Init Templates

InitTemplate is a cluster-scoped resource that allows you to define Kubernetes manifests using Go templates. To produce the final list of manifests, the init-agent renders the Go template while injecting some templating data into it.

InitTemplate objects must reside in the same workspace as the InitTargets that reference them. One InitTemplate may be used by any number of InitTargets.

Resource Structure

An InitTemplate has a simple structure:

apiVersion: initialization.kcp.io/v1alpha1
kind: InitTemplate
metadata:
  name: my-init-template
spec:
  template: |
    # Your Go template here, producing YAML manifests

The spec.template field contains a Go template that, when rendered, must produce valid YAML containing one or more Kubernetes manifests (separated by ---).

Template Syntax

InitTemplates use standard Go templates. In addition to the built-in functions, all functions from sprig/v3 are available (e.g. join, b64enc, default, etc.).

Warning

Sprig contains functions that return random data, like uuidv4. These should be rarely, if ever, used in InitTemplates. Since bootstrapping can temporarily fail (for example if a certain resource is not yet available inside a new cluster), the init-agent might render the same templates on multiple occasions for the same cluster.

Use these random functions only if you really do not care about idempotent templates.

Context Variables

When the template is rendered, the following variables are available in the template context:

Name	Type	Description
ClusterName	string	The internal cluster identifier (e.g. "34hg2j4gh24jdfgf") of the workspace being initialized.
ClusterPath	string	The workspace path (e.g. "root:customer:projectx") of the workspace being initialized.

Example

The following example creates a ConfigMap in the initialized workspace that contains information about the workspace itself:

apiVersion: initialization.kcp.io/v1alpha1
kind: InitTemplate
metadata:
  name: workspace-info
spec:
  template: |
    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: workspace-info
    data:
      clusterName: "{{ .ClusterName }}"
      clusterPath: "{{ .ClusterPath }}"

You can also use sprig functions to transform values:

apiVersion: initialization.kcp.io/v1alpha1
kind: InitTemplate
metadata:
  name: workspace-setup
spec:
  template: |
    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: workspace-metadata
      labels:
        workspace-hash: "{{ .ClusterName | sha256sum | trunc 8 }}"
    data:
      path: "{{ .ClusterPath }}"
      pathSegments: "{{ .ClusterPath | replace ":" "," }}"

To create multiple resources, separate them with ---:

apiVersion: initialization.kcp.io/v1alpha1
kind: InitTemplate
metadata:
  name: multi-resource-init
spec:
  template: |
    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: config-one
    data:
      workspace: "{{ .ClusterPath }}"

    ---
    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: config-two
    data:
      id: "{{ .ClusterName }}"