admission-webhook-example
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A Kubernetes mutating webhook server that implements sidecar injection
Kubernetes Admission Webhook example
This tutoral shows how to build and deploy an AdmissionWebhook.
The Kubernetes documentation contains a common set of recommended labels that allows tools to work interoperably, describing objects in a common manner that all tools can understand. In addition to supporting tooling, the recommended labels describe applications in a way that can be queried.
In our validating webhook example we make these labels required on deployments and services, so this webhook rejects every deployment and every service that doesn’t have these labels set. The mutating webhook in the example adds all the missing required labels with not_available
set as the value.
Prerequisites
Kubernetes 1.9.0 or above with the admissionregistration.k8s.io/v1beta1
API enabled. Verify that by the following command:
kubectl api-versions | grep admissionregistration.k8s.io/v1beta1
The result should be:
admissionregistration.k8s.io/v1beta1
In addition, the MutatingAdmissionWebhook
and ValidatingAdmissionWebhook
admission controllers should be added and listed in the correct order in the admission-control flag of kube-apiserver.
Build
Build and push docker image
./build
How does it work?
We have a blog post that explains webhooks in depth with the help of this example. Check it out!