Documentation

Templating

There are two options for templating in Cartographer, simple templates and ytt:

Simple Templates

Define simple templates in spec.template in Templates

Simple templates provide string interpolation in a $(...)$ tag with jsonpath syntax.

ytt

Define ytt templates in spec.ytt in Templates

ytt is complete YAML aware templating language.

Use ytt when your templates contain complex logic, such as conditionals or looping over collections.

Template Data

Both options for templating are provided a data structure that contains:

owner resource (workload, deliverable)
inputs, that are specified in the blueprint for the template (sources, images, configs, deployments)
parameters

Note: all ytt examples assume you have loaded the data module with #@ load("@ytt:data", "data").

Owner

The entire owner resource is available for retrieving values. To use an owner value, use the format:

Simple template: $(<workload|deliverable>.<field-name>.(...))$
ytt: #@ data.values.<workload|deliverable>.<field-name>.(...)

Owner Examples

Simple template	ytt
$(workload.metadata.name)$	`#@ data.values.workload.metadata.name`
$(deliverable.spec.source.url)$	`#@ data.values.deliverable.spec.source.url`

Inputs

The template specifies the inputs required in the blueprint.

You may specify a combination of one or more of these input types:

Input type	Accessor
sources	`sources.<input-name>.url`, `sources.<input-name>.revision`
images	`images.<input-name>`
configs	`configs.<input-name>`
deployments	`sources.<input-name>.url`, `sources.<input-name>.revision`

Where the <input-name> corresponds to the spec.resources[].<sources|images|configs|deployments>[].name expected in the blueprint.

Specifying inputs in a template:

Simple template: $(<sources|images|configs|deployments>.<input-name>(.<value>))$
ytt: #@ data.values.<sources|images|configs|deployments>.<input-name>(.<value>)

Inputs Examples

Given a supply chain where a resource has multiple sources and a config:

---
spec:
  resources:
    - name: my-template
      sources:
        - resource: source-tester
          name: tested
        - resource: source-original
          name: original
      configs:
        - resource: configurator
          name: app-configuration

They could be used in the template as follows:

Simple template	ytt
$(sources.original.url)$	`#@ data.values.sources.original.url`
$(sources.tested.revision)$	`#@ data.values.sources.tested.revision`
$(configs.app-configuration)$	`#@ data.values.configs.app-configuration`

Input Aliases

If only one input of a given input-type is required, refer to it in the singular and omit the input-name.

Simple template: $<sources|images|configs|deployments>(.<value>)$
ytt: #@ data.values.<sources|images|configs|deployments>(.<value>)

Input Alias Examples

Given a supply chain where a resource has a single source and a single config:

---
spec:
  resources:
    - name: my-template
      sources:
        - resource: source-original
          name: original
      configs:
        - resource: configurator
          name: app-configuration

They could be used in the template as follows:

Simple template	ytt
$(source.url)$	`#@ data.values.source.url`
$(source.revision)$	`#@ data.values.source.revision`
$(config)$	`#@ data.values.config`

Parameters

See Parameter Hierarchy for more information on the precedence of parameters for owner, blueprint and templates.

To use a parameter in the template, use the format:

Simple template: $(params.<param-name>)$
ytt: data.values.params.<param-name>

Parameter Example

Simple template	ytt
$(params.image_prefix)$	`#@ data.values.params.image_prefix`

Complete Examples

Simple Template

apiVersion: carto.run/v1alpha1
kind: ClusterImageTemplate
metadata:
  name: kpack-template
spec:
  params:
    - name: image_prefix
      default: projectcartographer/demo-

  imagePath: .status.latestImage

  template:
    apiVersion: kpack.io/v1alpha2
    kind: Image
    metadata:
      name: $(workload.metadata.name)$
    spec:
      tag: $(params.image_prefix)$$(workload.metadata.name)$
      serviceAccountName: service-account
      builder:
        kind: ClusterBuilder
        name: go-builder
      source:
        blob:
          url: $(sources.source.url)$
      build:
        env: $(workload.spec.build.env)$

ytt

---
apiVersion: carto.run/v1alpha1
kind: ClusterImageTemplate
metadata:
  name: kpack-template
spec:
  imagePath: .status.latestImage
  params:
    - name: serviceAccount
      default: default
    - name: clusterBuilder
      default: default
    - name: registry
      default: {}
  ytt: |
    #@ load("@ytt:data", "data")

    #@ def image():
    #@   return "/".join([
    #@    data.values.params.registry.server,
    #@    data.values.params.registry.repository,
    #@    "-".join([
    #@      data.values.workload.metadata.name,
    #@      data.values.workload.metadata.namespace,
    #@    ])
    #@   ])
    #@ end

    apiVersion: kpack.io/v1alpha2
    kind: Image
    metadata:
      name: #@ data.values.workload.metadata.name
      labels:
        app.kubernetes.io/component: build
        #@ if/end hasattr(data.values.workload.metadata, "labels") and hasattr(data.values.workload.metadata.labels, "app.kubernetes.io/part-of"):
        app.kubernetes.io/part-of: #@ data.values.workload.metadata.labels["app.kubernetes.io/part-of"]
    spec:
      tag: #@ image()
      serviceAccountName: #@ data.values.params.serviceAccount
      builder:
        kind: ClusterBuilder
        name: #@ data.values.params.clusterBuilder
      source:
        blob:
          url: #@ data.values.source.url
        #@ if/end hasattr(data.values.workload.spec.source, "subPath"):
        subPath: #@ data.values.workload.spec.source.subPath
      build:
        env:
        - name: BP_OCI_SOURCE
          value: #@ data.values.source.revision
        #@ if hasattr(data.values.workload.spec.build, "env"):
        #@ for var in data.values.workload.spec.build.env:
        - name: #@ var.name
          value: #@ var.value
        #@ end
        #@ end