Using Go Templates

spec.gotemplate is an inline Go template that renders into one or more Kubernetes manifests. It uses Go's text/template syntax with Sprig functions.

Template variables

The following variables are available inside the template:

Path	Description
.parameters.<name>	Resolved value for parameter <name>.
.instance.name	Name of the consuming TemplateInstance.
.instance.namespace	Namespace of the consuming TemplateInstance.
.instance.labels	The TemplateInstance's labels, as a map.

Example: ConfigMap and Service

apiVersion: templates.v2.stakater.com/v2alpha1
kind: Template
metadata:
  name: app-bundle
  namespace: provider
spec:
  parameters:
    - name: name
    - name: port
      value: "8080"
    - name: env
      value: production
  gotemplate: |
    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: {{ .parameters.name }}-config
      labels:
        app: {{ .parameters.name }}
        env: {{ .parameters.env }}
    data:
      PORT: "{{ .parameters.port }}"
      INSTANCE: {{ .instance.name }}
    ---
    apiVersion: v1
    kind: Service
    metadata:
      name: {{ .parameters.name }}
    spec:
      selector:
        app: {{ .parameters.name }}
      ports:
        - port: {{ .parameters.port }}
          targetPort: {{ .parameters.port }}

A single gotemplate may emit any number of manifests separated by ---. The operator parses each non-empty document as one rendered resource.

Default namespace handling

If a rendered manifest omits metadata.namespace for a namespaced resource, the operator sets it to the TemplateInstance's namespace before applying. Cluster-scoped resources (e.g. ClusterRole, Namespace) are applied as-is.

Sprig examples

spec:
  gotemplate: |
    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: {{ .parameters.name | lower }}-config
      labels:
        app: {{ .parameters.name | lower }}
    data:
      uppercased: {{ .parameters.name | upper | quote }}
      generated: {{ now | date "2006-01-02" }}
      hash: {{ .parameters.name | sha256sum | trunc 8 }}

Iterating over list-valued parameters

When a parameter is resolved via objectFieldRef in LIST mode, the value is always a list. Iterate with range:

spec:
  parameters:
    - name: serviceNames
  gotemplate: |
    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: discovered-services
    data:
      services: |
        {{- range .parameters.serviceNames }}
        - {{ . }}
        {{- end }}

Validation behavior

When the Template is created or updated, the controller:

1. Parses the template string. A parse error sets Valid=False, Reason=ValidationFailed.
2. If every parameter has a literal value, the controller dry-run renders the template with those values and validates the YAML output. Any rendering or YAML validation error sets DryRunRendered=False, Reason=RenderFailed.
3. If even one parameter is dynamic (no literal value), the dry-run is skipped and the controller sets DryRunRendered=False, Reason=DryRunSkipped. The Template is still considered Valid overall.

This means a Template with parameters that are resolved at the TemplateInstance level will not be dry-run rendered at template-creation time. The first end-to-end validation happens when the first TemplateInstance is created.

Restrictions

• The output must be parseable as YAML once rendered.
• Each top-level manifest must be a valid Kubernetes object (have apiVersion, kind, metadata.name).
• Empty documents between --- separators are skipped.