Are you using anything like fast-http, or such? Have you tried running the server with the race-detector enabled? I could see a race condition causing a rare failure that causes the code to go into a ‘spinning loop’ preventing GC to work properly. It’s a guess but I would try that to rule out the possibility.
> On Jul 1, 2019, at 11:06 PM, Mighty Guava <mightygu...@gmail.com> wrote: > > I don't think GC is being blocked. GC ran multiple times during the time the > service was exploding in memory. > > I'm not using mmap in the service. It's just a straightforward CRUD webserver > backed by DynamoDB. The only thing non-standard I can think of is that it > connects to its backing database over HTTP/1.1 (using AWS Go SDK) instead of > a custom database protocol. It's serving a fair amount of requests (500 qps > per replica), so I initially assumed it was under-provisioned to handle > latency spikes. But I tripled the memory and it's still OOMing on occasion, > even though RSS is 9% of allocated memory just seconds before. > > Yunchi > On Jul 2, 2019, 12:00 AM -0400, Robert Engels <reng...@ix.netcom.com>, wrote: >> Does your process use mmap? Maybe you are leaking there, as this counts >> against process memory size. >> >> On Jul 1, 2019, at 9:11 PM, Mighty Guava <mightygu...@gmail.com >> <mailto:mightygu...@gmail.com>> wrote: >> >>> I don't understand. What would adding runtime.Goscheduled() do here? I >>> don't have any explicit loops in this service. >>> On Jul 1, 2019, 9:11 PM -0400, Michael Jones <michael.jo...@gmail.com >>> <mailto:michael.jo...@gmail.com>>, wrote: >>>> Does adding runtime.GoSched() calls make any difference? >>>> >>>> On Mon, Jul 1, 2019 at 5:37 PM 'Yunchi Luo' via golang-nuts >>>> <golang-nuts@googlegroups.com <mailto:golang-nuts@googlegroups.com>> wrote: >>>> Following that logic, a leak of TCP connections should manifest as a file >>>> descriptor leak. We have the process_open_fds metric from Prometheus, that >>>> is the number of open file descriptors as found in /proc/<pid>/fd. The >>>> number of descriptors overtime correlates well with the amount of traffic, >>>> pretty cyclic. There doesn't appear to be a leak. >>>> >>>> We don't do our own memory management and the binary is compiled with >>>> CGO_ENABLED=0. >>>> >>>> I still think the issue I'm seeing should be GC (or heap) related, given >>>> the explosion in mark & sweep time, HeapSys, HeapIdle, and HeapReleased >>>> just before the process dies. But I'm lacking ideas on how to track down >>>> the cause of the increase. >>>> >>>> On Mon, Jul 1, 2019 at 5:39 PM Robert Engels <reng...@ix.netcom.com >>>> <mailto:reng...@ix.netcom.com>> wrote: >>>> I think don't think you are going to find it in the 'heap', rather it >>>> would be in native memory. >>>> >>>> I would use the monitor the /proc/[pid] for the process, and pay attention >>>> to the 'fd','net' and 'statm' - if my theory is correct you will see >>>> growth here long before the process is killed. Since you are running under >>>> k8s and cgroups, you will need to do this along side the Go process >>>> (unless you have root access to the server). >>>> >>>> I 'think' depending on kernel version, that kernel memory used goes >>>> against the process for OOM purposes, so this is a likely candidate if >>>> pprof is showing nothing. >>>> >>>> Do you by chance do any of your own memory management (via malloc/CGO)? If >>>> so, this is not going to show in pprof either. >>>> -----Original Message----- >>>> From: 'Yunchi Luo' via golang-nuts >>>> Sent: Jul 1, 2019 4:26 PM >>>> To: Robert Engels >>>> Cc: golang-nuts@googlegroups.com <mailto:golang-nuts@googlegroups.com>, >>>> Alec Thomas >>>> Subject: Re: [go-nuts] OOM occurring with a small heap >>>> >>>> I actually have a heap profile (pasted at the bottom) from about 1 second >>>> before the service died (the goroutine that is logging "[Memory]" triggers >>>> heap profiles once RSS > 100MB). I don't see TCP connections there. Maybe >>>> it's too few to be sampled. How would I verify your theory? That the >>>> service dies within 2 seconds after several hours makes it very hard to >>>> debug. >>>> >>>> The top thing in the heap profile is from the reflect package. I initially >>>> found that suspect, but it turns out this comes from a use of >>>> httptrace.ClientTrace I had for counting new connections to DynamoDB. >>>> >>>> tracer := &httptrace.ClientTrace{ >>>> ConnectStart: func(_, _ string) { >>>> newConns.Inc() >>>> }, >>>> } >>>> >>>> `newConns` is just a prometheus counter. The `tracer` object itself is >>>> created once and re-used with every client request context. On