KCL Operator

KCL Operator provides cluster integration, allowing you to use Access Webhook to generate, mutate, or validate resources based on KCL configuration when apply resources to the cluster. Webhook will capture creation, application, and editing operations, and execute KCLRun on the configuration associated with each operation, and the KCL programming language can be used to

• Add labels or annotations based on a condition.
• Inject a sidecar container in all KRM resources that contain a PodTemplate.
• Validate all KRM resources using KCL schema.
• Use an abstract model to generate KRM resources.

Architecture

CR Example

apiVersion: krm.kcl.dev/v1alpha1
kind: KCLRun
metadata:
  name: set-annotation
spec:
  params:
    annotations:
      config.kubernetes.io/local-config: "true"
  source: oci://ghcr.io/kcl-lang/set-annotation

Developing

• Install Go 1.20+
• Install Operator SDK

Run make help to get the help.

Guides for Developing KCL

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

• Read resources from option("resource_list"). The option("resource_list") complies with the KRM Functions Specification. You can read the input resources from option("items") and the params from option("params").
• Return a KRM list for output resources.
• Return an error using assert {condition}, {error_message}.
• Read the environment variables. e.g. option("PATH") (Not yet implemented).
• Read the OpenAPI schema. e.g. option("open_api")["definitions"]["io.k8s.api.apps.v1.Deployment"] (Not yet implemented).

Library

You can directly use KCL standard libraries such as regex.match, math.log.

Tutorial

See here to study more features of KCL.

Examples

See here for more examples.