Identifiers

You can implement your own identifier template, if ours is not practical for you. Let’s see how it’s done.

An Identifier template receives the following context:

## Content Of the Resources
content:
  apiVersion: v1
  kind: Service
  metadata:
    name: frontend
  spec:
    ports:
    - name: http
      port: 80
      protocol: TCP
      targetPort: http
    selector:
      app: frontend
    type: ClusterIP


## File Information
id:
  file: structure/base/podinfo/service.yaml
  filename: service.yaml
  fix: ""
  path: structure/base/


## Global Helm Context
ctx:
  ...

An Identifier can have following return values (YAML Print):

• id - <string>
  The evaluated ID. If empty uses file name.

• errors - <list>
  A list of errors which occured during identifier evaluation. The error will make helmize fail with your error message.

• debug - <list>
  Debug output which can be seen in summary (If something isn’t doing what you thought it does).

• requireId - <string/bool>
  For every evulated id ($.id) the result can not be empty. If it’s empty, it’s an error.

In the helmize.yaml which template we want to use:

..
custom_identifier_template: "reference.identifier.template"
..

Let’s create a simple custom identifier template. This template searches each received file for the field $.content.helmize_identifier. If the field is set, then it’s value is used as identifier. If it’s not set, an error is returned.

{{- define "reference.identifier.template" -}}
  {{- $return := dict "id" "" "errors" list "debug" list -}}
  {{- if $.content.helmize_identifier -}}
    {{- $_ := set $return "id" $.content.helmize_identifier -}}
    {{- $_ := unset $.content "helmize_identifier" -}}
  {{- else -}}
    {{- $_ := set $return "errors" (append $return.errors (dict "error" "Missing field helmize_identifier")) -}}
  {{- end }}
  {{- printf "%s" (toYaml $return) -}}
{{- end -}}

If we run this for the first time, we will get errors on all of our files, since none of them have set the field yet:

$ helm template examples/reference

Found errors, please resolve those errors or use the force options:

  - errors:
    - error: Missing field helmize_identifier
    file: structure/base/podinfo/deploy.yaml
  - errors:
    - error: Missing field helmize_identifier
    file: structure/base/podinfo/service.yaml
  - errors:
    - error: Missing field helmize_identifier
    file: structure/env/test/podinfo/deployment-frontend.yaml
  - errors:
    - error: Missing field helmize_identifier
    file: structure/env/test/podinfo/hpa.yaml
  - errors:
    - error: Missing field helmize_identifier
    file: structure/location/east/podinfo/deploy.yaml

To make it work let’s add to each of the files a helmize_identifier. Each Kubernetes kind is it’s own identifier:

• *service.yaml -> helmize_identifier: service etc.

If we rerun in summary mode, we will see, that the identifiers were taken from the attribute, but the attribute is no longer in the content. The identifier is represented via the id field:

$ helm template . --set debug=true --set summary=true

...

- checksum: 4669de4bb6631c64c7459e44b38c32a1236a0b7fb419b642d4a52b76ff51747c
  content:
    apiVersion: autoscaling/v2beta2
    kind: HorizontalPodAutoscaler
    metadata:
      name: frontend
    spec:
      maxReplicas: 4
      metrics:
      - resource:
          name: cpu
          target:
            averageUtilization: 99
            type: Utilization
        type: Resource
      minReplicas: 1
      scaleTargetRef:
        apiVersion: apps/v1
        kind: Deployment
        name: frontend
  debug: []
  errors: []
  id: hpa
- checksum: 08b06c48a587e3fe6179875f70331bb97562a6e584dcb32807ce9eac7572fc8d
  content:
    apiVersion: v1
    kind: Service
    metadata:
      name: frontend
    spec:
      ports:
      - name: http
        port: 80
        protocol: TCP
        targetPort: http
      selector:
        app: frontend
      type: ClusterIP
  debug: []
  errors: []
  id: service

...

And that’s how you can write your own identifier.