k3s/docs/devel/adding-an-APIGroup.md

PLEASE NOTE: This document applies to the HEAD of the source tree

If you are using a released version of Kubernetes, you should refer to the docs that go with that version.

The latest release of this document can be found [here](http://releases.k8s.io/release-1.4/docs/devel/adding-an-APIGroup.md).

Documentation for other releases can be found at releases.k8s.io.

Adding an API Group

This document includes the steps to add an API group. You may also want to take a look at PR #16621 and PR #13146, which add API groups.

Please also read about API conventions and API changes before adding an API group.

Your core group package:

We plan on improving the way the types are factored in the future; see #16062 for the directions in which this might evolve.

1. Create a folder in pkg/apis to hold your group. Create types.go in pkg/apis/<group>/ and pkg/apis/<group>/<version>/ to define API objects in your group;

2. Create pkg/apis/<group>/{register.go, <version>/register.go} to register this group's API objects to the encoding/decoding scheme (e.g., pkg/apis/authentication/register.go and pkg/apis/authentication/v1beta1/register.go;

3. Add a pkg/apis/<group>/install/install.go, which is responsible for adding the group to the latest package, so that other packages can access the group's meta through latest.Group. You probably only need to change the name of group and version in the example). You need to import this install package in {pkg/master, pkg/client/unversioned}/import_known_versions.go, if you want to make your group accessible to other packages in the kube-apiserver binary, binaries that uses the client package.

Step 2 and 3 are mechanical, we plan on autogenerate these using the cmd/libs/go2idl/ tool.

Scripts changes and auto-generated code:

1. Generate conversions and deep-copies:

   1. Add your "group/" or "group/version" into cmd/libs/go2idl/conversion-gen/main.go;
   2. Make sure your pkg/apis/<group>/<version> directory has a doc.go file with the comment // +k8s:deepcopy-gen=package,register, to catch the attention of our generation tools.
   3. Make sure your pkg/apis/<group>/<version> directory has a doc.go file with the comment // +k8s:conversion-gen=<internal-pkg>, to catch the attention of our generation tools. For most APIs the only target you need is k8s.io/kubernetes/pkg/apis/<group> (your internal API).
   4. Make sure your pkg/apis/<group> and pkg/apis/<group>/<version> directories have a doc.go file with the comment +groupName=<group>.k8s.io, to correctly generate the DNS-suffixed group name.
   5. Run hack/update-all.sh.

2. Generate files for Ugorji codec:

   1. Touch types.generated.go in pkg/apis/<group>{/, <version>};
   2. Run hack/update-codecgen.sh.

3. Generate protobuf objects:

   1. Add your group to cmd/libs/go2idl/go-to-protobuf/protobuf/cmd.go to New() in the Packages field
   2. Run hack/update-generated-protobuf.sh

Client (optional):

We are overhauling pkg/client, so this section might be outdated; see #15730 for how the client package might evolve. Currently, to add your group to the client package, you need to:

1. Create pkg/client/unversioned/<group>.go, define a group client interface and implement the client. You can take pkg/client/unversioned/extensions.go as a reference.

2. Add the group client interface to the Interface in pkg/client/unversioned/client.go and add method to fetch the interface. Again, you can take how we add the Extensions group there as an example.

3. If you need to support the group in kubectl, you'll also need to modify pkg/kubectl/cmd/util/factory.go.

Make the group/version selectable in unit tests (optional):

1. Add your group in pkg/api/testapi/testapi.go, then you can access the group in tests through testapi.<group>;

2. Add your "group/version" to KUBE_TEST_API_VERSIONS in hack/make-rules/test.sh and hack/make-rules/test-integration.sh

TODO: Add a troubleshooting section.