Hi Kevin, One more thing I want to make sure about the job. Is this a datastream job with operator state (not only keyed states after `keyby()`)?
Thanks! Best, Zakelly On Fri, Sep 5, 2025 at 9:53 PM Kevin Kim <kevin....@alumni.princeton.edu> wrote: > Thanks so much! > > More context: this file merging feature is really promising for our use > case. Given the large state size and parallelism, we occasionally run into > S3 rate limits at checkpoint/savepoint time. > > The few times I tried this file merging, it helped quite a bit, but I've > had to turn it off for now due to this NPE, which happens occasionally but > not always > > On Fri, Sep 5, 2025, 1:58 AM Gabor Somogyi <gabor.g.somo...@gmail.com> > wrote: > >> Hi Guys, >> >> This sounds severe and I'm also taking a look... >> >> G >> >> >> On Fri, Sep 5, 2025 at 4:44 AM Zakelly Lan <zakelly....@gmail.com> wrote: >> >>> Hi Kevin, >>> >>> Thanks for the details. It's really helpful. I'm trying to reproduce >>> this according to your setup. Will let you know if any updates. >>> >>> I create a jira issue to track this: >>> https://issues.apache.org/jira/browse/FLINK-38327 >>> >>> >>> Best, >>> Zakelly >>> >>> On Thu, Sep 4, 2025 at 7:42 PM Kevin Kim <kevin....@alumni.princeton.edu> >>> wrote: >>> >>>> Hi Zakelly, >>>> >>>> Thanks for the reply. >>>> >>>> This job is running on Kubernetes using the Apache Flink Kubernetes >>>> operator. This NullPointerException happened during a job restart after one >>>> of the TaskManagers restarted because the underlying node running the >>>> TaskManager pod was scaled down for maintenance. There was no rescaling or >>>> parallelism change. >>>> >>>> The job is quite large due to heavy input traffic + state size: >>>> 2100 parallelism >>>> taskmanager.numberOfTaskSlots: 14 (so 150 TaskManagers total) >>>> RocksDBStateBackend used for state management. Checkpoints/savepoints >>>> are written to S3 in AWS. >>>> According to the Flink Checkpoint UI, the full state size is ~600GB >>>> >>>> Please let me know if more details would be helpful. >>>> >>>> Best regards, >>>> Kevin >>>> >>>> >>>> On Thu, Sep 4, 2025 at 6:16 AM Zakelly Lan <zakelly....@gmail.com> >>>> wrote: >>>> >>>>> Hi Kevin, >>>>> >>>>> Would you please provide more info about the setup? Is this a failover >>>>> or manual job restart with or without a change of parallelism (rescale)? >>>>> >>>>> >>>>> Best, >>>>> Zakelly >>>>> >>>>> >>>>> >>>>> On Wed, Sep 3, 2025 at 2:43 AM Kevin Kim <kkim...@gmail.com> wrote: >>>>> >>>>>> Has anyone seen this NullPointerException after enabling checkpoint >>>>>> file merging? I'm running a job with Flink 1.20.2 with these configs: >>>>>> >>>>>> execution.checkpointing.file-merging.enabled: true >>>>>> execution.checkpointing.file-merging.max-file-size: 32m >>>>>> execution.checkpointing.timeout: "10min" >>>>>> execution.checkpointing.tolerable-failed-checkpoints: 3 >>>>>> execution.checkpointing.min-pause: "2min" >>>>>> execution.checkpointing.interval: "2min" >>>>>> >>>>>> java.lang.NullPointerException >>>>>> at >>>>>> org.apache.flink.runtime.checkpoint.filemerging.FileMergingSnapshotManagerBase.isManagedByFileMergingManager(FileMergingSnapshotManagerBase.java:927) >>>>>> at >>>>>> org.apache.flink.runtime.checkpoint.filemerging.FileMergingSnapshotManagerBase.lambda$restoreStateHandles$11(FileMergingSnapshotManagerBase.java:866) >>>>>> at java.base/java.util.HashMap.computeIfAbsent(HashMap.java:1220) >>>>>> at >>>>>> org.apache.flink.runtime.checkpoint.filemerging.FileMergingSnapshotManagerBase.lambda$restoreStateHandles$12(FileMergingSnapshotManagerBase.java:861) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:179) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:179) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197) >>>>>> at >>>>>> java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1625) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:276) >>>>>> at >>>>>> java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:992) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:276) >>>>>> at >>>>>> java.base/java.util.ArrayList$Itr.forEachRemaining(ArrayList.java:1003) >>>>>> at >>>>>> java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1845) >>>>>> at >>>>>> java.base/java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:734) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:276) >>>>>> at >>>>>> java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:992) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150) >>>>>> at >>>>>> java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173) >>>>>> at >>>>>> java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) >>>>>> at >>>>>> java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596) >>>>>> at >>>>>> org.apache.flink.runtime.checkpoint.filemerging.FileMergingSnapshotManagerBase.restoreStateHandles(FileMergingSnapshotManagerBase.java:858) >>>>>> at >>>>>> org.apache.flink.runtime.checkpoint.filemerging.SubtaskFileMergingManagerRestoreOperation.restore(SubtaskFileMergingManagerRestoreOperation.java:102) >>>>>> at >>>>>> org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.registerRestoredStateToFileMergingManager(StreamTaskStateInitializerImpl.java:353) >>>>>> at >>>>>> org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:163) >>>>>> at >>>>>> org.apache.flink.streaming.api.operators.AbstractStreamOperator.initializeState(AbstractStreamOperator.java:275) >>>>>> at >>>>>> org.apache.flink.streaming.runtime.tasks.RegularOperatorChain.initializeStateAndOpenOperators(RegularOperatorChain.java:106) >>>>>> at >>>>>> org.apache.flink.streaming.runtime.tasks.StreamTask.restoreStateAndGates(StreamTask.java:858) >>>>>> at >>>>>> org.apache.flink.streaming.runtime.tasks.StreamTask.lambda$restoreInternal$5(StreamTask.java:812) >>>>>> at >>>>>> org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$1.call(StreamTaskActionExecutor.java:55) >>>>>> at >>>>>> org.apache.flink.streaming.runtime.tasks.StreamTask.restoreInternal(StreamTask.java:812) >>>>>> at >>>>>> org.apache.flink.streaming.runtime.tasks.StreamTask.restore(StreamTask.java:771) >>>>>> at >>>>>> org.apache.flink.runtime.taskmanager.Task.runWithSystemExitMonitoring(Task.java:970) >>>>>> at >>>>>> org.apache.flink.runtime.taskmanager.Task.restoreAndInvoke(Task.java:939) >>>>>> at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:763) >>>>>> at org.apache.flink.runtime.taskmanager.Task.run(Task.java:575) >>>>>> at java.base/java.lang.Thread.run(Thread.java:840) >>>>>> >>>>>
