Add feature flag pod-is-always-schedulable

[SaschaSchwarze0]

Same as #15397 I had missed that that one was auto-closed.

The feature flag allows to declare that Pods in the system will eventually all get scheduled and Revisions should therefore not be marked unschedulable

Fixes #14862

Proposed Changes

Unfortunately, I never got feedback in above issue, so trying with a PR now:

• New feature pod-is-always-schedulable is added with default false.
• If set to true, the revision reconciler will skip the check whether a pod is not scheduled and therefore never mark a revision as unschedulable.

EDIT: there was some feedback in the issue in the meantime and it has since then also been auto-closed. @dprotaso @skonto you were involved in a few discussions there, but without real outcome. Appreciate clear feedback whether we can take this forward or not.

Release Note

You can now set the new feature `pod-is-always-schedulable` to `true` in the config-deployment ConfigMap. As a result, Knative will not mark revisions as Unschedulable when a Pod is not scheduled. This makes sense if you want to omit this transient state in clusters that have cluster-autoscaling set up, and you can guarantee that all Pods will be eventually scheduled.

[knative-prow]

Hi @SaschaSchwarze0. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.18%. Comparing base (9786b60) to head (9eac88a).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/reconciler/revision/config/store.go	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16146      +/-   ##
==========================================
+ Coverage   80.16%   80.18%   +0.02%     
==========================================
  Files         216      216              
  Lines       13435    13440       +5     
==========================================
+ Hits        10770    10777       +7     
- Misses       2298     2300       +2     
+ Partials      367      363       -4     

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[dprotaso]

@SaschaSchwarze0 just some minor stuff.

Let's bring this change in and revisit whether we want to make any tweaks to this in the future.

Also To confirm we're still bound by the revision's progress deadline?

[dprotaso]

@SaschaSchwarze0 let me know if you're still following up with this

[SaschaSchwarze0]

@SaschaSchwarze0 let me know if you're still following up with this

Done, thanks for pinging.

[dprotaso]

/ok-to-test

[dprotaso]

I pushed minor change tweaking the test helper funcs

otherwise

/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dprotaso, SaschaSchwarze0

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