[jira] [Commented] (FLINK-7388) ProcessFunction.onTimer() sets processing time as timestamp

["Aljoscha Krettek (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-7388?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16118122#comment-16118122 ] 

Aljoscha Krettek commented on FLINK-7388:
-----------------------------------------

This sounds legit, as long as we don't have explicit control over the timestamp of data that is emitted as the result of a timer firing. See also relevant Beam issue: BEAM-2535.

> ProcessFunction.onTimer() sets processing time as timestamp
> -----------------------------------------------------------
>
>                 Key: FLINK-7388
>                 URL: https://issues.apache.org/jira/browse/FLINK-7388
>             Project: Flink
>          Issue Type: Improvement
>          Components: DataStream API
>    Affects Versions: 1.4.0, 1.3.2
>            Reporter: Fabian Hueske
>
> The {{ProcessFunction.onTimer()}} method sets the current processing time as event-time timestamp when it is called from a processing time timer.
> I don't think this behavior is useful. Processing time timestamps won't be aligned with watermarks and are not deterministic. The only reason would be to have _some_ value in the timestamp field. However, the behavior is very subtle and might not be noticed by users.
> IMO, it would be better to erase the timestamp. This will cause downstream operator that rely on timestamps to fail and notify the users that the logic they implemented was probably not what they intended to do.
> What do you think [~aljoscha]?



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