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https://issues.apache.org/jira/browse/KAFKA-7591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17016294#comment-17016294
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Sophie Blee-Goldman commented on KAFKA-7591:
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Right, that is why I say if we can't distinguish between a window size change
(incompatible) and a retention period change (fine) we should _not_ alter the
configs, and just log a warning if there is a mismatch. Once KAFKA-8307 is
fixed then we can consider allowing Streams to change existing topic configs.
For now, I think it would still be valuable to check whether there are
contradictory configs and raise it to the user if so.
> Changelog retention period doesn't synchronise with window-store size
> ---------------------------------------------------------------------
>
> Key: KAFKA-7591
> URL: https://issues.apache.org/jira/browse/KAFKA-7591
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Jon Bates
> Priority: Major
>
> When a new windowed state store is created, the associated changelog topic's
> `retention.ms` value is set to `window-size +
> CHANGELOG_ADDITIONAL_RETENTION_MS`
> h3. Expected Behaviour
> If the window-size is updated, the changelog topic's `retention.ms` config
> should be updated to reflect the new size
> h3. Actual Behaviour
> The changelog-topic's `retention.ms` setting is not amended, resulting in
> possible loss of data upon application restart
>
> n.b. Although it is easy to update changelog topic config, I logged this as
> `major` due to the potential for data-loss for any user of Kafka-Streams who
> may not be intimately aware of the relationship between a windowed store and
> the changelog config
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