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https://issues.apache.org/jira/browse/FLINK-23190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17396739#comment-17396739
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Till Rohrmann commented on FLINK-23190:
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Sorry for my late reply [~loyi]. The distribution looks indeed a lot better. I
like the change to the {{AdaptiveScheduler}} since it could simply be a
different {{SlotAllocator}} implementation.
Concerning the implementation for the default scheduler I am not so sure. I
think that the {{SlotRequestId}} should not be the place to record which groups
are intended to be deployed in this slot. It would be better if we could solve
this problem as a special {{ExecutionSlotAllocator}} for example.
> Make task-slot allocation much more evenly
> ------------------------------------------
>
> Key: FLINK-23190
> URL: https://issues.apache.org/jira/browse/FLINK-23190
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / Coordination
> Affects Versions: 1.12.3
> Reporter: loyi
> Priority: Major
> Labels: pull-request-available
> Attachments: image-2021-07-16-10-34-30-700.png
>
>
> FLINK-12122 only guarantees spreading out tasks across the set of TMs which
> are registered at the time of scheduling, but our jobs are all runing on
> active yarn mode， the job with smaller source parallelism offen cause
> load-balance issues.
>
> For this job:
> {code:java}
> // -ys 4 means 10 taskmanagers
> env.addSource(...).name("A").setParallelism(10).
> map(...).name("B").setParallelism(30)
> .map(...).name("C").setParallelism(40)
> .addSink(...).name("D").setParallelism(20);
> {code}
>
> Flink-1.12.3 task allocation:
> ||operator||tm1 ||tm2||tm3||tm4||tm5||5m6||tm7||tm8||tm9||tm10||
> |A|
> 1|{color:#de350b}2{color}|{color:#de350b}2{color}|1|1|{color:#de350b}3{color}|{color:#de350b}0{color}|{color:#de350b}0{color}|{color:#de350b}0{color}|{color:#de350b}0{color}|
> |B|3|3|3|3|3|3|3|3|{color:#de350b}2{color}|{color:#de350b}4{color}|
> |C|4|4|4|4|4|4|4|4|4|4|
> |D|2|2|2|2|2|{color:#de350b}1{color}|{color:#de350b}1{color}|2|2|{color:#de350b}4{color}|
>
> Suggestions:
> When TaskManger start register slots to slotManager , current processing
> logic will choose the first pendingSlot which meet its resource
> requirements. The "random" strategy usually causes uneven task allocation
> when source-operator's parallelism is significantly below process-operator's.
> A simple feasible idea is {color:#de350b}partition{color} the current
> "{color:#de350b}pendingSlots{color}" by their "JobVertexIds" (such as let
> AllocationID bring the detail) , then allocate the slots proportionally to
> each JobVertexGroup.
>
> For above case, the 40 pendingSlots could be divided into 4 groups：
> [ABCD]: 10 // A、B、C、D reprents {color:#de350b}jobVertexId{color}
> [BCD]: 10
> [CD]: 10
> [D]: 10
>
> Every taskmanager will provide 4 slots one time, and each group will get 1
> slot according their proportion (1/4), the final allocation result is below:
> [ABCD] : deploye on 10 different taskmangers
> [BCD]: deploye on 10 different taskmangers
> [CD]: deploye on 10 different taskmangers
> [D]: deploye on 10 different taskmangers
>
> I have implement a [concept
> code|https://github.com/saddays/flink/commit/dc82e60a7c7599fbcb58c14f8e3445bc8d07ace1]
> based on Flink-1.12.3 , the patch version has {color:#de350b}fully
> evenly{color} task allocation , and works well on my workload . Are there
> other point that have not been considered or does it conflict with future
> plans? Sorry for my poor english.
>
>
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