Rasmus Helbig Hansen created KAFKA-12963:
--------------------------------------------

             Summary: Improve error message for Class cast exception
                 Key: KAFKA-12963
                 URL: https://issues.apache.org/jira/browse/KAFKA-12963
             Project: Kafka
          Issue Type: Improvement
          Components: streams
    Affects Versions: 2.7.0
            Reporter: Rasmus Helbig Hansen


After a topology change and starting the application again, we got this type of 
error message:
{noformat}
[g9z-StreamThread-1] ERROR 
org.apache.kafka.streams.processor.internals.TaskManager  - stream-thread 
[g9z-StreamThread-1] Failed to process stream task 1_12 due to the following 
error: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. Make sure the Processor can 
accept the deserialized input of type key: org.acme.SomeKey, and value: 
org.acme.SomeValue.Note that although incorrect Serdes are a common cause of 
error, the cast exception might have another cause (in user code, for example). 
For example, if a processor wires in a store, but casts the generics 
incorrectly, a class cast exception could be raised during processing, but the 
cause would not be wrong Serdes.       at 
org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:185)
    at 
org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forwardInternal(ProcessorContextImpl.java:273)
    at 
org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:252)
    at 
org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:219)
    at 
org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:172)
    at 
org.apache.kafka.streams.kstream.internals.KStreamJoinWindow$KStreamJoinWindowProcessor.process(KStreamJoinWindow.java:55)
    at 
org.apache.kafka.streams.processor.internals.ProcessorAdapter.process(ProcessorAdapter.java:71)
    at 
org.apache.kafka.streams.processor.internals.ProcessorNode.lambda$process$2(ProcessorNode.java:181)
    at 
org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl.maybeMeasureLatency(StreamsMetricsImpl.java:883)
    at 
org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:181)
    at 
org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forwardInternal(ProcessorContextImpl.java:273)
    at 
org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:252)
    at 
org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:219)
    at 
org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:86)
    at 
org.apache.kafka.streams.processor.internals.StreamTask.lambda$process$1(StreamTask.java:703)
    at 
org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl.maybeMeasureLatency(StreamsMetricsImpl.java:883)
    at 
org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:703)
    at 
org.apache.kafka.streams.processor.internals.TaskManager.process(TaskManager.java:1105)
    at 
org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:647)
    at 
org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:553)
    at 
org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:512)Caused
 by: java.lang.ClassCastException: class org.acme.SomeValue cannot be cast to 
class org.acme.OtherValue (org.acme.SomeValue and org.acme.OtherValue are in 
unnamed module of loader 'app')    at 
org.apache.kafka.streams.kstream.internals.KStreamKStreamJoin$KStreamKStreamJoinProcessor.process(KStreamKStreamJoin.java:112)
    at 
org.apache.kafka.streams.processor.internals.ProcessorAdapter.process(ProcessorAdapter.java:71)
    at 
org.apache.kafka.streams.processor.internals.ProcessorNode.lambda$process$2(ProcessorNode.java:181)
    at 
org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl.maybeMeasureLatency(StreamsMetricsImpl.java:883)
    at 
org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:181){noformat}
 It doesn't give enough context, like processor name and topic, which made 
troubleshooting unnecessary tricky.
 
Very similar to KAFKA-8884 which was fixed in 2.4.0. It seems like a regression.



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