kubeadm: UnifiedControlPlaneImage string -> UseHyperKubeImage bool #70793

rosti · 2018-11-08T11:24:16Z

What type of PR is this?
/kind api-change

What this PR does / why we need it:

Up until now UnifiedControlPlaneImage existed as a string value as part of the ClusterConfiguration. This provided an override for the Kubernetes core component images with a single custom image. It is mostly used to override the control plane images with the hyperkube image. This saves both bandwidth and disk space on the control plane nodes.
Unfortunately, this specified an entire image string (complete with its prefix, image name and tag). This disables upgrades of setups that use hyperkube.
Therefore, to enable upgrades on hyperkube setups and to make configuration more convenient, the UnifiedControlPlaneImage option is replaced with a boolean option, called UseHyperKubeImage. If set to true, this option replaces the image name of any Kubernetes core components with hyperkube, thus allowing for upgrades and respecting the image repository and version, specified in the ClusterConfiguration.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Refs kubernetes/kubeadm#911

Special notes for your reviewer:

/cc @kubernetes/sig-cluster-lifecycle-pr-reviews
/area kubeadm
/assign @fabriziopandini
/assign @timothysc
/assign @luxas

Does this PR introduce a user-facing change?:

kubeadm: UnifiedControlPlaneImage is replaced by UseHyperKubeImage boolean value.

neolit123

thanks @rosti
/priority important-soon

neolit123 · 2018-11-08T13:36:33Z

cmd/kubeadm/app/apis/kubeadm/types.go

-	// used for all control plane components.
-	UnifiedControlPlaneImage string
+	// UseHyperKubeImage controls if hyperkube should be used for Kubernetes components instead of their respective separate images
+	UseHyperKubeImage bool


someone might decide to build a custom "unified control plane" image that is not called hyperkube.
in such a case they would have to name it "hyperkube" for kubeadm to be able to work with it.

this at least solves upgrade issues for us...

If some users override this with their own image, then it should be based on hyperkube. Hence tagging it appropriately and setting it up on their own repository is the way to go.
Definitely we should not allow users to put whatever image they see fit in here and the bool value is the best solution for me.

fabriziopandini

@rosti well done!
Only one small point to be addressed, then ready to go for me

fabriziopandini · 2018-11-08T17:40:46Z

cmd/kubeadm/app/apis/kubeadm/v1alpha3/conversion.go

@@ -103,6 +108,14 @@ func Convert_v1alpha3_ClusterConfiguration_To_kubeadm_ClusterConfiguration(in *C
 		return err
 	}

+	if len(in.UnifiedControlPlaneImage) == 0 {
+		out.UseHyperKubeImage = false
+	} else if strings.Contains(in.UnifiedControlPlaneImage, "/hyperkube:") {


This check is weak and can lead to unsupported behaviours:

What if the user is using a custom image repository? This will get switched to a different image repository
Same questions about image tag

However, from the other side I don't think we should make this check too complex, so I will be fine with whatever check we agree upon

@neolit123 @timothysc opinions?

the string "hypercube" has to be moved to constants.go.
the tag and repo conversation might be a bit too much, i think it's OK to have it like that.

we can also show a warning here too, right?

rosti · 2018-11-09T13:28:22Z

Added HyperKube constant and extended the check to print warning if there is a image repository or tag mismatch upon conversion.

neolit123

/lgtm
thanks for the update.

timothysc · 2018-11-09T15:00:01Z

cmd/kubeadm/app/apis/kubeadm/v1alpha3/conversion.go

+		return nil
+	}
+
+	if strings.Contains(in.UnifiedControlPlaneImage, "/"+constants.HyperKube+":") {


TBH I don't think this should be here. I think you should hard fail and force the user to adjust their config.

timothysc · 2018-11-09T15:01:49Z

cmd/kubeadm/app/images/images.go

+
+	// start with core kubernetes images
+	if cfg.UseHyperKubeImage {
+		imgs = append(imgs, GetKubeControlPlaneImage("", cfg))


Why wouldn't this be the const for the hyperkube image?

timothysc · 2018-11-09T15:02:08Z

cmd/kubeadm/app/images/images.go

-	if cfg.UnifiedControlPlaneImage != "" {
-		return cfg.UnifiedControlPlaneImage
+	actualImage := image
+	if cfg.UseHyperKubeImage {


If you change the line below I don't think this is necessary

Up until now UnifiedControlPlaneImage existed as a string value as part of the ClusterConfiguration. This provided an override for the Kubernetes core component images with a single custom image. It is mostly used to override the control plane images with the hyperkube image. This saves both bandwith and disk space on the control plane nodes. Unfortunately, this specified an entire image string (complete with its prefix, image name and tag). This disables upgrades of setups that use hyperkube. Therefore, to enable upgrades on hyperkube setups and to make configuration more convenient, the UnifiedControlPlaneImage option is replaced with a boolean option, called UseHyperKubeImage. If set to true, this option replaces the image name of any Kubernetes core components with hyperkube, thus allowing for upgrades and respecting the image repository and version, specified in the ClusterConfiguration. Signed-off-by: Rostislav M. Georgiev <[email protected]>

timothysc

/approve
/lgtm

k8s-ci-robot · 2018-11-09T15:38:44Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rosti, timothysc

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rosti · 2018-11-09T17:09:13Z

/test pull-kubernetes-verify
/test pull-kubernetes-e2e-kops-aws

Always use CoreDNS and remove the feature gate from config. Add workaround for `unifiedControlPlaneImage` removal kubernetes/kubernetes#70793 Fixes kubernetes-retired#250

k8s-ci-robot added the release-note Denotes a PR that will be considered when it comes time to generate release notes. label Nov 8, 2018

k8s-ci-robot assigned fabriziopandini and luxas Nov 8, 2018

k8s-ci-robot added the sig/cluster-lifecycle Categorizes an issue or PR as relevant to SIG Cluster Lifecycle. label Nov 8, 2018

k8s-ci-robot assigned timothysc Nov 8, 2018

rosti force-pushed the use-hyperkube branch from 0c13751 to e4ab564 Compare November 8, 2018 13:06

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k8s-ci-robot added size/L Denotes a PR that changes 100-499 lines, ignoring generated files. and removed size/M Denotes a PR that changes 30-99 lines, ignoring generated files. needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. labels Nov 9, 2018

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rosti force-pushed the use-hyperkube branch from f97cbae to b551ad5 Compare November 9, 2018 15:35

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k8s-ci-robot merged commit d90f868 into kubernetes:master Nov 9, 2018

ivan4th mentioned this pull request Nov 14, 2018

Fix k8s master (1.14) kubernetes-retired/kubeadm-dind-cluster#251

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rosti deleted the use-hyperkube branch November 22, 2018 15:24

benkulbertis mentioned this pull request Feb 18, 2019

Pull Kubernetes control plane images during kube image build slateci/minislate#15

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kubeadm: UnifiedControlPlaneImage string -> UseHyperKubeImage bool #70793

kubeadm: UnifiedControlPlaneImage string -> UseHyperKubeImage bool #70793

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kubeadm: UnifiedControlPlaneImage string -> UseHyperKubeImage bool #70793

kubeadm: UnifiedControlPlaneImage string -> UseHyperKubeImage bool #70793

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