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https://issues.apache.org/jira/browse/KAFKA-8410?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Matthias J. Sax updated KAFKA-8410:
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Fix Version/s: 2.7.0
> Strengthen the types of Processors, at least in the DSL, maybe in the PAPI as
> well
> ----------------------------------------------------------------------------------
>
> Key: KAFKA-8410
> URL: https://issues.apache.org/jira/browse/KAFKA-8410
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: John Roesler
> Assignee: John Roesler
> Priority: Major
> Labels: tech-debt
> Fix For: 2.7.0
>
>
> Presently, it's very difficult to have confidence when adding to or modifying
> processors in the DSL. There's a lot of raw types, duck-typing, and casting
> that contribute to this problem.
> The root, though, is that the generic types on `Processor<K,V>` refer only to
> the _input_ key and value types. No information is captured or verified about
> what the _output_ types of a processor are. For example, this leads to
> widespread confusion in the code base about whether a processor produces `V`s
> or `Change<V>`s. The type system actually makes matters worse, since we use
> casts to make the processors conform to declared types that are in fact
> wrong, but are never checked due to erasure.
> We can start to make some headway on this tech debt by adding some types to
> the ProcessorContext that bound the `<K,V>` that may be passed to
> `context.forward`. Then, we can build on this by fully specifying the input
> and output types of the Processors, which in turn would let us eliminate the
> majority of unchecked casts in the DSL operators.
> I'm not sure whether adding these generic types to the existing
> ProcessorContext and Processor interfaces, which would also affect the PAPI
> has any utility, or whether we should make this purely an internal change by
> introducing GenericProcessorContext and GenericProcessor peer interfaces for
> the DSL to use.
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