[
https://issues.apache.org/jira/browse/KAFKA-6049?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17011070#comment-17011070
]
ASF GitHub Bot commented on KAFKA-6049:
---------------------------------------
mjsax commented on pull request #7847: KAFKA-6049: extend Kafka Streams Scala
API for cogroup (KIP-150)
URL: https://github.com/apache/kafka/pull/7847
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
> 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
>
> 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)
