Application Lifecycle Management

# Rollout 상태 확인
kubectl rollout status deployment/my-app

# Revision 히스토리 조회
kubectl rollout history deployment/my-app

# 특정 Revision 상세 정보
kubectl rollout history deployment/my-app --revision=2

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 3
  strategy:
    type: Recreate
  template:
    spec:
      containers:
      - name: app
        image: nginx:1.20

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1        # 최대 추가 Pod 수 (또는 비율)
      maxUnavailable: 1  # 최대 비가용 Pod 수 (또는 비율)
  template:
    spec:
      containers:
      - name: app
        image: nginx:1.21

# 이미지 업데이트 (권장)
kubectl set image deployment/my-app nginx=nginx:1.21

# YAML 수정 후 적용
kubectl apply -f deployment.yaml

# 직접 편집
kubectl edit deployment my-app

# 바로 이전 버전으로 롤백
kubectl rollout undo deployment/my-app

# 특정 Revision으로 롤백
kubectl rollout undo deployment/my-app --to-revision=2

# Rollout 일시 중지/재개
kubectl rollout pause deployment/my-app
kubectl rollout resume deployment/my-app

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  revisionHistoryLimit: 10  # 보관할 ReplicaSet 수 (기본값 10)

# Shell form
CMD echo "Hello World"

# Exec form (권장)
CMD ["echo", "Hello World"]

# 파라미터만 지정 (ENTRYPOINT와 함께 사용)
CMD ["5"]

# Exec form (권장)
ENTRYPOINT ["sleep"]

# Shell form
ENTRYPOINT sleep

FROM ubuntu
ENTRYPOINT ["sleep"]
CMD ["10"]

# 기본 실행: sleep 10
docker run sleeper

# CMD 덮어쓰기: sleep 20
docker run sleeper 20

# ENTRYPOINT 덮어쓰기: echo hello
docker run --entrypoint echo sleeper hello

apiVersion: v1
kind: Pod
metadata:
  name: sleeper
spec:
  containers:
  - name: sleeper
    image: ubuntu
    command: ["sleep"]    # ENTRYPOINT 대체
    args: ["100"]         # CMD 대체

# 예시 1: args만 지정 (이미지의 ENTRYPOINT 사용)
containers:
- name: app
  image: sleeper
  args: ["200"]

# 예시 2: command만 지정
containers:
- name: app
  image: ubuntu
  command: ["sleep", "300"]

# 예시 3: 복잡한 명령어
containers:
- name: app
  image: busybox
  command: ["/bin/sh", "-c"]
  args:
  - |
    echo "Starting..."
    sleep 100
    echo "Done"

# 예시 4: 환경변수 참조
containers:
- name: app
  image: busybox
  command: ["sleep"]
  args: ["$(SLEEP_DURATION)"]
  env:
  - name: SLEEP_DURATION
    value: "500"

apiVersion: v1
kind: Pod
metadata:
  name: app
spec:
  containers:
  - name: app
    image: my-app
    env:
    - name: APP_ENV
      value: "production"
    - name: DEBUG
      value: "false"
    - name: PORT
      value: "8080"

env:
- name: POD_NAME
  valueFrom:
    fieldRef:
      fieldPath: metadata.name
- name: POD_NAMESPACE
  valueFrom:
    fieldRef:
      fieldPath: metadata.namespace
- name: POD_IP
  valueFrom:
    fieldRef:
      fieldPath: status.podIP
- name: NODE_NAME
  valueFrom:
    fieldRef:
      fieldPath: spec.nodeName
- name: CPU_LIMIT
  valueFrom:
    resourceFieldRef:
      containerName: app
      resource: limits.cpu

env:
- name: DATABASE_URL
  valueFrom:
    configMapKeyRef:
      name: app-config
      key: database_url

env:
- name: DB_PASSWORD
  valueFrom:
    secretKeyRef:
      name: db-secret
      key: password

