[jira] [Commented] (FLINK-14536) Make clear the way to aggregate specified cpuCores resources

["Till Rohrmann (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-14536?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16963079#comment-16963079 ] 

Till Rohrmann commented on FLINK-14536:
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This is a very good point. Tbh I'm not exactly sure why we chose {{max()}} in {{ResourceSpec#merge}}. Maybe [~zjwang] can shed some light on the matter since we introduced it with FLINK-5132.

I think the behaviour should be aligned. Moreover, I would have picked {{sum()}} since {{cpuCores}} should represent the number of required cores for one operator.

> Make clear the way to aggregate specified cpuCores resources
> ------------------------------------------------------------
>
>                 Key: FLINK-14536
>                 URL: https://issues.apache.org/jira/browse/FLINK-14536
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Runtime / Coordination
>    Affects Versions: 1.10.0
>            Reporter: Zhu Zhu
>            Priority: Major
>             Fix For: 1.10.0
>
>
> I'm raising this question because I find {{cpuCores}} in {{ResourceSpec#merge}} are aggregated with {{max()}}, while in {{ResourceProfile#merge}} it is {{sum()}}.
> This means that when calculating resources of a vertex from within operators, the {{cpuCores}} is the max value. While it is a sum(or subtraction in {{ResourceProfile#subtract}}) when dealing with shared slot bookkeeping and related checks. 
> This is confusing to me, especially when I'm considering how to generate a shared slot resource spec merged from all vertices in it(see FLINK-14314).
> I'm not pretty sure if we already have a concise definition for it?
> If there is, we need to respect it and change {{ResourceSpec}} or {{ResourceProfile}} accordingly.
> If not, we need to decide it first before we can move on with fine grained resources.
> Need to mention that if we take the {{max()}} way, we need to re-consider how we can conduct a correct {{ResourceProfile#subtract}} regarding {{cpuCores}}, since there is not a clear way to reverse a {{max()}} computation.
> cc [~trohrmann] [~xintongsong] [~azagrebin]



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