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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