# 리터럴 값으로 생성
kubectl create configmap app-config \
  --from-literal=DB_HOST=mysql \
  --from-literal=LOG_LEVEL=info

# 파일에서 생성
kubectl create configmap app-config --from-file=config.properties

# 디렉토리에서 생성
kubectl create configmap app-config --from-file=config/

# 특정 키로 파일 내용 저장
kubectl create configmap nginx-config --from-file=nginx.conf=/etc/nginx/nginx.conf

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  # 단순 키-값
  DB_HOST: "mysql"
  LOG_LEVEL: "info"

  # 파일 형태
  application.properties: |
    server.port=8080
    spring.profiles.active=prod

  nginx.conf: |
    server {
        listen 80;
        location / {
            proxy_pass http://backend:8080;
        }
    }

apiVersion: v1
kind: Pod
metadata:
  name: app
spec:
  containers:
  - name: app
    image: my-app
    # 개별 키 참조
    env:
    - name: DATABASE_HOST
      valueFrom:
        configMapKeyRef:
          name: app-config
          key: DB_HOST
    # 모든 키를 환경변수로 주입
    envFrom:
    - configMapRef:
        name: app-config

apiVersion: v1
kind: Pod
metadata:
  name: app
spec:
  containers:
  - name: app
    image: nginx
    volumeMounts:
    - name: config-volume
      mountPath: /etc/nginx/conf.d
      readOnly: true
  volumes:
  - name: config-volume
    configMap:
      name: nginx-config
      # 특정 키만 선택
      items:
      - key: nginx.conf
        path: default.conf

# 직접 편집
kubectl edit configmap app-config

# YAML 적용
kubectl apply -f configmap.yaml

# 리터럴 값으로 생성
kubectl create secret generic db-secret \
  --from-literal=username=admin \
  --from-literal=password=S3cr3t!

# 파일에서 생성
kubectl create secret generic tls-secret \
  --from-file=tls.crt=/path/to/tls.crt \
  --from-file=tls.key=/path/to/tls.key

# TLS Secret 생성
kubectl create secret tls my-tls-secret \
  --cert=/path/to/tls.crt \
  --key=/path/to/tls.key

# Docker Registry Secret
kubectl create secret docker-registry regcred \
  --docker-server=https://index.docker.io/v1/ \
  --docker-username=user \
  --docker-password=pass \
  --docker-email=user@example.com

apiVersion: v1
kind: Secret
metadata:
  name: db-secret
type: Opaque
data:
  # Base64 인코딩된 값
  username: YWRtaW4=      # admin
  password: UzNjcjN0IQ==  # S3cr3t!
---
# stringData는 평문으로 작성 (저장 시 자동 인코딩)
apiVersion: v1
kind: Secret
metadata:
  name: app-secret
type: Opaque
stringData:
  api-key: "my-api-key-12345"
  config.yaml: |
    database:
      password: secret123

# 인코딩
echo -n "admin" | base64
# YWRtaW4=

# 디코딩
echo "YWRtaW4=" | base64 -d
# admin

apiVersion: v1
kind: Pod
metadata:
  name: app
spec:
  containers:
  - name: app
    image: my-app
    env:
    - name: DB_USERNAME
      valueFrom:
        secretKeyRef:
          name: db-secret
          key: username
    - name: DB_PASSWORD
      valueFrom:
        secretKeyRef:
          name: db-secret
          key: password
    # 모든 Secret 키를 환경변수로
    envFrom:
    - secretRef:
        name: db-secret

apiVersion: v1
kind: Pod
metadata:
  name: app
spec:
  containers:
  - name: app
    image: my-app
    volumeMounts:
    - name: secret-volume
      mountPath: /etc/secrets
      readOnly: true
  volumes:
  - name: secret-volume
    secret:
      secretName: db-secret
      defaultMode: 0400  # 파일 권한

apiVersion: v1
kind: Pod
metadata:
  name: app-with-logging
spec:
  containers:
  # 메인 애플리케이션
  - name: app
    image: my-app
    volumeMounts:
    - name: logs
      mountPath: /var/log/app

