Add EstimateComponentsPlugins support to estimator framework

[seanlaii]

What type of PR is this?
/kind feature

What this PR does / why we need it:
Add EstimateComponentsPlugins support to estimator framework to allow customizing scheduling logic for Components.

Which issue(s) this PR fixes:

Part of #6734

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

`karmada-scheduler-estimator`: Allow adding plugins in estimator for component scheduling.
`karmada-scheduler-estimator`: Deprecated the `Estimator` label value for `estimating_plugin_extension_point` in the `estimating_plugin_execution_duration_seconds` and `estimating_plugin_extension_point_duration_seconds` metrics. Use `estimate_replicas` instead; `Estimator` will be removed in a future release. To avoid double counting during the deprecation period, update PromQL to filter on `estimating_plugin_extension_point="estimate_replicas"` (or exclude `Estimator`).

[gemini-code-assist]

Summary of Changes

Hello @seanlaii, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the estimator framework by introducing a new plugin extension point for EstimateComponentsPlugins. This allows for greater flexibility and customization in defining the scheduling logic for component sets, enabling users to implement their own strategies for estimating the maximum number of complete component sets based on given requirements. The changes include interface definitions, core framework implementation, and robust testing to ensure proper functionality and integration.

Highlights

• New Plugin Extension Point: Introduced EstimateComponentsPlugins to the estimator framework, allowing for custom scheduling logic when estimating component sets.
• Framework Interface Update: The Framework interface now includes RunEstimateComponentsPlugins and the EstimateComponentsPlugin interface for defining component set estimation logic.
• Implementation and Metrics: The frameworkImpl now supports registering and running EstimateComponentsPlugins, with updated metrics to track their execution, ensuring backward compatibility with existing EstimateReplicas metrics.
• Comprehensive Testing: New unit tests have been added to validate the behavior of RunEstimateComponentsPlugins under various scenarios, including success, error, unschedulable, and no-operation results from plugins.

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[gemini-code-assist]

Code Review

This pull request introduces support for EstimateComponentsPlugins to the estimator framework, a valuable feature for customizing component scheduling logic. The implementation is well-aligned with the existing EstimateReplicasPlugins framework, covering new interfaces, framework logic, and metrics. The test coverage for the new functionality is also thorough. I have a couple of suggestions: one to clarify a comment in the new interface and another to fix a bug in a new test case related to loop variable capturing, which would improve the reliability of the tests. Overall, this is a solid contribution.

[seanlaii]

Hi @RainbowMango ,

In order to differentiate the metrics between EstimateReplica and EstimateComponents plugins, I decided to introduce a new metrics with EstimateComponents label and plan to use EstimateReplica to replace the old Estimator label.

Additionally, to avoid breaking change I decided to emit the same metrics twice but with different label.
What do you think? I am OK with reusing Estimator but EstimateReplica might be clearer.

[zhzhuang-zju]

I'm okay with introducing EstimateReplica to replace Estimator. However, if we proceed with this change, the release note should include an additional section on the deprecation of the existing metrics.

[RainbowMango]

I'm OK with this way by introducing a new metric to deprecate the old one.

+1 on the release note

In addition, I realized both the old and new label names are written in camel case, which is not recommended.
I failed to find some documentation about the naming rule, but there is a metrics linter in the Prometheus project:
https://github.com/RainbowMango/client_golang/blob/e729ba11961abb3a50910c324221d06a35bdce4f/prometheus/testutil/promlint/validations/generic_name_validations.go#L74-L89

PS: I introduced this tool to Kubernetes several years ago, but I didn't get a chance to do the same thing in Karmada. I think Karmada should adopt this tool as well.

[seanlaii]

Thanks for the info! Updated the label values with snake case and the release note.

[RainbowMango]

In addition, I realized both the old and new label names are written in camel case, which is not recommended.

Hey, I need to correct my previous comment about the label format, according to the validation tools I linked above, only the label name should be written in snake_case. Actually, what we are talking about here is the value, I don't see any rules for it.

I see you updated the label value to snake_case, which also looks fine to me.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 45.67%. Comparing base (ce66819) to head (7df8e9e).
⚠️ Report is 2 commits behind head on master.
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6864      +/-   ##
==========================================
+ Coverage   45.63%   45.67%   +0.04%     
==========================================
  Files         692      692              
  Lines       57703    57732      +29     
==========================================
+ Hits        26331    26371      +40     
+ Misses      29725    29716       -9     
+ Partials     1647     1645       -2     

Flag	Coverage Δ
unittests	45.67% <100.00%> (+0.04%)	⬆️

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[seanlaii]

cc @RainbowMango @mszacillo

[zhzhuang-zju]

Thanks
/assign

[zhzhuang-zju]

/lgtm

[RainbowMango]

/assign

[zhzhuang-zju]

/lgtm

[RainbowMango]

/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: RainbowMango

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