[
https://issues.apache.org/jira/browse/KAFKA-8884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16924267#comment-16924267
]
ASF GitHub Bot commented on KAFKA-8884:
---------------------------------------
astubbs commented on pull request #7309: MINOR: KAFKA-8884: class cast
exception improvement
URL: https://github.com/apache/kafka/pull/7309
If a processor causes a class cast exception, atm you get a bit of a cryptic
error if you're not used to them, and without a context sensitive suggestion as
to what could be wrong. Often these can be cause by miss-configured Serdes
(defaults).
Old error:
```
Caused by: java.lang.ClassCastException: class [B cannot be cast to class
java.lang.String ([B and java.lang.String are in module java.base of loader
'bootstrap')
```
An example of the improvement over the case exception:
```
org.apache.kafka.streams.errors.StreamsException: Exception caught in
process. taskId=0_0, processor=KSTREAM-SOURCE-0000000000,
topic=streams-plaintext-input, partition=0, offset=0,
stacktrace=org.apache.kafka.streams.errors.StreamsException:
ClassCastException invoking Processor. Do the Processor's input types match
the deserialized types? Check
the Serde setup and change the default Serdes in StreamConfig or provide
correct Serdes via method
parameters. Deserialized input types are: key: [B, value: [B
at
org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:123)
at
org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:201)
at
org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:180)
at
org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:133)
at
org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:87)
at
org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:366)
at
org.apache.kafka.streams.TopologyTestDriver.pipeInput(TopologyTestDriver.java:419)
at
org.apache.kafka.streams.processor.internals.ProcessorNodeTest.testTopologyLevelClassCastException(ProcessorNodeTest.java:176)
at
java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at
java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at
org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
at
org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at
org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
at
org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:305)
at
org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:365)
at
org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
at
org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
at org.junit.runners.ParentRunner$4.run(ParentRunner.java:330)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:78)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:328)
at org.junit.runners.ParentRunner.access$100(ParentRunner.java:65)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:292)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:305)
at org.junit.runners.ParentRunner.run(ParentRunner.java:412)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at
com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at
com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at
com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at
com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.lang.ClassCastException: class [B cannot be cast to class
java.lang.String ([B and java.lang.String are in module java.base of loader
'bootstrap')
at
org.apache.kafka.streams.kstream.internals.AbstractStream.lambda$withKey$1(AbstractStream.java:103)
at
org.apache.kafka.streams.kstream.internals.KStreamFlatMapValues$KStreamFlatMapValuesProcessor.process(KStreamFlatMapValues.java:40)
at
org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:119)
... 32 more
```
### Committer Checklist (excluded from commit message)
- [ ] Verify design and implementation
- [ ] Verify test coverage and CI build status
- [ ] Verify documentation (including upgrade notes)
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> Improve streams errors on class cast exception in ProcessorsNodes
> -----------------------------------------------------------------
>
> Key: KAFKA-8884
> URL: https://issues.apache.org/jira/browse/KAFKA-8884
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Affects Versions: 2.3.1
> Reporter: Antony Stubbs
> Priority: Minor
>
> If a processor causes a class cast exception, atm you get a bit of a cryptic
> error if you're not used to them, and without a context sensitive suggestion
> as to what could be wrong. Often these can be cause by missconfigured Serdes
> (defaults).
>
> As an example of the improvement over the case exception:
> {{{{ }}{{org.apache.kafka.streams.errors.StreamsException: Exception caught
> in process. taskId=0_0, processor=KSTREAM-SOURCE-0000000000,
> topic=streams-plaintext-input, partition=0, offset=0,
> stacktrace=org.apache.kafka.streams.errors.StreamsException:
> ClassCastException invoking Processor. Do the Processor's input types match
> the deserialized types? Check the Serde setup and change the default Serdes
> in StreamConfig or provide correct Serdes via method parameters. Deserialized
> input types are: key: [B, value: [B}}}}
> {{ \{{ at
> org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:123)}}}}
> {{ \{{ at
> org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:201)}}}}
> {{ \{{ at
> org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:180)}}}}
> {{ \{{ at
> org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:133)}}}}
> {{ \{{ at
> org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:87)}}}}
> {{ \{{ at
> org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:366)}}}}
> {{ \{{ at
> org.apache.kafka.streams.TopologyTestDriver.pipeInput(TopologyTestDriver.java:419)}}}}
> {{ \{{ at
> org.apache.kafka.streams.processor.internals.ProcessorNodeTest.testTopologyLevelClassCastException(ProcessorNodeTest.java:176)}}}}
> {{ \{{ at
> java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native
> Method)}}}}
> {{ \{{ at
> java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)}}}}
> {{ \{{ at
> java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)}}}}
> {{ \{{ at java.base/java.lang.reflect.Method.invoke(Method.java:566)}}}}
> {{ \{{ at
> org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)}}}}
> {{ \{{ at
> org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)}}}}
> {{ \{{ at
> org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)}}}}
> {{ \{{ at
> org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)}}}}
> {{ \{{ at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:305)}}}}
> {{ \{{ at
> org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)}}}}
> {{ \{{ at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:365)}}}}
> {{ \{{ at
> org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)}}}}
> {{ \{{ at
> org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)}}}}
> {{ \{{ at org.junit.runners.ParentRunner$4.run(ParentRunner.java:330)}}}}
> {{ \{{ at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:78)}}}}
> {{ \{{ at
> org.junit.runners.ParentRunner.runChildren(ParentRunner.java:328)}}}}
> {{ \{{ at org.junit.runners.ParentRunner.access$100(ParentRunner.java:65)}}}}
> {{ \{{ at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:292)}}}}
> {{ \{{ at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:305)}}}}
> {{ \{{ at org.junit.runners.ParentRunner.run(ParentRunner.java:412)}}}}
> {{ \{{ at org.junit.runner.JUnitCore.run(JUnitCore.java:137)}}}}
> {{ \{{ at
> com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)}}}}
> {{ \{{ at
> com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)}}}}
> {{ \{{ at
> com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)}}}}
> {{ \{{ at
> com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)}}}}
> {{ \{{ Caused by: java.lang.ClassCastException: class [B cannot be cast to
> class java.lang.String ([B and java.lang.String are in module java.base of
> loader 'bootstrap')}}}}
> {{ \{{ at
> org.apache.kafka.streams.kstream.internals.AbstractStream.lambda$withKey$1(AbstractStream.java:103)}}}}
> {{ \{{ at
> org.apache.kafka.streams.kstream.internals.KStreamFlatMapValues$KStreamFlatMapValuesProcessor.process(KStreamFlatMapValues.java:40)}}}}
> {{ \{{ at
> org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:119)}}}}
> {{ \{{ ... 32 more}}}}
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