CRD Version Bumper

Bump the CRD version, adding conversion webhooks and tests.

See Kubebuilder's Tutorial: Multi-Version API for a description of the mechanism. For more detail read the Kubernetes document Versions in CustomResourceDefinitions.

Hub and Spokes

This tool implements the hub-and-spoke model of CRD versioning. See Kubebuilder's Hubs, spokes, and other wheel metaphors for a description of the model.

The new CRD version will be the new hub, and the previous hub will become a new spoke. (Note: in the Kubebuilder book example, the old version is the hub and never changes, and all new versions are spokes.)

Using CRD Bumper

Create the environment prior to running the tool:

$ python3 -m venv venv
$ . venv/bin/activate
(venv) $ pip install -r requirements.txt

Prior to Creating the new API

For the easiest vendoring experience, the downstream repos should be up to date with this repo prior to creating the new API, and this new API should be vendored into the downstream repos before any further changes go into this repo or any of the downstream repos.

Run the Tool

Clone a fresh copy of the repository that contains the CRDs and controllers, checking out to the default branch (master or main). The tool expects a repository that is compatible with kubebuilder and will use the ./PROJECT file that is maintained by kubebuilder.

The following example creates a new API version v1beta2 for the lustre-fs-operator repository, where v1beta1 is the existing hub and v1alpha1 is the most recent existing spoke. It begins by creating a new branch off "master" named api-v1beta2, where it does all of its work.

REPO=git@github.com:NearNodeFlash/lustre-fs-operator.git
crd-bumper.py --repo $REPO --most-recent-spoke v1alpha1 --prev-ver v1beta1 --new-ver v1beta2 all

The repository with its new API is found under a directory named workingspace/lustre-fs-operator.

The new api-v1beta2 branch has a series of commits showing a progression of steps. Some of these commit messages have an ACTION comment describing something that must be manually verified, and possibly adjusted, before the tests succeed.

Verification

After the entire progression of steps has completed, verify the results by running make vet, and paying attention to any of the ACTION comments described above. Once make vet is clean, move to the next debug step by running make test.

Do not run make vet or make test before the entire progression of steps has completed. The individual commits do not build--the whole set of commits is required.

Stepping

Sometimes it can be helpful to do the steps one at a time. If the first step has not yet been done, then begin by using the step command in place of the all command. It begins, as with the all command, by creating a new branch off master named api-v1beta2, where it will do all of its work.

crd-bumper.py --repo $REPO --most-recent-spoke v1alpha1 --prev-ver v1beta1 --new-ver v1beta2 step

Follow that with more steps, telling the tool to continue in the current branch that was created during the first step by adding --this-branch. The other args must remain the same as they were on the first command. The tool knows when there are no more steps to be done.

crd-bumper.py --repo $REPO --most-recent-spoke v1alpha1 --prev-ver v1beta1 --new-ver v1beta2 --this-branch step

Do not attempt to run make vet or make test between steps. The individual commits do not build.

Vendor the New API

Vendor this new API into another repository using the vendor-new-api tool. This tool updates that repo to change its Go code references and its Kustomize config references to point at the new API.

Executing the Tool

The following example vendors the new v1beta2 API we created above for lustre-fs-operator into the nnf-sos repository. The current hub version for nnf-sos is v1alpha3, and is specified with the --hub-ver option. The module representing lustre-fs-operator is specified in the same form that it would appear in the go.mod file in nnf-sos. The --version option can be used to specify a version if necessary. It begins by creating a new branch in nnf-sos off "master" named api-lustre-fs-operator-v1beta2, where it does all of its work.

DEST_REPO=git@github.com:NearNodeFlash/nnf-sos.git
vendor-new-api.py -r $DEST_REPO --hub-ver v1alpha3 --vendor-hub-ver v1beta2 --module github.com/NearNodeFlash/lustre-fs-operator --version master

The repository with its new API is found under a directory named workingspace/nnf-sos.

The new api-lustre-fs-operator-v1beta2 branch has a commit containing the newly-vendored API and adjusted code. This commit message has ACTION comments describing something that must be manually verified, and possibly adjusted, before the tests succeed.

Removing an Old API Version

An old API version should first be shipped in a deprecated state. Use the unserve tool to mark that API version as no longer being served by the API server. After that has shipped, that version of the API can be removed in a later release.

