Helmテンプレートエンジン深層分析: Goテンプレート、Sprig、名前付きテンプレート

テンプレートテキスト → レキサー → トークンストリーム → パーサー → AST

# パイプライン: 左の出力が右の入力に渡される
name: { { .Values.name | lower | trunc 63 | trimSuffix "-" } }

{{- include "my-chart.labels" . | nindent 4 }}
#^ 左の空白/改行を除去

{{ include "my-chart.labels" . | nindent 4 -}}
#                                           ^ 右の空白/改行を除去

upper: {{ "hello" | upper }}          # HELLO
lower: {{ "HELLO" | lower }}          # hello
title: {{ "hello world" | title }}    # Hello World
trim: {{ "  hello  " | trim }}        # hello
trunc: {{ "hello" | trunc 3 }}        # hel
contains: {{ contains "lo" "hello" }} # true
replace: {{ "hello world" | replace " " "-" }}  # hello-world
snakecase: {{ "HelloWorld" | snakecase }}        # hello_world
kebabcase: {{ "HelloWorld" | kebabcase }}        # hello-world
randAlphaNum: {{ randAlphaNum 10 }}

add: {{ add 1 2 }}    # 3
sub: {{ sub 10 3 }}   # 7
mul: {{ mul 2 3 }}    # 6
max: {{ max 1 2 3 }}  # 3
ceil: {{ ceil 1.1 }}  # 2
floor: {{ floor 1.9 }}# 1

sha256sum: {{ "hello" | sha256sum }}
b64enc: {{ "hello" | b64enc }}
uuid: {{ uuidv4 }}

list: { { list "a" "b" "c" } }
first: { { first (list "a" "b" "c") } } # a
append: { { append (list "a" "b") "c" } } # [a b c]
has: { { has "b" (list "a" "b" "c") } } # true
sortAlpha: { { sortAlpha (list "c" "a" "b") } } # [a b c]

{{- $myDict := dict "key1" "value1" "key2" "value2" }}
get: {{ get $myDict "key1" }}          # value1
hasKey: {{ hasKey $myDict "key1" }}     # true
keys: {{ keys $myDict }}                # [key1 key2]

# templates/_helpers.tpl
{{- define "my-chart.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
{{- end }}

{{- define "my-chart.fullname" -}}
{{- $name := default .Chart.Name .Values.nameOverride }}
{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" }}
{{- end }}

# template: 結果を直接出力（パイプライン使用不可）
{{ template "my-chart.name" . }}

# include: 結果を文字列として返す（パイプライン使用可能）
{{ include "my-chart.labels" . | nindent 4 }}

{{- define "my-chart.labels" -}}
helm.sh/chart: {{ include "my-chart.chart" . }}
{{ include "my-chart.selectorLabels" . }}
{{- if .Chart.AppVersion }}
app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
{{- end }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
{{- end }}

{{- define "my-chart.selectorLabels" -}}
app.kubernetes.io/name: {{ include "my-chart.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}

{{- if .Values.ingress.enabled }}
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: {{ include "my-chart.fullname" . }}
{{- end }}

{{- if eq .Values.service.type "NodePort" }}
  nodePort: {{ .Values.service.nodePort }}
{{- else if eq .Values.service.type "LoadBalancer" }}
  loadBalancerIP: {{ .Values.service.loadBalancerIP }}
{{- end }}

{{- with .Values.nodeSelector }}
nodeSelector:
  {{- toYaml . | nindent 2 }}
{{- end }}

# withブロック内で上位スコープにアクセスする場合は$を使用
{{- with .Values.container }}
  name: {{ $.Chart.Name }}
  image: {{ .image }}
{{- end }}

{{- range .Values.extraEnvVars }}
- name: {{ .name }}
  value: {{ .value | quote }}
{{- end }}

{{- range $key, $value := .Values.configData }}
{{ $key }}: {{ $value | quote }}
{{- end }}

{{- range until 5 }}
- replica-{{ . }}
{{- end }}

# values.yaml
configTemplate: |
  server.name={{ .Release.Name }}

# templates/configmap.yaml
data:
  config.properties: |
    {{ tpl .Values.configTemplate . | nindent 4 }}

{{- $secret := lookup "v1" "Secret" .Release.Namespace "my-secret" }}
{{- if $secret }}
password: {{ index $secret.data "password" }}
{{- else }}
password: {{ randAlphaNum 16 | b64enc }}
{{- end }}

apiVersion: v2
name: my-library
type: library
version: 1.0.0

helm template my-release ./my-chart
helm template my-release ./my-chart -s templates/deployment.yaml --debug
helm lint ./my-chart --strict