[
https://issues.apache.org/jira/browse/BEAM-145?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15359666#comment-15359666
]
ASF GitHub Bot commented on BEAM-145:
-------------------------------------
Github user asfgit closed the pull request at:
https://github.com/apache/incubator-beam/pull/573
> 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: 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}})
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
