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https://issues.apache.org/jira/browse/KAFKA-8870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16926066#comment-16926066
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Vinoth Chandar commented on KAFKA-8870:
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Picking it up, since I have not heard objections
> Prevent dirty reads of Streams state store from Interactive queries
> -------------------------------------------------------------------
>
> Key: KAFKA-8870
> URL: https://issues.apache.org/jira/browse/KAFKA-8870
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Vinoth Chandar
> Priority: Major
>
> Today, Interactive Queries (IQ) against Streams state store could see
> uncommitted data, even with EOS processing guarantees (these are actually
> orthogonal, but clarifying since EOS may give the impression that everything
> is dandy). This is causes primarily because state updates in rocksdb are
> visible even before the kafka transaction is committed. Thus, if the instance
> fails, then the failed over instance will redo the uncommited old transaction
> and the following could be possible during recovery,.
> Value for key K can go from *V0 → V1 → V2* on active instance A, IQ reads V1,
> instance A fails and any failure/rebalancing will leave the standy instance B
> rewinding offsets and reprocessing, during which time IQ can again see V0 or
> V1 or any number of previous values for the same key.
> In this issue, we will plan work towards providing consistency for IQ, for a
> single row in a single state store. i.e once a query sees V1, it can only see
> either V1 or V2.
>
>
>
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