skipper VS api

So my advice is: Don‘t implement anything someone else already did better and have a look at Skipper: https://github.com/zalando/skipper

That's all! You can find a complete example of an Admit func from the Validating Admission Webhook in Skipper. I've also included an abridged version at the end of this blog post.

This series is based on my experience adding a ValidatingAdmissionWebhook to Skipper, modern HTTP proxy.

You can find an abridged version of admission.Handler under "Reference". For a complete example of a validating admission webhook being used in production, checkout the validating admission webhook in Skipper, our HTTP reverse proxy.

Good point, here it is https://github.com/kubernetes/api

Better is probably subjective, but you have options. You can run the doc website locally (https://github.com/kubernetes/website) or search the API definitions directly (https://github.com/kubernetes/api). Good ol `git grep` I suppose.

I understand that I need to do some (un)marshalling of the YAML bytes into the correct API types defined in package: https://github.com/kubernetes/api

Despite that though, someone was generous enough to ensure that there are protobuf files laying around for us to use.

Then we have to create the admissionHandler to receive all the requests from our webhooks. These requests are coming with a JSON-encoded AdmissionReview (with the Request field filled) in the request body. The response should be a JSON AdmissionReview with the Response field filled.

k8s.io/client-go isn’t enough to talk to kubernetes API, you need k8s.io/api and k8s.io/apimachinery too You have to match their versions for it to all work! See the client-go versioning for simple instructions!

You can find the definitions of the AdmissionReview object in k8s.io/api repository.

Note how I am just using the upstream AdmissionReview type from k8s.io/api/admission/v1 here. You can find other Kubernetes types in the k8s.io/api repo as well.