KPT KCL SDK
kpt is a package-centric toolchain that enables a configuration authoring, automation, and delivery experience, which simplifies managing Kubernetes platforms and KRM-driven infrastructure (e.g., Config Connector, Crossplane) at scale by manipulating declarative Configuration as Data for automating Kubernetes configuration editing including transforming and validating.
KCL can be used to create functions to transform and/or validate the YAML Kubernetes Resource Model (KRM) input/output format, but we provide KPT KCL SDKs to simplify the function authoring process.
Prerequisites
- Install kpt
- Install Docker
Quick Start
Let’s write a KCL function which add annotation managed-by=kpt only to Deployment resources.
Get the Example
git clone https://github.com/kcl-lang/kpt-kcl-sdk.git/
cd ./kpt-kcl-sdk/get-started/set-annotation
Show the KRM
kpt pkg tree
The output is
set-annotation
├── [kcl-fn-config.yaml] KCLRun set-annotation
└── data
├── [resources.yaml] Deployment nginx-deployment
└── [resources.yaml] Service test
Update the FunctionConfig
# kcl-fn-config.yaml
apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata: # kpt-merge: /set-annotation
name: set-annotation
spec:
# EDIT THE SOURCE!
# This should be your KCL code which preloads the `ResourceList` to `option("resource_list")
source: |
[resource | {if resource.kind == "Deployment": metadata.annotations: {"managed-by" = "kpt"}} for resource in option("resource_list").items]
Test and Run
Run the KCL code via kpt
# Note: you need add sudo and --as-current-user flags to ensure KCL has permission to write temp files in the container filesystem.
sudo kpt fn eval ./data -i docker.io/kcllang/kpt-kcl:v0.2.0 --as-current-user --fn-config kcl-fn-config.yaml
# Verify that the annotation is added to the `Deployment` resource and the other resource `Service`
# does not have this annotation.
cat ./data/resources.yaml | grep annotations -A1 -B5