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https://issues.apache.org/jira/browse/KAFKA-4322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15671093#comment-15671093
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Guozhang Wang commented on KAFKA-4322:
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Thanks [~markshelton], the reason I mentioned a KIP proposal is that we seem
have different opinions (having a callback, or rather just adding the metrics /
log entries) on this issue, and KIP discussion was designed for such cases
where people can speak out openly and bring community's attention to any
changes to public APIs.
Given your use case, I'm wondering if it would OK to just adding logging to
record how many keys were restored and also metrics regarding restoration,
instead of adding a generalized callback? If in the future we observed other
use cases that can be captured in a callback I'm more than happy to propose the
KIP myself and push this change to public APIs, since after all it is easier to
add a new function later than adding the function now and reverting it for
simplicity.
> StateRestoreCallback begin and end indication
> ---------------------------------------------
>
> Key: KAFKA-4322
> URL: https://issues.apache.org/jira/browse/KAFKA-4322
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Affects Versions: 0.10.1.0
> Reporter: Mark Shelton
> Assignee: Mark Shelton
> Priority: Minor
>
> In Kafka Streams, the StateRestoreCallback interface provides only a single
> method "restore(byte[] key, byte[] value)" that is called for every key-value
> pair to be restored.
> It would be nice to have "beginRestore" and "endRestore" methods as part of
> StateRestoreCallback.
> Kafka Streams would call "beginRestore" before restoring any keys, and would
> call "endRestore" when it determines that it is done. This allows an
> implementation, for example, to report on the number of keys restored and
> perform a commit after the last key was restored. Other uses are conceivable.
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