request, >>>> `httptrace.WithClientTrace(ctx, tracer)` uses reflection to compose the >>>> trace functions under-the-hood and uses reflection to invoke it, hence the >>>> reflect.funcLayout and reflect.Value.call. Objects in `reflect` account >>>> for about 50% of heap in terms of size, and does seem to grow as the >>>> service is running out of memory, but that's only 12MB so I thought it was >>>> a red herring. >>>> >>>> Heap profile: >>>> Type: inuse_space >>>> Time: Jun 30, 2019 at 4:46am (EDT) >>>> Entering interactive mode (type "help" for commands, "o" for options) >>>> (pprof) inuse_objects >>>> (pprof) top >>>> Showing nodes accounting for 414485, 100% of 414485 total >>>> Showing top 10 nodes out of 81 >>>> flat flat% sum% cum cum% >>>> 344074 83.01% 83.01% 344074 83.01% reflect.funcLayout.func1 >>>> 32768 7.91% 90.92% 376842 90.92% reflect.callReflect >>>> 16384 3.95% 94.87% 16384 3.95% >>>> github.com/json-iterator/go.processTags >>>> <http://github.com/json-iterator/go.processTags> >>>> 10923 2.64% 97.51% 10923 2.64% context.WithValue >>>> 8192 1.98% 99.48% 8192 1.98% crypto/hmac.New >>>> 1260 0.3% 99.79% 1260 0.3% >>>> github.com/aws/aws-sdk-go/aws/signer/v4.(*signingCtx).buildCanonicalHeaders >>>> >>>> <http://github.com/aws/aws-sdk-go/aws/signer/v4.(*signingCtx).buildCanonicalHeaders> >>>> 820 0.2% 100% 820 0.2% >>>> github.com/stripe/veneur/tdigest.NewMerging >>>> <http://github.com/stripe/veneur/tdigest.NewMerging> >>>> 64 0.015% 100% 64 0.015% reflect.addReflectOff >>>> 0 0% 100% 820 0.2% >>>> git.sqcorp.co/cash/digester/lib/pkg/histogram.(*SlidingWindowDigest).Observe >>>> >>>> <http://git.sqcorp.co/cash/digester/lib/pkg/histogram.(*SlidingWindowDigest).Observe> >>>> 0 0% 100% 820 0.2% >>>> git.sqcorp.co/cash/digester/lib/pkg/histogram.(*SlidingWindowDigest).openDigests >>>> >>>> <http://git.sqcorp.co/cash/digester/lib/pkg/histogram.(*SlidingWindowDigest).openDigests> >>>> (pprof) cum >>>> (pprof) top >>>> Showing nodes accounting for 376842, 90.92% of 414485 total >>>> Showing top 10 nodes out of 81 >>>> flat flat% sum% cum cum% >>>> 0 0% 0% 376842 90.92% >>>> net/http/httptrace.(*ClientTrace).compose.func1 >>>> 0 0% 0% 376842 90.92% reflect.Value.Call >>>> 0 0% 0% 376842 90.92% reflect.Value.call >>>> 32768 7.91% 7.91% 376842 90.92% reflect.callReflect >>>> 0 0% 7.91% 376842 90.92% reflect.makeFuncStub >>>> 344074 83.01% 90.92% 344074 83.01% reflect.funcLayout.func1 >>>> 0 0% 90.92% 344074 83.01% sync.(*Pool).Get >>>> 0 0% 90.92% 16448 3.97% >>>> github.com/json-iterator/go._createDecoderOfType >>>> <http://github.com/json-iterator/go._createDecoderOfType> >>>> 0 0% 90.92% 16448 3.97% >>>> github.com/json-iterator/go.createDecoderOfType >>>> <http://github.com/json-iterator/go.createDecoderOfType> >>>> 0 0% 90.92% 16448 3.97% >>>> github.com/json-iterator/go.decoderOfStruct >>>> <http://github.com/json-iterator/go.decoderOfStruct> >>>> >>>> >>>> On Mon, Jul 1, 2019 at 4:32 PM Robert Engels <reng...@ix.netcom.com >>>> <mailto:reng...@ix.netcom.com>> wrote: >>>> >>>> A leak of the TCP connections (maybe not properly closed)? Each TCP >>>> connection will use kernel memory and process memory (local buffers), that >>>> won't be on the heap (the reference to the TCP connection will be in the >>>> Go heap, but is probably much smaller than the buffer allocation). >>>> >>>> That would be my guess - but just a guess. >>>> -----Original Message----- >>>> From: 'Yunchi Luo' via golang-nuts >>>> Sent: Jul 1, 2019 2:14 PM >>>> To: golang-nuts@googlegroups.com <mailto:golang-nuts@googlegroups.com> >>>> Cc: Alec Thomas >>>> Subject: [go-nuts] OOM occurring with a small heap >>>> >>>> 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 >>>> <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 >>>> <mailto:golang-nuts+unsubscr...@googlegroups.com>. >>>> To view this discussion on the web visit >>>> 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<https://groups.google.com/d/msgid/golang-nuts/CANnT9siMD4L5oC0nvmGYYM3Qo4rVSSCT%2BK5__fR9%3DzuyXV6S0Q%40mail.gmail.com?utm_medium=email&utm_source=footer>. >>>> For more options, visit https://groups.google.com/d/optout >>>> <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 >>>> <mailto:golang-nuts+unsubscr...@googlegroups.com>. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/golang-nuts/CANnT9sjEo%2Bp2HYOVDjB_EzaGE474QuBy-9Yp_HaCn95wHSFsHQ%40mail.gmail.com >>>> >>>> <https://groups.google.com/d/msgid/golang-nuts/CANnT9sjEo%2Bp2HYOVDjB_EzaGE474QuBy-9Yp_HaCn95wHSFsHQ%40mail.gmail.com?utm_medium=email&utm_source=footer>. >>>> For more options, visit 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