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From "Eno Thereska (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KAFKA-4322) StateRestoreCallback begin and end indication
Date Wed, 30 Nov 2016 14:53:58 GMT

    [ https://issues.apache.org/jira/browse/KAFKA-4322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15708790#comment-15708790

Eno Thereska commented on KAFKA-4322:

[~markshelton] We tend not to have such callbacks in streams. Would a listener word, e.g.,
you can register a listener and it's called upon restore completion (with number of records
restored). That way we can get rid of the start restore callback. We have a PR open that adds
listeners for monitoring the state an instance is at (https://github.com/apache/kafka/pull/2135).
You can see how the listeners work there. 

> 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:
>            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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