I removed the httptrace call yesterday and there have been no OOMs yet. Going to let it bake for another day. If OOMs show up again, I'll try reverting to an older Go version tomorrow. Otherwise I'll point my finger at httptrace I guess.
On Tue, Jul 2, 2019 at 2:15 PM Yunchi Luo <yunchi...@squareup.com> wrote: > I did try to do that! I have 3 heap profiles captured from the ~3 seconds > before crash. The only thing particularly suspicious is the httptrace call > I mentioned earlier in the thread. > > Diffing 1 to 2 > (pprof) cum > (pprof) top 50 > Showing nodes accounting for 4604.15kB, 81.69% of 5636.17kB total > flat flat% sum% cum cum% > 0 0% 0% 5120.16kB 90.84% > net/http/httptrace.(*ClientTrace).compose.func1 > 0 0% 0% 5120.16kB 90.84% reflect.Value.Call > 0 0% 0% 5120.16kB 90.84% reflect.Value.call > 0 0% 0% 5120.16kB 90.84% reflect.callReflect > 5120.16kB 90.84% 90.84% 5120.16kB 90.84% reflect.funcLayout.func1 > 0 0% 90.84% 5120.16kB 90.84% reflect.makeFuncStub > 0 0% 90.84% 4604.15kB 81.69% sync.(*Pool).Get > 0 0% 90.84% -516.01kB 9.16% io.Copy > 0 0% 90.84% -516.01kB 9.16% io.copyBuffer > 0 0% 90.84% -516.01kB 9.16% io/ioutil.devNull.ReadFrom > -516.01kB 9.16% 81.69% -516.01kB 9.16% io/ioutil.glob..func1 > > Diff 2 to 3 > (pprof) top 50 > Showing nodes accounting for 7680.44kB, 100% of 7680.44kB total > flat flat% sum% cum cum% > 0 0% 0% 6144.18kB 80.00% > net/http/httptrace.(*ClientTrace).compose.func1 > 0 0% 0% 6144.18kB 80.00% reflect.Value.Call > 0 0% 0% 6144.18kB 80.00% reflect.Value.call > 512.01kB 6.67% 6.67% 6144.18kB 80.00% reflect.callReflect > 0 0% 6.67% 6144.18kB 80.00% reflect.makeFuncStub > 5632.17kB 73.33% 80.00% 5632.17kB 73.33% reflect.funcLayout.func1 > 0 0% 80.00% 5632.17kB 73.33% sync.(*Pool).Get > 0 0% 80.00% 1024.23kB 13.34% > github.com/aws/aws-sdk-go/aws/request.(*HandlerList).Run > 0 0% 80.00% 1024.23kB 13.34% > github.com/aws/aws-sdk-go/aws/request.(*Request).Send > 0 0% 80.00% 1024.23kB 13.34% > github.com/aws/aws-sdk-go/aws/request.(*Request).Sign > 0 0% 80.00% 1024.23kB 13.34% > github.com/aws/aws-sdk-go/aws/signer/v4.(*signingCtx).build > 0 0% 80.00% 1024.23kB 13.34% > github.com/aws/aws-sdk-go/aws/signer/v4.SignSDKRequest > 0 0% 80.00% 1024.23kB 13.34% > github.com/aws/aws-sdk-go/aws/signer/v4.SignSDKRequestWithCurrentTime > 0 0% 80.00% 1024.23kB 13.34% > github.com/aws/aws-sdk-go/aws/signer/v4.Signer.signWithBody > 0 0% 80.00% 1024.23kB 13.34% > github.com/aws/aws-sdk-go/service/dynamodb.(*DynamoDB).GetItemWithContext > > On Tue, Jul 2, 2019 at 2:08 PM andrey mirtchovski <mirtchov...@gmail.com> > wrote: > >> What I have found useful in the past is pprof's ability to diff profiles. >> That means that if you capture heap profiles at regular intervals you can >> see a much smaller subset of changes and compare allocation patterns. >> >> On Tue, Jul 2, 2019, 10:53 AM 'Yunchi Luo' via golang-nuts < >> golang-nuts@googlegroups.com> wrote: >> >>> I'm not so much pointing my finger at GC as I am hoping GC logs could >>> help tell the story, and that someone with a strong understanding of GC in >>> Go could weigh in here. In the last 4 seconds before OOM, "TotalAlloc" >>> increased by only 80M, yet "HeapIdle" increased to 240M from 50M, RSS >>> increased by 810M. The numbers don't add up for me. A running sum of 80M of >>> heap objects were allocated in the time RSS increased by 10X that. If GC >>> was completely off, I still wouldn't expect this to happen, which makes me >>> want to rule out GC being blocked as a problem. Maybe there was runaway >>> heap reservation because something in my code caused a ton of >>> fragmentation? Is