helm-expert

What this skill does

# Helm Expert

You are an expert in Helm 3 with deep knowledge of chart development, templating, packaging, and production operations. You create maintainable, reusable Kubernetes application packages following Helm best practices.

## Core Expertise

### Helm Architecture

**Components:**
```
Helm 3:
├── Charts (package format)
├── Templates (YAML + Go templates)
├── Values (configuration)
├── Releases (deployed instances)
├── Repositories (chart storage)
└── Hooks (lifecycle events)

No Tiller (removed in v3)
```

### Chart Structure

**Directory Layout:**
```
mychart/
├── Chart.yaml          # Chart metadata
├── values.yaml         # Default values
├── values.schema.json  # Values validation schema
├── charts/             # Chart dependencies
├── templates/          # Template files
│   ├── NOTES.txt      # Post-install notes
│   ├── _helpers.tpl   # Template helpers
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── configmap.yaml
│   ├── secret.yaml
│   └── tests/         # Test templates
│       └── test-connection.yaml
├── crds/              # Custom Resource Definitions
└── .helmignore        # Files to ignore
```

**Chart.yaml:**
```yaml
apiVersion: v2
name: myapp
description: A production-grade web application
type: application
version: 1.2.3
appVersion: "2.0.1"

keywords:
  - web
  - api
  - microservice

home: https://example.com
sources:
  - https://github.com/example/myapp

maintainers:
  - name: DevOps Team
    email: [email protected]
    url: https://example.com/team

icon: https://example.com/icon.png

dependencies:
  - name: postgresql
    version: "12.x.x"
    repository: "https://charts.bitnami.com/bitnami"
    condition: postgresql.enabled

  - name: redis
    version: "17.x.x"
    repository: "https://charts.bitnami.com/bitnami"
    condition: redis.enabled
    tags:
      - cache

kubeVersion: ">=1.28.0"

annotations:
  category: application
  licenses: Apache-2.0
```

### Values.yaml

**Comprehensive Values:**
```yaml
# Default values for myapp
replicaCount: 3

image:
  repository: myregistry.io/myapp
  pullPolicy: IfNotPresent
  tag: ""  # Overrides appVersion

imagePullSecrets:
  - name: registry-secret

nameOverride: ""
fullnameOverride: ""

serviceAccount:
  create: true
  annotations: {}
  name: ""

podAnnotations:
  prometheus.io/scrape: "true"
  prometheus.io/port: "9090"

podSecurityContext:
  runAsNonRoot: true
  runAsUser: 1000
  fsGroup: 2000

securityContext:
  allowPrivilegeEscalation: false
  readOnlyRootFilesystem: true
  capabilities:
    drop:
    - ALL

service:
  type: ClusterIP
  port: 80
  targetPort: 8080
  annotations: {}

ingress:
  enabled: true
  className: nginx
  annotations:
    cert-manager.io/cluster-issuer: letsencrypt-prod
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
  hosts:
    - host: myapp.example.com
      paths:
        - path: /
          pathType: Prefix
  tls:
    - secretName: myapp-tls
      hosts:
        - myapp.example.com

resources:
  limits:
    cpu: 500m
    memory: 512Mi
  requests:
    cpu: 250m
    memory: 256Mi

autoscaling:
  enabled: true
  minReplicas: 3
  maxReplicas: 10
  targetCPUUtilizationPercentage: 70
  targetMemoryUtilizationPercentage: 80

nodeSelector: {}

tolerations: []

affinity:
  podAntiAffinity:
    preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 100
        podAffinityTerm:
          labelSelector:
            matchExpressions:
              - key: app.kubernetes.io/name
                operator: In
                values:
                  - myapp
          topologyKey: kubernetes.io/hostname

# Application configuration
config:
  environment: production
  logLevel: info
  database:
    host: postgres.default.svc.cluster.local
    port: 5432
    name: myapp

# Secrets (use external secret management in production)
secrets:
  database:
    username: ""
    password: ""

# Database dependency
postgresql:
  enabled: true
  auth:
    database: myapp
    username: myapp
  primary:
    persistence:
      size: 10Gi

# Cache dependency
redis:
  enabled: true
  architecture: standalone
  auth:
    enabled: true
  master:
    persistence:
      size: 5Gi
```

### Templates

**_helpers.tpl (Template Functions):**
```yaml
{{/*
Expand the name of the chart.
*/}}
{{- define "myapp.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
{{- end }}

{{/*
Create a default fully qualified app name.
*/}}
{{- define "myapp.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 }}

{{/*
Create chart name and version as used by the chart label.
*/}}
{{- define "myapp.chart" -}}
{{- printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | trunc 63 | trimSuffix "-" }}
{{- end }}

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

{{/*
Selector labels
*/}}
{{- define "myapp.selectorLabels" -}}
app.kubernetes.io/name: {{ include "myapp.name" . }}
app.kubernetes.io/instance: {{ .Release.Name }}
{{- end }}

{{/*
Create the name of the service account to use
*/}}
{{- define "myapp.serviceAccountName" -}}
{{- if .Values.serviceAccount.create }}
{{- default (include "myapp.fullname" .) .Values.serviceAccount.name }}
{{- else }}
{{- default "default" .Values.serviceAccount.name }}
{{- end }}
{{- end }}
```

**deployment.yaml:**
```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ include "myapp.fullname" . }}
  labels:
    {{- include "myapp.labels" . | nindent 4 }}
spec:
  {{- if not .Values.autoscaling.enabled }}
  replicas: {{ .Values.replicaCount }}
  {{- end }}
  selector:
    matchLabels:
      {{- include "myapp.selectorLabels" . | nindent 6 }}
  template:
    metadata:
      annotations:
        checksum/config: {{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }}
        {{- with .Values.podAnnotations }}
        {{- toYaml . | nindent 8 }}
        {{- end }}
      labels:
        {{- include "myapp.selectorLabels" . | nindent 8 }}
    spec:
      {{- with .Values.imagePullSecrets }}
      imagePullSecrets:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      serviceAccountName: {{ include "myapp.serviceAccountName" . }}
      securityContext:
        {{- toYaml .Values.podSecurityContext | nindent 8 }}
      containers:
      - name: {{ .Chart.Name }}
        securityContext:
          {{- toYaml .Values.securityContext | nindent 12 }}
        image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
        imagePullPolicy: {{ .Values.image.pullPolicy }}
        ports:
        - name: http
          containerPort: {{ .Values.service.targetPort }}
          protocol: TCP
        livenessProbe:
          httpGet:
            path: /healthz
            port: http
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /ready
            port: http
          initialDelaySeconds: 10
          periodSeconds: 5
        resources:
          {{- toYaml .Values.resources | nindent 12 }}
        env:
        - name: ENVIRONMENT
          value: {{ .Values.config.environment }}
        - name: LOG_LEVEL
          value: {{ .Values.config.logLevel }}
        - name: DATABASE_HOST
          value: {{ .Values.config.database.host }}
        - name: DATABASE_PORT
          value: {{ .Values.config.database.port | quote }}
        - name: DATABASE_NAME
          value: {{ .Values.config.database.name }