template-operator

Overview

The template operator is an operator to create Kubernetes objects from other objects at runtime.

The need for this operator came up when we created certificates and their corresponding secrets via cert-manager and wanted to use the generated certificate inside a kubeconfig that then should be passed into a pod (via Kubernetes secret).

Installation

The project also comes with a well-defined Makefile. The CRDs can be deployed using

make install

To run the controllers locally, just run

make run

To deploy the controllers into the currently selected (determined by your current kubeconfig) cluster, just run

make deploy

This will apply the [default kustomization)[config/default] with correct RBAC permissions.

Usage

The main resource of the template operator is a Template. This resource manages the actual go template, the source values and how they are obtained as well as the pruning in case any object templated via that template isn't needed anymore.

Given an existing ConfigMap in the cluster like

apiVersion: v1
kind: ConfigMap
metadata:
  namespace: default
  name: my-cm
data:
  foo: "bar"

We can create a Template that creates a secret from the ConfigMap's data by applying a template with

apiVersion: template.onmetal.de/v1alpha1
kind: Template
metadata:
  name: my-template
spec:
  groupKinds:
    - group: ""
      kind: Secret
  commonLabels:
    managed-by: my-template
  selector:
    matchLabels:
      managed-by: my-template
  prune: true
  sources:
    - name: myCM
      object:
        apiVersion: v1
        kind: ConfigMap
        namespace: default
        name: my-cm
  data:
    inline: |-
      apiVersion: v1
      kind: Secret
      metadata:
        namespace: default
        name: my-secret
      type: Opaque
      data:
        foo: "{{ .Values.myCM.data.foo | b64enc }}"

After a short while, our cluster should then have a secret

apiVersion: v1
kind: Secret
metadata:
  namespace: default
  name: kubeconfig
  labels:
    managed-by: my-template
type: Opaque
data:
  foo: YmFy

Contributing

We'd love to get feedback from you. Please report bugs, suggestions or post questions by opening a GitHub issue.

License

Apache-2.0