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From "Nico Kruber (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-12122) Spread out tasks evenly across all available registered TaskManagers
Date Wed, 22 May 2019 08:51:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-12122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16845683#comment-16845683
] 

Nico Kruber commented on FLINK-12122:
-------------------------------------

Since every subtask gets its own thread (not every slot / slot sharing group), you don't need
to split into slot sharing groups in order to have concurrent processing. You may just need
to break an operator chain.

What I was saying: if you have a parallelism 50 job and only 50 slots in total, you'll get
your even distribution - as a workaround at least (I'm not saying anything against offering
the ability for users to control this behaviour). Apparently, you have more slots than your
desired parallelism.

> Spread out tasks evenly across all available registered TaskManagers
> --------------------------------------------------------------------
>
>                 Key: FLINK-12122
>                 URL: https://issues.apache.org/jira/browse/FLINK-12122
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Runtime / Coordination
>    Affects Versions: 1.6.4, 1.7.2, 1.8.0
>            Reporter: Till Rohrmann
>            Assignee: Till Rohrmann
>            Priority: Major
>             Fix For: 1.7.3, 1.9.0, 1.8.1
>
>         Attachments: image-2019-05-21-12-28-29-538.png, image-2019-05-21-13-02-50-251.png
>
>
> With Flip-6, we changed the default behaviour how slots are assigned to {{TaskManages}}.
Instead of evenly spreading it out over all registered {{TaskManagers}}, we randomly pick
slots from {{TaskManagers}} with a tendency to first fill up a TM before using another one.
This is a regression wrt the pre Flip-6 code.
> I suggest to change the behaviour so that we try to evenly distribute slots across all
available {{TaskManagers}} by considering how many of their slots are already allocated.



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