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https://issues.apache.org/jira/browse/FLINK-3178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15105118#comment-15105118
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Aljoscha Krettek commented on FLINK-3178:
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I can't come up with cases where emitting the unfinished windows would actually
be the desirable behavior. As I see it there are two cases that involve closing
the window operator:
1. The job crashes, in that case the job will hopefully restart and I don't
want the unfinished windows emitted before
2. The job is gracefully stopped in order to be restarted later (possibly with
save points), in that case I also don't want the unfinished windows in my output
So I would suggest simply changing the behavior to not emit windows on closing.
Most people I talked to that are developing real-world jobs would actually
expect non-emission to be the default behavior.
What do you think?
> Make Closing Behavior of Window Operators Configurable
> ------------------------------------------------------
>
> Key: FLINK-3178
> URL: https://issues.apache.org/jira/browse/FLINK-3178
> Project: Flink
> Issue Type: Improvement
> Components: Streaming
> Affects Versions: 1.0.0
> Reporter: Aljoscha Krettek
> Priority: Blocker
>
> Right now, all window operators emit (incomplete) in-flight windows when they
> are closing down. This happens for two reasons:
> 1. sources emit a final Long.MAX_VALUE watermark to flush out windows when
> they close.
> 2. window operators emit in-flight windows in their close() method
> For some users this might not be the desired behavior so we should either
> change it or make it configurable.
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