java.lang.OutOfMemoryError: PermGen space

austinium · 05-11-2011, 04:04 AM

I am running Tomcat(6.0.18)/jdk1.6.0_02, ~ after every couple of hours tomcat crashes with the following exception logged:

Code:

SEVERE: An exception or error occurred in the container during the request processing
java.lang.OutOfMemoryError: PermGen space

Google comes up with quite a lot of info on this, i haven't managed to find a conclusive solution to this though.

I have increased the PermGen size from it's default 64MB, and tomcat seems to be working "fine" now, however, theres quite a lot of info on the Internet pointing a possibility of tomcat crashing again as PermGen gets filled up gradually with the applications being deployed/undeployed/redeployed.

Is GC enabled on the PermGen memory area by default?
Would enabling GC on PermGen memory area using

Code:

-XX:+CMSPermGenSweepingEnabled

in JAVA_OPTS prevent PermGen from running out of memory with time? Also, would there be performance hit as a result of using this option?

Hoping to hear from your experience on this.

thanks

paulsm4 · 05-12-2011, 11:49 PM

Believe it or not, Java applications *can* have resource leaks ... and it sounds like you've got one of those apps.

STRONG SUGGESTION:
1. Identify the apps you have running on your Tomcat server

2. Try to identify which of the apps might be causing the problem
<= Key question: "What changed?" before the problem first manifested itself?

3. Debug that app

You absolutely need to get a copy of JConsole (Java 1.5 or lower) or VisualVM (Java 1.6 or higher):

http://java.sun.com/developer/techni...SE/monitoring/

http://download.oracle.com/javase/1..../jconsole.html

4. Here's another link that might help:
http://stufftohelpyouout.blogspot.co...ot-deploy.html

Quote:

Generally speaking, when you have a permgen "leak" across webapp redeployments, this is the situation:

1. Webapp invokes some code that stores a reference to the webapp's WebappClassLoader

2. That reference is not cleared during undeploy [this is the leak]

The big problem is that the WebappClassLoader keeps a reference to all java.lang.Class objects it loads, so it can be quite bulky when it leaks, depending on exactly how many classes your webapp has locally.

markt has a great presentation which lays out the anatomy of these types of memory leaks, how to diagnose them, and often how to fix them. These are slides from a presentation at last year's ApacheCon NA. It's /very/ readable.

http://people.apache.org/~markt/pres...aks-60mins.pdf

PS:
1. Run - don't walk. Get JConsole. Try it out.

2. Absolutely try to identify the app that might be responsible.

3. Do NOT try debugging further before you've completed steps 1) and 2)

paulsm4 · 05-13-2011, 10:48 PM

austinium -

Any headway on the Java PermGen issue?

Did you get a chance to try JConsole (or VisualVM)?

Thanx in advance .. PSM

PS:
I had a similar problem about a year and a half ago. It turned out to be a resource leak in a 3rd party .jar. The solution was to install a patch from the vendor.

austinium · 05-14-2011, 06:55 AM

Tomcat hasn't crashed after having increased PermGen. The PermGen memory usage has also more of less stable. There is just this one application running on tomcat.

I tried deploying the war file on Tomcat 6.0.32, this version has a listener which logs possible memory leak conditions, will be going through the log in depth once the weekends over. Most of the warnings seem to be related to our use of tomcat along with terracotta, we have a setup similar to the one mentioned here. So there are warnings about timers and processing buckets not being unloaded, i don't suppose these could be causing any trouble. Heres a pastebin to the part of the log with the warnings.

I must admit this is the first time i am doing this, your post has been very helpful. Would love to hear your thoughts on the log.

Thanks again