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Posted to dev@kafka.apache.org by Xavier Léauté <xa...@confluent.io> on 2016/12/08 18:11:10 UTC

[DISCUSS] KIP-100 - Relax Type constraints in Kafka Streams API

I recently filed https://issues.apache.org/jira/browse/KAFKA-4481, which
Guozhang agreed was a bug. However fixing this will require some minor
changes to the existing Kafka Streams APIs.

I've outlined the required changes and binary / source compatibility
implications in the KIP
https://cwiki.apache.org/confluence/display/KAFKA/KIP-100+-+Relax+Type+constraints+in+Kafka+Streams+API

Thank you,
Xavier

Re: [DISCUSS] KIP-100 - Relax Type constraints in Kafka Streams API

Posted by Xavier Léauté <xa...@confluent.io>.

Hi everyone, Ismael made a good point in the voting thread to expand the
scope of this KIP to make functions covariant in their result types as
well, so I did.

Please read the updated KIP
https://cwiki.apache.org/confluence/display/KAFKA/KIP-100+-+Relax+Type+constraints+in+Kafka+Streams+API

and the corresponding PR for the gory details
https://github.com/apache/kafka/pull/2205

There were some subtleties related to functions applied to groupBy /
aggregate methods due to differences in type inference between jdk 1.7 and
1.8. See the rejected alternatives section for an explanation of why the
decision was made to go with invariant result types in those cases (for
now).

Let me know if you think everything makes sense.

Xavier

On Thu, Dec 8, 2016 at 10:35 AM Damian Guy <da...@gmail.com> wrote:

Hi Xavier,

The KIP looks good  - thanks!

Damian

On Thu, 8 Dec 2016 at 18:12 Xavier Léauté <xa...@confluent.io> wrote:

> I recently filed https://issues.apache.org/jira/browse/KAFKA-4481, which
> Guozhang agreed was a bug. However fixing this will require some minor
> changes to the existing Kafka Streams APIs.
>
> I've outlined the required changes and binary / source compatibility
> implications in the KIP
>
>
https://cwiki.apache.org/confluence/display/KAFKA/KIP-100+-+Relax+Type+constraints+in+Kafka+Streams+API
>
> Thank you,
> Xavier
>

Re: [DISCUSS] KIP-100 - Relax Type constraints in Kafka Streams API

Posted by Damian Guy <da...@gmail.com>.

Hi Xavier,

The KIP looks good  - thanks!

Damian

On Thu, 8 Dec 2016 at 18:12 Xavier Léauté <xa...@confluent.io> wrote:

> I recently filed https://issues.apache.org/jira/browse/KAFKA-4481, which
> Guozhang agreed was a bug. However fixing this will require some minor
> changes to the existing Kafka Streams APIs.
>
> I've outlined the required changes and binary / source compatibility
> implications in the KIP
>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-100+-+Relax+Type+constraints+in+Kafka+Streams+API
>
> Thank you,
> Xavier
>