  # 로그 수집 Sidecar
  - name: log-shipper
    image: fluentd
    volumeMounts:
    - name: logs
      mountPath: /var/log/app
      readOnly: true

  volumes:
  - name: logs
    emptyDir: {}

apiVersion: v1
kind: Pod
metadata:
  name: app-with-adapter
spec:
  containers:
  - name: app
    image: legacy-app
    volumeMounts:
    - name: logs
      mountPath: /var/log/app

  # 로그 형식 변환 Adapter
  - name: log-adapter
    image: log-transformer
    volumeMounts:
    - name: logs
      mountPath: /var/log/app
    - name: transformed-logs
      mountPath: /var/log/transformed

  volumes:
  - name: logs
    emptyDir: {}
  - name: transformed-logs
    emptyDir: {}

apiVersion: v1
kind: Pod
metadata:
  name: app-with-ambassador
spec:
  containers:
  - name: app
    image: my-app
    env:
    - name: DATABASE_HOST
      value: "localhost"  # Ambassador로 연결
    - name: DATABASE_PORT
      value: "5432"

  # DB 연결 Ambassador
  - name: db-ambassador
    image: haproxy
    ports:
    - containerPort: 5432

# localhost로 통신 (같은 네트워크 네임스페이스)
containers:
- name: web
  image: nginx
  ports:
  - containerPort: 80
- name: metrics
  image: metrics-collector
  env:
  - name: TARGET_URL
    value: "http://localhost:80/metrics"

apiVersion: v1
kind: Pod
metadata:
  name: app
spec:
  initContainers:
  # 1. 의존 서비스 대기
  - name: wait-for-db
    image: busybox
    command: ['sh', '-c',
      'until nc -z mysql 3306; do echo waiting for mysql; sleep 2; done']

  # 2. 설정 파일 다운로드
  - name: download-config
    image: busybox
    command: ['wget', '-O', '/config/app.conf', 'http://config-server/app.conf']
    volumeMounts:
    - name: config
      mountPath: /config

  # 3. 데이터베이스 마이그레이션
  - name: db-migrate
    image: my-app:migrate
    command: ['./migrate', '--database', '$(DATABASE_URL)']
    env:
    - name: DATABASE_URL
      valueFrom:
        secretKeyRef:
          name: db-secret
          key: url

  containers:
  - name: app
    image: my-app
    volumeMounts:
    - name: config
      mountPath: /etc/app

  volumes:
  - name: config
    emptyDir: {}

# Pod 상태에서 Init Container 확인
kubectl get pod app

# 상세 정보
kubectl describe pod app

# Init Container 로그 확인
kubectl logs app -c wait-for-db

# 수평: 레플리카 수 조정
kubectl scale deployment my-app --replicas=5

# 수직: 리소스 제한 변경
kubectl edit deployment my-app
# resources.requests/limits 수정

# CPU 기반 HPA 생성
kubectl autoscale deployment my-app \
  --cpu-percent=50 \
  --min=2 \
  --max=10

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: my-app-hpa
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: my-app
  minReplicas: 2
  maxReplicas: 10
  metrics:
  # CPU 기반
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 50
  # 메모리 기반
  - type: Resource
    resource:
      name: memory
      target:
        type: Utilization
        averageUtilization: 70

metrics:
# 1. Resource (CPU/Memory)
- type: Resource
  resource:
    name: cpu
    target:
      type: Utilization
      averageUtilization: 50

# 2. Pods (커스텀 메트릭)
- type: Pods
  pods:
    metric:
      name: packets-per-second
    target:
      type: AverageValue
      averageValue: 1k

# 3. Object (다른 K8s 오브젝트의 메트릭)
- type: Object
  object:
    metric:
      name: requests-per-second
    describedObject:
      apiVersion: networking.k8s.io/v1
      kind: Ingress
      name: main-route
    target:
      type: Value
      value: 10k

# 4. External (외부 메트릭 - Datadog, Prometheus 등)
- type: External
  external:
    metric:
      name: queue_messages_ready
      selector:
        matchLabels:
          queue: worker-tasks
    target:
      type: AverageValue
      averageValue: 30

