Ugh memory leak! This is what I encountered a couple days ago at work. My java application is not too complicated - parsing data, normalizing it, and then inserting into the database. Its a kinda "critical" application and should always be chugging away. Its a a very random occurrence and I haven't been able to re-produce it yet. Sometimes I get this error after 1 day, sometimes 10 days, and sometimes none at all ( or like maybe at infinity ).
So one of the 2 causes of OOM is inadequate heap space - so I allocated more and ran the app, this time with the Xms and Xmx arguments. It ran for a longer time but again crashed with the OOM error. OK so time to look into the second reason - Memory Leak.
I looked around for a decent profiling tool, and downloaded JProfiler. It's free for 10 days and I hope I can figure out what the issue is before that. Installing it on my RedHat box was a piece of cake, but setting up the environment wasn't! Anyway, after setting it up, I started it. Way too cool!! ( Not the debugging/diagnostic part of the analysis ) I haven't really had experience with JProfiler so this is very new to me. The amount of data that is available is very impressive (and in pretty colors too ;) ). Tons of different views and graphs to help make the software more efficient and memory-leak free. Looks like I am going to be using the Heap stack view in my search for the memory leak.
Right now, I am familiarizing myself with this tool, reading up on what should be my best approach. It's more of an art to find the runway non-GC'ed variables than science! A couple of things I am going to take a look at - objects like String, HashMapEntry, Char, Long maybe a problem due to their growing numbers (but maybe thats valid ?), database connection pooling and result sets not getting closed properly....
I am looking forward to playing around with JProfiler, but not as much to finding this "random" memory leak.
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Check out YourKit Java Profile as well. It is in the same price range, and is very capable.
Kewl I will. I got a few clues, but I need more time to do rigorous testing => my license ran out! So I downloaded it one more time, so lets see now.
what was the root cause of your problem sonali?
Pratik,
There were tons of problems with the code! They were mainly due to a bad threading design, where variables were shared so much that over time, we got an OOM.
This is mainly due to small size of permanent generation of heap.just increase size by using JVM option -XX:MaxPermSize=256m" as shown how to solve OutOfMemoryError in java
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