Deploying Admission Webhooks

cert-manager

You need to follow this to install the cert-manager bundle.

Build your image

Run the following command to build your image locally.

make docker-build docker-push IMG=<some-registry>/<project-name>:tag

Using Kind

Consider incorporating Kind into your workflow for a faster, more efficient local development and CI experience. Note that, if you’re using a Kind cluster, there’s no need to push your image to a remote container registry. You can directly load your local image into your specified Kind cluster:

kind load docker-image <your-image-name>:tag --name <your-kind-cluster-name>

To know more, see: Using Kind For Development Purposes and CI

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.
#labels:
#- includeSelectors: true
#  pairs:
#    someName: someValue

resources:
- ../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
# [METRICS] Expose the controller manager metrics service.
- metrics_service.yaml
# [NETWORK POLICY] Protect the /metrics endpoint and Webhook Server with NetworkPolicy.
# Only Pod(s) running a namespace labeled with 'metrics: enabled' will be able to gather the metrics.
# Only CR(s) which requires webhooks and are applied on namespaces labeled with 'webhooks: enabled' will
# be able to communicate with the Webhook Server.
#- ../network-policy

# Uncomment the patches line if you enable Metrics, and/or are using webhooks and cert-manager
patches:
# [METRICS] The following patch will enable the metrics endpoint using HTTPS and the port :8443.
# More info: https://book.kubebuilder.io/reference/metrics
- path: manager_metrics_patch.yaml
  target:
    kind: Deployment

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

# [CERTMANAGER] To enable cert-manager, uncomment all sections with 'CERTMANAGER' prefix.
# Uncomment the following replacements to add the cert-manager CA injection annotations
replacements:
 - source: # Uncomment the following block if you have any webhook
     kind: Service
     version: v1
     name: webhook-service
     fieldPath: .metadata.name # Name of the service
   targets:
     - select:
         kind: Certificate
         group: cert-manager.io
         version: v1
       fieldPaths:
         - .spec.dnsNames.0
         - .spec.dnsNames.1
       options:
         delimiter: '.'
         index: 0
         create: true
 - source:
     kind: Service
     version: v1
     name: webhook-service
     fieldPath: .metadata.namespace # Namespace of the service
   targets:
     - select:
         kind: Certificate
         group: cert-manager.io
         version: v1
       fieldPaths:
         - .spec.dnsNames.0
         - .spec.dnsNames.1
       options:
         delimiter: '.'
         index: 1
         create: true

 - source: # Uncomment the following block if you have a ValidatingWebhook (--programmatic-validation)
     kind: Certificate
     group: cert-manager.io
     version: v1
     name: serving-cert # This name should match the one in certificate.yaml
     fieldPath: .metadata.namespace # Namespace of the certificate CR
   targets:
     - select:
         kind: ValidatingWebhookConfiguration
       fieldPaths:
         - .metadata.annotations.[cert-manager.io/inject-ca-from]
       options:
         delimiter: '/'
         index: 0
         create: true
 - source:
     kind: Certificate
     group: cert-manager.io
     version: v1
     name: serving-cert # This name should match the one in certificate.yaml
     fieldPath: .metadata.name
   targets:
     - select:
         kind: ValidatingWebhookConfiguration
       fieldPaths:
         - .metadata.annotations.[cert-manager.io/inject-ca-from]
       options:
         delimiter: '/'
         index: 1
         create: true

 - source: # Uncomment the following block if you have a DefaultingWebhook (--defaulting )
     kind: Certificate
     group: cert-manager.io
     version: v1
     name: serving-cert # This name should match the one in certificate.yaml
     fieldPath: .metadata.namespace # Namespace of the certificate CR
   targets:
     - select:
         kind: MutatingWebhookConfiguration
       fieldPaths:
         - .metadata.annotations.[cert-manager.io/inject-ca-from]
       options:
         delimiter: '/'
         index: 0
         create: true
 - source:
     kind: Certificate
     group: cert-manager.io
     version: v1
     name: serving-cert # This name should match the one in certificate.yaml
     fieldPath: .metadata.name
   targets:
     - select:
         kind: MutatingWebhookConfiguration
       fieldPaths:
         - .metadata.annotations.[cert-manager.io/inject-ca-from]
       options:
         delimiter: '/'
         index: 1
         create: true
#
# - source: # Uncomment the following block if you have a ConversionWebhook (--conversion)
#     kind: Certificate
#     group: cert-manager.io
#     version: v1
#     name: serving-cert # This name should match the one in certificate.yaml
#     fieldPath: .metadata.namespace # Namespace of the certificate CR
#   targets:
#     - select:
#         kind: CustomResourceDefinition
#       fieldPaths:
#         - .metadata.annotations.[cert-manager.io/inject-ca-from]
#       options:
#         delimiter: '/'
#         index: 0
#         create: true
# - source:
#     kind: Certificate
#     group: cert-manager.io
#     version: v1
#     name: serving-cert # This name should match the one in certificate.yaml
#     fieldPath: .metadata.name
#   targets:
#     - select:
#         kind: CustomResourceDefinition
#       fieldPaths:
#         - .metadata.annotations.[cert-manager.io/inject-ca-from]
#       options:
#         delimiter: '/'
#         index: 1
#         create: true

And config/crd/kustomization.yaml should now look like the following:

# This kustomization.yaml is not intended to be run by itself,
# since it depends on service name and namespace that are out of this kustomize package.
# It should be run by config/default
resources:
- bases/batch.tutorial.kubebuilder.io_cronjobs.yaml
# +kubebuilder:scaffold:crdkustomizeresource

patches:
# [WEBHOOK] To enable webhook, uncomment all the sections with [WEBHOOK] prefix.
# patches here are for enabling the conversion webhook for each CRD
# +kubebuilder:scaffold:crdkustomizewebhookpatch

# [CERTMANAGER] To enable cert-manager, uncomment all the sections with [CERTMANAGER] prefix.
# patches here are for enabling the CA injection for each CRD
# +kubebuilder:scaffold:crdkustomizecainjectionpatch

# [WEBHOOK] To enable webhook, uncomment the following section
# the following config is for teaching kustomize how to do kustomization for CRDs.
#configurations:
#- kustomizeconfig.yaml

Now you can deploy it to your cluster by

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

Wait a while till 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.