add a feature-gate for Lazy Reconcile feature

[chaosi-zju]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Small-step commit related code implementation for Policy Lazy Reconcile feature.

This PR only handle: add a feature-gate for Lazy Reconcile feature

More info refer to #4563

add a feature-gate for Lazy Reconcile feature

Which issue(s) this PR fixes:

Fixes part of #4563

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

add a feature-gate for Policy Lazy Reconcile feature

[karmada-bot]

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (0e501b6) 51.82% compared to head (0914915) 51.90%.
Report is 3 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4564      +/-   ##
==========================================
+ Coverage   51.82%   51.90%   +0.07%     
==========================================
  Files         244      246       +2     
  Lines       24234    24328      +94     
==========================================
+ Hits        12560    12627      +67     
- Misses      10993    11015      +22     
- Partials      681      686       +5     

Flag	Coverage Δ
unittests	51.90% <ø> (+0.07%)	⬆️

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[zhzhuang-zju]

Hi~ Do this pr need to add a release note?
others LGTM

[chaunceyjiang]

Why is there only one global switch? Will you also introduce related fields in PP next?

What I mean is, can the system have both an immediately effective PP and a Lazy Reconcile PP at the same time?

[chaunceyjiang]

Because if there's only one of two options, then assuming all future defaults are Lazy Reconcile, most users would refuse to upgrade due to their lack of experience with Lazy Reconcile.

[RainbowMango]

+1
lazy should not be the default behavior.

[chaosi-zju]

Lazy is not the default behavior as PolicyLazyReconcile{Default: false}

What chaunceyjiang mean is that it is better to add a filed to Policy to control the the effect strategy.

[chaunceyjiang]

What I mean is: It would be best if these two behaviors could coexist in the karmada.

[chaunceyjiang]

I still have one question I don't fully understand, which is: if a resource has not changed but the PP has changed, then this resource will continue to use the old PP. If a rescheduling happens at this time, should the scheduler use the old PP or the new PP? If it uses the new PP, then that behavior would be somewhat inconsistent with our expected behavior.
Our expectation is that the new PP would only be applied if the resource itself has changed.

[chaosi-zju]

/close

this feature-gate is depracated, replaced by Policy field, refer to #4577.

[karmada-bot]

@chaosi-zju: Closed this PR.

In response to this:

/close

this feature-gate is depracated, replaced by Policy field, refer to #4577.

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