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From Chesnay Schepler <ches...@apache.org>
Subject Re: Scheduling task slots in round-robin
Date Mon, 13 Jun 2016 12:58:29 GMT
FLINK-1003 may be related.

On 13.06.2016 12:46, Gyula Fóra wrote:
> Hey,
>
> The Flink scheduling mechanism has become quite a bit of a pain lately for
> us when trying to schedule IO heavy streaming jobs. And by IO heavy I mean
> it has a fairly large state that is being continuously updated/read.
>
> The main problem is that the scheduled task slots are not evenly
> distributed among the different task managers but usually the first TM
> takes as much slots as possibles and the other TMs get much fewer. And
> since the job is RocksDB IO bound the uneven load causes a significant
> performance penalty.
>
> This is further accentuated during historical runs when we are trying to
> "fast-forward" the application. The difference can be quite substantial in
> a 3-4 node cluster: with even task distribution the history might run 3
> times faster compared to an uneven one.
>
> I was wondering if there was a simple way to modify the scheduler so it
> allocates resources in a round-robin fashion. Probably someone has a lot of
> experience with this already :) (I'm running 1.0.3 for this job btw)
>
> Cheers,
> Gyula
>


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