:sparkles: Implement devmachinepools by Karthik-K-N · Pull Request #13346 · kubernetes-sigs/cluster-api

Karthik-K-N · 2026-02-17T09:48:04Z

What this PR does / why we need it:

Implement DevMachinePool with DevCluster and backed by DevMachines.

[root@karthik-vm-centos cluster-api]# kubectl get cluster
NAME          CLUSTERCLASS      AVAILABLE   CP DESIRED   CP AVAILABLE   CP UP-TO-DATE   W DESIRED   W AVAILABLE   W UP-TO-DATE   PHASE         AGE     VERSION
dev-mp-7608   dev-quick-start   True        1            0              1                                                        Provisioned   9m26s   v1.35.0

[root@karthik-vm-centos cluster-api]# kubectl get machinepool
NAME                     CLUSTER       DESIRED   CURRENT   READY   AVAILABLE   UP-TO-DATE   PHASE       AGE     VERSION
dev-mp-7608-mp-0-pmchk   dev-mp-7608   1         1         0       0           1            ScalingUp   9m30s   v1.35.0

[root@karthik-vm-centos cluster-api]# kubectl get devmachinepool
NAME                     AGE
dev-mp-7608-mp-0-szq42   9m34s

[root@karthik-vm-centos cluster-api]# kubectl get devmachine
NAME                      CLUSTER       FAILURE DOMAIN   PROVISIONED   AGE
dev-mp-7608-zwwdv-vpgtd   dev-mp-7608   fd1              true          9m37s
worker-jysrly             dev-mp-7608                    true          7m18s

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Part of #13270

linux-foundation-easycla · 2026-02-17T09:48:10Z

The committers listed above are authorized under a signed CLA.

✅ login: Karthik-K-N / name: Karthik Bhat (3bfd3ab, 50a357b)

k8s-ci-robot · 2026-02-17T09:48:13Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

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

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

sbueringer · 2026-03-07T10:43:25Z

/test pull-cluster-api-e2e-main-gke

k8s-ci-robot · 2026-03-07T10:47:17Z

@Karthik-K-N: 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
pull-cluster-api-e2e-main-gke	`4c249d0`	link	true	`/test pull-cluster-api-e2e-main-gke`

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

Details

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. I understand the commands that are listed here.

sbueringer

Thank you very much!

First round of review. I skipped over some of the controller implementation for now as the changes to the API will ripple through

sbueringer · 2026-03-07T11:21:40Z

test/infrastructure/docker/api/v1beta2/devmachinepool_types.go

+const (
+	// DevMachinePoolFinalizer allows ReconcileDevMachinePool to clean up resources.
+	DevMachinePoolFinalizer = "devmachinepool.infrastructure.cluster.x-k8s.io"
+)


Suggested change

const (

// DevMachinePoolFinalizer allows ReconcileDevMachinePool to clean up resources.

DevMachinePoolFinalizer = "devmachinepool.infrastructure.cluster.x-k8s.io"

)

I think let's follow the pattern we have in other types and not introduce a new finalizer (this constant is also unused atm)

Removed.
Also I checked the devmachine controller, we always set the dockermachine finalizer even for inmemory backed, Is that expected.

sbueringer · 2026-03-07T11:28:54Z

test/infrastructure/docker/api/v1beta2/devmachinepool_types.go

+	// Template contains the details used to build a replica machine within the Machine Pool
+	// +optional
+	Template DevMachinePoolBackendTemplate `json:"template"`


Suggested change

// Template contains the details used to build a replica machine within the Machine Pool

// +optional

Template DevMachinePoolBackendTemplate `json:"template"`

// backend contains the details used to build a replica machine within the Machine Pool

// +optional

Backend DevMachinePoolBackendSpec `json:"backend"`

Let's rename the field/type to be more consistent with other dev types (I'm comparing against DevMachine)

sbueringer · 2026-03-07T11:30:19Z

test/infrastructure/docker/api/v1beta2/devmachinepool_types.go

+type DevMachinePoolBackendTemplate struct {
+	// docker defines a backend for a DevMachine using docker containers.
+	// +optional
+	Docker *DockerMachinePoolMachineTemplate `json:"docker,omitempty"`


Suggested change

Docker *DockerMachinePoolMachineTemplate `json:"docker,omitempty"`

Docker *DockerMachinePoolBackendSpec `json:"docker,omitempty"`

Let's create a copy of DockerMachinePoolMachineTemplate named DockerMachinePoolBackendSpec here in this file

(please add it above DevMachinePoolSpec, to make it easy to diff with dockermachinepool_types.go)

sbueringer · 2026-03-07T11:34:34Z

test/infrastructure/docker/api/v1beta2/devmachinepool_types.go

+
+	// Instances contains the status for each instance in the pool
+	// +optional
+	Instances []DevMachinePoolBackendInstanceStatus `json:"instances,omitempty"`


