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https://issues.apache.org/jira/browse/KAFKA-4322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15715221#comment-15715221
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Mark Shelton commented on KAFKA-4322:
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>> "We tend not to have such callbacks"
The StateRestoreCallback already exists and is just being extended by "begin"
and "end" indication calls.
>> Would a listener word, e.g., you can register a listener and it's called
>> upon restore completion (with number of records restored).
Sure we can have yet another listener interface to implement. I don't quite
understand what that would buy.
>> We have a PR open that adds listeners for monitoring the state an instance
>> is at.
As long as it gets done. Please get it done.
> 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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