[jira] [Created] (FLINK-28034) ClassCastException occurred in creating a checkpoint with merge windows

["Takayuki Eimizu (Jira)" <ji...@apache.org>]

Takayuki Eimizu created FLINK-28034:
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             Summary: ClassCastException occurred in creating a checkpoint with merge windows 
                 Key: FLINK-28034
                 URL: https://issues.apache.org/jira/browse/FLINK-28034
             Project: Flink
          Issue Type: Bug
          Components: Runtime / Checkpointing, Runtime / State Backends
    Affects Versions: 1.15.0
            Reporter: Takayuki Eimizu


h1. Summary

In Flink 1.15.0, the combination of following functions always occur ClassCastException.
 - Session Window
 - Checkpoint
 - Keyed State

The following repository provides minimal source code that can combine these features to reproduce the exception.

[https://github.com/t-eimizu/flink-checkpoint-with-merging-window]

 
h1. Description
h2. How the Exception Occurred
 
In the process window function of the session window, we must use `context.globalState()`
instead of `context.windowState()`. If you use `context.windowState()` in this situation, Flink throws `UnsupportedOperationException`.
 
So we have to do following:
 
{code:java}
   stPreviousValue = context.globalState().getState(desc4PreviousValue);     {code}
 
Then stPreviousValue will have the following fields:
||Field Name||Value||
|currentNamespace|VoidNamespace|
|namespaceSerializer|TimeWindow$serializer|
As a result, when flink create checkpoint on this job, ClassCastException occurs.
{code:java}
2022-06-14 11:04:57,212 INFO  org.apache.flink.streaming.runtime.tasks.AsyncCheckpointRunnable [] - ProcessingData -> Sink: PrintData (1/1)#0 - asynchronous part of checkpoint 1 could not be completed. java.util.concurrent.ExecutionException: java.lang.ClassCastException: class org.apache.flink.runtime.state.VoidNamespace cannot be cast to class org.apache.flink.streaming.api.windowing.windows.TimeWindow (org.apache.flink.runtime.state.VoidNamespace and org.apache.flink.streaming.api.windowing.windows.TimeWindow are in unnamed module of loader 'app')     at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:?]     at java.util.concurrent.FutureTask.get(FutureTask.java:191) ~[?:?]     at org.apache.flink.util.concurrent.FutureUtils.runIfNotDoneAndGet(FutureUtils.java:645) ~[flink-core-1.15.0.jar:1.15.0]     at org.apache.flink.streaming.api.operators.OperatorSnapshotFinalizer.<init>(OperatorSnapshotFinalizer.java:54) ~[flink-streaming-java-1.15.0.jar:1.15.0]     at org.apache.flink.streaming.runtime.tasks.AsyncCheckpointRunnable.finalizeNonFinishedSnapshots(AsyncCheckpointRunnable.java:191) ~[flink-streaming-java-1.15.0.jar:1.15.0]     at org.apache.flink.streaming.runtime.tasks.AsyncCheckpointRunnable.run(AsyncCheckpointRunnable.java:124) [flink-streaming-java-1.15.0.jar:1.15.0]     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]     at java.lang.Thread.run(Thread.java:834) [?:?] Caused by: java.lang.ClassCastException: class org.apache.flink.runtime.state.VoidNamespace cannot be cast to class org.apache.flink.streaming.api.windowing.windows.TimeWindow (org.apache.flink.runtime.state.VoidNamespace and org.apache.flink.streaming.api.windowing.windows.TimeWindow are in unnamed module of loader 'app')     at org.apache.flink.streaming.api.windowing.windows.TimeWindow$Serializer.serialize(TimeWindow.java:130) ~[flink-streaming-java-1.15.0.jar:1.15.0]     at org.apache.flink.runtime.state.heap.CopyOnWriteStateMapSnapshot.writeState(CopyOnWriteStateMapSnapshot.java:145) ~[flink-runtime-1.15.0.jar:1.15.0]     at org.apache.flink.runtime.state.heap.AbstractStateTableSnapshot.writeStateInKeyGroup(AbstractStateTableSnapshot.java:116) ~[flink-runtime-1.15.0.jar:1.15.0]     at org.apache.flink.runtime.state.heap.CopyOnWriteStateTableSnapshot.writeStateInKeyGroup(CopyOnWriteStateTableSnapshot.java:38) ~[flink-runtime-1.15.0.jar:1.15.0]     at org.apache.flink.runtime.state.heap.HeapSnapshotStrategy.lambda$asyncSnapshot$3(HeapSnapshotStrategy.java:172) ~[flink-runtime-1.15.0.jar:1.15.0]     at org.apache.flink.runtime.state.SnapshotStrategyRunner$1.callInternal(SnapshotStrategyRunner.java:91) ~[flink-runtime-1.15.0.jar:1.15.0]     at org.apache.flink.runtime.state.SnapshotStrategyRunner$1.callInternal(SnapshotStrategyRunner.java:88) ~[flink-runtime-1.15.0.jar:1.15.0]     at org.apache.flink.runtime.state.AsyncSnapshotCallable.call(AsyncSnapshotCallable.java:78) ~[flink-runtime-1.15.0.jar:1.15.0]     at java.util.concurrent.FutureTask.run(FutureTask.java:264) ~[?:?]     at org.apache.flink.util.concurrent.FutureUtils.runIfNotDoneAndGet(FutureUtils.java:642) ~[flink-core-1.15.0.jar:1.15.0]     ... 6 more  {code}
h2.  workaround
Turn off the checkpoint function.



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