Kubernetes in Production: Helm Charts, Operators, and Monitoring Strategies

# Chart.yaml - Helm chart metadata
apiVersion: v2
name: my-app
description: Web application
version: 1.0.0
appVersion: "2.1.0"

# values.yaml - Configuration values
replicaCount: 3

image:
  repository: myregistry.azurecr.io/my-app
  tag: "2.1.0"
  pullPolicy: IfNotPresent

service:
  type: ClusterIP
  port: 80

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

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

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

# Install:
# helm install my-app ./my-app-chart
# helm upgrade my-app ./my-app-chart --values values-production.yaml
# helm rollback my-app 1  # Instant rollback to previous version

# Rolling Update (default - zero downtime)
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app
spec:
  replicas: 5
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1        # Extra pod during update
      maxUnavailable: 0  # No downtime
  template:
    spec:
      containers:
      - name: app
        image: app:v2
        readinessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 3
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 15
          periodSeconds: 10

---
# Blue-Green Deployment (instant rollback)
apiVersion: v1
kind: Service
metadata:
  name: app-service
spec:
  selector:
    app: app
    version: green  # Switch between blue/green
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8080

---
# Canary Deployment (gradual rollout)
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: app
spec:
  hosts:
  - app.example.com
  http:
  - match:
    - headers:
        user-agent:
          regex: ".*Mobile.*"
    route:
    - destination:
        host: app
        subset: v2
  - route:
    - destination:
        host: app
        subset: v1
      weight: 90
    - destination:
        host: app
        subset: v2
      weight: 10  # 10% traffic to new version

apiVersion: v1
kind: Pod
metadata:
  name: guaranteed-pod
spec:
  containers:
  - name: app
    resources:
      # Guaranteed QoS: requests == limits
      requests:
        memory: "64Mi"
        cpu: "250m"
      limits:
        memory: "64Mi"
        cpu: "250m"

---
apiVersion: v1
kind: ResourceQuota
metadata:
  name: compute-quota
  namespace: production
spec:
  hard:
    requests.cpu: "100"
    requests.memory: 200Gi
    limits.cpu: "200"
    limits.memory: 400Gi
    pods: "100"

---
apiVersion: v1
kind: LimitRange
metadata:
  name: default-limits
  namespace: production
spec:
  limits:
  - default:
      cpu: "500m"
      memory: "512Mi"
    defaultRequest:
      cpu: "250m"
      memory: "256Mi"
    type: Container

# ServiceMonitor for automatic scraping
apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: app-metrics
spec:
  selector:
    matchLabels:
      app: my-app
  endpoints:
  - port: metrics
    interval: 30s
    path: /metrics

---
# PrometheusRule for alerts
apiVersion: monitoring.coreos.com/v1
kind: PrometheusRule
metadata:
  name: app-alerts
spec:
  groups:
  - name: app
    interval: 30s
    rules:
    - alert: HighErrorRate
      expr: rate(http_requests_total{status=~"5.."}[5m]) > 0.05
      for: 5m
      labels:
        severity: critical
      annotations:
        summary: "High error rate detected"
        description: "Error rate is {{ $value | humanizePercentage }}"
    
    - alert: PodCrashLooping
      expr: rate(kube_pod_container_status_restarts_total[15m]) > 0
      labels:
        severity: warning
      annotations:
        summary: "Pod {{ $labels.pod }} is crash looping"
    
    - alert: HighMemoryUsage
      expr: container_memory_usage_bytes / container_spec_memory_limit_bytes > 0.9
      for: 5m
      labels:
        severity: warning

# 1. Create secret from literal values
kubectl create secret generic app-secrets \
  --from-literal=database-password=mysecretpass \
  --from-literal=api-key=abc123

# 2. Create secret from file
kubectl create secret generic app-config \
  --from-file=config.json

# 3. Use in pod
apiVersion: v1
kind: Pod
metadata:
  name: app
spec:
  containers:
  - name: app
    envFrom:
    - secretRef:
        name: app-secrets
    volumeMounts:
    - name: config
      mountPath: /etc/config
      readOnly: true
  volumes:
  - name: config
    secret:
      secretName: app-config

# 4. External secrets with Sealed Secrets
# Install controller:
kubectl apply -f https://github.com/bitnami-labs/sealed-secrets/releases/download/v0.18.0/controller.yaml

# Seal secret (safe to commit to Git):
kubeseal --format=yaml < secret.yaml > sealed-secret.yaml

# 5. Use AWS Secrets Manager / Azure Key Vault
# Install external-secrets operator
helm install external-secrets external-secrets/external-secrets -n external-secrets-system

# SecretStore
apiVersion: external-secrets.io/v1beta1
kind: SecretStore
metadata:
  name: aws-secrets
spec:
  provider:
    aws:
      service: SecretsManager
      region: us-east-1