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https://issues.apache.org/jira/browse/KAFKA-4322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15716086#comment-15716086
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Mark Shelton commented on KAFKA-4322:
-------------------------------------
I do not at all like the idea of using the metrics API in order to be informed
that my state has completed restoring.
This API change only affects the low-level processor and only when using an own
state provider so its pretty limited.
The original developer of the API made a mistake in thinking that a row-by-row
API is sufficient and not considering the need for a begin and end indication.
> 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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