You may be able to get some additional insight if you configure Dataflow to save a heap dump before killing the JVM (--dumpHeapOnOOM, --saveHeapDumpsToGcsPath) and inspecting the dump. There are directions for that (and a lot of other advice about memory issues) at [1].
Another question - is this a batch pipeline? There's an open Jira about thrashing detection in Dataflow's batch worker [2]. The fact that we shut down a worker's JVM after sustained periods of thrashing is part of a larger system for dealing with memory pressure intended for use in streaming pipelines. We may want to make it opt-in for batch pipelines. I wrote a PR that made the JVM shutdown opt-in for all Dataflow pipelines earlier this year, but I closed it when I realized it's an important feature in streaming [3]. I could revisist that PR and make the feature opt-in for batch, opt-out for streaming, but that wouldn't help you until the next Beam release. Brian [1] https://cloud.google.com/community/tutorials/dataflow-debug-oom-conditions [2] https://issues.apache.org/jira/browse/BEAM-9049 [3] https://github.com/apache/beam/pull/10499#issuecomment-570743842 On Thu, Sep 3, 2020 at 10:48 AM Talat Uyarer <tuya...@paloaltonetworks.com> wrote: > Hi, > > One more update. Sorry When I created a code sample that I shared. I put > StringBuilder under the setup function but actually it was on the start > bundle function. So far I tested below scenarios > - with StringWriter construct object every processElement call > - with StringBuilder construct object every processElement call > - with StringBuilder construct object every startBundle call (and also > tried setLength(0) and delete(0,sb.length() to clean StringBuilder) > > None of the cases prevent DF jobs from getting below error. > >> Shutting down JVM after 8 consecutive periods of measured GC thrashing. >> Memory is used/total/max = 4112/5994/5994 MB, GC last/max = 97.36/97.36 %, >> #pushbacks=3, gc thrashing=true. Heap dump not written. > > > And also my process rate is 4kps per instance. I would like to hear your > suggestions if you have any. > > Thanks > > On Wed, Sep 2, 2020 at 6:22 PM Talat Uyarer <tuya...@paloaltonetworks.com> > wrote: > >> I also tried Brian's suggestion to clear stringbuilder by calling delete >> with stringbuffer length. No luck. I am still getting the same error >> message. Do you have any suggestions ? >> >> Thanks >> >> On Wed, Sep 2, 2020 at 3:33 PM Talat Uyarer <tuya...@paloaltonetworks.com> >> wrote: >> >>> If I'm understanding Talat's logic correctly, it's not necessary to >>>> reuse the string builder at all in this case. >>> >>> Yes. I tried it too. But DF job has the same issue. >>> >>> >>> On Wed, Sep 2, 2020 at 3:17 PM Kyle Weaver <kcwea...@google.com> wrote: >>> >>>> > It looks like `writer.setLength(0)` may actually allocate a new >>>> buffer, and then the buffer may also need to be resized as the String >>>> grows, so you could be creating a lot of orphaned buffers very quickly. I'm >>>> not that familiar with StringBuilder, is there a way to reset it and re-use >>>> the existing capacity? Maybe `writer.delete(0, writer.length())` [1]? >>>> >>>> If I'm understanding Talat's logic correctly, it's not necessary to >>>> reuse the string builder at all in this case. >>>> >>>> On Wed, Sep 2, 2020 at 3:11 PM Brian Hulette <bhule...