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https://issues.apache.org/jira/browse/KAFKA-4322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15716971#comment-15716971
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Guozhang Wang commented on KAFKA-4322:
--------------------------------------
I think I agree that some app-specific logic during restoration cannot be
simply wrapped in library logging or metrics, and as one of the "original
developer" I'm happy to take the blame :)
One way I can think of to remedy the backward incompatibility issue is to add a
new interface class like the following
{code}
public interface AdvancedStateRestoreCallback extends StateRestoreCallback {
void beginRestore(StateRestoreCallbackContext context)
void endRestore(StateRestoreCallbackContext context);
}
{code}
And then in {{ProcessorStateManager}} check if the restore callback is of
{{AdvancedStateRestoreCallback}} or not dynamically and trigger the functions
accordingly (by the way I'm not married to the interface name, just for demos).
What do you think [~markshelton]? Would you like to file a KIP along with
updating the PR?
> 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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