Empaquetar Manifests de Kubernetes con Helm Charts

Overview

Helm es el package manager para Kubernetes. Un Helm chart es una colección de manifests de Kubernetes templetados que pueden ser customizados con un archivo values.yaml. En lugar de escribir archivos YAML separados para cada entorno, escribís un chart y overrideás values por entorno. Helm renderiza los templates, los aplica al cluster, y trackea releases para upgrades y rollbacks.

When to Use

• Desplegar la misma app a múltiples entornos (dev, staging, production)
• Compartir deployments de Kubernetes reusables a través de equipos
• Manejar el lifecycle de la aplicación (install, upgrade, rollback)
• Cuando necesitás manifests parametrizados (different replicas, images, resources por env)
• Instalar herramientas de terceros (Prometheus, Grafana, ingress controllers)

When NOT to Use

• Entorno único con manifests estáticos — plain kubectl apply es más simple
• Cuando necesitás GitOps — usá ArgoCD o Flux (pueden consumir Helm charts)
• Cuando los manifests cambian raramente y no necesitan parametrización
• Cuando el templating de Helm es muy limitado — Kustomize puede ser mejor para overlays

Solution

Estructura del chart

my-chart/
├── Chart.yaml          # Metadata del chart
├── values.yaml         # Values default
├── values/
│   ├── staging.yaml    # Overrides por entorno
│   └── production.yaml
├── templates/
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── configmap.yaml
│   ├── ingress.yaml
│   ├── _helpers.tpl    # Named templates
│   └── NOTES.txt       # Post-install notes
└── charts/             # Subchart dependencies

Chart.yaml

apiVersion: v2
name: my-app
description: A Helm chart for my application
type: application
version: 1.0.0          # Versión del chart
appVersion: "2.5.0"     # Versión de la app
keywords:
  - web
  - api
maintainers:
  - name: Mathias Paulenko
    email: mathias@example.com
dependencies:
  - name: postgresql
    version: 12.x.x
    repository: https://charts.bitnami.com/bitnami
    condition: postgresql.enabled

values.yaml

replicaCount: 2

image:
  repository: my-app
  tag: "2.5.0"
  pullPolicy: IfNotPresent

service:
  type: ClusterIP
  port: 8080

resources:
  requests:
    cpu: 100m
    memory: 128Mi
  limits:
    cpu: 500m
    memory: 512Mi

ingress:
  enabled: false
  className: nginx
  hosts:
    - host: my-app.example.com
      paths:
        - path: /
          pathType: Prefix

config:
  LOG_LEVEL: info
  DATABASE_URL: ""

postgresql:
  enabled: false

Template de Deployment

# templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "my-app.fullname" . }}
  labels:
    {{- include "my-app.labels" . | nindent 4 }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      {{- include "my-app.selectorLabels" . | nindent 6 }}
  template:
    metadata:
      labels:
        {{- include "my-app.selectorLabels" . | nindent 8 }}
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          imagePullPolicy: {{ .Values.image.pullPolicy }}
          ports:
            - name: http
              containerPort: {{ .Values.service.port }}
              protocol: TCP
          resources:
            {{- toYaml .Values.resources | nindent 12 }}
          env:
            - name: LOG_LEVEL
              value: {{ .Values.config.LOG_LEVEL | quote }}
            - name: DATABASE_URL
              value: {{ .Values.config.DATABASE_URL | quote }}

Helper templates

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

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

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

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

Conditional blocks

# templates/ingress.yaml
{{- if .Values.ingress.enabled -}}
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: {{ include "my-app.fullname" . }}
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  ingressClassName: {{ .Values.ingress.className }}
  {{- with .Values.ingress.tls }}
  tls:
    {{- toYaml . | nindent 4 }}
  {{- end }}
  rules:
    {{- range .Values.ingress.hosts }}
    - host: {{ .host | quote }}
      http:
        paths:
          {{- range .paths }}
          - path: {{ .path }}
            pathType: {{ .pathType }}
            backend:
              service:
                name: {{ include "my-app.fullname" $ }}
                port:
                  number: {{ $.Values.service.port }}
          {{- end }}
    {{- end }}
{{- end }}

Range sobre values

# templates/configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: {{ include "my-app.fullname" . }}
data:
  {{- range $key, $value := .Values.config }}
  {{ $key }}: {{ $value | quote }}
  {{- end }}

