Custom Resource

Updated Apr 07, 2022 ·

Custom Resource

A Custom Resource (CR) is an extension of the Kubernetes API that allows new resource types.

• Specialized configurations for specific applications
• Automation of complex tasks through custom objects
• Extends Kubernetes functionality without core modifications

CRD Manifest

Below is an example Custom Resource Definition (CRD):

• Name: internals.datasets.kodekloud.com
• Group: datasets.kodekloud.com
• Scope: Namespaced, meaning it’s only accessible within a specific namespace.

## crd.yaml 
---
apiVersion: apiextensions.k8s.io/v1
kind: CustomResourceDefinition
metadata:
  name: internals.datasets.kodekloud.com 
spec:
  group: datasets.kodekloud.com
  versions:
    - name: v1
      served: true
      storage: true
      schema:
        openAPIV3Schema:
          type: object
          properties:
            spec:
              type: object
              properties:
                internalLoad:
                  type: string
                range:
                  type: integer
                percentage:
                  type: string
  scope: Namespaced 
  names:
    plural: internals
    singular: internal
    kind: Internal
    shortNames:
    - int

After creating the CRD, you can define custom resources based on it:

## custom.yaml  
---
kind: Internal
apiVersion: datasets.kodekloud.com/v1
metadata:
  name: internal-space
  namespace: default
spec:
  internalLoad: "high"
  range: 80
  percentage: "50"

Ensure both files are ready:

controlplane ~ ➜  ls -l
total 8
-rw-rw-rw- 1 root root 678 Jan  6 01:56 crd.yaml
-rw-rw-rw- 1 root root 171 Dec  1 06:17 custom.yaml

Create the CRD first, followed by the custom resource:

• Apply the crd.yaml:

  kubectl apply -f crd.yaml 

  Output:

  customresourcedefinition.apiextensions.k8s.io/internals.datasets.kodekloud.com created

• Apply the custom.yaml:

  kubectl apply -f custom.yaml 

  Output:

  internal.datasets.kodekloud.com/internal-space created

Verify CRDs:

kubectl get crd

Output:

NAME                               CREATED AT
collectors.monitoring.controller   2024-01-06T06:20:57Z
globals.traffic.controller         2024-01-06T06:20:58Z
internals.datasets.kodekloud.com   2024-01-06T07:00:06Z

Example: Datacenter Resource

Define another custom resource, datacenter, with apiVersion set to traffic.controller/v1. Set dataField length to 2 and access permission to true:

## datacenter.yaml
kind: Global 
apiVersion: traffic.controller/v1
metadata:
  name: datacenter
spec:
  dataField: 2
  access: true

Create the resource:

kubectl apply -f datacenter.yaml 

Output:

global.traffic.controller/datacenter created 

Check the created resource:

kubectl get global

Output:

NAME         AGE
datacenter   64s