tuusberg / k8s-pod-labeler

K8s Admission Webhook for labeling pods

K8s pod labeler

This repo implelents a MutatingAdmissionWebhook that can add missing labels and annotations to pods. The webhook only adds the given label or mutation if it is not already present on the pod definition.

TODO:

• add unit tests!
• support external cert generation like cert-manager

Configuration

Configure the desired labels/annotations for your pods by setting the appInputs.labels and appInputs.annotations values.

appInputs:
  labels:
    "foo": "bar"
  annotations:
    "bar": "baz"

By default, this uses namespace selectors to enable the labeler in a given namespace by adding a namespace label troop.com/k8s-pod-labeler: enabled.

For all configurable settings, see the values.yaml file.

Deployment

Helm install...

# this enables pulling helm charts from github packages
export HELM_EXPERIMENTAL_OCI=1
# test your local config at local-values.yml
helm template \
  -f ./local-values.yml \
  --version 0.3.6 \
  oci://ghcr.io/troop-dev/helm/k8s-pod-labeler
# install helm from a local-values.yml config
helm install \
  -f ./local-values.yml \
  pod-labeler \
  --version 0.3.6 \
  oci://ghcr.io/troop-dev/helm/k8s-pod-labeler

Local Dev

This repo uses Earthly to build the golang application.

# install earthly on osx with homebrew
brew install earthly/earthly/earthly && earthly bootstrap
# build the docker image
earthly +build

Motivation

Troop uses the Linkerd service mesh in GKE, which requires a special annotation to inform the cluster autoscaler that it can evict pods despite them having a local volume.

Resources

• https://github.com/slackhq/simple-kubernetes-webhook
• https://github.com/operator-framework/operator-sdk
• https://github.com/openshift/generic-admission-server
• https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.23/#webhookclientconfig-v1-apiextensions-k8s-io
• https://github.com/morvencao/kube-mutating-webhook-tutorial