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https://issues.apache.org/jira/browse/FLINK-10327?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16613537#comment-16613537
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ASF GitHub Bot commented on FLINK-10327:
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kl0u commented on issue #6687: [FLINK-10327][streaming] Expose
processWatermarks notifications to (Co)ProcessFunction
URL: https://github.com/apache/flink/pull/6687#issuecomment-421017411
Hi @pnowojski !
I can understand that this can be an interesting addition for some usecases,
but it is a big one, and it should be discussed more thoroughly and, most
importantly, more publicly. I would be against merging it as just a sub-commit
of another feature.
The reason is that this allows users to "play" with watermarks from the
level of a `Function` and not `Operator`, which was, intentionally, the case so
far.
If you want to "hold back" the watermark, the this should be done by a
watermark assigner.
If you want to run a "callback" upon watermark, then so far the trick is to
register a timer for `watermark + 1`.
I can find usecases which do not fall into any of the above, but for those
so far we implement custom operators.
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> Pass processWatermark calls from (Co)ProcessOperator to (Co)ProcessFunction
> ---------------------------------------------------------------------------
>
> Key: FLINK-10327
> URL: https://issues.apache.org/jira/browse/FLINK-10327
> Project: Flink
> Issue Type: New Feature
> Components: Streaming
> Reporter: Piotr Nowojski
> Assignee: Piotr Nowojski
> Priority: Major
> Labels: pull-request-available
>
> Currently {{CoProcessFunction}} can not react to changes watermark
> advancement. By passing {{processWatermark}} calls to function we would give
> a way to perform some actions on watermark advancement, like state clean up
> or emitting some results after accumulating some data.
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