Kubernetes Seminar Code

우연치 않게, kubernetes에 대해 다른 분들께 소개할 기회가 생겼다. 이때 시연용으로 사용한 예시 코드들은 다음과 같다.

Workload

Pod

1. Create Pod with YAML

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:latest
    ports:
    - containerPort: 80

Use this file to create Pod.

kubectl apply -f nginx-pod.yaml

2. Basic Commands

# Search Pod
kubectl get pods

# Search detail
kubectl describe pod {pod_name}

# Delete Pod
kubectl delete pod {pod_name}

# Search Log of Pod
kubectl logs {pod_name}

# Execute Pod
kubectl exec -it {pod_name} -- /bin/bash

Deployment

1. Create Deployment(YAML)
   sample.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:latest
        ports:
        - containerPort: 80

Use this file to create deployment

kubectl apply -f nginx-deployment.yaml

2. Basic Commands

# Search Deployment
kubectl get deployments

# Show details
kubectl describe deployment {deploy_name}

# Scaling
kubectl scale deployment {deploy_name} --replicas=N

# Rollout check
kubectl rollout status deployment/{deploy_name}

# Rollout restart (kill and restart pods)
kubectl rollout restart deployment/{deploy_name}

# 새 이미지에 문제가 있다면, 이전 이미지로 rollback
kubectl rollout undo deployment/{deploy_name}

# Delete Deployment
kubectl delete deployment {deploy_name}

Node

Drain

Taint, Toleration

Service

Use service through kubectl

kubectl expose

# 1. Pod를 ClusterIP로 노출하기
kubectl expose pod {pod_name} --port={port_num} --target-port={target_port}

# 2. Deployment를 NodePort로 노출하기
kubectl expose deploy {deploy_name} --type=NodePort --port={port_num}

# 3. ReplicaSet을 LoadBalancer로 노출하기
kubectl expose rs {rs_name} --type=LoadBalancer --name={service_name} --port={port_num} --target-port={target_port} --protocol=TCP

Other Basic Commands

# 서비스 조회
kubectl get services

# 상세 정보 조회
kubectl describe services {service_name}

# Delete Service
kubectl delete services {service_name}

# Port-forwarding
kubectl port-forward pod/{pod_name} {external_port}:{internal_port}

ClusterIP

clusterip.yaml

apiVersion: v1
kind: Service
metadata:
  name: my-clusterip-service
spec:
  type: ClusterIP
  selector:
    app: myapp
  ports:
  - protocol: TCP
    port: 80
    targetPort: 9376

NodePort

apiVersion: v1
kind: Service
metadata:
  name: my-nodeport-service
spec:
  type: NodePort
  selector:
    app: myapp
  ports:
  - protocol: TCP
    port: 80
    targetPort: 9376
    nodePort: 30007

Ingress

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
  - host: www.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: myapp-service
            port:
              number: 80

Gateway API

apiVersion: networking.x-k8s.io/v1alpha1
kind: Gateway
metadata:
  name: my-gateway
spec:
  gatewayClassName: my-gateway-class
  listeners:  
  - protocol: HTTP
    port: 80
    routes:
      kind: HTTPRoute

---
apiVersion: networking.x-k8s.io/v1alpha1
kind: HTTPRoute
metadata:
  name: http-route
spec:
  gateways:
    allow: All
  hostnames:
  - "www.example.com"
  rules:
  - matches:
    - path:
        type: Prefix
        value: "/"
    forwardTo:
    - serviceName: myapp-service
      port: 80

Storage

Volume(emptyDir, HostPath, nfs)

emptyDir

apiVersion: v1
kind: Pod
metadata:
  name: pod-using-emptydir
spec:
  containers:
  - name: mycontainer
    image: nginx
    volumeMounts:
    - name: cache-volume
      mountPath: /cache
  volumes:
  - name: cache-volume
    emptyDir: {}

HostPath

apiVersion: v1
kind: Pod
metadata:
  name: pod-using-hostpath
spec:
  containers:
  - name: mycontainer
    image: nginx
    volumeMounts:
    - name: host-volume
      mountPath: /data
  volumes:
  - name: host-volume
    hostPath:
      path: /data
      type: Directory

nfs

apiVersion: v1
kind: Pod
metadata:
  name: pod-using-nfs
spec:
  containers:
  - name: mycontainer
    image: nginx
    volumeMounts:
    - name: nfs-volume
      mountPath: /data
  volumes:
  - name: nfs-volume
    nfs:
      server: nfs-server.local
      path: /path/to/data

ConfigMap

apiVersion: v1
kind: ConfigMap
metadata:
  name: myconfig
data:
  mykey: myvalue

---
apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
  containers:
  - name: myfrontend
    image: nginx
    env:
    - name: MYKEY
      valueFrom:
        configMapKeyRef:
          name: myconfig
          key: mykey

Secret

kind: Secret
metadata:
  name: mysecret
type: Opaque
data:
  password: cGFzc3dvcmQ=  # base64 encoded value

---
apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
  containers:
  - name: myfrontend
    image: nginx
    env:
    - name: PASSWORD
      valueFrom:
        secretKeyRef:
          name: mysecret
          key: password

PV

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mypvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deployment-using-pvc
spec:
  selector:
    matchLabels:
      app: myapp
  replicas: 2
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: mycontainer
        image: nginx
        volumeMounts:
        - name: pvc-volume
          mountPath: /data
      volumes:
      - name: pvc-volume
        persistentVolumeClaim:
          claimName: mypvc

PVC

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mypvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi

Objects in K8s

Labels

apiVersion: v1
kind: Pod
metadata:
  name: labeled-pod
  labels:
    app: myapp
    env: production
spec:
  containers:
    - name: nginx
      image: nginx

위 yaml을 apply하고 k get po -l env=k8s-seminar를 실행해준다.

# 라벨 추가 또는 업데이트
kubectl label pods labeled-pod newlabel=awesome

# 라벨 삭제
kubectl label pods labeled-pod newlabel-

Selector

Namespaces

III. Kubernetes 활용법

• 쿠버네티스를 썼을때 할 수 있는 것
• 개발자들이 쿠버네티스를 사용하는 시나리오
  IV. More about K8s
• Helm
• Istio & gateway