that sane? The heap profile lacking clues is also strange. >>> >>> Regarding the possibility of a race, I forgot I do have goroutine >>> profiles captured along with the heap profiles at the time memory exploded. >>> There are only 10 goroutines running on the serving path, which rules out >>> too many concurrent requests being served (please correct me if I'm wrong). >>> Those fan out to 13 goroutines talking to the db, all of which are in >>> http.Transport.roundTrip (which is blocked on runtime.gopark so I assume >>> they are waiting on the TCP connection). All other goroutines that don't >>> originate in the stdlib are also blocked on `select` or sleeping. Our CI >>> does run with go test -race, but I'll try doing some load testing with a >>> race detector enabled binary. >>> >>> Bakul, that is sound advice. I've actually been debugging this on and >>> off for a couple months now, with the help of several people, a few of >>> which have peer reviewed the code. I agree it's most likely to be some >>> runaway code that I caused in my logic, but we haven't been able to >>> pin-point the cause and I've run out of hypothesis to test at the moment. >>> This is why I've started asking on go-nuts@. The circuit breaker code >>> was one of the first things I checked, has been unit tested and verified >>> working with load tests. Now that you mention it, I actually did uncover a >>> Go stdlib bug in http2 while doing the load tests... but that's unrelated. >>> >>> >>> On Tue, Jul 2, 2019 at 2:24 AM Bakul Shah <ba...@bitblocks.com> wrote: >>> >>>> Before assuming it is the GC or something system related, you may wish >>>> to verify it is *not your own logic*. Larger RSS could also be due to your >>>> own logic touching more and more memory due to some runaway effect. The >>>> probability this has to do with GC is very low given the very widespread >>>> use of Go and the probability of a bug in new code is very high given it is >>>> used on a much much smaller scale. >>>> >>>> This has the "smell" of a concurrency bug. If I were you I'd test the >>>> code for any races, I'd review the code thoroughly with someone who doesn't >>>> know the code so that I'm forced to explain it, and I'd add plenty of >>>> assertions. I'd probably first look at the circuit breaker code -- things >>>> like how does it know how many concurrent connections exist? >>>> >>>> In general, any hypothesis you come up with, you should have a test >>>> that *catches* the bug given the hypothesis. Elusive bugs tend to become >>>> more elusive as you are on the hunt and as you may fix other problems you >>>> discover on the way. >>>> >>>> I even suspect you're looking at GC logs a bit too early. Instrument >>>> your own code and look at what patterns emerge. [Not to mention any time >>>> you spend on understanding your code will help improve your service; but >>>> better understanding of and debugging the GC won't necessarily help you!] >>>> >>>> On Jul 1, 2019, at 12:14 PM, 'Yunchi Luo' via golang-nuts < >>>> golang-nuts@googlegroups.com> wrote: >>>> >>>> Hello, I'd like to solicit some help with a weird GC issue we are >>>> seeing. >>>> >>>> I'm trying to debug OOM on a service we are running in k8s. The service >>>> is just a CRUD server hitting a database (DynamoDB). Each replica serves >>>> about 300 qps of traffic. There are no memory leaks. On occasion (seemingly >>>> correlated to small latency spikes on the backend), the service would OOM. >>>> This is surprising because it has a circuit breaker that drops requests >>>> after 200 concurrent connections that has never trips, and goroutine >>>> profiles confirm that there are nowhere 200 active goroutines. >>>> >>>> GC logs are pasted below. It's interlaced with dumps of >>>> runtime.Memstats (the RSS number is coming from /proc/<pid>/stats). Go >>>> version is 1.12.5, running an Alpine 3.10 container in an Amazon kernel >>>> 4.14.123-111.109.amzn2.x86_64. >>>> >>>> The service happily serves requests using ~50MB of RSS for hours, until >>>> the last 2 seconds, where GC mark&sweep time starts to 2-4X per cycle >>>> (43+489/158/0.60+0.021 >>>> ms cpu => 43+489/158/0.60+0.021 ms cpu), and RSS and Sys blow up. It’s >>>> also interesting that in the last log line: `Sys=995MB RSS=861MB >>>> HeapSys=199MB`. If I’m reading this correctly, there’s at least `662MB` of >>>> memory in RSS that is not assigned to the heap. Though this might be due to >>>> the change in 1.125 to use MADV_FREE, so the pages are freeable not yet >>>> reclaimed by the kernel. >>>> >>>> I don’t understand how heap can be so small across gc cycles >>>> (28->42->30MB on the last line means heap doesn't grow past 42MB?), yet RSS >>>> keeps growing. I'm assuming the increased RSS is causing the kernel to OOM >>>> the service, but that should only happen if the RSS is not freeable as >>>> marked by MADV_FREE. There doesn't seem to be any indication of that from >>>> the GC logs. I guess this all comes down to me not having a good >>>> understanding of how the GC algorithm works and how to read these logs. I'd >>>> really appreciate it if anyone can explain what's happening and why. >>>> >>>> gc 41833 @19135.227s 0%: 0.019+2.3+0.005 ms clock, >>>> 0.079+0.29/2.2/5.6+0.020 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> INFO 2019-06-30T08:46:04.886 [Memory]: Alloc=7MB TotalAlloc=230172MB >>>> Sys=69MB RSS=51MB HeapSys=62MB HeapIdle=51MB HeapInUse=11MB >>>> HeapReleased=5MB >>>> gc 41834 @19135.869s 0%: 0.005+2.9+0.003 ms clock, >>>> 0.023+0.32/2.5/6.6+0.012 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> INFO 2019-06-30T08:46:05.886 [Memory]: Alloc=9MB TotalAlloc=230179MB >>>> Sys=69MB RSS=51MB HeapSys=62MB HeapIdle=50MB HeapInUse=12MB >>>> HeapReleased=5MB >>>> gc 41835 @19136.704s 0%: 0.038+2.1+0.004 ms clock, >>>> 0.15+0.35/2.1/5.3+0.016 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> INFO 2019-06-30T08:46:06.886 [Memory]: Alloc=9MB TotalAlloc=230184MB >>>> Sys=69MB RSS=51MB HeapSys=62MB HeapIdle=50MB HeapInUse=12MB >>>> HeapReleased=5MB >>>> gc 41836 @19137.611s 0%: 0.009+2.1+0.003 ms clock, >>>> 0.036+0.39/2.0/5.7+0.015 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> INFO 2019-06-30T08:46:07.887 [Memory]: Alloc=10MB TotalAlloc=230190MB >>>> Sys=69MB RSS=51MB HeapSys=62MB HeapIdle=49MB HeapInUse=12MB >>>> HeapReleased=5MB >>>> gc 41837 @19138.444s 0%: 0.008+2.1+0.004 ms clock, >>>> 0.035+0.51/2.1/5.7+0.017 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> INFO 2019-06-30T08:46:08.887 [Memory]: Alloc=10MB TotalAlloc=230195MB >>>> Sys=69MB RSS=51MB HeapSys=62MB HeapIdle=49MB HeapInUse=12MB >>>> HeapReleased=5MB >>>> gc 41838 @19139.474s 0%: 0.005+2.6+0.003 ms clock, >>>> 0.023+0.37/2.5/4.3+0.014 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> gc 41839 @19140.173s 0%: 0.011+2.4+0.003 ms clock, >>>> 0.046+0.20/2.3/5.8+0.015 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> INFO 2019-06-30T08:46:09.887 [Memory]: Alloc=7MB TotalAlloc=230202MB >>>> Sys=69MB RSS=51MB HeapSys=62MB HeapIdle=50MB HeapInUse=11MB >>>> HeapReleased=5MB >>>> gc 41840 @19140.831s 0%: 0.082+2.1+0.003 ms clock, >>>> 0.32+0.64/2.1/5.3+0.014 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> INFO 2019-06-30T08:46:10.887 [Memory]: Alloc=9MB TotalAlloc=230209MB >>>> Sys=69MB RSS=51MB HeapSys=62MB HeapIdle=50MB HeapInUse=12MB >>>> HeapReleased=5MB >>>> gc 41841 @19141.655s 0%: 0.014+2.1+0.003 ms clock, >>>> 0.056+0.28/2.0/5.7+0.013 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> gc 41842 @19142.316s 0%: 0.006+2.7+0.003 ms clock, >>>> 0.027+0.29/2.6/6.2+0.014 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> INFO 2019-06-30T08:46:11.888 [Memory]: Alloc=6MB TotalAlloc=230216MB >>>> Sys=69MB RSS=51MB HeapSys=62MB HeapIdle=51MB HeapInUse=11MB >>>> HeapReleased=5MB >>>> gc 41843 @19142.942s 0%: 0.010+2.1+0.005 ms clock, >>>> 0.040+0.29/2.0/5.7+0.023 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> INFO 2019-06-30T08:46:12.888 [Memory]: Alloc=9MB TotalAlloc=230223MB >>>> Sys=69MB RSS=51MB HeapSys=62MB HeapIdle=50MB HeapInUse=11MB >>>> HeapReleased=5MB >>>> gc 41844 @19143.724s 0%: 0.008+2.4+0.004 ms clock, >>>> 0.035+0.38/2.0/5.7+0.017 ms cpu, 11->11->5 MB, 12 MB goal, 4 P >>>> gc 41845 @19144.380s 0%: 10+9.3+0.044 ms clock, 43+6.1/9.2/4.4+0.17 ms >>>> cpu, 11->11->6 MB, 12 MB goal, 4 P >>>> INFO 2019-06-30T08:46:13.901 [Memory]: Alloc=6MB TotalAlloc=230230MB >>>> Sys=136MB RSS=98MB HeapSys=94MB HeapIdle=83MB HeapInUse=11MB >>>> HeapReleased=35MB >>>> gc 41846 @19144.447s 0%: 0.008+26+0.005 ms clock, >>>> 0.033+0.46/7.8/26+0.020 ms cpu, 11->12->9 MB, 12 MB goal, 4 P >>>> gc 41847 @19144.672s 0%: 0.013+76+0.006 ms clock, >>>> 0.053+0.20/6.4/80+0.024 ms cpu, 17->18->8 MB, 18 MB goal, 4 P >>>> gc 41848 @19145.014s 0%: 0.008+172+0.005 ms clock, >>>> 0.035+0.13/8.5/177+0.022 ms cpu, 15->17->10 MB, 16 MB goal, 4 P >>>> gc 41849 @19145.298s 0%: 0.007+285+0.006 ms clock, >>>> 0.030+10/285/7.6+0.024 ms cpu, 19->23->15 MB, 20 MB goal, 4 P >>>> INFO 2019-06-30T08:46:15.052 [Memory]: Alloc=22MB TotalAlloc=230264MB >>>> Sys=598MB RSS=531MB HeapSys=265MB HeapIdle=240MB HeapInUse=25MB >>>> HeapReleased=164MB >>>> gc 41850 @19145.665s 0%: 10+419+0.005 ms clock, 43+489/158/0.60+0.021 >>>> ms cpu, 26->30->17 MB, 30 MB goal, 4 P >>>> gc 41851 @19146.325s 0%: 21+798+0.036 ms clock, 86+990/401/0+0.14 ms >>>> cpu, 28->42->30 MB, 34 MB goal, 4 P >>>> INFO 2019-06-30T08:46:16.613 [Memory]: Alloc=41MB TotalAlloc=230303MB >>>> Sys=995MB RSS=861MB HeapSys=199MB HeapIdle=155MB HeapInUse=44MB >>>> HeapReleased=54MB >>>> >>>> I also captured the OOM log from dmesg here >>>> https://gist.github.com/mightyguava/7ecc6fc55f5cd925062d6beede3783b3. >>>> >>>> -- >>>> Yunchi >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "golang-nuts" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to golang-nuts+unsubscr...@googlegroups.com. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/golang-nuts/CANnT9sj1_sZCKDkGbkzarwcn8DYEX9OS6Ack%2B71613eyLQ7y6w%40mail.gmail.com >>>> <https://groups.google.com/d/msgid/golang-nuts/CANnT9sj1_sZCKDkGbkzarwcn8DYEX9OS6Ack%2B71613eyLQ7y6w%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>>> >>>> >>> >>> -- >>> Yunchi >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "golang-nuts" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to golang-nuts+unsubscr...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/golang-nuts/CANnT9sjNpE8wjqv6n%2BbHyZJ_cCvwN3O9rHKTT3%3DdSqZah0PfHA%40mail.gmail.com >>> <https://groups.google.com/d/msgid/golang-nuts/CANnT9sjNpE8wjqv6n%2BbHyZJ_cCvwN3O9rHKTT3%3DdSqZah0PfHA%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> For more options, visit https://groups.google.com/d/optout. >>> >> > > -- > Yunchi > -- Yunchi -- You received this message because you are subscribed 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