[jira] [Commented] (BEAM-145) OutputTimeFn#assignOutputTime overrides WindowFn#getOutputTime in unfortunate ways

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEAM-145?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15276642#comment-15276642 ] 

ASF GitHub Bot commented on BEAM-145:
-------------------------------------

Github user asfgit closed the pull request at:

    https://github.com/apache/incubator-beam/pull/296


> 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
>
> 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}})



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)