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: my-app-hpa
spec:
  behavior:
    # 스케일 업 동작
    scaleUp:
      stabilizationWindowSeconds: 0  # 즉시 스케일 업
      policies:
      - type: Percent
        value: 100           # 최대 100% 증가
        periodSeconds: 15
      - type: Pods
        value: 4             # 또는 최대 4개 추가
        periodSeconds: 15
      selectPolicy: Max      # 더 많이 스케일하는 정책 선택

    # 스케일 다운 동작
    scaleDown:
      stabilizationWindowSeconds: 300  # 5분 안정화 기간
      policies:
      - type: Percent
        value: 10            # 최대 10% 감소
        periodSeconds: 60

# HPA 목록
kubectl get hpa

# 상세 정보
kubectl describe hpa my-app-hpa

# 출력 예시
NAME         REFERENCE           TARGETS   MINPODS   MAXPODS   REPLICAS   AGE
my-app-hpa   Deployment/my-app   45%/50%   2         10        4          1h

containers:
- name: app
  image: my-app
  resources:
    requests:
      cpu: "100m"      # HPA가 이 값 기준으로 사용률 계산
      memory: "128Mi"

# kube-apiserver, kube-scheduler, kubelet에 feature gate 설정
--feature-gates=InPlacePodVerticalScaling=true

apiVersion: v1
kind: Pod
metadata:
  name: app
spec:
  containers:
  - name: app
    image: nginx
    resources:
      requests:
        cpu: "100m"
        memory: "128Mi"
      limits:
        cpu: "200m"
        memory: "256Mi"
    # 리소스별 재시작 정책
    resizePolicy:
    - resourceName: cpu
      restartPolicy: NotRequired  # CPU 변경 시 재시작 불필요
    - resourceName: memory
      restartPolicy: RestartContainer  # 메모리 변경 시 재시작

# VPA는 기본 제공되지 않음, GitHub에서 설치
git clone https://github.com/kubernetes/autoscaler.git
cd autoscaler/vertical-pod-autoscaler
./hack/vpa-up.sh

apiVersion: autoscaling.k8s.io/v1
kind: VerticalPodAutoscaler
metadata:
  name: my-app-vpa
spec:
  targetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: my-app
  updatePolicy:
    updateMode: "Auto"
  resourcePolicy:
    containerPolicies:
    - containerName: app
      minAllowed:
        cpu: "100m"
        memory: "128Mi"
      maxAllowed:
        cpu: "4"
        memory: "8Gi"
      controlledResources: ["cpu", "memory"]

# VPA 상태 확인
kubectl describe vpa my-app-vpa

# 출력 예시
Recommendation:
  Container Recommendations:
    Container Name:  app
    Lower Bound:
      Cpu:     100m
      Memory:  262144k
    Target:
      Cpu:     500m
      Memory:  524288k
    Upper Bound:
      Cpu:     2
      Memory:  1Gi

# VPA: CPU/메모리 리소스 최적화 (Off 모드)
# HPA: 커스텀 메트릭 기반 스케일링

# Rollout
kubectl rollout status deployment/my-app
kubectl rollout history deployment/my-app
kubectl rollout undo deployment/my-app
kubectl rollout undo deployment/my-app --to-revision=2
kubectl rollout pause deployment/my-app
kubectl rollout resume deployment/my-app

# 스케일링
kubectl scale deployment my-app --replicas=5
kubectl autoscale deployment my-app --cpu-percent=50 --min=2 --max=10

# ConfigMap
kubectl create configmap app-config --from-literal=KEY=VALUE
kubectl create configmap app-config --from-file=config.properties
kubectl get configmap
kubectl describe configmap app-config

# Secret
kubectl create secret generic db-secret --from-literal=password=secret
kubectl create secret tls tls-secret --cert=tls.crt --key=tls.key
kubectl get secret
kubectl describe secret db-secret

# HPA
kubectl get hpa
kubectl describe hpa my-app-hpa
kubectl delete hpa my-app-hpa

# VPA
kubectl get vpa
kubectl describe vpa my-app-vpa

# 디버깅
kubectl describe pod my-pod
kubectl logs my-pod -c init-container
kubectl get events