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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3428) Add fixed time trailing timestamp/watermark extractor
Date Fri, 01 Apr 2016 18:39:25 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3428?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15222140#comment-15222140

ASF GitHub Bot commented on FLINK-3428:

Github user StephanEwen commented on the pull request:

    The code looks good now.
      - How about we move all the convenience timestamp extractors / watermark generators
into a separate packe `.functions.timestamps`?
    I am a bit unsure about the docs. They seem to get confusing now. What is a mechanism
(periodic / punctuated), what is just a convenience implementation (Ascending, BoundedOutOfOrderness).
    How about leaving the docs page on watermark generation as it is and add another sub-page
that lists pre-defined watermark generators. We would list all the future watermark generators
      - ascending timestamps
      - bounded out-of-orderness
      - historgam based

> Add fixed time trailing timestamp/watermark extractor
> -----------------------------------------------------
>                 Key: FLINK-3428
>                 URL: https://issues.apache.org/jira/browse/FLINK-3428
>             Project: Flink
>          Issue Type: Improvement
>            Reporter: Robert Metzger
>            Assignee: Kostas Kloudas
> Flink currently provides only one build-in timestamp extractor, which assumes strictly
ascending timestamps. In real world use cases, timestamps are almost never strictly ascending.
> Therefore, I propose to provide an utility watermark extractor which is generating watermarks
with a fixed-time trailing.
> The implementation should keep track of the highest event-time seen so far and subtract
a fixed amount of time from that event time.
> This way, users can for example specify that the watermarks should always "lag behind"
10 minutes.

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