Hi Zakelly, On my side, we've pulled and deployed the fix from the release-1.20 branch[1] in our production canary deployments, and we haven't seen any NPEs for ~3 days now. Thanks so much for the quick fix!
Kevin On Wed, Sep 10, 2025 at 8:24 AM Zakelly Lan <[email protected]> wrote: > Hi Kevin, > > We’ve merged the fix into the 1.20 branch, and AFAIK, the community will > kick off the next patch release (1.20.3) soon. In the meantime, if you’re > interested, you may build from the release-1.20 branch[1] to verify the fix. > > > Thank you again for reporting the issue and for your valuable feedback. > > [1] https://github.com/apache/flink/tree/release-1.20 > > Best, > Zakelly > > On Wed, Sep 10, 2025 at 1:33 AM Kevin Kim <[email protected]> > wrote: > >> Thank you! Looking forward to testing the fix on my side. >> >> Kevin >> >> On Tue, Sep 9, 2025 at 9:15 AM Gabor Somogyi <[email protected]> >> wrote: >> >>> Hi Kevin, >>> >>> We've already merged the fix to master, backports are on the way :) >>> >>> BR, >>> G >>> >>> >>> On Tue, Sep 9, 2025 at 2:26 PM Kevin Kim <[email protected]> >>> wrote: >>> >>>> Hi Zakelly, >>>> >>>> Yes, this job contains both operator state and keyed state. Happy to >>>> provide more details as needed. >>>> >>>> Kevin >>>> >>>> On Mon, Sep 8, 2025 at 10:48 PM Zakelly Lan <[email protected]> >>>> wrote: >>>> >>>>> 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 < >>>>> [email protected]> 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 <[email protected]> >>>>>> 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 <[email protected]> >>>>>>> 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 < >>>>>>>> [email protected]> 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 <[email protected]> >>>>>>>>> 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 <[email protected]> >>>>>>>>>> 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) >>>>>>>>>>> >>>>>>>>>>
