Kubernetes Temelleri

Giriş

Kubernetes, konteynerleri organize etmek, ölçeklendirmek ve yönetmek için kullanılan açık kaynaklı bir container orkestrasyon platformudur. Google tarafından geliştirilen Kubernetes, modern uygulama dağıtımının temel taşlarından biridir.

Kubernetes Mimarisi

Ana Bileşenler

# cluster-architecture.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: cluster-info
  namespace: kube-system
data:
  cluster-config: |
    Master Components:
    - API Server (kube-apiserver)
    - etcd (Cluster store)
    - Scheduler (kube-scheduler)
    - Controller Manager (kube-controller-manager)
    
    Node Components:
    - kubelet (Node agent)
    - kube-proxy (Network proxy)
    - Container Runtime (Docker/containerd/CRI-O)

Master Düğümü Bileşenleri

# Master düğümü durumunu kontrol et
kubectl get componentstatuses

# API Server durumu
kubectl cluster-info

# etcd cluster health
kubectl get --raw='/healthz/etcd'

Pod Yönetimi

Temel Pod Tanımı

# spring-boot-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: spring-boot-app
  labels:
    app: spring-boot-app
    version: "1.0"
    environment: production
spec:
  containers:
  - name: app-container
    image: spring-boot-app:1.0.0
    ports:
    - containerPort: 8080
      name: http
      protocol: TCP
    - containerPort: 8081
      name: management
      protocol: TCP
    env:
    - name: SPRING_PROFILES_ACTIVE
      value: "production"
    - name: SERVER_PORT
      value: "8080"
    - name: MANAGEMENT_SERVER_PORT
      value: "8081"
    resources:
      requests:
        memory: "512Mi"
        cpu: "250m"
      limits:
        memory: "1Gi"
        cpu: "500m"
    livenessProbe:
      httpGet:
        path: /actuator/health/liveness
        port: 8081
      initialDelaySeconds: 60
      periodSeconds: 30
      timeoutSeconds: 5
      failureThreshold: 3
    readinessProbe:
      httpGet:
        path: /actuator/health/readiness
        port: 8081
      initialDelaySeconds: 30
      periodSeconds: 10
      timeoutSeconds: 3
      failureThreshold: 3
  restartPolicy: Always
  terminationGracePeriodSeconds: 30

Deployment Yönetimi

Temel Deployment

# spring-boot-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: spring-boot-deployment
  labels:
    app: spring-boot-app
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1
      maxSurge: 1
  selector:
    matchLabels:
      app: spring-boot-app
  template:
    metadata:
      labels:
        app: spring-boot-app
        version: "1.0"
    spec:
      containers:
      - name: spring-boot-app
        image: spring-boot-app:1.0.0
        ports:
        - containerPort: 8080
        env:
        - name: SPRING_PROFILES_ACTIVE
          value: "kubernetes"
        - name: DATABASE_URL
          valueFrom:
            secretKeyRef:
              name: db-secret
              key: url
        resources:
          requests:
            memory: "512Mi"
            cpu: "250m"
          limits:
            memory: "1Gi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /actuator/health/liveness
            port: 8080
          initialDelaySeconds: 60
          periodSeconds: 30
        readinessProbe:
          httpGet:
            path: /actuator/health/readiness
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10

Service Türleri

ClusterIP Service

# clusterip-service.yaml
apiVersion: v1
kind: Service
metadata:
  name: spring-boot-service
  labels:
    app: spring-boot-app
spec:
  type: ClusterIP
  selector:
    app: spring-boot-app
  ports:
  - name: http
    port: 80
    targetPort: 8080
    protocol: TCP
  - name: management
    port: 8081
    targetPort: 8081
    protocol: TCP
  sessionAffinity: None

LoadBalancer Service

# loadbalancer-service.yaml
apiVersion: v1
kind: Service
metadata:
  name: spring-boot-loadbalancer
  labels:
    app: spring-boot-app
  annotations:
    service.beta.kubernetes.io/aws-load-balancer-type: "nlb"
spec:
  type: LoadBalancer
  selector:
    app: spring-boot-app
  ports:
  - name: http
    port: 80
    targetPort: 8080
    protocol: TCP

