On-Premise’den Cloud’a: Kubernetes ve Container Orchestration ile Hibrit Sanallaştırma Rehberi

Adım 2: Container Runtime Kurulumu (containerd)

# containerd kurulumu
sudo apt install -y apt-transport-https ca-certificates curl software-properties-common

# Docker repository ekleme
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
echo "deb  https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

# containerd yükleme
sudo apt update
sudo apt install -y containerd.io

# containerd konfigürasyonu
sudo mkdir -p /etc/containerd
sudo containerd config default | sudo tee /etc/containerd/config.toml

# SystemdCgroup = true yapma (önemli!)
sudo sed -i 's/SystemdCgroup = false/SystemdCgroup = true/g' /etc/containerd/config.toml

sudo systemctl restart containerd
sudo systemctl enable containerd

Adım 3: Kubernetes Bileşenlerini Yükleme

# Kubernetes repository ekleme
sudo apt-get install -y apt-transport-https ca-certificates curl
sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-archive-keyring.gpg
echo "deb  https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee /etc/apt/sources.list.d/kubernetes.list

# kubeadm, kubelet, kubectl yükleme
sudo apt-get update
sudo apt-get install -y kubelet=1.28.2-00 kubeadm=1.28.2-00 kubectl=1.28.2-00
sudo apt-mark hold kubelet kubeadm kubectl

Adım 4: Master Node Başlatma

# Master node'da çalıştırılacak
sudo kubeadm init --pod-network-cidr=10.244.0.0/16 \
  --control-plane-endpoint=master.k8s.local \
  --apiserver-advertise-address=192.168.1.100

# Kubectl konfigürasyonu
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

# Network plugin kurulumu (Flannel)
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

Adım 5: Worker Node'ları Ekleme

# Master node'dan token alma
kubeadm token create --print-join-command

# Worker node'larda çalıştırılacak (master'dan alınan komut)
sudo kubeadm join master.k8s.local:6443 --token abcdef.0123456789abcdef \
    --discovery-token-ca-cert-hash sha256:1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef

Bölüm 3: Production-Ready Konfigürasyonlar

High Availability (HA) Setup

# haproxy.cfg - Load Balancer konfigürasyonu
global
    maxconn 4096
    
defaults
    mode tcp
    timeout connect 5000ms
    timeout client 50000ms
    timeout server 50000ms
    
frontend kubernetes-api
    bind *:6443
    default_backend kubernetes-masters

backend kubernetes-masters
    balance roundrobin
    server master1 192.168.1.100:6443 check
    server master2 192.168.1.101:6443 check
    server master3 192.168.1.102:6443 check

Storage Configuration: Persistent Volumes

# local-storage-class.yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: local-storage
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer

---
# nfs-persistent-volume.yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv-data
spec:
  capacity:
    storage: 100Gi
  accessModes:
    - ReadWriteMany
  nfs:
    server: 192.168.1.50
    path: "/mnt/k8s-data"
  storageClassName: nfs-storage

Monitoring Stack: Prometheus + Grafana

# Helm ile Prometheus Stack kurulumu
helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm repo update

# values.yaml dosyası oluşturma
cat < prometheus-values.yaml
prometheus:
  prometheusSpec:
    retention: 30d
    storageSpec:
      volumeClaimTemplate:
        spec:
          accessModes: ["ReadWriteOnce"]
          resources:
            requests:
              storage: 50Gi
              
grafana:
  adminPassword: "SecurePassword123!"
  persistence:
    enabled: true
    size: 10Gi
    
alertmanager:
  config:
    global:
      smtp_smarthost: 'smtp.gmail.com:587'
      smtp_from: 'alerts@company.com'
    receivers:
    - name: 'email-notifications'
      email_configs:
      - to: 'devops-team@company.com'
EOF

# Kurulum
helm install monitoring prometheus-community/kube-prometheus-stack \
  --namespace monitoring --create-namespace \
  -f prometheus-values.yaml

Bölüm 4: Uygulama Deployment Best Practices

Multi-Stage Dockerfile Örneği

# Multi-stage build for Java application
FROM maven:3.8-openjdk-17 AS builder
WORKDIR /app
COPY pom.xml .
RUN mvn dependency:go-offline
COPY src ./src
RUN mvn clean package -DskipTests

FROM openjdk:17-jdk-alpine
RUN addgroup -g 1001 -S appuser && adduser -u 1001 -S appuser -G appuser
WORKDIR /app
COPY --from=builder /app/target/*.jar app.jar
USER appuser
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "app.jar"]

Kubernetes Deployment Manifest

# application-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: java-app
  labels:
    app: java-app
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
  selector:
    matchLabels:
      app: java-app
  template:
    metadata:
      labels:
        app: java-app
    spec:
      containers:
      - name: app
        image: registry.company.com/java-app:v1.2.3
        ports:
        - containerPort: 8080
        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"
          limits:
            memory: "512Mi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /ready
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 5
        env:
        - name: SPRING_PROFILES_ACTIVE
          value: "production"
        - name: DB_PASSWORD
          valueFrom:
            secretKeyRef:
              name: db-secret
              key: password

Horizontal Pod Autoscaler (HPA)

