Watching CustomResourceDefinitions (CRD) with client-go

To watch for new or changed resources of a custom resource definition (CRD) using client-go, it is necessary to generate a client for the specific CRD. While client-go includes support for standard Kubernetes resources like services and pods, it does not automatically recognize custom resources.

Code Generation for CRD Clients

To generate a client for the CRD, you can use the tools provided by Kubernetes. Code generation requires you to define the structs representing your CRD's API. You can refer to the blog post by Stefan Schimanski for detailed instructions on code generation.

Sample Controller Using Client-go

Once you have generated a client for your CRD, you can use it to write a controller or other application that watches for changes to resources of that type. The sample-controller example provided by Kubernetes demonstrates how to watch for CRD resources and perform specific tasks.

Simplified Approach with Kubebuilder

Alternatively, you can use Kubebuilder, a tool maintained by Kubernetes-sigs, to simplify the process of generating client configs and controllers for CRDs. Kubebuilder can automate various aspects of building a controller for your CRD. By utilizing tools like code generation and simplified controller generation, you can efficiently watch for and manage CRD resources using client-go.