[jira] [Commented] (FLINK-14109) Improve javadocs and tests for high-availability backend

["TisonKun (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-14109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16932053#comment-16932053 ] 

TisonKun commented on FLINK-14109:
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Hi [~bremac] thanks for reporting this!

There are two topics under this issue from my perspective.

1. Correct & enrich document.
2. Modify tests.

For 1, I it looks nice to have to me. For 2, maybe it's worth a separated thread. So a suggestion is narrowing this issue to focus on 1 and starting a separated issue focus on 2.

Besides, the community started a survey weeks ago on the topic "How do you use high-availability services in Flink?"[1]. It is recommend to you sharing your customization experience so that the ongoing refactor to high-availability service[2] would take your use case into consideration :-)

[1] https://lists.apache.org/x/thread.html/c0cc07197e6ba30b45d7709cc9e17d8497e5e3f33de504d58dfcafad@%3Cuser.flink.apache.org%3E
[2] https://issues.apache.org/jira/browse/FLINK-10333

> Improve javadocs and tests for high-availability backend
> --------------------------------------------------------
>
>                 Key: FLINK-14109
>                 URL: https://issues.apache.org/jira/browse/FLINK-14109
>             Project: Flink
>          Issue Type: Improvement
>          Components: Runtime / Coordination
>            Reporter: Brendan MacDonell
>            Priority: Minor
>
> My team at Sight Machine just finished building a custom HA backend for our infrastructure. The process was mostly painless, but we ran into a few pain points on the way:
>  * {{CompletedCheckpointStore#getLatestCheckpoint}} is not marked as \{{@Nullable}}, so there was some confusion about whether the Javadocs or (lack of) annotation is correct. The interface would be clearer if the annotation was present.
>  * The javadocs for {{CompletedCheckpointStore#recover}} disagree with the documentation for {{ZooKeeperCompletedCheckpointStore#recover}}. It's not immediately clear to someone working on the code that the ZK javadoc is outdated and the interface documentation is correct.
>  * The base {{CompletedCheckpointStore}} tests only work with high-availability backends that keep a list of checkpoints in memory. If the backend persists and retrieves data from another source the tests will fail. It's fairly simple to change the tests to lift this requirement though. See [this gist|https://gist.github.com/bremac/1b3365bc0257dfbd33bcd0b7a7627c00] for an example.
> We've got patches for the points above that we'd be happy to contribute. :)



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