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https://issues.apache.org/jira/browse/FLINK-36349?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17883888#comment-17883888
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xuhuang commented on FLINK-36349:
---------------------------------
The ClassNotFoundException log related to the _FlinkScalaKryoInstantiator_ is
generated in the
_org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer#getKryoInstance_
method.
This occurs because the _FlinkScalaKryoInstantiator_ is defined in the
_flink-scala_ module, but the dependency for _flink-scala_ has been removed
from the pom.xml file in most modules (in pull request
[25324|https://github.com/apache/flink/pull/25324]). The
_FlinkScalaKryoInstantiator_ is specifically used for serializing Scala
objects. Given the deprecation of Scala APIs, it is likely that the
_FlinkScalaKryoInstantiator_ will be removed entirely once these Scala APIs are
removed.
Thus, the ClassNotFoundException log is anticipated at this stage. When all
Scala APIs are eventually removed, this log will no longer be necessary, as
there will be no requirement to handle Scala-specific objects in Kryo.
> ClassNotFoundException due to
> org.apache.flink.runtime.types.FlinkScalaKryoInstantiator missing
> -----------------------------------------------------------------------------------------------
>
> Key: FLINK-36349
> URL: https://issues.apache.org/jira/browse/FLINK-36349
> Project: Flink
> Issue Type: Bug
> Components: API / Type Serialization System
> Affects Versions: 2.0-preview
> Reporter: Matthias Pohl
> Priority: Blocker
> Labels: pull-request-available, test-stability
>
> This is most likely caused by FLINK-29741 which was recently merged.
> https://dev.azure.com/apache-flink/apache-flink/_build/results?buildId=62359&view=logs&j=8fd9202e-fd17-5b26-353c-ac1ff76c8f28&t=ea7cf968-e585-52cb-e0fc-f48de023a7ca&l=17558
> {code}
> Sep 23 01:58:51 01:58:50,533 12326 [AsyncOperations-thread-1] INFO
> org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer [] - Kryo
> serializer scala extensions are not available.
> Sep 23 01:58:51 java.lang.ClassNotFoundException:
> org.apache.flink.runtime.types.FlinkScalaKryoInstantiator
> Sep 23 01:58:51 at
> java.net.URLClassLoader.findClass(URLClassLoader.java:382) ~[?:1.8.0_292]
> Sep 23 01:58:51 at
> java.lang.ClassLoader.loadClass(ClassLoader.java:418) ~[?:1.8.0_292]
> Sep 23 01:58:51 at
> sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352) ~[?:1.8.0_292]
> Sep 23 01:58:51 at
> java.lang.ClassLoader.loadClass(ClassLoader.java:351) ~[?:1.8.0_292]
> Sep 23 01:58:51 at java.lang.Class.forName0(Native Method)
> ~[?:1.8.0_292]
> Sep 23 01:58:51 at java.lang.Class.forName(Class.java:264)
> ~[?:1.8.0_292]
> [...]
> {code}
> It causes ClosureCleanerITCase to fail in the AdaptiveScheduler test profile.
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