@google.com> >>>> wrote: >>>> >>>>> That error isn't exactly an OOM, it indicates the JVM is spending a >>>>> significant amount of time in garbage collection. >>>>> >>>>> It looks like `writer.setLength(0)` may actually allocate a new >>>>> buffer, and then the buffer may also need to be resized as the String >>>>> grows, so you could be creating a lot of orphaned buffers very quickly. >>>>> I'm >>>>> not that familiar with StringBuilder, is there a way to reset it and >>>>> re-use >>>>> the existing capacity? Maybe `writer.delete(0, writer.length())` [1]? >>>>> >>>>> [1] >>>>> https://stackoverflow.com/questions/242438/is-it-better-to-reuse-a-stringbuilder-in-a-loop >>>>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__stackoverflow.com_questions_242438_is-2Dit-2Dbetter-2Dto-2Dreuse-2Da-2Dstringbuilder-2Din-2Da-2Dloop&d=DwMFaQ&c=V9IgWpI5PvzTw83UyHGVSoW3Uc1MFWe5J8PTfkrzVSo&r=BkW1L6EF7ergAVYDXCo-3Vwkpy6qjsWAz7_GD7pAR8g&m=8xskmxTZ2EbxwBknWfeIiV2kEsXsu9dzjWT_yG6A0s4&s=ZL6S353ZUzPRmxrPo8Sei_mdxsWDxs4Km2RwwiwefEU&e=> >>>>> >>>>> On Wed, Sep 2, 2020 at 3:02 PM Talat Uyarer < >>>>> tuya...@paloaltonetworks.com> wrote: >>>>> >>>>>> Sorry for the wrong import. You can see on the code I am using >>>>>> StringBuilder. >>>>>> >>>>>> On Wed, Sep 2, 2020 at 2:55 PM Ning Kang <ni...@google.com> wrote: >>>>>> >>>>>>> Here is a question answered on StackOverflow: >>>>>>> https://stackoverflow.com/questions/27221292/when-should-i-use-javas-stringwriter >>>>>>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__stackoverflow.com_questions_27221292_when-2Dshould-2Di-2Duse-2Djavas-2Dstringwriter&d=DwMFaQ&c=V9IgWpI5PvzTw83UyHGVSoW3Uc1MFWe5J8PTfkrzVSo&r=BkW1L6EF7ergAVYDXCo-3Vwkpy6qjsWAz7_GD7pAR8g&m=mVBqxC5kNOARPduF-c17S1VnIw8gwS6alvgONJKfheY&s=ggveahdPKo3vaAhADvjz4ucjndSmzyOZ8FPBvJ_0oZQ&e=> >>>>>>> >>>>>>> Could you try using StringBuilder instead since the usage is not >>>>>>> appropriate for a StringWriter? >>>>>>> >>>>>>> >>>>>>> On Wed, Sep 2, 2020 at 2:49 PM Talat Uyarer < >>>>>>> tuya...@paloaltonetworks.com> wrote: >>>>>>> >>>>>>>> Hi, >>>>>>>> >>>>>>>> I have an issue with String Concatenating. You can see my code >>>>>>>> below.[1] I have a step on my df job which is concatenating strings. >>>>>>>> But >>>>>>>> somehow when I use that step my job starts getting jvm restart errors. >>>>>>>> >>>>>>>> Shutting down JVM after 8 consecutive periods of measured GC >>>>>>>>> thrashing. Memory is used/total/max = 4112/5994/5994 MB, GC last/max = >>>>>>>>> 97.36/97.36 %, #pushbacks=3, gc thrashing=true. Heap dump not written. >>>>>>>> >>>>>>>> >>>>>>>> And also I try to use Avro rather than String. When I use Avro, it >>>>>>>> works fine without any issue. Do you have any suggestions? >>>>>>>> >>>>>>>> Thanks >>>>>>>> >>>>>>>> [1] https://dpaste.com/7RTV86WQC >>>>>>>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__dpaste.com_7RTV86WQC&d=DwMFaQ&c=V9IgWpI5PvzTw83UyHGVSoW3Uc1MFWe5J8PTfkrzVSo&r=BkW1L6EF7ergAVYDXCo-3Vwkpy6qjsWAz7_GD7pAR8g&m=mVBqxC5kNOARPduF-c17S1VnIw8gwS6alvgONJKfheY&s=eSd0NcP8fw5BOZlSXtUMRfYuGWlN-gcXENVwgCmrapY&e=> >>>>>>>> >>>>>>>> >>>>>>>>