Unserve the API

The following example marks the old v1alpha1 API in lustre-fs-operator as no longer being served. This places a +kubebuilder:unservedversion in each CRD of that version, which controller-gen translates into served: false for that version when it regenerates the CRD manifest. It begins by creating a new branch in lustre-fs-operator off "master" named api-v1alpha1-unserve, where it does all of its work.

REPO=git@github.com:NearNodeFlash/lustre-fs-operator.git
unserve.py -r $REPO --spoke-ver v1alpha1

The repository with its adjusted API is found under a directory named workingspace/lustre-fs-operator.

The new api-v1alpha1-unserve branch has a commit containing the adjusted API and adjusted code. This commit message has ACTION comments describing something that must be manually verified, and possibly adjusted, before the tests succeed.

Library and Tool Support

The library and tool support is taken from the Cluster API project. See release v1.6.6 for a version that contains multi-version support for CRDs where they have a hub with one spoke. (Note: In v1.7.0 they removed the old API--the old spoke--and their repo contains only one version, the hub.)

In the "References" section you'll find a link to a video from the Cluster API team where they go through an example of changing an API and providing conversion routines and tests for the change.

Lossless Conversions

The libraries from the Cluster API project use an annotation on the spoke version of a resource to contain a serialized copy of the hub version of that resource. The libraries and tests use this to avoid data loss during hub->spoke->hub conversions.

Writing Conversion Routines

Conversion Library Lifecycle in Spoke APIs

After an API version has been bumped, the spoke API should be frozen. However, the spoke API conversion library in api/<spoke-ver>/conversion.go continues to be updated, following the progression and development of the hub.

Conversion Must Not Fail

When writing conversion routines be aware that the conversion routine must not report a failure:

"Failing conversion can disrupt read and write access to the custom resources, including the ability to update or delete the resources. Conversion failures should be avoided whenever possible, and should not be used to enforce validation constraints (use validation schemas or webhook admission instead)." Kubernetes "Versions in CustomResourceDefinitions" Response.

Code Markers

This tool uses "marker comments" in the Go code to indicate where generated code should be placed. These markers are used the same way controller-gen uses code markers, as documented in Kubebuilder's Markers for Config/Code Generation.

The following markers must be present in the code prior to using this tool:

+crdbumper:scaffold:builder

Used in internal/controller/suite_test.go to indicate where additional calls to SetupWebhookWithManager should be placed. This should be in the BeforeSuite() function before the first reconciler is set up.

+crdbumper:scaffold:gvk

Used in github/cluster-api/util/conversion/conversion_test.go to indicate where additional schema.GroupVersionKind{} types should be placed.

+crdbumper:scaffold:marshaldata

Used in github/cluster-api/util/conversion/conversion_test.go to indicate where additional marshalling tests should be placed. This should be the last statement in the TestMarshalData() function.

+crdbumper:scaffold:unmarshaldata

Used in github/cluster-api/util/conversion/conversion_test.go to indicate where additional unmarshalling tests should be placed. This should be the last statement in the TestUnmarshalData() function.

+crdbumper:scaffold:webhooksuitetest

Used in internal/controller/conversion_test.go to indicate where additional tests for a new Kind may be placed. This should be the last statement within the main Describe() block.

+crdbumper:scaffold:spoketest="GROUP.KIND"

Used in internal/controller/conversion_test.go to indicate where additional spoke conversion tests should be placed. Each kind will have its own Context() block within the main Describe(), and this should be the last statement within each of those Context blocks. Replace "GROUP.KIND" with the API's group and kind, using the same spelling and use of lower/upper case letters as found in the ./PROJECT file.

+crdbumper:carryforward:begin="KIND.DIRECTION"

+crdbumper:carryforward:begin="Epilog"

Used in api/$SPOKE/conversion.go to indicate that a segment of code should be carried forward as new spokes are created or as old spokes are removed. Use of this marker should be uncommon; it's almost always wrong to carry-forward code to a new spoke. Replace "KIND" with the API's kind, using the same spelling and use of lower/upper case letters as found in the ./PROJECT file. Replace "DIRECTION" with "ConvertFrom" or "ConvertTo" to mark the section of code as being in a ConvertFrom() or ConvertTo() function. If the "Epilog" variation is used then this marks one or more Convert_$API1_$KIND_To_$API2_$KIND() conversion functions, or similar chunks of code, that are typically collected at the end of conversion.go.

+crdbumper:carryforward:end

This is used in api/$SPOKE/conversion.go to close the segment of code that was marked with +crdbumper:carryforward:begin.

References