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Version: 0.8

Helm KCL Plugin

Introduction​

Helm is a tool for managing Charts. Charts are packages of pre-configured Kubernetes resources. You can use the Helm-KCL-Plugin to

  • Edit the helm charts 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=helm-kcl-plugin only to Deployment resources in the helm chart.

1. Get the Example​

git clone https://github.com/kcl-lang/helm-kcl.git/
cd ./helm-kcl/examples/workload-charts-with-kcl

2. Test and Run​

Run the KCL code via the Helm KCL Plugin.

helm kcl template --file ./kcl-run.yaml

The output yaml is

apiVersion: v1
kind: Service
metadata:
  labels:
    app.kubernetes.io/instance: workload
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/name: workload
    app.kubernetes.io/version: 0.1.0
    helm.sh/chart: workload-0.1.0
  name: workload
spec:
  ports:
    - name: www
      port: 80
      protocol: TCP
      targetPort: 80
  selector:
    app.kubernetes.io/instance: workload
    app.kubernetes.io/name: workload
  type: ClusterIP
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app.kubernetes.io/instance: workload
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/name: workload
    app.kubernetes.io/version: 0.1.0
    helm.sh/chart: workload-0.1.0
  name: workload
  annotations:
    managed-by: helm-kcl-plugin
spec:
  selector:
    matchLabels:
      app.kubernetes.io/instance: workload
      app.kubernetes.io/name: workload
  template:
    metadata:
      labels:
        app.kubernetes.io/instance: workload
        app.kubernetes.io/name: workload
    spec:
      containers:
        - image: nginx:alpine
          name: frontend

Guides for Developing KCL​

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

  • Read resources from option("items"). The option("items") complies with the KRM Functions Specification.
  • Return a KRM list for output resources.
  • Return an error using assert {condition}, {error_message}.
  • Read the PATH variables. e.g. option("PATH").
  • Read the environment variables. e.g. option("env").

More Documents and Examples​