kubernetes-patterns

What this skill does

# Kubernetes Patterns

Best practices for Kubernetes deployments and cluster management.

## Deployment Patterns

### Production-Ready Deployment

```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app
  labels:
    app: myapp
    version: v1
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
  template:
    metadata:
      labels:
        app: myapp
        version: v1
    spec:
      serviceAccountName: myapp-sa
      securityContext:
        runAsNonRoot: true
        runAsUser: 1000
        fsGroup: 1000
      containers:
        - name: app
          image: myapp:1.0.0
          imagePullPolicy: Always
          ports:
            - containerPort: 8080
              protocol: TCP
          resources:
            requests:
              cpu: 100m
              memory: 128Mi
            limits:
              cpu: 500m
              memory: 512Mi
          livenessProbe:
            httpGet:
              path: /health/live
              port: 8080
            initialDelaySeconds: 15
            periodSeconds: 10
            failureThreshold: 3
          readinessProbe:
            httpGet:
              path: /health/ready
              port: 8080
            initialDelaySeconds: 5
            periodSeconds: 5
            failureThreshold: 3
          securityContext:
            allowPrivilegeEscalation: false
            readOnlyRootFilesystem: true
            capabilities:
              drop:
                - ALL
          env:
            - name: POD_NAME
              valueFrom:
                fieldRef:
                  fieldPath: metadata.name
          volumeMounts:
            - name: tmp
              mountPath: /tmp
            - name: config
              mountPath: /etc/config
              readOnly: true
      volumes:
        - name: tmp
          emptyDir: {}
        - name: config
          configMap:
            name: myapp-config
      affinity:
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
            - weight: 100
              podAffinityTerm:
                labelSelector:
                  matchLabels:
                    app: myapp
                topologyKey: kubernetes.io/hostname
      topologySpreadConstraints:
        - maxSkew: 1
          topologyKey: topology.kubernetes.io/zone
          whenUnsatisfiable: ScheduleAnyway
          labelSelector:
            matchLabels:
              app: myapp
```

### Service Configuration

```yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp
  labels:
    app: myapp
spec:
  type: ClusterIP
  ports:
    - port: 80
      targetPort: 8080
      protocol: TCP
      name: http
  selector:
    app: myapp
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp
  annotations:
    kubernetes.io/ingress.class: nginx
    cert-manager.io/cluster-issuer: letsencrypt-prod
    nginx.ingress.kubernetes.io/rate-limit: "100"
spec:
  tls:
    - hosts:
        - myapp.example.com
      secretName: myapp-tls
  rules:
    - host: myapp.example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: myapp
                port:
                  number: 80
```

## Helm Chart Structure

```
mychart/
├── Chart.yaml
├── values.yaml
├── values-dev.yaml
├── values-prod.yaml
├── templates/
│   ├── _helpers.tpl
│   ├── deployment.yaml
│   ├── service.yaml
│   ├── ingress.yaml
│   ├── configmap.yaml
│   ├── secret.yaml
│   ├── serviceaccount.yaml
│   ├── hpa.yaml
│   └── pdb.yaml
└── charts/
```

### values.yaml Best Practices

```yaml
# values.yaml
replicaCount: 3

image:
  repository: myapp
  tag: ""  # Set by CI/CD
  pullPolicy: IfNotPresent

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

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

podDisruptionBudget:
  enabled: true
  minAvailable: 2

serviceAccount:
  create: true
  annotations: {}

ingress:
  enabled: true
  className: nginx
  annotations: {}
  hosts:
    - host: chart-example.local
      paths:
        - path: /
          pathType: Prefix
```

## Resource Management

### Horizontal Pod Autoscaler

```yaml
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: myapp
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: myapp
  minReplicas: 3
  maxReplicas: 20
  metrics:
    - type: Resource
      resource:
        name: cpu
        target:
          type: Utilization
          averageUtilization: 70
    - type: Resource
      resource:
        name: memory
        target:
          type: Utilization
          averageUtilization: 80
  behavior:
    scaleDown:
      stabilizationWindowSeconds: 300
      policies:
        - type: Percent
          value: 10
          periodSeconds: 60
    scaleUp:
      stabilizationWindowSeconds: 0
      policies:
        - type: Percent
          value: 100
          periodSeconds: 15
```

### Pod Disruption Budget

```yaml
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: myapp
spec:
  minAvailable: 2  # or use maxUnavailable: 1
  selector:
    matchLabels:
      app: myapp
```

## Security Patterns

### Network Policy

```yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: myapp-network-policy
spec:
  podSelector:
    matchLabels:
      app: myapp
  policyTypes:
    - Ingress
    - Egress
  ingress:
    - from:
        - namespaceSelector:
            matchLabels:
              name: ingress-nginx
        - podSelector:
            matchLabels:
              app: frontend
      ports:
        - protocol: TCP
          port: 8080
  egress:
    - to:
        - podSelector:
            matchLabels:
              app: database
      ports:
        - protocol: TCP
          port: 5432
    - to:  # Allow DNS
        - namespaceSelector: {}
          podSelector:
            matchLabels:
              k8s-app: kube-dns
      ports:
        - protocol: UDP
          port: 53
```

### RBAC Configuration

```yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  name: myapp-sa
---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: myapp-role
rules:
  - apiGroups: [""]
    resources: ["configmaps"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["secrets"]
    resourceNames: ["myapp-secrets"]
    verbs: ["get"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: myapp-rolebinding
subjects:
  - kind: ServiceAccount
    name: myapp-sa
roleRef:
  kind: Role
  name: myapp-role
  apiGroup: rbac.authorization.k8s.io
```

## Troubleshooting Commands

```bash
# Check pod status and events
kubectl get pods -l app=myapp -o wide
kubectl describe pod <pod-name>
kubectl logs <pod-name> --previous

# Debug networking
kubectl run debug --rm -it --image=nicolaka/netshoot -- /bin/bash
kubectl exec -it <pod> -- curl localhost:8080/health

# Check resource usage
kubectl top pods -l app=myapp
kubectl top nodes

# View HPA status
kubectl get hpa myapp -o yaml

# Check events
kubectl get events --sort-by='.lastTimestamp' | tail -20
```

## References

- [Kubernetes Documentation](https://kubernetes.io/docs/)
- [Helm Best Practices](https://helm.sh/docs/chart_best_practices/)
- [Kubernetes Security Best Practices](https://kubernetes.io/docs/concepts/security/)