Helm | Kubernetes

Learn Conditionals in Helm faster than a two minute meal

Your one stop guide to using conditional statements in Helm

Photo by orbtal media on Unsplash

One of the best qualities of Helm is easily the ability to use conditional statements.

In this free step by step guide I explain how to best use conditional statements in helm templates to make your deployments easier.

Lets get started and if you find value in this article make sure to spend 2 extra seconds clapping for it as it helps.

The first part is how to use and the last part is an example

Some examples of using conditionals

The equal (eq) operator

{{- if eq.Values.app.env "prod" }}
  env: "Production environment"
{{- else }}
  env: "Non-production environment"
{{- end }}

If equal to prod then production environment else non prod.

The not equal (ne) operator

{{- if ne .Values.app.env "prod" }}
  env: "Non-production environment"
{{- else }}
  env: "Production environment"
{{- end }}

Conversely if not equal to prod then non prod

The and operator

{{- if and (eq .Values.app.env "prod") (gt .Values.replicaCount 2) }}
- name: sidecar-logger
  image: prod.registry.com/logger:latest
{{- end }}

Deploy sidecar container only if prod and more than 2 replicas

The or operator

image: {{- if or (eq .Values.app.env "dev") (eq .Values.app.env "staging") }}
  test.registry.com/{{ .Values.app.image }}:{{ .Values.app.tag }}
{{- else }}
  {{ .Values.app.registry }}/{{ .Values.app.image }}:{{ .Values.app.tag }}
{{- end }}

If dev or staging use the test registry

The greater than operator (gt)

replicas: {{- if gt .Values.replicaCount 3 }}
  {{ .Values.replicaCount }}
{{- else }}
  3
{{- end }}

Minimum replicas must be 3 or more for prod

The less than operator (lt)

{{- if lt .Values.replicaCount 2 }}
debug: "true"
{{- else }}
debug: "false"
{{- end }}

Enable debug mode if replicas less than 2

The hasKey operator

Enable a feature if a key exists

{{- if hasKey .Values.features "logging" }}
logging: enabled
{{- else }}
logging: disabled
{{- end }}

The Example Tutorial

I want to setup my cluster in multiple environments and use helm to manage them. However since each environment uses their own separate image repository I don’t want to change it every time.

To tackle this issue we are going to use helm.

Create Helm Directory

Run the following commands to create helm directory

helm create ziggo

Create the values file for dev and prod environment.

values-dev.yaml
app:
  env: dev
  registry: dev.registry.com

the file for prod environment

values-prod.yaml
app:
  env: prod
  registry: prod.registry.com

the default values file has the custom configuration which is used if the template does not find any of the values in the above files

app:
  env: "dev"
  registry: "docker.io"
  name: "ziggo"
  image: "ziggoi"
  tag: "v5"

replicaCount: 3

Running the deployment

Structure the deployment to use the conditionals.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Values.app.name }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: {{ .Values.app.name }}
  template:
    metadata:
      labels:
        app: {{ .Values.app.name }}
    spec:
      containers:
        - name: {{ .Values.app.name }}
          {{- if eq .Values.app.env "prod" }}
          image: {{ .Values.app.registry }}/{{ .Values.app.image }}:stable
          {{- else }}
          image:  {{ .Values.app.registry }}/{{ .Values.app.image }}:{{ .Values.app.tag }}
          {{- end }}
          ports:
            - containerPort: 80

This is the conditional part , if env is prod or dev

{{- if eq .Values.app.env "prod" }}
 image: {{ .Values.app.registry }}/{{ .Values.app.image }}:stable
 {{- else }}
  image:  {{ .Values.app.registry }}/{{ .Values.app.image }}:{{ .Values.app.tag }}
  {{- end }}

And now run with the dev file

helm template ziggo/ -f ziggo/values-dev.yaml

Run with the prod file

helm template ziggo/ -f ziggo/values-prod.yaml

As you can see based on the different conditionals it chooses different images.

Conclusion

This is how we use conditional statements in helm to seperate concerns. If you found it useful make sure to subscribe and like the article.