Deploying Admission Webhooks

Kind Cluster

It is recommended to develop your webhook with a kind cluster for faster iteration. Why?

• You can bring up a multi-node cluster locally within 1 minute.
• You can tear it down in seconds.
• You don’t need to push your images to remote registry.

Cert Manager

You need follow this to install the cert manager bundle.

Build your image

Run the following command to build your image locally.

make docker-build

You don’t need to push the image to a remote container registry if you are using a kind cluster. You can directly load your local image to your kind cluster:

kind load docker-image your-image-name:your-tag

Deploy Webhooks

You need to enable the webhook and cert manager configuration through kustomize. config/default/kustomization.yaml should now look like the following:

# Adds namespace to all resources.
namespace: project-system

# Value of this field is prepended to the
# names of all resources, e.g. a deployment named
# "wordpress" becomes "alices-wordpress".
# Note that it should also match with the prefix (text before '-') of the namespace
# field above.
namePrefix: project-

# Labels to add to all resources and selectors.
#commonLabels:
#  someName: someValue

bases:
- ../crd
- ../rbac
- ../manager
# [WEBHOOK] To enable webhook, uncomment all the sections with [WEBHOOK] prefix including the one in
# crd/kustomization.yaml
- ../webhook
# [CERTMANAGER] To enable cert-manager, uncomment all sections with 'CERTMANAGER'. 'WEBHOOK' components are required.
- ../certmanager
# [PROMETHEUS] To enable prometheus monitor, uncomment all sections with 'PROMETHEUS'.
#- ../prometheus

patchesStrategicMerge:
  # Protect the /metrics endpoint by putting it behind auth.
  # If you want your controller-manager to expose the /metrics
  # endpoint w/o any authn/z, please comment the following line.
- manager_auth_proxy_patch.yaml

# [WEBHOOK] To enable webhook, uncomment all the sections with [WEBHOOK] prefix including the one in
# crd/kustomization.yaml
- manager_webhook_patch.yaml

# [CERTMANAGER] To enable cert-manager, uncomment all sections with 'CERTMANAGER'.
# Uncomment 'CERTMANAGER' sections in crd/kustomization.yaml to enable the CA injection in the admission webhooks.
# 'CERTMANAGER' needs to be enabled to use ca injection
- webhookcainjection_patch.yaml

# the following config is for teaching kustomize how to do var substitution
vars:
# [CERTMANAGER] To enable cert-manager, uncomment all sections with 'CERTMANAGER' prefix.
- name: CERTIFICATE_NAMESPACE # namespace of the certificate CR
  objref:
    kind: Certificate
    group: cert-manager.io
    version: v1alpha2
    name: serving-cert # this name should match the one in certificate.yaml
  fieldref:
    fieldpath: metadata.namespace
- name: CERTIFICATE_NAME
  objref:
    kind: Certificate
    group: cert-manager.io
    version: v1alpha2
    name: serving-cert # this name should match the one in certificate.yaml
- name: SERVICE_NAMESPACE # namespace of the service
  objref:
    kind: Service
    version: v1
    name: webhook-service
  fieldref:
    fieldpath: metadata.namespace
- name: SERVICE_NAME
  objref:
    kind: Service
    version: v1
    name: webhook-service

Now you can deploy it to your cluster by

make deploy IMG=<some-registry>/<project-name>:tag

Wait a while til the webhook pod comes up and the certificates are provisioned. It usually completes within 1 minute.

Now you can create a valid CronJob to test your webhooks. The creation should successfully go through.

kubectl create -f config/samples/batch_v1_cronjob.yaml

You can also try to create an invalid CronJob (e.g. use an ill-formatted schedule field). You should see a creation failure with a validation error.