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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​