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From Kenneth Knowles <>
Subject Re: Setting synchronized processing time triggers
Date Mon, 20 Feb 2017 05:07:51 GMT
Moving this discussion to dev@ and user@ to BCC since I also doubt that
this should be user-facing. Feel free to restore it if you want.

The way it could really even be meaningful would be following a DoFn that
used timers in pretty advanced ways. I can't really come up with a real
example. It is public only due to Java visibility constraints to
appropriate map the trigger to an executable state machine. Work currently
in PR will remove those constraints, then we can make it package-private


On Sun, Feb 19, 2017 at 2:38 PM, Ben Chambers <> wrote:

> The continuation trigger is automatically used after the first group by
> key with a trigger. It is an attempt to trigger "as fast as reasonable"
> based on the original trigger. For example, if the trigger was 5 minutes
> after the hour (so aligned to an hour and then delayed by 5m) it wouldn't
> be good for every group by key to reintroduce the same delay. Instead it
> uses synchronized processing time to wait for all upstream firings of the
> same target time to fire. This ensures that all of the aligned triggers
> have been processed but non delay beyond that is introduced.
> Are there use cases for a user using synchronized processing time directly?
> On Sun, Feb 19, 2017, 2:30 PM Amit Sela <> wrote:
>> Hi all,
>> I was wondering how to use AfterSynchronizedProcessingTime trigger. for
>> processing time triggers there's the AfterProcessingTime.pastFirstElementInPane()
>> API but I've noticed that AfterSynchronizedProcessingTime constructor is
>> only called from a a continuation trigger.
>> I wonder if someone could explain how should pipeline authors use this
>> trigger, and maybe a general explanation about processing time triggers
>> since (as far as I could find) most of existing
>> documentations/presentations/talks are focused on watermark-based
>> triggers.
>> Thanks,
>> Amit

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