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From "Daniel Harper (JIRA)" <j...@apache.org>
Subject [jira] [Created] (BEAM-2807) NullPointerException during checkpoint during Flink CoderTypeSerializer phase
Date Fri, 25 Aug 2017 12:09:00 GMT
Daniel Harper created BEAM-2807:
-----------------------------------

             Summary: NullPointerException during checkpoint during Flink CoderTypeSerializer
phase
                 Key: BEAM-2807
                 URL: https://issues.apache.org/jira/browse/BEAM-2807
             Project: Beam
          Issue Type: Bug
          Components: beam-model
    Affects Versions: 2.1.0
            Reporter: Daniel Harper
            Assignee: Kenneth Knowles
            Priority: Blocker


*Beam version:* 2.1.0
*Runner:* FlinkRunner


We're seeing the following exception when checkpointing, which is causing our job to restart

{code}
2017-08-25 09:42:17,658 INFO  org.apache.flink.runtime.taskmanager.Task                  
  - Combine.perKey(Count) -> ParMultiDo(ToConcurrentStreamResult) -> ParMultiDo(Anonymous)
-> ParMultiDo(ApplyShardingKey) -> ToKeyedWorkItem (7/32) (f00a31b722a31030f18d83ac613de21d)
switched from RUNNING to FAILED.
AsynchronousException{java.lang.Exception: Could not materialize checkpoint 2 for operator
Combine.perKey(Count) -> ParMultiDo(ToConcurrentStreamResult) -> ParMultiDo(Anonymous)
-> ParMultiDo(ApplyShardingKey) -> ToKeyedWorkItem (7/32).}
    at org.apache.flink.streaming.runtime.tasks.StreamTask$AsyncCheckpointRunnable.run(StreamTask.java:966)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.Exception: Could not materialize checkpoint 2 for operator Combine.perKey(Count)
-> ParMultiDo(ToConcurrentStreamResult) -> ParMultiDo(Anonymous) -> ParMultiDo(ApplyShardingKey)
-> ToKeyedWorkItem (7/32).
    ... 6 more
Caused by: java.util.concurrent.ExecutionException: java.lang.NullPointerException
    at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:192)
    at org.apache.flink.util.FutureUtil.runIfNotDoneAndGet(FutureUtil.java:43)
    at org.apache.flink.streaming.runtime.tasks.StreamTask$AsyncCheckpointRunnable.run(StreamTask.java:893)
    ... 5 more
    Suppressed: java.lang.Exception: Could not properly cancel managed keyed state future.
        at org.apache.flink.streaming.api.operators.OperatorSnapshotResult.cancel(OperatorSnapshotResult.java:90)
        at org.apache.flink.streaming.runtime.tasks.StreamTask$AsyncCheckpointRunnable.cleanup(StreamTask.java:1018)
        at org.apache.flink.streaming.runtime.tasks.StreamTask$AsyncCheckpointRunnable.run(StreamTask.java:957)
        ... 5 more
    Caused by: java.util.concurrent.ExecutionException: java.lang.NullPointerException
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:192)
        at org.apache.flink.util.FutureUtil.runIfNotDoneAndGet(FutureUtil.java:43)
        at org.apache.flink.runtime.state.StateUtil.discardStateFuture(StateUtil.java:85)
        at org.apache.flink.streaming.api.operators.OperatorSnapshotResult.cancel(OperatorSnapshotResult.java:88)
        ... 7 more
    Caused by: java.lang.NullPointerException
        at java.io.DataOutputStream.writeUTF(DataOutputStream.java:347)
        at java.io.DataOutputStream.writeUTF(DataOutputStream.java:323)
        at org.apache.beam.runners.flink.translation.types.CoderTypeSerializer$CoderTypeSerializerConfigSnapshot.write(CoderTypeSerializer.java:189)
        at org.apache.flink.api.common.typeutils.TypeSerializerSerializationUtil$TypeSerializerConfigSnapshotSerializationProxy.write(TypeSerializerSerializationUtil.java:413)
        at org.apache.flink.api.common.typeutils.TypeSerializerSerializationUtil.writeSerializerConfigSnapshot(TypeSerializerSerializationUtil.java:229)
        at org.apache.flink.api.common.typeutils.TypeSerializerSerializationUtil.writeSerializersAndConfigsWithResilience(TypeSerializerSerializationUtil.java:151)
        at org.apache.flink.runtime.state.KeyedBackendStateMetaInfoSnapshotReaderWriters$KeyedBackendStateMetaInfoWriterV3.writeStateMetaInfo(KeyedBackendStateMetaInfoSnapshotReaderWriters.java:107)
        at org.apache.flink.runtime.state.KeyedBackendSerializationProxy.write(KeyedBackendSerializationProxy.java:104)
        at org.apache.flink.runtime.state.heap.HeapKeyedStateBackend$1.performOperation(HeapKeyedStateBackend.java:293)
        at org.apache.flink.runtime.state.heap.HeapKeyedStateBackend$1.performOperation(HeapKeyedStateBackend.java:286)
        at org.apache.flink.runtime.io.async.AbstractAsyncIOCallable.call(AbstractAsyncIOCallable.java:72)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at org.apache.flink.runtime.state.heap.HeapKeyedStateBackend.snapshot(HeapKeyedStateBackend.java:329)
        at org.apache.flink.streaming.api.operators.AbstractStreamOperator.snapshotState(AbstractStreamOperator.java:397)
        at org.apache.flink.streaming.runtime.tasks.StreamTask$CheckpointingOperation.checkpointStreamOperator(StreamTask.java:1157)
        at org.apache.flink.streaming.runtime.tasks.StreamTask$CheckpointingOperation.executeCheckpointing(StreamTask.java:1089)
        at org.apache.flink.streaming.runtime.tasks.StreamTask.checkpointState(StreamTask.java:653)
        at org.apache.flink.streaming.runtime.tasks.StreamTask.performCheckpoint(StreamTask.java:589)
        at org.apache.flink.streaming.runtime.tasks.StreamTask.triggerCheckpointOnBarrier(StreamTask.java:542)
        at org.apache.flink.streaming.runtime.io.BarrierTracker.notifyCheckpoint(BarrierTracker.java:263)
        at org.apache.flink.streaming.runtime.io.BarrierTracker.processBarrier(BarrierTracker.java:178)
        at org.apache.flink.streaming.runtime.io.BarrierTracker.getNextNonBlocked(BarrierTracker.java:97)
        at org.apache.flink.streaming.runtime.io.StreamInputProcessor.processInput(StreamInputProcessor.java:213)
        at org.apache.flink.streaming.runtime.tasks.OneInputStreamTask.run(OneInputStreamTask.java:69)
        at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:262)
        at org.apache.flink.runtime.taskmanager.Task.run(Task.java:702)
        ... 1 more
{code}

