Can you do me a favour and run with: 

-Dio.netty.recycler.maxCapacity=0

And let me know if you still see some leaks ?



> On 19 Jul 2016, at 20:50, Chris Conroy <[email protected]> wrote:
> 
> 4.1.0.Final
> 
> On Tue, Jul 19, 2016 at 2:48 PM, 'Norman Maurer' via Netty discussions 
> <[email protected] <mailto:[email protected]>> wrote:
> Are you using 4.0 or 4.1 ?
> 
>> On 19 Jul 2016, at 20:42, Chris Conroy <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
>> I have not been able to reproduce locally yet, but I do see it in a cluster 
>> that takes a lot of varied traffic. The leak detector has not fired for this 
>> under advanced. I will give paranoid a shot to be safe, but it's my 
>> understanding that the leak detection framework is more for dealing with 
>> pooled byte buf misuse, but in this case I am exclusively using unpooled 
>> heap byte bufs: these are just the socket direct byte bufs that appear to be 
>> leaking.
>> 
>> I meant to add this earlier: The path to GC root goes:
>> 
>> io.netty.buffer.ByteBufUtil$ThreadLocalUnsafeDirectByteBuf
>>   io.netty.util.Recycler$DefaultHandle
>>     io.netty.util.Recycler$DefaultHandle[]
>>       io.netty.util.Recycler#Stack
>>         java.lang.Object[]
>>           io.netty.util.internal.InternalThreadLocalMap
>>             ... (more thread local map refs up to java.lang.Thread)
>> 
>>         
>> 
>> On Tuesday, July 19, 2016 at 2:17:25 PM UTC-4, Norman Maurer wrote:
>> Can you provide a reproducer? Also did you try to run with paranoid leak 
>> detection
>> 
>> Am 19.07.2016 um 20:04 schrieb Chris Conroy <[email protected] <>>:
>> 
>>> Ah okay: I didn't see the calls to failFlushed since they occur above the 
>>> stanza I found suspicious. 
>>> 
>>> So, the above explanation is probably not correct. Still, I am seeing a 
>>> leak where DirectByteBufs are rooted to the recycler, and the speed at 
>>> which these buffers leak appears to be correlated with slow/partial readers.
>>> 
>>> On Monday, July 18, 2016 at 4:36:31 PM UTC-4, Norman Maurer wrote:
>>> failFlushed(...) should be called to fail and release all flushed messages.
>>> 
>>> Are you saying this not happens?
>>> 
>>> Am 18.07.2016 um 22:02 schrieb Chris Conroy <[email protected] <>>:
>>> 
>>>> I’ve been trying to track down a NIO memory leak that occurs in a Netty 
>>>> application I am porting from Netty 3 to Netty 4. This leak does not occur 
>>>> in the Netty 3 version of the application.
>>>> 
>>>> For now, I’m using only unpooled heap buffers in Netty 4, but NIO buffers 
>>>> do come into play for socket communication.
>>>> 
>>>> I’ve captured a few heap dumps from affected instances, and in each it 
>>>> appears that the leaked DirectByteBuf java objects are rooted in an 
>>>> io.netty.util.Recycler.
>>>> 
>>>> These buffers remain indefinitely: I can disable the application to drain 
>>>> traffic and force GCs, but the # of NIO buffers and NIO allocated space 
>>>> stays flat.
>>>> 
>>>> The issue is likely related to slow readers. However, the leak persists 
>>>> long after all channels have been closed.
>>>> 
>>>> I implemented a writability listener and the leak does appear to go away 
>>>> if I stop writing to a channel after it goes unwritable. This is good, but 
>>>> I’m still worried that this just makes the problem less likely since it’s 
>>>> still possible to write/flush and have pending data: writability just 
>>>> limits how much data will be buffered.
>>>> 
>>>> Digging into ChannelOutBoundBuffer I see the following stanza in close:
>>>> 
>>>> 
>>>> // Release all unflushed messages.
>>>> try {
>>>>     Entry e = unflushedEntry;
>>>>     while (e != null) {
>>>>         // Just decrease; do not trigger any events via 
>>>> decrementPendingOutboundBytes()
>>>>         int size = e.pendingSize;
>>>>         TOTAL_PENDING_SIZE_UPDATER.addAndGet(this, -size);
>>>> 
>>>>         if (!e.cancelled) {
>>>>             ReferenceCountUtil.safeRelease(e.msg);
>>>>             safeFail(e.promise, cause);
>>>>         }
>>>>         e = e.recycleAndGetNext();
>>>>     }
>>>> } finally {
>>>>     inFail = false;
>>>> }
>>>> clearNioBuffers();
>>>> This seems a bit curious to me: why are flushed buffers not released here? 
>>>> Since the leak seems to be rooted in the Recycler, this could be the 
>>>> culprit…What do you think?
>>>> 
>>>> 
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