starlark: Set Namespace #

Overview #

In this example, we are going to demonstrate how to declaratively run the starlark function with an inline starlark script as function configuration to set namespaces to KRM resources.

Fetch the example package #

Get the example package by running the following commands:

$ kpt pkg get https://github.com/kptdev/krm-functions-catalog.git/examples/starlark-set-namespace

We are going to use the following Kptfile and fn-config.yaml to configure the function:

apiVersion: kpt.dev/v1
kind: Kptfile
metadata:
  name: example
pipeline:
  mutators:
    - image: ghcr.io/kptdev/krm-functions-catalog/starlark:latest
      configPath: fn-config.yaml

# fn-config.yaml
apiVersion: fn.kpt.dev/v1alpha1
kind: StarlarkRun
metadata:
  name: set-namespace-to-prod
  annotations:
source: |
  # set the namespace on all resources except StarlarkRun and Kptfile kind.
  def setnamespace(resources, namespace):
    for resource in resources:
      # mutate the resource
      if resource["kind"] not in ["StarlarkRun", "Kptfile"]:
        resource["metadata"]["namespace"] = namespace
  setnamespace(ctx.resource_list["items"], "prod")

The Starlark script is embedded in the source field. This script reads the input KRM resources from ctx.resource_list and sets the .metadata.namespace to prod for all resources.

Function invocation #

Invoke the function by running the following commands:

$ kpt fn render starlark-set-namespace

Expected result #

Check the .metadata.namespace field has been set to prod for every resource.