Golang template (helm) iterating over a list of maps

Question

I'm using helm to generate kubernetes yamls.

My values.yaml looks like this:

...
jobs:
  - nme: job1
    command: [sh, -c, "/app/deployment/start.sh job1"]
    activeDeadlineSeconds: 600
  - name: job2
    command: [sh, -c, "/app/deployment/start.sh job2"]
    activeDeadlineSeconds: 600
...

templates/jobs.yaml

{{ range $i, $job := .Values.jobs -}}
apiVersion: batch/v1
kind: Job
metadata:
  name: {{ template "name" . }}-{{ $job.name }}
  labels:
    chart: "{{ .Chart.Name }}-{{ .Chart.Version | replace "+" "_" }}"
spec:
  activeDeadlineSeconds: {{ $job.activeDeadlineSeconds }}
  template:
    metadata:
      labels:
        app: {{ template "name" . }}-{{ $job.name }}
    spec:
      containers:
      - name: {{ .Chart.Name }}
        image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
        imagePullPolicy: {{ .Values.image.pullPolicy }}
        command: {{ $job.command }}
        env:
{{ toYaml .Values.service.env | indent 10 }}
        ports:
        - containerPort: {{ .Values.service.internalPort }}
{{- end }}

Helm is failing with this error:

Error: UPGRADE FAILED: render error in "app1/templates/jobs.yaml": template: app1/templates/_helpers.tpl:6:18: executing "name" at <.Chart.Name>: can't evaluate field Name in type interface {}

When I look at _helpers.tpl:

{{- define "name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" -}}
{{- end -}}

If I remove the range loop and references to $job in my jobs.yaml, the _helpers.tpl name template works fine. When I add in the loop, it fails.

It seems like within the loop, all dot . pipeline, which contains the scope for .Chart and .Values, is reassigned to something else.

What am I doing wrong?

Solution 1

Inside the loop the value of the . is set to the current element and you have to use $.Chart.Name to access your data.

I asked a similar question and I think the answer https://stackoverflow.com/a/44734585/8131948 will answer your question too.

Solution 2

I ended up saving the global context and then updating all of my references like this:

{{ $global := . }}
{{ range $i, $job := .Values.jobs -}}
apiVersion: batch/v1
kind: Job
metadata:
    name: {{ template "name" $global }}-{{ $job.name }}
    labels:
    chart: "{{ $global.Chart.Name }}-{{ $global.Chart.Version | replace "+" "_" }}"
spec:
    activeDeadlineSeconds: {{ $job.activeDeadlineSeconds }}
    template:
    metadata:
        labels:
        app: {{ template "name" $global }}-{{ $job.name }}
    spec:
        containers:
        - name: {{ $global.Chart.Name }}
        image: "{{ $global.Values.image.repository }}:{{ $global.Values.image.tag }}"
        imagePullPolicy: {{ $global.Values.image.pullPolicy }}
        command: {{ $job.command }}
        env:
{{ toYaml $global.Values.service.env | indent 10 }}
        ports:
        - containerPort: {{ $global.Values.service.internalPort }}
{{- end }}