Surfacing Status with Outputs

A rendered resource gets values at runtime that the author never wrote — an allocated address, a generated name, a downstream controller's health. outputs lift those back onto the TemplateInstance's status, so a consumer (or another Template) can read them from one object instead of querying the rendered resources.

Scenario 1: expose an allocated LoadBalancer IP

Anna renders a Service of type LoadBalancer and wants the address the cloud assigns, without running kubectl get svc herself.

apiVersion: templates.v2.stakater.com/v2alpha1
kind: Template
metadata:
  name: edge-service
  namespace: provider
spec:
  parameters:
    - name: name
      required: true
      exposeInStatus: true   # the output source name below reads it
  targetNamespaces:
    explicit:
      allow:
        literal:
          - consumer-a
  gotemplate: |
    apiVersion: v1
    kind: Service
    metadata:
      name: {{ .parameters.name }}
    spec:
      type: LoadBalancer
      selector:
        app: {{ .parameters.name }}
      ports:
        - port: 80
  outputs:
    - name: endpoint
      from:
        apiVersion: v1
        kind: Service
        name: "{.parameters.name}"      # JSONPath template over the Template context
      fields:
        - name: ip
          jsonPath: "{.status.loadBalancer.ingress[*].ip}"
        - name: clusterIP
          jsonPath: "{.spec.clusterIP}"

exposeInStatus matters here: under the default sync.mode: off, the instance freezes after its first apply and resolves from.name from the values recorded in status.resolvedParameters (see Sync).

Anna binds it:

apiVersion: templates.v2.stakater.com/v2alpha1
kind: TemplateInstance
metadata:
  name: edge-service
  namespace: consumer-a
spec:
  templateRef:
    name: edge-service
    namespace: provider
  parameters:
    - name: name
      value: edge

Once the cloud assigns an address, it appears on the instance, keyed by the Service name:

kubectl get templateinstance edge-service -n consumer-a \
  -o jsonpath='{.status.outputs}' | jq .
# { "clusterIP": { "edge": "10.96.12.34" }, "ip": { "edge": "[\"203.0.113.7\"]" } }

Until the cloud assigns an address, ip resolves to "[]" (an empty list). It does not fail the instance.

Scenario 2: roll up the health of many rendered resources

When one instance renders several resources of a kind, fromAll keys an entry per resource, so the instance's status answers "is every one healthy?":

  outputs:
    - name: deployments
      fromAll:
        apiVersion: apps/v1
        kind: Deployment
      keyTemplate: "{.metadata.name}"
      fields:
        - name: available
          jsonPath: "{.status.availableReplicas}"

kubectl get templateinstance <name> -n <ns> -o jsonpath='{.status.outputs.available}' | jq .
# { "web": "3", "worker": "1" }

Notes

• An array or object result is JSON-encoded into the status string ({.status.loadBalancer.ingress[*].ip} → '["203.0.113.7"]'); a scalar is stored as-is.
• A Secret may not be an output source, so secret material can never be copied into status.

See also

• Outputs for the full semantics of from, fromAll, forEach and keyTemplate.
• Status for where outputs sit and the OutputsResolved condition.