Helm: Include definitions on templates

2 min read | by Jordi Prats

Sometimes we might need to add the same content twice on the same Helm chart. A tipical example would be the labels on the Pods that need to match the selectos on the Service. For this when you create a helm chart there are already some default definitions, for example:

{{/* Common labels */}} {{- define "pet2cattle.labels" -}} helm.sh/chart: {{ include "pet2cattle.chart" . }} {{ include "pet2cattle.selectorLabels" . }} app.kubernetes.io/managed-by: {{ .Release.Service }} {{- end }} {{/* Selector labels */}} {{- define "pet2cattle.selectorLabels" -}} app.kubernetes.io/name: {{ include "pet2cattle.name" . }} app.kubernetes.io/instance: {{ .Release.Name }} {{- end }} 

By convention, any file that begins with an underscore (for example: _helpers.tpl) in the templates/ directory is not expected to output a Kubernetes manifest but contain partial definitions that will be used elsewhere. We can create a new file that begins with underscore and place any definitions we want, for example:

{{- define "exampleconfig" }} redis:  enabled: true  connection: '{{ .Values.redis.connection }}'  configuration:  secure: true  cache:  enabled: false  scheduler:  enabled: true {{- end }} 

And then use it elsewhere as many times a we need using the include function, for example:

apiVersion: v1 kind: ConfigMap metadata:  name: example-config-map data:  demo-1.yml: | {{ include "exampleconfig" . | indent 4 }}  demo-2.yml: | {{ include "exampleconfig" . | indent 4 }} 

On this example we are including multiple times the same data without having to defined it twice

Posted on 16/11/2021