Hi All,

I am using hibernate 2.1.2 with cglib 2.01 and tomcat 5.

When I redeploy my war I see that my memory usage is growing.
I investigated it and I came to conclusion that the jvm is not destructing my war classes because it can not destruct the WebappClassLoader, and it can not destruct the WebappClassLoader because there are hard references to it from cglib.

Meaning there is some kind of loop, the WebappClassLoader have references to the cglib classes and the cglib classes have refrences to the WebappClassLoader.

There is an option to use hibernate without cglib?
Did any one has the same problem and/or have a solution to it?

Avi

Discuss this on the cglib forums/mailinglists please. You can try hibernate.cglib.use_reflection_optimizer=false in your hibernate.properties and not using proxys.

I will ask the question in th cglib forum, but the peoblem still exists!
Can I use hibernate without cglib?

As I said, You can try hibernate.cglib.use_reflection_optimizer=false in your hibernate.properties and not using proxys. But i don't know if that solves the problem.

I tried that but it didn't solve the problem.
Any other suggestions?

No

So it mean that anyone who use hibernate and need to redeploy his application for several times must expect OutOfMemoryError sometime.

I would expect from skilled people like hibernate guys not to use problematic frameworks because it's very unprofessional, even though hibernate is free.

Please do not use Hibernate, this project is intended for people with a basic level of respect for others, and basic problem solving skills.

Christian please ban this guy.

Try to download cglib 2.0.1, I am sure this version will not cause memory leak after redeploy (tested), but cglib 2 causes it (tested too).

I see you use cglib 2.01, it must drop classloader (if it is not loaded by the same classloader itself).
Are you sure there is no "old" jar, Proxool depends on cglib too.

Just an FYI... we use cglib-full-2.0.2.jar, and we still see CGLIB generated proxies never getting garbage collected. I am using JProfiler to watch memory usage.

Also, it seems dom4j has some caches it never cleans up, as we see the edu.oswego.* classes grow in usage, and they are traced back to dom4j's NamespaceCache.

So there are at least 2 reasons why Hibernate leaks memory on webapp redeploys, but both are not directly hibernate, but jars hibernate uses (cglib and dom4j).

Try to isolate and reproduce it in test case, watching memory usage with doe's not help to fix bugs.

It's easy to reproduce... just create a simple Hibernate app and redeploy using your container's hot deploy mechanism. You will receive an OOM Exception after a limited (< 20) number of redeploys (depending on how much memory you have given to your container, of course).

The problem is the web application classloader is never garbage collected. We believe this is because dom4j uses threadlocals internally and never cleans them up. This essentially binds a class loaded by the (transient) web application classloader into a container's thread. Since the container's thread never dies, the classloader never goes away.

We're still performing tests to verify it's dom4j's problem. We're nearly certain.

have anyone found a solution???

Actually, I think there is a solution now.

- upgrade to latest DOM4J (1.6.1 ?)
- upgrade to latest CGLIB (I forget)
- do one of the following:

- put your database drivers into your app server classpath, and keep them out of your webapp

OR

- keep them in your webapp, but unload the drivers on webapp redeploy. You can do this pretty easily with a servlet context listener. Use this: http://www.patrickpeak.com/page/patrick ... is_leaking

Also,

it's a classloader issue. Don't share classloaders. Also, don't put anything into ThreadLocal you can't guarantee you can take out.