Koolbuilder

Build your kubernetes operator easily

Getting Started

Choose one of the following:

Cloudflare Pages (China-mainland-friendly)

https://koolbuilder.pages.dev

GitHub Pages

https://flyingonion.github.io/koolbuilder/index.html

Concepts

Controller Name

Controller name is the name of the controller. It also decides go module name if you choose not to customize it.

Select controller.go and see the controller structure name.

Go Module Name

Go module name is the name of the go module. By default, it is the lowercase of controller name, but you can customize it.

Select go.mod file and try changing the module name.

Go Version

Go version is the version of the Go compiler.

See the go 1.21.4 line in go.mod file.

Kubernetes API Version

Kubernetes API version is the version of the Kubernetes API.

See dependencies in go.mod file.

Namespace

Namespace sets limits on resources.

Set to empty string to use all namespaces.

If set, then for each resource whose scope is namespaced, the controller will only manage resources in the specified namespace.

Retry

Retry is the number of times to retry when controller failed to add a main resource to workqueue.

Main Resource

Main resource is the resource that the controller controls. When a new event (add/update/delete) comes, the corresponding resource should be added to workqueue and got synced.

Other Resources 1~n (optional)

Other resources are the resources that the controller requires when managing the main resource. Controller can get their information by resource listers.

For example, official deployment controller takes Deployment as main resource. Meanwhile, it requires to monitor ReplicaSet and Pod too. In this case, the yaml configuration should be like this:

resources:
- kind: Deployment # main resource
- kind: ReplicaSet
- kind: Pod

To see the code, click Load Example and choose Custom Deployment Controller.

FAQ

The generated code could not compile.

To ensure user friendliness, we do not adopt strict validation on the form. Even invalid inputs can generate code.

If you encounter an error, please check following issues:

• Check if there's any undefined or UnknownType in the code. If so, there may be wrong filling of Group, Version or Kind field.

• Check if you have same Kind in different resources. Kind should be unique.

• Check if each custom resource has a definition struct and has already implemented this method:

  DeepCopyObject() runtime.Object

  Each resource must be a runtime.Object, or the controller program will panic.

If you have any other issues, please don't hesitate to let us know.

What's the difference between official and custom resource?

Official resources are like Deployment, Pod, Service, ConfigMap, Job, etc. They have a predefined group like ""(aka core), apps, batch, etc.

Custom resources are defined by third-party user.

How do I choose "Generate Resource Template"?

"Generate Resource Template" is made to ensure that each resource is a runtime.Object.

Official resources are already runtime.Objects. They don't need to generate DeepCopyObject method.

For custom resources, things are a little bit complex.

If you want to control a predefined resource from a third-party operator, choose None. The DeepCopyObject method must be already generated using deepcopy-gen.

If you want a newly-defined resource for the controller, choose Both in "Generate Resource Template" field. In this case, koolbuilder will generate definition struct and DeepCopyObject for you. All you need is to fill Spec and Status field.

My Kubernetes version is old, is it still supported?

Yes. Some official resources do have different versions. You can choose supported version for each resource based on your Kubernetes.

The Kubernetes api version does not have great influence. If Group and Version both match, the operator will work.

Will the server record any information?

No. All the functions (including download) are implemented by front-end code.

How do I update the generated code?

Please use the command line tool.

(Currently it is out-of-date. We are working on it to match the latest frontend.)

go install github.com/FlyingOnion/koolbuilder@latest

cd <your-project>
koolbuilder -f controller.yaml

Files that will be overwritten:

• main.go
• controller.go

Files that will be updated:

• custom.go

Why use mapstructure to implement deepcopy?

Well, it's not a big deal. You can choose to generate structure only and use deepcopy-gen to generate method.

(It's because we don't have much time reading and understanding deepcopy-gen and write a generator like that.)

License

The project is licensed under the MIT license.

Acknowledgement

This project is inspired by zhaohuabing's tutorial, which gives a brief and clear introduction to kubernetes operator.

Kubernetes Controller 机制详解（一）

Kubernetes Controller 机制详解（二）

Besides, with a lot of useful frontend libraries, I saved a lot of time writing my pages. They are:

• Vue
• Vite
• Unocss
• FileSaver
• JSZip
• Codemirror-editor-vue3

Future Works

• Add GitHub corner
• Update go command line tool
• Add config.yaml to support command line tool
• Add Generate Definition Struct option
• Add Generate DeepCopyObject option
• Add the rest of the official resources (currently we just add some resources in core, apps, and batch group)
• Support custom sync period (currently all resources are 30s)
• Add Dockerfile, Makefile, k8s yaml config files
• Add Load Example