starlark: Load Library #

Overview #

In this example, we are going to demonstrate how to load a library in the starlark function.

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-load-library

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
source: |
  load('encoding/json.star', 'json')

  def updateReplicas(resources):
    for resource in resources:
      if resource["kind"] == "Deployment":
        obj = json.decode(resource["metadata"]["annotations"]["last-applied"])
        resource["spec"]["replicas"] = obj["spec"]["replicas"]+1
  updateReplicas(ctx.resource_list["items"])

We load the json library by load('encoding/json.star', 'json'). Then we invoke the json.decode method to deserialize the content from an annotation.

Function invocation #

Invoke the function by running the following commands:

$ kpt fn render starlark-load-library

Expected result #

Check the .spec.replicas field should have been updated to 4.