Values específicos por entorno

# values/production.yaml
replicaCount: 5

image:
  tag: "2.5.0-prod"

resources:
  requests:
    cpu: 500m
    memory: 512Mi
  limits:
    cpu: 2000m
    memory: 2Gi

ingress:
  enabled: true
  className: nginx
  hosts:
    - host: my-app.production.com
      paths:
        - path: /
          pathType: Prefix

config:
  LOG_LEVEL: warn
  DATABASE_URL: "postgres://prod-db:5432/myapp"

Helm hooks

# templates/post-install-job.yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: {{ include "my-app.fullname" . }}-post-install
  annotations:
    "helm.sh/hook": post-install,post-upgrade
    "helm.sh/hook-weight": "1"
    "helm.sh/hook-delete-policy": before-hook-creation,hook-succeeded
spec:
  template:
    spec:
      restartPolicy: Never
      containers:
        - name: migrate
          image: "{{ .Values.image.repository }}:{{ .Values.image.tag }}"
          command: ["./migrate", "up"]
          env:
            - name: DATABASE_URL
              value: {{ .Values.config.DATABASE_URL | quote }}

Instalar y upgradear

# Instalar con values default
helm install my-app ./my-chart

# Instalar con values custom
helm install my-app ./my-chart -f values/production.yaml

# Instalar con overrides inline
helm install my-app ./my-chart --set replicaCount=5 --set image.tag=2.5.0

# Upgrade
helm upgrade my-app ./my-chart -f values/production.yaml

# Rollback
helm rollback my-app 1

# Uninstall
helm uninstall my-app

# Template (dry-run, render manifests)
helm template my-app ./my-chart -f values/production.yaml > manifests.yaml

# Lint
helm lint ./my-chart

Variants

Usar subcharts

# Chart.yaml
dependencies:
  - name: redis
    version: 17.x.x
    repository: https://charts.bitnami.com/bitnami
    condition: redis.enabled

# values.yaml — configurar subchart
redis:
  enabled: true
  auth:
    password: "my-redis-password"
  architecture: standalone

Library chart (bloques reusables)

# Chart.yaml
apiVersion: v2
name: common
type: library          # Library chart — no deployable
version: 1.0.0

# templates/_container.tpl
{{- define "common.container" -}}
- name: {{ .name }}
  image: {{ .image }}
  ports:
    - containerPort: {{ .port }}
  resources:
    {{- toYaml .resources | nindent 4 }}
{{- end }}

# En el template de otro chart
{{- include "common.container" (dict "name" "api" "image" "my-api:1.0" "port" 8080 "resources" .Values.resources) | nindent 8 }}

Helm con sealed secrets

# templates/sealedsecret.yaml
{{- if .Values.sealedSecret.enabled }}
apiVersion: bitnami.com/v1alpha1
kind: SealedSecret
metadata:
  name: {{ include "my-app.fullname" . }}
spec:
  encryptedData:
    database-password: {{ .Values.sealedSecret.encryptedPassword | quote }}
  template:
    metadata:
      name: {{ include "my-app.fullname" . }}
    type: Opaque
{{- end }}

Best Practices

• For a deeper guide, see Helm Charts: Structure, Templating, Dependencies, Registry.

• Usá include sobre template — include permite chaining con nindent

• Siempre usá nindent no indent — maneja el leading newline correctamente

• Seteá resource requests y limits — previene resource starvation en el cluster

• Usá {{ .Values.xxx | quote }} para string values — previene YAML parsing issues

• Mantené values.yaml minimal — poné values específicos por entorno en archivos separados

• Usá helm lint antes de deployar — atrapa template errors temprano

• Usá helm template para dry runs — renderiza manifests sin aplicar

• Pinea versiones de subchart — evita cambios inesperados de charts upstream

Common Mistakes

• Olvidar nindent vs indent: indent no agrega leading newline. nindent sí. La mayoría de las veces querés nindent.
• No quotear values: YAML interpreta yes/no/on/off como booleans. Usá quote para forzar strings.
• Hardcodear values en templates: derrota el propósito de Helm. Mové todo a values.yaml.
• No usar helm lint: los template errors solo se muestran al install. Lint los atrapa temprano.
• Sobrescribir todos los values con --set: difícil de debuggear. Usá -f values/production.yaml para overrides complejos.