# hpa.yaml
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: java-app-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: java-app
  minReplicas: 3
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 70
  - type: Resource
    resource:
      name: memory
      target:
        type: Utilization
        averageUtilization: 80

Bölüm 5: Network Policies ve Güvenlik

Calico Network Policy Örneği

# network-policy.yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: backend-netpol
spec:
  podSelector:
    matchLabels:
      tier: backend
  policyTypes:
  - Ingress
  - Egress
  ingress:
  - from:
    - podSelector:
        matchLabels:
          tier: frontend
    ports:
    - protocol: TCP
      port: 8080
  egress:
  - to:
    - podSelector:
        matchLabels:
          tier: database
    ports:
    - protocol: TCP
      port: 5432

Pod Security Standards

# pod-security-policy.yaml
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: restricted
spec:
  privileged: false
  allowPrivilegeEscalation: false
  requiredDropCapabilities:
    - ALL
  volumes:
    - 'configMap'
    - 'emptyDir'
    - 'projected'
    - 'secret'
    - 'downwardAPI'
    - 'persistentVolumeClaim'
  runAsUser:
    rule: 'MustRunAsNonRoot'
  seLinux:
    rule: 'RunAsAny'
  fsGroup:
    rule: 'RunAsAny'

Bölüm 6: CI/CD Pipeline Entegrasyonu

GitLab CI/CD Pipeline

# .gitlab-ci.yml
stages:
  - build
  - test
  - deploy

variables:
  DOCKER_REGISTRY: registry.company.com
  APP_NAME: java-app
  NAMESPACE: production

build:
  stage: build
  script:
    - docker build -t $DOCKER_REGISTRY/$APP_NAME:$CI_COMMIT_SHA .
    - docker push $DOCKER_REGISTRY/$APP_NAME:$CI_COMMIT_SHA
    - docker tag $DOCKER_REGISTRY/$APP_NAME:$CI_COMMIT_SHA $DOCKER_REGISTRY/$APP_NAME:latest
    - docker push $DOCKER_REGISTRY/$APP_NAME:latest

test:
  stage: test
  script:
    - docker run --rm $DOCKER_REGISTRY/$APP_NAME:$CI_COMMIT_SHA ./mvnw test

deploy:
  stage: deploy
  script:
    - kubectl set image deployment/$APP_NAME $APP_NAME=$DOCKER_REGISTRY/$APP_NAME:$CI_COMMIT_SHA -n $NAMESPACE
    - kubectl rollout status deployment/$APP_NAME -n $NAMESPACE
  only:
    - main

Bölüm 7: Troubleshooting ve Debugging

Yaygın Sorunlar ve Çözümleri

# Pod'ların neden başlamadığını kontrol etme
kubectl describe pod 
kubectl logs  --previous

# Node kaynak kullanımı
kubectl top nodes
kubectl top pods --all-namespaces

# Network connectivity testi
kubectl run tmp-shell --rm -i --tty --image nicolaka/netshoot -- /bin/bash

# DNS troubleshooting
kubectl exec -it  -- nslookup kubernetes.default

# etcd backup
ETCDCTL_API=3 etcdctl snapshot save backup.db \
  --endpoints=https://127.0.0.1:2379 \
  --cacert=/etc/etcd/ca.crt \
  --cert=/etc/etcd/server.crt \
  --key=/etc/etcd/server.key

Bölüm 8: Maliyet Optimizasyonu

Resource Quotas ve Limit Ranges

# resource-quota.yaml
apiVersion: v1
kind: ResourceQuota
metadata:
  name: compute-quota
  namespace: production
spec:
  hard:
    requests.cpu: "100"
    requests.memory: 200Gi
    limits.cpu: "200"
    limits.memory: 400Gi
    persistentvolumeclaims: "10"
    services.loadbalancers: "2"

Spot Instance Kullanımı (Cloud Providers)

# spot-instance-nodepool.yaml
apiVersion: v1
kind: Node
metadata:
  labels:
    node.kubernetes.io/instance-type: spot
    kubernetes.io/arch: amd64
spec:
  taints:
  - key: "spot-instance"
    value: "true"
    effect: "NoSchedule"

Performans Karşılaştırması: Geleneksel VM vs Kubernetes

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Sonuç ve Öneriler

Kubernetes'e geçiş, ilk bakışta karmaşık görünse de, doğru planlama ve aşamalı geçiş ile 6 ay içinde ROI sağlayabilir. Türkiye'deki kurumlar için öneriler:

1. Pilot Proje: Kritik olmayan bir uygulama ile başlayın

2. Eğitim: DevOps ekibine Kubernetes sertifikasyonu (CKA/CKAD)

3. Hybrid Yaklaşım: VM ve Container'ları birlikte kullanın

4. Managed Services: İlk aşamada EKS, GKE veya AKS düşünün

5. Local Expertise: Yerel Kubernetes danışmanları ile çalışın

Kaynaklar

Anahtar Kelimeler: Kubernetes, container, Docker, sanallaştırma, orchestration, microservices, cloud native, DevOps, CI/CD, container security, Helm, Prometheus, Grafana, pod, deployment, service mesh, Istio, hybrid cloud, multi-cloud, Türkiye bulut teknolojileri, dijital dönüşüm