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Version: 0.7

Kustomize KCL Plugin

Introduction

Kustomize lets you customize raw, template-free YAML files for multiple purposes, leaving the original YAML untouched and usable as is.

KCL can be used to create functions to mutate and/or validate the YAML Kubernetes Resource Model (KRM) input/output format, and we provide Kustomize KCL functions to simplify the function authoring process.

Prerequisites

Quick Start

Let’s write a KCL function which add annotation managed-by=kustomize-kcl only to Deployment resources.

1. Get the Example

git clone https://github.com/kcl-lang/kustomize-kcl.git
cd ./kustomize-kcl/examples/set-annotation/

2. Test and Run

kustomize fn run ./local-resource/ --dry-run

The output YAML is

apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
name: set-annotation
annotations:
config.kubernetes.io/function: |
container:
image: docker.io/kcllang/kustomize-kcl:v0.2.0
config.kubernetes.io/path: example-use.yaml
internal.config.kubernetes.io/path: example-use.yaml
# 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" = "kustomize-kcl"}} for resource in option("resource_list").items]
---
apiVersion: v1
kind: Service
metadata:
name: test
annotations:
config.kubernetes.io/path: example-use.yaml
internal.config.kubernetes.io/path: example-use.yaml
spec:
selector:
app: MyApp
ports:
- protocol: TCP
port: 80
targetPort: 9376
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
labels:
app: nginx
annotations:
config.kubernetes.io/path: example-use.yaml
internal.config.kubernetes.io/path: example-use.yaml
managed-by: kustomize-kcl
spec:
replicas: 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.14.2
ports:
- containerPort: 80

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 KRM list for output resources.
  • Return an error using assert {condition}, {error_message}.

More Documents and Examples