Memory leak in WebSocketImpl.outQueue

[martin-g]

Hi,

This is not a bug report or feature request but actually I'd like to ask for help debugging a possible memory leak.

In the following screenshot you can see that ~51% of the used heap is kept by WebSocketWorker and WebSocketImpl.

And here we see that actually WebSocketImpl#outQueue (with hashcode 0x7127e8b30) is the one keeping the memory.

Its size is 25320:

Debugging the code I've seen that outQueue is populated when I use org.java_websocket.WebSocket#send(java.lang.String) method. At that time there is a check whether the connection is still opened and WebsocketNotConnectedException is being thrown in case it is not. Then org.java_websocket.WebSocketImpl#write(java.nio.ByteBuffer) is called where there the buf is just put into outQueue.
Later in the run loop of org.java_websocket.server.WebSocketServer#run() the outQueue must be drained and actually sent to the client. In case of an error an IOException is thrown and org.java_websocket.server.WebSocketServer#onClose(WebSocket, int, String, boolean) callback is called.

One thing that I notice is that neither org.java_websocket.server.WebSocketServer#handleIOException() nor org.java_websocket.WebSocketImpl#closeConnection(int, java.lang.String, boolean) clear the contents of inQueue and outQueue. But I am not sure whether this is the reason for the huge out queues I have in the heap dump.

Do you have an idea what could be the problem and what I could do to debug more ?

I use version 1.3.8. I see that 1.3.9 is released and I will upgrade to it but I do not see anything that might fix it in the changelog.

For the heap analysis I use Eclipse Memory Analyzer (v 1.8.0).

Thank you!

[marci4]

Hello @martin-g,

thank you for your bug report!

Running everything with the profiler, I saw some left over references to WebSocketImpl instances.

The problem is in my eyes, that the WebSocketWorker is referencing an instance but will still keep it until a new WebSocketImpl instance is put into the queue and therefore gc cannot clean up everything.

I attached a patched version. Could you please check if this solves the issue. If not I may need additional steps to repeat!
Java-WebSocket-1.3.10-SNAPSHOT.zip

Best regards,
marci4

[martin-g]

Thank you, @marci4 !
I will test it soon!

Could you please push your changes in a branch so I can see them ?

[marci4]

Hello @martin-g,

you can find it here. Just merged it locally back to 1.3.9 for you.

Best regards,
marci4

[marci4]

@martin-g any news?

[martin-g]

I will take some heap dumps and take a look later today!

[martin-g]

Hi @marci4,

Everything looks in today's heap dump!
Thank you!