This leak resulted in exhaustion of 4G of NIO memory. The same application under Netty 3 only ever uses <200MB of NIO memory. I have run several experiments where I take some traffic, disable the node from serving traffic, and then force a full GC. The allocated NIO memory does not return to normal levels.
Spot checking the byte buf handles from my heap dump, I see lots (all?) `recycle` and `lastRecycleIds` of `int -2147483648 = 0x80000000` The experiment yesterday with the recycler disabled did not result in any such leaks over several hours of traffic. On Wed, Jul 20, 2016 at 12:41 AM, 'Norman Maurer' via Netty discussions < [email protected]> wrote: > Are you actually sure these are really leaked ? > > The point of the “ThreadLocalUnsafeDirectByteBuf” is that it can be > reused so it is expected that it not gets released after its written but > put back in the recycler. Or you saying there are too many of these ? > > > On 19 Jul 2016, at 22:39, Chris Conroy <[email protected]> wrote: > > Yes all the leaked buffers look to be ThreadLocalUnsafeDirectByteBuf > > Disabling the recycler w/o backpressure on slow readers resulted in > several massive allocation events. I was able to free them by forcing GC so > no leaks there. Memory usage with backpressure on slow readers is back down > to Netty 3 w/o backpressure levels. I don't see any leaks so far. > > Assuming that disabling the recycler does indeed prevent leaks, where do > we go from there? Any ideas of things to look for in my application that > might cause the recycler to get into a bad state? > > On Tue, Jul 19, 2016 at 3:40 PM, 'Norman Maurer' via Netty discussions < > [email protected]> wrote: > >> Btw all the “leaking” buffers are always: >> >> ThreadLocalUnsafeDirectByteBuf >> >> ? >> >> >> On 19 Jul 2016, at 21:29, Chris Conroy <[email protected]> wrote: >> >> I ran with paranoid while observing the leak and got no messages from the >> ResourceLeakDetector. >> >> Initial results from recycler maxCapacity of 0 are looking positive with >> respect to the leak. However, I did see a large spike of NIO memory >> allocated (1G) where the Netty 3 version of this app receiving similar >> traffic peaks at about 1/10th that. I'll let this run for a while and >> report back later with the full results. >> >> On Tue, Jul 19, 2016 at 2:59 PM, 'Norman Maurer' via Netty discussions < >> [email protected]> wrote: >> >>> 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]> wrote: >>> >>>> Are you using 4.0 or 4.1 ? >>>> >>>> On 19 Jul 2016, at 20:42, Chris Conroy <[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? >>>>>> >>>>>> >>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "Netty discussions" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>> send an email to [email protected]. >>>>>> To view this discussion on the web visit >>>>>> https://groups.google.com/d/msgid/netty/CA%2B%3DgZKADssKFcs-WCc8%2Br2RWrvbgg3csaJPdcsXL_mCD5yG2bg%40mail.gmail.com >>>>>> <https://groups.google.com/d/msgid/netty/CA%2B%3DgZKADssKFcs-WCc8%2Br2RWrvbgg3csaJPdcsXL_mCD5yG2bg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>>>> . >>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>> >>>>>> >>>>> -- >>>>> You received this message because you are subscribed to the Google >>>>> Groups "Netty discussions" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>> an email to 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