Memory leak when redeploying application in Tomcat

Tomcat is usually not a good option on production environments. I was using Tomcat on a few production applications and I found that even if the heap size and other configurations are properly setup - and every time you reload your application, the memory consumption goes up and up. Until you don't restart the tomcat service, memory is not fully reclaimed. We did testing all such experiments like, clearing logs, redeploying all apps, regularly restarting tomcat once a month or a week during least busy hours. But at the end I have to say that we have shifted our production environments to Glassfish and WebSphere.

I hope you would already have gone through these pages:

Memory leak in a Java web application

Tomcat Fix Memory Leak?

https://developers.redhat.com/blog/2014/08/14/find-fix-memory-leaks-java-application/

http://www.tomcatexpert.com/blog/2010/04/06/tomcats-new-memory-leak-prevention-and-detection

If your web applications are not tightly coupled with Tomcat then you can think of using another web container. Now we use the Glassfish even on development machines and production and the day we make this decision, we saved a lot of our time. Though Glassfish and other such server take more time while they start as they are not as lightweight as the Tomcat is but after life is bit more easy.

From my experience with this problem, what was preventing tomcat to properly GC older class loaders was some ThreadLocals a couple of frameworks I was using were creating (and not properly handling).

Something similar to what is explained here: ThreadLocal & Memory Leak

I tried to properly finalize this ThreadLocals and my leak reduced A LOT. It was still leaking, but I could handle 10 times more redeploys than before.

I would definitely check your memory dumps to objects that could be connected somehow to ThreadLocals (they are very common, specially if you use something to control transactions or anything that is thread-isolated).

I hope it helps!

Memory leak in tomcat's redeploing is very old problem. The only real way to solve it is restart tomcat instead of redeploy application. If you have several apps you need to run several tomcat's services on different ports and join it with nginx.