Propose binding priority and preemption

[whitewindmills]

What type of PR is this? /kind design

What this PR does / why we need it: Propose binding priority and preemption

Which issue(s) this PR fixes: Fixes #4938

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[whitewindmills]

/cc @RainbowMango @XiShanYongYe-Chang

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All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 48.12%. Comparing base (d4c2793) to head (59a6afd). Report is 1195 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4993      +/-   ##
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- Coverage   53.33%   48.12%   -5.21%     
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  Files         252      668     +416     
  Lines       20482    55291   +34809     
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+ Hits        10924    26609   +15685     
- Misses       8836    26948   +18112     
- Partials      722     1734    +1012     

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[XiShanYongYe-Chang]

Thanks~ /assign

[whitewindmills]

/assign @RainbowMango

[RainbowMango]

Hi @whitewindmills I guess it's a good chance to introduce this proposal at tomorrow's community meeting, what do you think?

[whitewindmills]

hi all, can we continue this proposal?

[Monokaix]

hi all, can we continue this proposal?

+1

[seanlaii]

Hi all,

Thank you all for the amazing feedback today! In summary, our design currently only targets the resource that is scheduled in a single cluster, and the preemption only happens for the bindings in one cluster.

Here are the points we agree with in this proposal:

1. Need to redesign the scheduler queue so that it is aware of the priority and it will pop out the resource binding with highest priority first.
2. Reuse the native priorityClass and create a new API if we need to extend the functionality in the future.
3. Resolving the priority value and preemptionPolicy/preemptionBehavior to the resource binding so that the scheduler won’t need to query the priorityClass to find the values.
4. If scheduling fails due to insufficient resources (or can not find feasible clusters), we should continue attempting to schedule other pending ResourcesBindings instead of blocking the whole scheduling process.
5. Reschedule the preempted bindings. (Need to carefully consider the backoff time for the preempted bindings to avoid reschedule the preempted bindings before the preemptor binding.)

These are the points where we have different views or additional questions and thoughts:

1. Could you please clarify if there are any use cases that require binding the priorityClassName with the PropagationPolicy/ClusterPropagationPolicy? Maybe because you don't want to enforce that all the resources must have a priorityClassName filed? We plan to put the priority and preemptionBehavior/preemptionPolicy in the replicaRequirements. So the user can just specify the priorityClassName in the resource and create the resource the same as what they do in the single cluster. We can use custom resource interpreter to propagate the priority and preemptionPolicy to the replicaRequirements.
2. We propose using scheduler-estimators to find the victim bindings since they have the accurate information of the clusters, and the scheduler will use the victim bindings to decide which bindings to preempt and perform preemption.
3. If possible, we would like to have an option or feature gate or a field in the binding for controlling if preempted bindings should be rescheduled.

Thanks for your time again! Please feel free to provide any comment. Reference: Our Proposal - https://docs.google.com/document/d/1MixmgLwnmiRrukyFP25JvE2hqiqB3f_JKT12tXiOsbc/edit?tab=t.0 cc @RainbowMango @kevin-wangzefeng @wengyao04 @LeonZh0u

[whitewindmills]

@RainbowMango can this proposal be merged?

[RainbowMango]

I want to give it another look and see if any comments from the others.

[whitewindmills]

@kevin-wangzefeng @RainbowMango PTAL

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