[jira] [Created] (KAFKA-5632) Message headers not supported by Kafka Streams

["CJ Woolard (JIRA)" <ji...@apache.org>]

CJ Woolard created KAFKA-5632:
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             Summary: Message headers not supported by Kafka Streams
                 Key: KAFKA-5632
                 URL: https://issues.apache.org/jira/browse/KAFKA-5632
             Project: Kafka
          Issue Type: Bug
          Components: consumer
    Affects Versions: 0.11.0.0
            Reporter: CJ Woolard
            Priority: Minor


The new message headers functionality introduced in Kafka 0.11.0.0 (https://cwiki.apache.org/confluence/display/KAFKA/KIP-82+-+Add+Record+Headers) do not appear to be respected by Kafka Streams, specifically message headers set on input topics to a Kafka Streams topology do not get propagated to the corresponding output topics of the topology. 

It appears that it's at least partially due to the SourceNodeRecordDeserializer not properly respecting message headers here:

https://github.com/apache/kafka/blob/trunk/streams/src/main/java/org/apache/kafka/streams/processor/internals/SourceNodeRecordDeserializer.java#L60

where it isn't using the new ConsumerRecord constructor which supports headers:

https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/clients/consumer/ConsumerRecord.java#L122

For additional background here is the line before which we noticed that we still have the message headers, and after which we no longer have them:

https://github.com/apache/kafka/blob/trunk/streams/src/main/java/org/apache/kafka/streams/processor/internals/RecordQueue.java#L93

In terms of a potential solution there are a few different scenarios to consider:
1. A stream processor with one input and one output, i.e. 1-to-1, (A map/transformation for example). This is the simplest case, and one proposal would be to directly propagate any message headers from input to output.
2. A stream processor with one input and many outputs, i.e. 1-to-many, (A flatmap step for example). 
3. A stream processor with multiple inputs per output, i.e. many-to-1, (A join step for example). 
One proposal for supporting all possible scenarios would be to expose overloads in the Kafka Streams DSL methods to allow the user the ability to specify logic for handling of message headers. 

For additional background the use case is similar to a distributed tracing use case, where the following previous work may be useful for aiding in design discussions:
Dapper (https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/36356.pdf) 
or 
Zipkin (https://github.com/openzipkin/zipkin)





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