if revision is inactive, scale to zero instead of waiting for last pod retention

[eddy-oum]

Fixes #13812

Proposed Changes

• if revision is inactive, scale to zero instead of waiting for last pod retention

Release Note

[knative-prow]

Welcome @eddy-oum! It looks like this is your first PR to knative/serving 🎉

[knative-prow]

Hi @eddy-oum. 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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[dprotaso]

/ok-to-test

[dprotaso]

/hold

I'm going on vacation but will want to review this in detail when I'm back in 2 weeks. I made some code changes in this area of the code before and broke some stuff so I want to be cautious here.

cc @ReToCode @skonto for their reviews in the meantime

[dprotaso]

Note with v1.14 coming out this week next release is in July so there's need to rush

[ReToCode]

If I understand the discussion in #13812 correctly I think this is fine. Dave is now on PTO, as he has done the recent larger rework in that area, let's also wait for his opinion.

[skonto]

Does this change respect the scale down delay or we are already after that period?

[eddy-oum]

Does this change respect the scale down delay or we are already after that period?

I think it is the latter; scale down delays are considered here, before applying handleToScaleZero

edit: seems like current code doesn't respect the scale down delay, thx.

[eddy-oum]

I am wondering if I should do the reachability check together with the last pod retention check, instead of returning early, so that unreachable revisions can go through other checks.

edit: never mind the above approach doesn't work.

I think another approach (instead of returning early in handleScaleZero) would be to return 0 in lastPodRetention(pa *autoscalingv1alpha1.PodAutoscaler, cfg *autoscalerconfig.Config) if pa is unreachable.

func lastPodRetention(pa *autoscalingv1alpha1.PodAutoscaler, cfg *autoscalerconfig.Config) time.Duration {
	if pa.Spec.Reachability == autoscalingv1alpha1.ReachabilityUnreachable {
		return 0
	}
	d, ok := pa.ScaleToZeroPodRetention()
	if ok {
		return d
	}
	return cfg.ScaleToZeroPodRetentionPeriod
}

this approach lets the pa go through other checks, especially the scale to zero grace period.

	}, {
		label:         "scale to zero, if revision is unreachable do not wait for last pod retention",
		startReplicas: 1,
		scaleTo:       0,
		wantReplicas:  0,
		wantScaling:   true,
		paMutation: func(k *autoscalingv1alpha1.PodAutoscaler) {
			paMarkInactive(k, time.Now().Add(-gracePeriod))
			WithReachabilityUnreachable(k)
		},
		configMutator: func(c *config.Config) {
			c.Autoscaler.ScaleToZeroPodRetentionPeriod = 10 * gracePeriod
		},
	}, {
		label:         "revision is unreachable, but before deadline",
		startReplicas: 1,
		scaleTo:       0,
		wantReplicas:  0,
		wantScaling:   false,
		paMutation: func(k *autoscalingv1alpha1.PodAutoscaler) {
			paMarkInactive(k, time.Now().Add(-gracePeriod+time.Second))
			WithReachabilityUnreachable(k)
		},
		configMutator: func(c *config.Config) {
			c.Autoscaler.ScaleToZeroPodRetentionPeriod = 10 * gracePeriod
		},
		wantCBCount: 1,

current implementation will fail the second test, but returning 0 in lastPodRetention for unreachable revisions would pass both tests.

What are your thoughts @ReToCode @skonto? Thanks!

[eddy-oum]

/retest

[dprotaso]

/hold cancel

[eddy-oum]

/retest

[knative-prow]

@eddy-oum: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
certmanager-integration-tests_serving_main	b4f6a8a	link	true	/test certmanager-integration-tests

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[dprotaso]

/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dprotaso, eddy-oum

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.77%. Comparing base (b0dfed2) to head (fe7d6a1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15161   +/-   ##
=======================================
  Coverage   84.76%   84.77%           
=======================================
  Files         218      218           
  Lines       13478    13480    +2     
=======================================
+ Hits        11425    11428    +3     
+ Misses       1686     1685    -1     
  Partials      367      367           

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