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https://issues.apache.org/jira/browse/KAFKA-4969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15947575#comment-15947575
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Damian Guy commented on KAFKA-4969:
-----------------------------------
This also needs to take into account task stickyness, i.e., see
{{StickyTaskAssignor}}
> State-store workload-aware StreamsPartitionAssignor
> ---------------------------------------------------
>
> Key: KAFKA-4969
> URL: https://issues.apache.org/jira/browse/KAFKA-4969
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Matthias J. Sax
>
> Currently, {{StreamPartitionsAssigner}} does not distinguish different
> "types" of tasks. For example, task can be stateless of have one or multiple
> stores.
> This can lead to an suboptimal task placement: assume there are 2 stateless
> and 2 stateful tasks and the app is running with 2 instances. To share the
> "store load" it would be good to place one stateless and one stateful task
> per instance. Right now, there is no guarantee about this, and it can happen,
> that one instance processed both stateless tasks while the other processes
> both stateful tasks.
> We should improve {{StreamPartitionAssignor}} and introduce "task types"
> including a cost model for task placement. We should consider the following
> parameters:
> - number of stores
> - number of sources/sinks
> - number of processors
> - regular task vs standby task
> This improvement should be backed by a design document in the project wiki
> (no KIP required though) as it's a fairly complex change.
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