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https://issues.apache.org/jira/browse/KAFKA-7591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17015502#comment-17015502
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Matthias J. Sax commented on KAFKA-7591:
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{quote}Shouldn't you need to reset the app if the window size changes?
{quote}
Maybe, but this seems to be orthogonal.
{quote}But it wouldn't be able to distinguish a change in retention from a
change in window size,
{quote}
As above, seems to be orthogonal.
I would still prefer if KS would automatically update the topic configuration.
Note, that we do have an explicit `topic.` prefix to specify topic configs and
it seem reasonable to allow user to change those configs and that KS updates
the corresponding topic configuration (this also holds for `replication.factor`
btw). But I think we can cover all this with a single PR – if a topic exists,
we fetch it's config, compare it to whatever config we computed and issue
AlterTopicConfig request to update the config. (We would also log an INFO
statement when this happens).
> 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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