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https://issues.apache.org/jira/browse/BEAM-1641?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15988973#comment-15988973
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Aljoscha Krettek commented on BEAM-1641:
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Quick side note: In Flink, if you set your "stream time characteristic" (a bit
of a mouthful) to _ingestion time_ then you will essentially get the behaviour
of synchronised processing time. What this does is assign the current system
time as the element timestamp at the sources and generates watermarks based on
the current system time. After the sources it uses the same mechanism as
event-time. The problem is that it uses exactly the same mechanism, i.e. you
can either have proper event-time or ingestion time and there is actually no
difference to operators. All they see is "event time" and it might be actual
event time or ingestion time.
I think the proper solution would be for Flink to track ingestion time (which
is synchronised processing time) and event-time at the same time in one job.
[~kenn] and [~lzljs3620320], what do you think?
> Support synchronized processing time in Flink runner
> ----------------------------------------------------
>
> Key: BEAM-1641
> URL: https://issues.apache.org/jira/browse/BEAM-1641
> Project: Beam
> Issue Type: Bug
> Components: runner-flink
> Reporter: Kenneth Knowles
> Assignee: Aljoscha Krettek
> Priority: Blocker
> Fix For: First stable release
>
>
> The "continuation trigger" for a processing time trigger is a synchronized
> processing time trigger. Today, this throws an exception in the FlinkRunner.
> The supports the following:
> - GBK1
> - GBK2
> When GBK1 fires due to processing time past the first element in the pane and
> that element arrives at GBK2, it will wait until all the other upstream keys
> have also processed and emitted corresponding data.
> Sorry for the terseness of explanation - writing quickly so I don't forget.
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