We have to keep this the same way as it is in DockerMachinePool
This entire field is covered by the contract (https://cluster-api.sigs.k8s.io/developer/providers/contracts/infra-machinepool#inframachinepool-instances)

Accordingly the field has to be exactly like documented and we can't introduce sub-levels (but that's fine)

So the delta to DockerMachinePool in status should be just that we use a copy of DockerMachinePoolInstanceStatus called DevMachinePoolInstanceStatus

(and it's correct that we don't have the deprecated field in DevMachinePool)

sbueringer · 2026-03-07T11:40:17Z

test/infrastructure/docker/config/crd/kustomization.yaml

 - bases/infrastructure.cluster.x-k8s.io_devmachinetemplates.yaml
+- bases/infrastructure.cluster.x-k8s.io_devmachinepools.yaml
+- bases/infrastructure.cluster.x-k8s.io_devmachinepooltemplates.yaml
 # +kubebuilder:scaffold:crdkustomizeresource


Let's please cleanup a bit and delete test/infrastructure/docker/internal/webhooks/dockermachinepool.go (it's not doing anything)

Deleted the dockermachine pool webhook and patch.

sbueringer · 2026-03-07T11:40:56Z

test/infrastructure/docker/config/crd/kustomization.yaml

+- bases/infrastructure.cluster.x-k8s.io_devmachinepooltemplates.yaml
 # +kubebuilder:scaffold:crdkustomizeresource

 patches:


Let's add patches below for devmachinepool and devmachinepooltemplate.

I know they don't need conversion at the moment because they only exist in v1beta2, but it doesn't hurt to have it already configured so we don't miss it in the future

sbueringer · 2026-03-07T11:48:29Z

test/infrastructure/docker/templates/cluster-template-dev-mp.yaml

@@ -0,0 +1,23 @@
+apiVersion: cluster.x-k8s.io/v1beta2
+kind: Cluster
+metadata:


This entire folder is published as release manifests. I would prefer not publishing this for now (same for the ClusterClass)

I would suggest to just use these files for your local tests for now and not check them in.

I've added a follow-up sub task to the umbrella issue that we move all existing templates over to Dev* resources

Removed, them. Thanks

sbueringer · 2026-03-07T11:56:16Z

test/infrastructure/docker/internal/controllers/devmachinepool_controller.go

+		return err
+	}
+
+	c, err := capicontrollerutil.NewControllerManagedBy(mgr, predicateLog).


Let's rebase onto latest main. The location of this util changed so right now the PR is not compiling anymore

Karthik-K-N · 2026-03-09T12:23:50Z

Addressed first set of review comments. Thanks.

k8s-ci-robot requested review from elmiko and richardcase February 17, 2026 09:48

k8s-ci-robot added the do-not-merge/needs-area PR is missing an area label label Feb 17, 2026

k8s-ci-robot added size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. labels Feb 17, 2026

Karthik-K-N force-pushed the dev-machinepool branch 2 times, most recently from 4ad0aea to 4c249d0 Compare February 17, 2026 12:35

k8s-ci-robot added cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. and removed cncf-cla: no Indicates the PR's author has not signed the CNCF CLA. labels Feb 17, 2026

sbueringer added the area/provider/infrastructure-docker Issues or PRs related to the docker infrastructure provider label Mar 7, 2026

k8s-ci-robot removed the do-not-merge/needs-area PR is missing an area label label Mar 7, 2026

sbueringer reviewed Mar 7, 2026

View reviewed changes

Karthik-K-N added 2 commits March 9, 2026 13:46

Implement devmachinepool

3bfd3ab

Adderss reveiw comments

50a357b

Karthik-K-N force-pushed the dev-machinepool branch from 4c249d0 to 50a357b Compare March 9, 2026 12:12

	Docker *DockerMachinePoolMachineTemplate `json:"docker,omitempty"`
	Docker *DockerMachinePoolBackendSpec `json:"docker,omitempty"`

Conversation

Karthik-K-N commented Feb 17, 2026 • edited by sbueringer Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

linux-foundation-easycla bot commented Feb 17, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

k8s-ci-robot commented Feb 17, 2026

Uh oh!

sbueringer commented Mar 7, 2026

Uh oh!

k8s-ci-robot commented Mar 7, 2026

Uh oh!

sbueringer left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

sbueringer Mar 7, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Karthik-K-N commented Mar 9, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Karthik-K-N commented Feb 17, 2026 •

edited by sbueringer

Loading

linux-foundation-easycla bot commented Feb 17, 2026 •

edited

Loading

sbueringer Mar 7, 2026 •

edited

Loading