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https://issues.apache.org/jira/browse/BEAM-145?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kenneth Knowles resolved BEAM-145.
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Resolution: Duplicate
Fix Version/s: First stable release
The appropriate status would be "Redundant" in that the existing Runner API
proto combined with our intent to use it and imminent use of it make this
irrelevant now.
> OutputTimeFn#assignOutputTime overrides WindowFn#getOutputTime in unfortunate
> ways
> ----------------------------------------------------------------------------------
>
> Key: BEAM-145
> URL: https://issues.apache.org/jira/browse/BEAM-145
> Project: Beam
> Issue Type: Bug
> Components: runner-core
> Reporter: Kenneth Knowles
> Assignee: Kenneth Knowles
> Priority: Minor
> Labels: windowing
> Fix For: First stable release
>
>
> Today the {{OutputTimeFn}} includes {{#assignOutputTime}}, {{#combine}}, and
> {{#merge}}. Together these express the grouping of timestamps, analogous to
> the grouping of values in a GBK / Combine, in a canonical way.
> The default {{OutputTimeFn}} is provided by the {{WindowFn}}. In particular,
> {{SlidingWindows}} provides an {{OutputTimeFn}} that shifts input timestamps
> later to avoid watermark stuckness and then takes the minimum to compute the
> output timestamp.
> The SDK additionally provides instance for "min", "max" and "end of window"
> output timestamps.
> Unfortunately, if one overrides the {{OutputTimeFn}} to one of these, the
> shifting done by {{SlidingWindows}} is lost.
> This is actually only a minor problem for now, since "min" is the default,
> "end of window" is unaffected, and "max" has only esoteric uses.The fix is
> easy:
> This is interrelated with another suggested change: Since there are only
> three common {{OutputTimeFn}} instances, and it is a high bandwidth API, it
> does not seem worthwhile to leave it in userland. So it is proposed to reduce
> it to an enum, which would leave only the {{WindowFn}} as a userland place
> for timestamp adjustments. (requiring special casing for end-of-window, since
> it cannot be implemented without owning {{#assignOutputTime}})
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