[jira] [Commented] (SPARK-33827) Unload State Store asap once it becomes inactive

["L. C. Hsieh (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-33827?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17251262#comment-17251262 ] 

L. C. Hsieh commented on SPARK-33827:
-------------------------------------

[~kabhwan] Thanks for the discussion before.

Though, unloading inactive state stores asap sounds reasonable to me, but after rethinking it, as we can reduce inactive state store by setting task locality, is it worth making non-trivial for it?

WDYT?

> Unload State Store asap once it becomes inactive
> ------------------------------------------------
>
>                 Key: SPARK-33827
>                 URL: https://issues.apache.org/jira/browse/SPARK-33827
>             Project: Spark
>          Issue Type: Improvement
>          Components: Structured Streaming
>    Affects Versions: 3.2.0
>            Reporter: L. C. Hsieh
>            Priority: Major
>
> SS maintains state stores in executors across batches. Due to the nature of Spark scheduling, a state store might be allocated on another executor in next batch. The state store in previous batch becomes inactive.
> Now we run a maintenance task periodically to unload inactive state stores. So there will be some delays between a state store becomes inactive and it is unloaded.
> Per the discussion on https://github.com/apache/spark/pull/30770 with [~kabhwan], I think the preference is to unload inactive state asap.
> However, we can force Spark to always allocate a state store to same executor, by using task locality configuration. This can reduce the possibility to have inactive state store.
> Normally, I think with locality configuration, we might not able to see inactive state store generally. There is still chance an executor can be failed and reallocated, but in this case, inactive state store is also lost too. So it is not an issue.
> The required change to make driver-executor bi-directional for state store management looks non-trivial. If we already can reduce possibility of inactive store, is it still worth making non-trivial here?



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