java.lang.IllegalStateException:不应发生这种情况，因为headers()仅应在处理记录时调用 [英] java.lang.IllegalStateException: This should not happen as headers() should only be called while a record is processed

问题描述

(使用Kafka Streams)启动Stream应用程序失败，并显示"java.lang.IllegalStateException:这不应发生，因为headers()仅应在处理记录时调用"

Starting up a Stream application (using Kafka Streams) fails with the "java.lang.IllegalStateException: This should not happen as headers() should only be called while a record is processed"

这似乎仅在主题中已经有数据的情况下启动应用程序时发生.如果主题为空并且我开始向其推送数据，那么一切都很好.

This seems to only happen when I start up the application if there is already data in the topic. If the topic is empty and I start pushing data to it, all is fine.

有人知道为什么会这样吗?

Would someone know why this would happen?

谢谢

This should not happen as headers() should only be called while a record is processed
java.lang.IllegalStateException: This should not happen as headers() should only be called while a record is processed
        at org.apache.kafka.streams.processor.internals.AbstractProcessorContext.headers(AbstractProcessorContext.java:149)
        at org.apache.kafka.streams.state.internals.CachingKeyValueStore.putInternal(CachingKeyValueStore.java:235)
        at org.apache.kafka.streams.state.internals.CachingKeyValueStore.put(CachingKeyValueStore.java:222)
        at org.apache.kafka.streams.state.internals.CachingKeyValueStore.put(CachingKeyValueStore.java:37)
        at org.apache.kafka.streams.state.internals.MeteredKeyValueStore.put(MeteredKeyValueStore.java:153)
        at org.apache.kafka.streams.processor.internals.ProcessorContextImpl$KeyValueStoreReadWriteDecorator.put(ProcessorContextImpl.java:446)
        at fr.mediametrie.GeoIPEnrichmentProcessor.transform(GeoIPEnrichmentProcessor.java:97)
        at fr.mediametrie.GeoIPEnrichmentProcessor.transform(GeoIPEnrichmentProcessor.java:1)
        at org.apache.kafka.streams.kstream.internals.TransformerSupplierAdapter$1.transform(TransformerSupplierAdapter.java:47)
        at org.apache.kafka.streams.kstream.internals.TransformerSupplierAdapter$1.transform(TransformerSupplierAdapter.java:36)
        at org.apache.kafka.streams.kstream.internals.KStreamFlatTransform$KStreamFlatTransformProcessor.process(KStreamFlatTransform.java:56)
        at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:117)
        at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:183)
        at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:162)
        at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:122)
        at org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:87)
        at org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:364)
        at org.apache.kafka.streams.processor.internals.AssignedStreamsTasks.process(AssignedStreamsTasks.java:199)
        at org.apache.kafka.streams.processor.internals.TaskManager.process(TaskManager.java:420)
        at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:890)
        at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:805)
        at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:774)

推荐答案

基于Matthias共享的信息，这是一个实际示例:

Building on the information Matthias shared, here's a practical example:

• 返回相同的转换器对象(对Processor和ValueTransformer也有效)会导致 IllegalStateException :

var transformer = new Transformer();

inputStream
  .transformValues(() -> transformer)
// further operations...

• 每次返回一个新实例可防止出现异常:

inputStream
  .transformValues(() -> new Transformer())
// further operations...

p.s:我知道文档非常清楚，但是希望可以节省一些滚动.

p.s: I am aware that the documentation is quite clear, but hope this saves some scrolling.

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