Finding memory leaks in java

Question

Hello,
I have a memory leak in my application. I have found other memory leaks in the software using JProfiler, but I have a problem with JProfiler finding this one. My biggest problem is the JProfiler itself. If I use short runs, the JProfiler works fine. If I run my application for more than half a day, the JProfiler eats up memory and after a while it stops responding.
I tried JProbe, but after profiling my application for 18 hours straight, it got buggy and wouldn't work correctly. It also ate up alot of memory, and couldn't process my snapshot after 18 hours of run. I saved all snapshots, and restarted JProbe. The initial snapshot was read correctly, but the final snapshot threw an NegativeArraySizeException.
So, now I am looking for other tools which are able to find memory leaks without hanging or crashing after running 24 hours. Any recommendations?

Answer 1

I dont know any other profiler you can use, but how about using the divide and conquer approach?
Disable a significant section of your application and let it run for a day. If the leak occurs, its in the non disabled part.
If it doesn't, its in the disabled part. Next, enable all the code. Then disable about half of the half that failed and try that. Continue doing so until
you isolate the code enough that you can look at it and hopefully find the problem. Note you will need to keep track of what you previously enabled and disabled as a test (I put comments in the code).
Alternately, you can look at functions that perform complex functionality that you suspect might be the problem and have the function return
dummy data rather than perform the functionality. If the leak goes away, its that function(s).
Example:
public String getComplexData(String arg1, String arg2){
//this section bypasses the complex code and returns dummy data
boolean x1= true;
if(x1==true)
return new String("some dummy data");
//complex functionality goes here.
Also of help would be to list everything that can cause a memory leak (I assume its a memory leak and not a resource leak such as not closing connections).
Here are some ideas:
1) persistant class variables that are a collection that have objects added to them but never deleted and allowed to be garbage collected
such as static class variables, session scope variables, or application scope variables.
2) An object tree where one of its nodes is never set to null to be garbage collected (such as a static class variable).
If you are running a web application in a clustered enviornment, try running it on only one server.