[
https://issues.apache.org/jira/browse/KAFKA-6049?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Matthias J. Sax resolved KAFKA-6049.
------------------------------------
Fix Version/s: 2.5.0
Resolution: Fixed
> Kafka Streams: Add Cogroup in the DSL
> -------------------------------------
>
> Key: KAFKA-6049
> URL: https://issues.apache.org/jira/browse/KAFKA-6049
> Project: Kafka
> Issue Type: New Feature
> Components: streams
> Reporter: Guozhang Wang
> Assignee: Walker Carlson
> Priority: Major
> Labels: api, kip, user-experience
> Fix For: 2.5.0
>
>
> When multiple streams aggregate together to form a single larger object (e.g.
> a shopping website may have a cart stream, a wish list stream, and a
> purchases stream. Together they make up a Customer), it is very difficult to
> accommodate this in the Kafka-Streams DSL: it generally requires you to group
> and aggregate all of the streams to KTables then make multiple outer join
> calls to end up with a KTable with your desired object. This will create a
> state store for each stream and a long chain of ValueJoiners that each new
> record must go through to get to the final object.
> Creating a cogroup method where you use a single state store will:
> * Reduce the number of gets from state stores. With the multiple joins when a
> new value comes into any of the streams a chain reaction happens where the
> join processor keep calling ValueGetters until we have accessed all state
> stores.
> * Slight performance increase. As described above all ValueGetters are called
> also causing all ValueJoiners to be called forcing a recalculation of the
> current joined value of all other streams, impacting performance.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
