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https://issues.apache.org/jira/browse/BEAM-291?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15286608#comment-15286608
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Aljoscha Krettek commented on BEAM-291:
---------------------------------------
Also, I think {{PDone}} is never to be used as the return type of a {{DoFn}} or
any operation that produces data. It is just the {{OutputT}} of a
{{PTransform}} when we want to signify that it is a terminal operation.
> PDone type translation fails
> ----------------------------
>
> Key: BEAM-291
> URL: https://issues.apache.org/jira/browse/BEAM-291
> Project: Beam
> Issue Type: Bug
> Components: runner-flink
> Reporter: Maximilian Michels
> Assignee: Maximilian Michels
>
> The {{PDone}} output type is currently not supported by the Flink Runner
> because it doesn't have a Coder associated. This could also get in the way
> when translating native Beam sinks which would likely return PDone.
> The simplest solution is to create a dummy PDone coder. Alternatively, we
> could check for the PDone return type during translation and not retrieve the
> coder at all.
> {noformat}
> Exception in thread "main" java.lang.IllegalStateException: Unable to return
> a default Coder for AnonymousParDo.out [PCollection]. Correct one of the
> following root causes:
> No Coder has been manually specified; you may do so using .setCoder().
> Inferring a Coder from the CoderRegistry failed: Unable to provide a
> default Coder for org.apache.beam.sdk.values.PDone. Correct one of the
> following root causes:
> Building a Coder using a registered CoderFactory failed: Cannot provide
> coder based on value with class org.apache.beam.sdk.values.PDone: No
> CoderFactory has been registered for the class.
> Building a Coder from the @DefaultCoder annotation failed: Class
> org.apache.beam.sdk.values.PDone does not have a @DefaultCoder annotation.
> Building a Coder from the fallback CoderProvider failed: Cannot provide
> coder for type org.apache.beam.sdk.values.PDone:
> org.apache.beam.sdk.coders.protobuf.ProtoCoder$1@72ef8d15 could not provide a
> Coder for type org.apache.beam.sdk.values.PDone: Cannot provide ProtoCoder
> because org.apache.beam.sdk.values.PDone is not a subclass of
> com.google.protobuf.Message;
> org.apache.beam.sdk.coders.SerializableCoder$1@6aa8e115 could not provide a
> Coder for type org.apache.beam.sdk.values.PDone: Cannot provide
> SerializableCoder because org.apache.beam.sdk.values.PDone does not implement
> Serializable.
> Using the default output Coder from the producing PTransform failed: Unable
> to provide a default Coder for org.apache.beam.sdk.values.PDone. Correct one
> of the following root causes:
> Building a Coder using a registered CoderFactory failed: Cannot provide
> coder based on value with class org.apache.beam.sdk.values.PDone: No
> CoderFactory has been registered for the class.
> Building a Coder from the @DefaultCoder annotation failed: Class
> org.apache.beam.sdk.values.PDone does not have a @DefaultCoder annotation.
> Building a Coder from the fallback CoderProvider failed: Cannot provide
> coder for type org.apache.beam.sdk.values.PDone:
> org.apache.beam.sdk.coders.protobuf.ProtoCoder$1@72ef8d15 could not provide a
> Coder for type org.apache.beam.sdk.values.PDone: Cannot provide ProtoCoder
> because org.apache.beam.sdk.values.PDone is not a subclass of
> com.google.protobuf.Message;
> org.apache.beam.sdk.coders.SerializableCoder$1@6aa8e115 could not provide a
> Coder for type org.apache.beam.sdk.values.PDone: Cannot provide
> SerializableCoder because org.apache.beam.sdk.values.PDone does not implement
> Serializable.
> at
> org.apache.beam.sdk.values.TypedPValue.inferCoderOrFail(TypedPValue.java:196)
> at org.apache.beam.sdk.values.TypedPValue.getCoder(TypedPValue.java:49)
> at org.apache.beam.sdk.values.PCollection.getCoder(PCollection.java:138)
> at
> org.apache.beam.runners.flink.translation.FlinkStreamingTransformTranslators$ParDoBoundStreamingTranslator.translateNode(FlinkStreamingTransformTranslators.java:315)
> at
> org.apache.beam.runners.flink.translation.FlinkStreamingTransformTranslators$ParDoBoundStreamingTranslator.translateNode(FlinkStreamingTransformTranslators.java:305)
> at
> org.apache.beam.runners.flink.translation.FlinkStreamingPipelineTranslator.applyStreamingTransform(FlinkStreamingPipelineTranslator.java:108)
> at
> org.apache.beam.runners.flink.translation.FlinkStreamingPipelineTranslator.visitPrimitiveTransform(FlinkStreamingPipelineTranslator.java:89)
> at
> org.apache.beam.sdk.runners.TransformTreeNode.visit(TransformTreeNode.java:225)
> at
> org.apache.beam.sdk.runners.TransformTreeNode.visit(TransformTreeNode.java:220)
> at
> org.apache.beam.sdk.runners.TransformHierarchy.visit(TransformHierarchy.java:104)
> at org.apache.beam.sdk.Pipeline.traverseTopologically(Pipeline.java:292)
> at
> org.apache.beam.runners.flink.translation.FlinkPipelineTranslator.translate(FlinkPipelineTranslator.java:34)
> at
> org.apache.beam.runners.flink.FlinkPipelineExecutionEnvironment.translate(FlinkPipelineExecutionEnvironment.java:132)
> at
> org.apache.beam.runners.flink.FlinkPipelineRunner.run(FlinkPipelineRunner.java:108)
> at
> org.apache.beam.runners.flink.FlinkPipelineRunner.run(FlinkPipelineRunner.java:49)
> at org.apache.beam.sdk.Pipeline.run(Pipeline.java:182)
> at
> org.apache.beam.runners.flink.examples.streaming.KafkaBeamExample.main(KafkaBeamExample.java:57)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke(Method.java:497)
> at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
> {noformat}
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