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https://issues.apache.org/jira/browse/KAFKA-7591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17016352#comment-17016352
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Matthias J. Sax commented on KAFKA-7591:
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Personally, I don't see why updating the config and enabling this feature would
make the situation worse and why we would need to block this feature? We can't
detect the discussed case today, and hence, enabling this feature does not
change the current "level of protection" (not better but also not worth), but
would just make Kafka Streams more feature rich (ie, better).
I don't see what we gain by logging a WARN if the expected config does not
match the actual config: if the reason is indeed a change of the window size,
the program is already starting up and if we just log a WARN and proceed, the
state will get "corrupted", so we don't really gain anything from my point of
view.
> 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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