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set-labels

Overview

The set-labels function adds a list of labels to all resources. It's a common practice to add a set of labels for all the resources in a package. Kubernetes has some recommended labels.

For example, labels can be used in the following scenarios:

  • Identify the KRM resources by querying their labels.
  • Set labels for all resources within a package (e.g. environment=staging).

You can learn more about labels here.

Usage

This function can be used with any KRM function orchestrators (e.g. kpt).

For each label, the function adds it if it doesn't exist. Otherwise, it replaces the existing label with the same name.

In addition to updating the metadata.labels field for each resource, the function will also update the selectors that target the labels by default. e.g. the selectors for Service will be updated to include the desired labels.

This function can be used both declaratively and imperatively.

FunctionConfig

There are 2 kinds of functionConfig supported by this function:

  • ConfigMap
  • A custom resource of kind SetLabels

To use a ConfigMap as the functionConfig, the desired labels must be specified in the data field.

To add 2 labels color: orange and fruit: apple to all resources, we use the following functionConfig:

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-config
data:
  color: orange
  fruit: apple

To use a SetLabels custom resource as the functionConfig, the desired labels must be specified in the labels field.

To add 2 labels color: orange and fruit: apple to all built-in resources, we use the following functionConfig:

apiVersion: fn.kpt.dev/v1alpha1
kind: SetLabels
metadata:
  name: my-config
labels:
  color: orange
  fruit: apple

The set-labels function adds the desired labels to more fields than just the one found in .metadata. For example, the Deployment resource has a spec.selector, which gets updated by the set-labels function by default. This is not always desired.

To disable updating of .spec.selectors, define a SetLabels custom resource, and set .options.setSelectorLabels to false like so:

apiVersion: fn.kpt.dev/v1alpha1
kind: SetLabels
metadata:
  name: my-config
labels:
  color: orange
  fruit: apple
options:
  setSelectorLabels: false # default is true