vpa-recommender: Prevent nil pointer dereference

[ialidzhikov]

What type of PR is this?

/kind regression

What this PR does / why we need it:

With 628fc39 I introduced the following nil pointer dereference to VPA 1.2.0:

I0814 11:04:28.216725       1 cluster_feeder.go:265] Loading VPA kube-system/kube-proxy-cpu-8-64-v1.29 checkpoint for conntrack-fix
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x161e6d5]

goroutine 102 [running]:
k8s.io/autoscaler/vertical-pod-autoscaler/pkg/recommender/input.(*clusterStateFeeder).setVpaCheckpoint(0xc00bc06450?, 0xc010efa1e0)
	/gopath/src/k8s.io/autoscaler/vertical-pod-autoscaler/pkg/recommender/input/cluster_feeder.go:236 +0x1d5
k8s.io/autoscaler/vertical-pod-autoscaler/pkg/recommender/input.(*clusterStateFeeder).InitFromCheckpoints(0xc001fc8160)
	/gopath/src/k8s.io/autoscaler/vertical-pod-autoscaler/pkg/recommender/input/cluster_feeder.go:266 +0x6bc
main.run(0xc0004ff890)
	/gopath/src/k8s.io/autoscaler/vertical-pod-autoscaler/pkg/recommender/main.go:269 +0xf38
main.main.func1({0xc000003c80?, 0x0?})
	/gopath/src/k8s.io/autoscaler/vertical-pod-autoscaler/pkg/recommender/main.go:169 +0x17
created by k8s.io/client-go/tools/leaderelection.(*LeaderElector).Run in goroutine 1
	/gopath/src/k8s.io/autoscaler/vertical-pod-autoscaler/vendor/k8s.io/client-go/tools/leaderelection/leaderelection.go:213 +0xe6

In

autoscaler/vertical-pod-autoscaler/pkg/recommender/input/cluster_feeder.go

Lines 233 to 237 in 3b8fdfe

	vpaID := model.VpaID{Namespace: checkpoint.Namespace, VpaName: checkpoint.Spec.VPAObjectName}
	vpa, exists := feeder.clusterState.Vpas[vpaID]
	if !exists {
	return fmt.Errorf("cannot load checkpoint to missing VPA object %s/%s", vpa.ID.Namespace, vpa.ID.VpaName)
	}

for returning the err we have to use the vpaID var as the vpa var will be always nil when entry with the given key does not exist in the map.

Which issue(s) this PR fixes:

N/A
but see the panic above

Special notes for your reviewer:

The issue occurs when there is a VPACheckpoint and the corresponding VPA does not exists:

% ks get verticalpodautoscalercheckpoints.autoscaling.k8s.io kube-proxy-cpu-8-64-v1.29-conntrack-fix -o jsonpath='{.spec.vpaObjectName}'
kube-proxy-cpu-8-64-v1.29

% ks get vpa kube-proxy-cpu-8-64-v1.29
Error from server (NotFound): verticalpodautoscalers.autoscaling.k8s.io "kube-proxy-cpu-8-64-v1.29" not found

Does this PR introduce a user-facing change?

A `nil pointer dereference` regression introduced in vpa-recommender v1.2.0 is now fixed.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[ialidzhikov]

/cc @raywainman @kwiesmueller @gjtempleton

[raywainman]

/lgtm

[adrianmoisey]

/lgtm

[k8s-ci-robot]

@adrianmoisey: changing LGTM is restricted to collaborators

In response to this:

/lgtm

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[raywainman]

Sounds like we'll probably want to cherrypick this into 1.2.0, right?

@ialidzhikov

[ialidzhikov]

Sounds like we'll probably want to cherrypick this into 1.2.0, right?

Yes, it is a very subtle bug. I am sorry again.

[ialidzhikov]

/cherry-pick vpa-release-1.2

[k8s-infra-cherrypick-robot]

@ialidzhikov: once the present PR merges, I will cherry-pick it on top of vpa-release-1.2 in a new PR and assign it to you.

In response to this:

/cherry-pick vpa-release-1.2

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.

[raywainman]

Sounds like we'll probably want to cherrypick this into 1.2.0, right?

Yes, it is a very subtle bug. I am sorry again.

No worries :) A bunch of missed this in review as well. We can cut a new release with this patched in.

[kwiesmueller]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ialidzhikov, kwiesmueller

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[k8s-infra-cherrypick-robot]

@ialidzhikov: new pull request created: #7169

In response to this:

/cherry-pick vpa-release-1.2

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.

[raywainman]

Tracking release in #7170.