how to test netty memory leak

Question

I add -Dio.netty.leakDetection.level=ADVANCED for leak detecting on production. And there are some logs:

ERROR io.netty.util.ResourceLeakDetector - LEAK: ByteBuf.release() was not called before it's garbage-collected. See http://netty.io/wiki/reference-counted-objects.html for more information. WARNING: 4 leak records were discarded because the leak record count is limited to 4. Use system property io.netty.leakDetection.maxRecords to increase the limit. Recent access records: 5

Does it means it must will happen memory leak?

I want to test it on local environment, so I set -Dio.netty.leakDetection.level=PARANOID , but there are no the above memory leak records logs.

Answer 1

To detect leak on my development environment, I have reduce the heap size to 12 MB with this vm argument: -mx12m

Now with this, Netty is able to detect some leaks.

Answer 2

The log means that you have a memory-leak, so yes there is a leak. You can either configure leak detection via the system property (as you did) or via ResourceLeakDetector.setLevel(...) .

That you are not able to see the leak on your local machine may mean that you not see the same "allocation" patterns as on the prod server.