory leak, static class and reference of object Circular and complex bi-directional references, cleaning object in click of the menu(not related to login), fix release of sessionMemoryObject in change site/close windows.
So now I don't have more idea for reduce usage memory..
We have a JEE EAR web application with more than one Java Jar project made by us and we using this principal thirt part lib icefaces,jsf,facelets,spring,hibernate,cxf ecc. with JRE 1.5.

We have yet OutOfMemory(OOM) during automatic test case Sad

My last step of analisys is..

start test in my local Server, after 30 minute, stop test and verify status of memory in server, forcing dump of memory server.

Now my question:
what is null LEAKING LOADER?(see attachment)

is a classLoader memory leak?

how can I understand and solve this type of issue!? (If it is a issue..)

many Thanks, Ste

P.s. when I post more that 5 message I can put also the image and Link, if required.
Re: null LEAKING ClassLoader [message #753437 is a reply to message #748138] Thu, 27 October 2011 09:24 Go to previous messageGo to next message
Andrew Johnson is currently offline Andrew Johnson
Messages: 122
Registered: July 2009
Senior Member
I don't recognize the text 'LEAKING LOADER' from the standard installation of MAT.

Are you using the IBM Extensions for Memory Analyzer ?
New! IBM Extensions for Memory Analyzer

This blog entry shows a "WebSphere Application Server" > "Application Class Loader leaks" query which might help.

Otherwise try paths to GC roots to see why the loader is still alive.
Re: null LEAKING ClassLoader [message #753732 is a reply to message #753437] Fri, 28 October 2011 14:30 Go to previous messageGo to next message
stefano zanchin is currently offline stefano zanchin
Messages: 2
Registered: October 2011
Junior Member
First of all, Andrew, thank for your reply.
I think that null LEAKING LOADER was generate because I have analyse a PHD (Portable Heap Dump).
We now try reduce Heap memory of JVM and set server for generate System dump, hoping for better luck.
I also suggest read this good link
www.ibm.com/developerworks/opensource/library/j-memoryanalyzer/index.html#ibm-pcon

p.s.
If I try action Path to GC Roots in some Object, with PHD, it show only che object selected and a not usefull information Unknown

Best regard, Ste.
Re: null LEAKING ClassLoader [message #756722 is a reply to message #753732] Mon, 14 November 2011 19:54 Go to previous message
Kevin Grigorenko is currently offline Kevin Grigorenko
Messages: 1
Registered: November 2011
Junior Member
Stefano, the "null LEAKING LOADER" is indeed part of the IBM Extensions for Memory Analyzer (IEMA) plugins. IEMA has a name resolver for instances of com.ibm.ws.classloader.CompoundClassLoader. The resolver will run some heuristics to see if the CompoundClassLoader is likely to be a leak. The reason it says "null" in front of LEAKING LOADER is that we try to get the name of the application but with a PHD there are no Strings. I will modify it to not print null. We have recently revamped the leaking classloader analysis, so to further investigate, run IBM Extensions > WebSphere Application Server > Class Loaders > Path to Leaking Application Classloaders.

Basically, this is usually caused by a static object or ThreadLocal holding a reference to something in the class graph of the CompoundClassLoader (or a child CompoundClassLoader). This means that if you update an application or stop an application, the CompoundClassLoader cannot be garbage collected. If this happens enough, this can cause native or Java OutOfMemoryErrors.
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