Helm Templates
Working with Helm templates and template functions.
Basic Templating
Values Access
apiVersion: v1
kind: Pod
metadata:
name: {{ .Values.name }}
namespace: {{ .Release.Namespace }}
spec:
containers:
- name: {{ .Chart.Name }}
image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"Built-in Objects
.Values: Values from values.yaml and overrides.Release: Release information (Name, Namespace, IsUpgrade, IsInstall).Chart: Chart metadata from Chart.yaml.Files: Access non-template files in chart.Capabilities: Kubernetes cluster capabilities.Template: Current template information
Template Functions
String Functions
# upper, lower, title
name: {{ .Values.name | upper }}
user-invocable: false
# quote
value: {{ .Values.password | quote }}
# trimSuffix, trimPrefix
image: {{ .Values.image | trimSuffix ":latest" }}
# replace
url: {{ .Values.url | replace "http" "https" }}Default Values
# default function
port: {{ .Values.port | default 8080 }}
tag: {{ .Values.image.tag | default .Chart.AppVersion }}
# required function
database: {{ required "database.host is required" .Values.database.host }}Type Conversion
# toString, toJson, toYaml
replicas: {{ .Values.replicas | toString }}
annotations:
{{ toYaml .Values.annotations | indent 2 }}
config: |
{{ toJson .Values.config | indent 2 }}Conditionals
{{- if .Values.ingress.enabled }}
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: {{ .Release.Name }}
spec:
# ...
{{- end }}
{{- if and .Values.persistence.enabled .Values.persistence.existingClaim }}
# Use existing claim
{{- else if .Values.persistence.enabled }}
# Create new claim
{{- end }}Loops
{{- range .Values.environments }}
- name: {{ .name }}
value: {{ .value | quote }}
{{- end }}
{{- range $key, $value := .Values.config }}
{{ $key }}: {{ $value | quote }}
{{- end }}Named Templates (_helpers.tpl)
Define Templates
{{/*
Common labels
*/}}
{{- define "mychart.labels" -}}
app.kubernetes.io/name: {{ .Chart.Name }}
app.kubernetes.io/instance: {{ .Release.Name }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}
{{/*
Selector labels
*/}}
{{- define "mychart.selectorLabels" -}}
app.kubernetes.io/name: {{ .Chart.Name }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}Use Templates
metadata:
labels:
{{- include "mychart.labels" . | nindent 4 }}
spec:
selector:
matchLabels:
{{- include "mychart.selectorLabels" . | nindent 6 }}Flow Control
With
{{- with .Values.service }}
apiVersion: v1
kind: Service
metadata:
name: {{ .name }}
spec:
type: {{ .type }}
ports:
- port: {{ .port }}
{{- end }}Range with Index
{{- range $index, $value := .Values.items }}
item-{{ $index }}: {{ $value }}
{{- end }}Whitespace Control
# Remove leading whitespace
{{- .Values.name }}
# Remove trailing whitespace
{{ .Values.name -}}
# Remove both
{{- .Values.name -}}Files Access
Read Files
config: |
{{ .Files.Get "config/app.conf" | indent 2 }}Glob Files
{{- range $path, $content := .Files.Glob "config/*.yaml" }}
{{ $path }}: |
{{ $content | indent 2 }}
{{- end }}Advanced Functions
Ternary
environment: {{ ternary "production" "development" .Values.production }}Coalesce
# Returns first non-empty value
port: {{ coalesce .Values.service.port .Values.port 8080 }}List Functions
# list, append, prepend, concat
args:
{{- range list "arg1" "arg2" "arg3" }}
- {{ . }}
{{- end }}Dict Functions
# dict, set, unset, hasKey
{{- $config := dict "key1" "value1" "key2" "value2" }}
{{- if hasKey $config "key1" }}
found: true
{{- end }}Debugging
# Print debug info
{{ printf "%#v" .Values | indent 2 }}
# Fail on purpose to see values
{{ fail (printf "Debug: %#v" .Values) }}Best Practices
Use Helpers for Repeated Logic
{{- define "mychart.fullname" -}}
{{- if .Values.fullnameOverride }}
{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }}
{{- else }}
{{- printf "%s-%s" .Release.Name .Chart.Name | trunc 63 | trimSuffix "-" }}
{{- end }}
{{- end }}Validate Input
{{- if not (has .Values.service.type (list "ClusterIP" "NodePort" "LoadBalancer")) }}
{{- fail "service.type must be ClusterIP, NodePort, or LoadBalancer" }}
{{- end }}Quote String Values
# Always quote strings
value: {{ .Values.string | quote }}