>From debugging locally I've narrowed it down to here 

{code}
    Caused by: java.lang.NullPointerException
        at java.io.DataOutputStream.writeUTF(DataOutputStream.java:347)
        at java.io.DataOutputStream.writeUTF(DataOutputStream.java:323)
        at org.apache.beam.runners.flink.translation.types.CoderTypeSerializer$CoderTypeSerializerConfigSnapshot.write(CoderTypeSerializer.java:189)
        at org.apache.flink.api.common.typeutils.TypeSerializerSerializationUtil$TypeSerializerConfigSnapshotSerializationProxy.write(TypeSerializerSerializationUtil.java:413)
{code}

Specifically in [CoderTypeSerializer.java#189|https://github.com/apache/beam/blob/609016d700c84800cf942482fb7cd2ddaa420b00/runners/flink/src/main/java/org/apache/beam/runners/flink/translation/types/CoderTypeSerializer.java#L189],
when it calls {{DataOutputStream.write(String)}}, there is some logic in the {{write}} method
that gets the string length. This is what is causing the NPE as the {{coderName}} field is
null.

I think this stems from the [constructor|https://github.com/apache/beam/blob/609016d700c84800cf942482fb7cd2ddaa420b00/runners/flink/src/main/java/org/apache/beam/runners/flink/translation/types/CoderTypeSerializer.java#L164]
which sets the {{coderName}} by calling {{.getClass().getCanonicalName();}} on the {{coder}}
that is passed into the constructor

On debugging I've noticed this returns {{null}} when calling {{.getClass().getCanonicalName();}}
on an instance of [Count$CountFn|https://github.com/apache/beam/blob/2040e2bd4203f81ea63966110e4eef3a1ff72393/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/Count.java#L134]









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