Add feature flag treat-pod-as-always-schedulable

[SaschaSchwarze0]

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 treat-pod-as-always-schedulable is added with default Disabled.
• If enabled, the revision reconciler will skip the check whether a pod is not scheduled and therefore never mark a revision as unschedulable.

Release Note

You can now set the new feature `treat-pod-as-always-schedulable` to enabled in the config-defaults 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 knative 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.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[SaschaSchwarze0]

Hm, I debugged the failing unit test and can see that when the code checks the config, that there is some config in the context with the right value but somehow what it gets has it empty. Need to check ...

[skonto]

@SaschaSchwarze0 gentle ping.

[skonto]

/ok-to-test

[knative-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: SaschaSchwarze0
Once this PR has been reviewed and has the lgtm label, please assign dprotaso for approval. For more information see the Code Review Process.

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[SaschaSchwarze0]

@SaschaSchwarze0 gentle ping.

Rebased, but I still do not understand the unit test case failure in pkg/reconciler/revision/table_test.go. In particular, the custom context with the custom feature flag does not work = the code does not get the expected feature flag status and I do not understand why.

EDIT1: I think I now understand it. table_test.go does the following which overwrites all config customizations done on the Ctx of the row.

		return revisionreconciler.NewReconciler(ctx, logging.FromContext(ctx), servingclient.Get(ctx),
			listers.GetRevisionLister(), controller.GetEventRecorder(ctx), r,
			controller.Options{
				ConfigStore: &testConfigStore{
					config: reconcilerTestConfig(),
				},
			})

EDIT2: Though, I do not understand why it works for other unit tests then (like the one that sets PodSpecInitContainers to Enabled).

EDIT3: Maybe because only the controller uses the configstore from its options.

EDIT4: Fixed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.84%. Comparing base (19b9a09) to head (5303dc0).
⚠️ Report is 213 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15397      +/-   ##
==========================================
+ Coverage   80.78%   80.84%   +0.06%     
==========================================
  Files         222      222              
  Lines       18025    18029       +4     
==========================================
+ Hits        14561    14576      +15     
+ Misses       3092     3084       -8     
+ Partials      372      369       -3     

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[knative-prow-robot]

PR needs rebase.

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[github-actions]

This Pull Request is stale because it has been open for 90 days with
no activity. It will automatically close after 30 more days of
inactivity. Reopen with /reopen. Mark as fresh by adding the
comment /remove-lifecycle stale.

[SaschaSchwarze0]

Hm, I missed that this PR was auto-closed. Let me try if I can revive it or need to open a new one.

/reopen

[knative-prow]

@SaschaSchwarze0: Failed to re-open PR: state cannot be changed. The sascha-treat-pod-as-always-schedulable branch was force-pushed or recreated.

Details

In response to this:

Hm, I missed that this PR was auto-closed. Let me try if I can revive it or need to open a new one.

/reopen

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[SaschaSchwarze0]

Above PR was closed. But the change in the meantime got included through PR #16146. I do not see this critical enough for a patch, but we can instead adopt it (requires a feature flag being set in config-deployment) when it is included in a release.