Ingress Yönetimi

Temel Ingress

# spring-boot-ingress.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: spring-boot-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
    cert-manager.io/cluster-issuer: "letsencrypt-prod"
spec:
  ingressClassName: nginx
  tls:
  - hosts:
    - api.example.com
    secretName: api-tls-secret
  rules:
  - host: api.example.com
    http:
      paths:
      - path: /api
        pathType: Prefix
        backend:
          service:
            name: spring-boot-service
            port:
              number: 80

ConfigMap ve Secret Yönetimi

ConfigMap Kullanımı

# application-configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: spring-boot-config
  labels:
    app: spring-boot-app
data:
  application.properties: |
    server.port=8080
    management.server.port=8081
    management.endpoints.web.exposure.include=health,info,metrics,prometheus
    spring.datasource.hikari.maximum-pool-size=20
    logging.level.com.example=INFO

Secret Yönetimi

# database-secret.yaml
apiVersion: v1
kind: Secret
metadata:
  name: db-secret
  labels:
    app: spring-boot-app
type: Opaque
data:
  url: amRiYzpwb3N0Z3Jlc3FsOi8vcG9zdGdyZXNxbC1zZXJ2aWNlOjU0MzIvc3ByaW5nYm9vdGRi
  username: c3ByaW5nYm9vdA==
  password: U3VwZXJTZWNyZXRQYXNzd29yZDEyMyE=

Horizontal Pod Autoscaler (HPA)

# hpa-configuration.yaml
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: spring-boot-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: spring-boot-deployment
  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

RBAC (Role-Based Access Control)

# rbac-configuration.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  name: spring-boot-sa
  namespace: production

---
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: spring-boot-role
  namespace: production
rules:
- apiGroups: [""]
  resources: ["configmaps", "secrets"]
  verbs: ["get", "list", "watch"]
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["get", "list", "watch"]

---
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: spring-boot-role-binding
  namespace: production
subjects:
- kind: ServiceAccount
  name: spring-boot-sa
  namespace: production
roleRef:
  kind: Role
  name: spring-boot-role
  apiGroup: rbac.authorization.k8s.io

kubectl Komutları

Temel Komutlar

# Cluster bilgilerini görüntüle
kubectl cluster-info
kubectl get nodes
kubectl get namespaces

# Pod yönetimi
kubectl get pods
kubectl get pods -o wide
kubectl describe pod <pod-name>
kubectl logs <pod-name>
kubectl exec -it <pod-name> -- /bin/bash

# Deployment yönetimi
kubectl get deployments
kubectl scale deployment <deployment-name> --replicas=5
kubectl rollout status deployment <deployment-name>
kubectl rollout undo deployment <deployment-name>

# Service yönetimi
kubectl get services
kubectl port-forward service/<service-name> 8080:80

# Resource uygulama
kubectl apply -f <file.yaml>
kubectl delete -f <file.yaml>

# Resource monitoring
kubectl top nodes
kubectl top pods

Best Practices

Resource Yönetimi

1. Resource Limits ve Requests

   • Her container için resource requests ve limits tanımlayın
   • QoS sınıflarını doğru kullanın
   • Memory ve CPU kullanımını monitoring edin

2. Health Checks

   • Liveness ve readiness probe'ları tanımlayın
   • Uygun timeout ve threshold değerleri kullanın

3. Security

   • Non-root user kullanın
   • SecurityContext tanımlayın
   • Network policies uygulayın

Deployment Stratejileri

1. Rolling Updates

   • Uygun maxUnavailable ve maxSurge değerleri kullanın
   • Deployment'ları aşamalı olarak test edin

2. Namespace Organizasyonu

   • Environment'lara göre namespace ayırın
   • Resource quota'ları kullanın

3. Monitoring ve Logging

   • Centralized logging sistemi kurun
   • Metrics collection'ı implement edin

Kubernetes, modern uygulama deployment'ının temel taşıdır. Doğru konfigürasyon ve best practice'ler ile yüksek performanslı, güvenilir ve ölçeklenebilir uygulamalar deploy edebilirsiniz.