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      Description

      The documentation of watermarks is not correct. It states

      A Watermark(t) declares that event time has reached time t in that stream, meaning that all events with a timestamps t’ < t have occurred.

      whereas the JavaDocs which is aligned with implementation says

      A Watermark tells operators that receive it that no elements with a
      timestamp older or equal to the watermark timestamp should arrive at the
      operator.

      The documentation needs to be updated. Moreover, we need to carefully check that the watermark semantics are correctly described in other pages of the documentation and blog posts published on the Flink website.

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          tzulitai Tzu-Li (Gordon) Tai added a comment -

          Resolved for master via f98af8cc1d997280d307a4942539957e35ee7141.
          Resolved for 1.2 via 9b2c89dbc0ce67030e33947d47102b6d4a53058f.

          Show
          tzulitai Tzu-Li (Gordon) Tai added a comment - Resolved for master via f98af8cc1d997280d307a4942539957e35ee7141. Resolved for 1.2 via 9b2c89dbc0ce67030e33947d47102b6d4a53058f.
          Hide
          githubbot ASF GitHub Bot added a comment -

          Github user asfgit closed the pull request at:

          https://github.com/apache/flink/pull/3185

          Show
          githubbot ASF GitHub Bot added a comment - Github user asfgit closed the pull request at: https://github.com/apache/flink/pull/3185
          Hide
          githubbot ASF GitHub Bot added a comment -

          Github user tzulitai commented on the issue:

          https://github.com/apache/flink/pull/3185

          @aljoscha thank you for the review. I'll address the inline comment and merge this to `master` and `release-1.2`

          Show
          githubbot ASF GitHub Bot added a comment - Github user tzulitai commented on the issue: https://github.com/apache/flink/pull/3185 @aljoscha thank you for the review. I'll address the inline comment and merge this to `master` and `release-1.2`
          Hide
          githubbot ASF GitHub Bot added a comment -

          Github user aljoscha commented on a diff in the pull request:

          https://github.com/apache/flink/pull/3185#discussion_r97507114

          — Diff: docs/dev/event_time.md —
          @@ -142,7 +143,7 @@ to use timestamp assignment and watermark generation in the Flink DataStream API

          1. Event Time and Watermarks

          -Note: Flink implements many techniques from the Dataflow Model. For a good introduction to Event Time and, have also a look at these articles
          +Note: Flink implements many techniques from the Dataflow Model. For a good introduction to Event Time and Watermarks, have also a look at these articles -
          — End diff –

          Is there a superfluous dash at the end?

          Show
          githubbot ASF GitHub Bot added a comment - Github user aljoscha commented on a diff in the pull request: https://github.com/apache/flink/pull/3185#discussion_r97507114 — Diff: docs/dev/event_time.md — @@ -142,7 +143,7 @@ to use timestamp assignment and watermark generation in the Flink DataStream API Event Time and Watermarks - Note: Flink implements many techniques from the Dataflow Model. For a good introduction to Event Time and, have also a look at these articles + Note: Flink implements many techniques from the Dataflow Model. For a good introduction to Event Time and Watermarks, have also a look at these articles - — End diff – Is there a superfluous dash at the end?
          Hide
          githubbot ASF GitHub Bot added a comment -

          GitHub user tzulitai opened a pull request:

          https://github.com/apache/flink/pull/3185

          FLINK-5375 [doc] Fix Watermark Semantics

          Fix watermark semantics in documenation to be correctly aligned with implementation: a Watermark t declares that event time has reached time t in that stream, meaning that there should be no more elements from the stream with a timestamp *t' <= t* (i.e. events with timestamps older or equal to the watermark).

          Also proof-read and corrected some mistakes in event-time / watermark related docs.

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

          $ git pull https://github.com/tzulitai/flink FLINK-5375

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

          https://github.com/apache/flink/pull/3185.patch

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

          This closes #3185


          commit a9469b982f58a37f395fb53fc7b762b557437e4f
          Author: Tzu-Li (Gordon) Tai <tzulitai@apache.org>
          Date: 2017-01-20T18:12:27Z

          FLINK-5375 [doc] Fix Watermark Semantics


          Show
          githubbot ASF GitHub Bot added a comment - GitHub user tzulitai opened a pull request: https://github.com/apache/flink/pull/3185 FLINK-5375 [doc] Fix Watermark Semantics Fix watermark semantics in documenation to be correctly aligned with implementation: a Watermark t declares that event time has reached time t in that stream, meaning that there should be no more elements from the stream with a timestamp * t' <= t * (i.e. events with timestamps older or equal to the watermark). Also proof-read and corrected some mistakes in event-time / watermark related docs. You can merge this pull request into a Git repository by running: $ git pull https://github.com/tzulitai/flink FLINK-5375 Alternatively you can review and apply these changes as the patch at: https://github.com/apache/flink/pull/3185.patch To close this pull request, make a commit to your master/trunk branch with (at least) the following in the commit message: This closes #3185 commit a9469b982f58a37f395fb53fc7b762b557437e4f Author: Tzu-Li (Gordon) Tai <tzulitai@apache.org> Date: 2017-01-20T18:12:27Z FLINK-5375 [doc] Fix Watermark Semantics

            People

            • Assignee:
              tzulitai Tzu-Li (Gordon) Tai
              Reporter:
              fhueske Fabian Hueske
            • Votes:
              0 Vote for this issue
              Watchers:
              4 Start watching this issue

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              • Created:
                Updated:
                Resolved:

                Development