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https://issues.apache.org/jira/browse/BEAM-12816?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Beam JIRA Bot updated BEAM-12816:
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Labels: (was: stale-P2)
> Inconsistent behaviour of triggers and/or that requires clarification
> ---------------------------------------------------------------------
>
> Key: BEAM-12816
> URL: https://issues.apache.org/jira/browse/BEAM-12816
> Project: Beam
> Issue Type: Bug
> Components: runner-py-direct
> Affects Versions: 2.31.0
> Environment: macOS 11.5.1, Python 3.7.10
> Reporter: Flo Vouin
> Priority: P3
>
> Hi,
> I've been using the Direct Runner in Python recently, as part of tests for a
> job aimed to be run on Dataflow. It's been a bit hard to know exactly what
> triggers do, but resorting to simple test cases, it seems like I've noticed
> some inconsistencies. I haven't checked whether those appear when running in
> Dataflow, though.
>
> *1. AfterAny(AfterProcessingTime(XX)) acts as
> Repeatedly(AfterProcessingTime(XX))*
> I would have expected {{AfterAny(SomeTrigger) <=> SomeTrigger}}, i.e.
> {{AfterAny}} acting as the identity when provided a single trigger. However
> this is not the case for {{AfterProcessingTime}}, because its {{on_fire}}
> result is not forwarded by {{AfterAny}}, due to the [call to should_fire not
> passing the right time
> domain|https://github.com/apache/beam/blob/cbb363f2f01d44dd3f7c063c6cd9d529b5fa9104/sdks/python/apache_beam/transforms/trigger.py#L790].
> This means that {{on_fire}} always returns {{False}}, hence {{AfterAny}}
> acting as {{Repeatedly}} in this case.
> Was this the purpose of [saving the time domain from the should_fire
> call|https://github.com/apache/beam/blob/cbb363f2f01d44dd3f7c063c6cd9d529b5fa9104/sdks/python/apache_beam/transforms/trigger.py#L779],
> which does not seem to be used?
> *2. AfterAny(AfterCount, AfterProcessingTime) triggers both children when
> AfterCount triggers first*
> This is less of a problem, but {{AfterProcessingTime}} will still trigger
> after {{AfterCount}} has triggered, when combined into an {{AfterAny}}. If no
> element has been added to the window, this means an empty pane will be
> emitted (or identical to the previous one, depending on the accumulation
> mode). My guess is that this happens because [AfterProcessingTime does not
> implement
> reset()|https://github.com/apache/beam/blob/cbb363f2f01d44dd3f7c063c6cd9d529b5fa9104/sdks/python/apache_beam/transforms/trigger.py#L390],
> but I guess there's a reason for this?
> *3. Unsafe trigger warning*
> It is unclear to me how the {{DataLossReason}}s are combined. For example:
> {{Repeatedly(AfterAny(AfterCount, AfterProcessingTime))}}
> is detected as an unsafe trigger, but
> {{Repeatedly(AfterAny(AfterCount, Repeatedly(AfterProcessingTime)))}}
> isn't, although if I'm not mistaken they should basically provide the same
> behaviour.
>
> Happy to provide more details if needed, and sorry if the issue doesn't quite
> fit the template you're expecting.
> Thanks,
> Flo
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