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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Commented] (BEAM-145) OutputTimeFn#assignOutputTime overrides WindowFn#getOutputTime in unfortunate ways
Date Fri, 01 Jul 2016 16:57:11 GMT


ASF GitHub Bot commented on BEAM-145:

GitHub user kennknowles opened a pull request:

    [BEAM-145] Fix timestamps in GroupAlsoByWindowsProperties

    Be sure to do all of the following to help us incorporate your contribution
    quickly and easily:
     - [x] Make sure the PR title is formatted like:
       `[BEAM-<Jira issue #>] Description of pull request`
     - [x] Make sure tests pass via `mvn clean verify`. (Even better, enable
           Travis-CI on your fork and ensure the whole test matrix passes).
     - [x] Replace `<Jira issue #>` in the title with the actual Jira issue
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    Some of the timestamps were not adjusted when [BEAM-145](
was fixed to respect the `WindowFn`'s timestamps.

You can merge this pull request into a Git repository by running:

    $ git pull GABWProperties

Alternatively you can review and apply these changes as the patch at:

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #573
commit 190740f7971be506df5416dc4dfc5714bba0c972
Author: Kenneth Knowles <>
Date:   2016-07-01T16:53:37Z

    Fix timestamps in GroupAlsoByWindowsProperties
    Some of the timestamps were not adjusted when
    BEAM-145 was fixed to respect the WindowFn's


> OutputTimeFn#assignOutputTime overrides WindowFn#getOutputTime in unfortunate ways
> ----------------------------------------------------------------------------------
>                 Key: BEAM-145
>                 URL:
>             Project: Beam
>          Issue Type: Bug
>          Components: runner-core
>            Reporter: Kenneth Knowles
>            Assignee: Kenneth Knowles
>            Priority: Minor
>              Labels: windowing
>             Fix For: 0.1.0-incubating
> 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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