Skip to main content
Version: 0.5

Kubectl KCL Plugin

Introduction​

Kubectl is a command line tool for communicating with a Kubernetes cluster's control plane, using the Kubernetes API. You can use the Kubectl-KCL-Plugin to

  • Edit the YAML configuration in a hook way to separate data and logic for the Kubernetes manifests management.
  • For multi-environment and multi-tenant scenarios, you can maintain these configurations gracefully rather than simply copy and paste.
  • Validate all KRM resources using the KCL schema.

Prerequisites​

Quick Start​

Let’s write a KCL function which add annotation managed-by=krm-kcl only to Deployment resources in the helm chart.

1. Get the Example​

git clone https://github.com/kcl-lang/kubectl-kcl.git/
cd ./kubectl-kcl/examples/

2. Test and Run​

Run the KCL code via the Kubectl KCL Plugin.

kubectl kcl run -f ./kcl-run.yaml

The output yaml is

apiVersion: config.kubernetes.io/v1
kind: ResourceList
items:
  - apiVersion: apps/v1
    kind: Deployment
    metadata:
      annotations:
        managed-by: krm-kcl
      labels:
        app: nginx
      name: nginx-deployment
    spec:
      replicas: 3
      selector:
        matchLabels:
          app: nginx
      template:
        metadata:
          labels:
            app: nginx
        spec:
          containers:
            - image: "nginx:1.14.2"
              name: nginx
              ports:
                - containerPort: 80
  - apiVersion: v1
    kind: Service
    metadata:
      name: test
    spec:
      ports:
        - port: 80
          protocol: TCP
          targetPort: 9376
      selector:
        app: MyApp
functionConfig:
  # kcl-fn-config.yaml
  apiVersion: krm.kcl.dev/v1alpha1
  kind: KCLRun
  metadata:
  # EDIT THE SOURCE!
  # This should be your KCL code which preloads the `ResourceList` to `option("resource_list")
  spec:
    source: |
      [resource | {if resource.kind == "Deployment": metadata.annotations: {"managed-by" = "krm-kcl"}} for resource in option("resource_list").items]

Guides for Developing KCL​

Here's what you can do in the KCL code:

  • Read resources from option("resource_list"). The option("resource_list") complies with the KRM Functions Specification. You can read the input resources from option("resource_list")["items"] and the functionConfig from option("resource_list")["functionConfig"].
  • Return a KPM list for output resources.
  • Return an error using assert {condition}, {error_message}.

More Documents and Examples​