[jira] [Commented] (BEAM-1696) Allow explicit output time for processing time timers

["Reuven Lax (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEAM-1696?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15906833#comment-15906833 ] 

Reuven Lax commented on BEAM-1696:
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I don't think this should be limited to processing-time timers - should be supported for event-time timers as well. Event-time timers have a good default value (the timestamp of the timer), but should be allowed to use earlier values as well IMO.

> Allow explicit output time for processing time timers
> -----------------------------------------------------
>
>                 Key: BEAM-1696
>                 URL: https://issues.apache.org/jira/browse/BEAM-1696
>             Project: Beam
>          Issue Type: New Feature
>          Components: sdk-java-core
>            Reporter: Kenneth Knowles
>            Assignee: Kenneth Knowles
>
> Today, a processing time timer is not associated with a particular output timestamp; instead the user must explicitly output to the desired timestamp.
> This has a few drawbacks:
>  - Probably need to maintain state that indicates what the timestamp should be
>  - The output watermark is not held to that timestamp
> Something like {{processingTimer.set(...).withOutputTimestamp(...)}} (or perhaps some more involved API with an {{OutputTimeFn}}-like policy attached) would work nicely, so when {{@OnTimer}} is called the right timestamp is automatic.



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