apply-setters

README

apply-setters

Overview

Apply setter values on resource fields. Setters serve as parameters for template-free setting of field values.

Synopsis

Setters are a safer alternative to other substitution techniques which do not have the context of the structured data. Setters may be invoked to modify the package resources using apply-setters function to set desired values.

We use ConfigMap to configure the apply-setters function. The desired setter values are provided as key-value pairs using data field where key is the name of the setter and value is the new desired value for the setter.

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-func-config
data:
  setter_name1: setter_value1
  setter_name2: setter_value2

Examples

Setting scalar values

Let's start with the input resource in a package

apiVersion: v1
kind: Deployment
metadata:
  name: nginx-deployment # kpt-set: ${image}-deployment
spec:
  replicas: 1 # kpt-set: ${replicas}

Discover the names of setters in the function config file and declare desired values.

apiVersion: v1
kind: ConfigMap
metadata:
  name: apply-setters-fn-config
data:
  image: ubuntu
  replicas: "3"

Render the declared values by invoking:

$ kpt fn run --image gcr.io/kpt-fn/apply-setters:unstable --fn-config ./apply-setters-fn-config

Alternatively, setter values can be passed as key-value pairs in the CLI

$ kpt fn run --image gcr.io/kpt-fn/apply-setters:unstable -- 'image=ubuntu' 'replicas=3'

Rendered resource looks like the following:

apiVersion: v1
kind: Deployment
metadata:
  name: ubuntu-deployment # kpt-set: ${image}-deployment
spec:
  replicas: 3 # kpt-set: ${replicas}

Setting array values

Array values can also be parameterized using setters. Since the values of configMap in pipeline definition must be of string type, the array values must be wrapped into string. However, the rendered values in the resources will be array type.

Let's start with the input resource

apiVersion: v1
kind: MyKind
metadata:
  name: foo
environments: # kpt-set: ${env}
  - dev
  - stage

Declare the desired array values, wrapped into string.

apiVersion: v1
kind: ConfigMap
metadata:
  name: apply-setters-fn-config
data:
  env: |
    - prod
    - dev

Render the declared values by invoking:

$ kpt fn run --image gcr.io/kpt-fn/apply-setters:unstable --fn-config ./apply-setters-fn-config

Rendered resource looks like the following:

apiVersion: v1
kind: MyKind
metadata:
  name: foo
environments: # kpt-set: ${env}
  - prod
  - dev