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kubebuilder_v0_v1_difference.md

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Kubebuilder v0 vs. v1

Kubebuilder 1.0 adds a new flag --project-version, it accepts two different values, v0 and v1. When v0 is used, the kubebuilder behavior and workflow are the same as kubebuilder 0.*. When v1 is specified, the generated v1 project layout is architecturally different from v0 project. v1 project use controller-runtime set of libraries for controller implementation and used tools under controller-tools for scaffolding and generation.

Command difference

  • kubebuilder v0 has init, create controller, create resource, create config, generate commands and the workflow is:
  kubebuilder init --domain example.com
  kubebuilder create resource --group <group> --version <version> --kind <Kind>
  GOBIN=${PWD}/bin go install ${PWD#$GOPATH/src/}/cmd/controller-manager
  bin/controller-manager --kubeconfig ~/.kube/config

  kubectl apply -f hack/sample/<resource>.yaml
  docker build -f Dockerfile.controller . -t <image:tag>
  docker push <image:tag>
  kubebuilder create config --controller-image <image:tag> --name <project-name>
  kubectl apply -f hack/install.yaml

Every time the resource or controller is updated, users need to run kubebuilder generate to regenerate the project.

  • kubebuilder v1 has init, create api commands and the workflow is
  kubebuilder init --domain example.com --license apache2 --owner "The Kubernetes authors"
  kubebuilder create api --group ship --version v1beta1 --kind Frigate
  make install
  make run

In a v1 project, there is no generate command. When the resource or controller is updated, users don't need to regenerate the project.

Scaffolding difference

  • v0 project contains a directory pkg/client while v1 project doesn't
  • v0 project contains a directory inject while v1 project doesn't
  • v0 project layout follows predefined directory layout pkg/apis and pkg/controller while v1 project accepts user-specified path
  • In v1 project, there is a init() function for every api and controller.

Library difference

Controller libraries

  • v0 projects import the controller library from kubebuilder kubebuilder/pkg/controller. It provides a GenericController type with a list of functions.

  • v1 projects import the controller libraries from controller-runtime, such as controller-runtime/pkg/controller, controller-runtime/pkg/reconcile.

Client libraries

  • In v0 projects, the client libraries is generated by kubebuilder generate under directory pkg/client and imported wherever they are used in the project.

  • v1 projects import the dynamic client library from controller-runtime controller-runtime/pkg/client.

Wiring difference

Wiring refers to the mechanics of integrating controllers into controller-managers and injecting the dependencies in them.

  • v0 projects have an inject package and it provides functions for adding the controller to controller-manager as well as registering CRDs.
  • v1 projects don't have a inject package, the controller is added to controller-manager by a init function inside add_.go file inside the controller directory. The types are registered by an init function inside _types.go file inside the apis directory.