Kubernetes_5

2023.02.01

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6장 컨트롤러

ReplicaSet

cat > nginx-rs.yaml

>
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: rs-nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: webui
  template:
    metadata:
      name: nginx-pod
      labels:
        app: webui
    spec:
      containers:
      - name: nginx-container
        image: nginx:1.14

kubectl get rs
kubectl get replicasets.apps
kubectl describe rs rs-nginx

kubectl describe rs rs-nginx

pod를 지워보면
kubectl delete pod [pod이름]
먼저 pod를 creation하고 나중에 지운다.

관계를 끊어주고
kubectl delete rs rs-nginx --cascade=false
다시 pod를 지워보면 pod가 살아나지 않는 것을 볼 수 있음.

연습문제

cat > rs-lab.yaml

>
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: rs-mainui
spec:
  replicas: 2
  selector:
    matchLabels:
      app: main
  template:
    metadata:
      name: apache
      labels:
        app: main
        rel: stable
    spec:
      containers:
      - name: httpd-container
        image: httpd:2.2

kubectl apply -f rs-lab.yaml
kubectl scale rs rs-mainui --replicas=1

---

Deployment

cat > nginx-deployment.yaml

>
apiVersion: apps/v1
kind: Deployment
metadata:
  name: rs-nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: webui
  template:
    metadata:
      name: nginx-pod
      labels:
        app: webui
    spec:
      containers:
      - name: nginx-container
        image: nginx:1.14

kubectl apply -f nginx-deployment.yaml
kubectl scale deployment rs-nginx --replicas=2

Rolling Update & Rolling Back

<ex.1>

cat > nginx-deployment-exam.yaml

>
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-deploy
spec:
  selector:
    matchLabels:
      app: webui
  replicas: 3
  template:
    metadata:
      labels:
        app: webui
    spec:
      containers:
      - image: nginx:1.14
        name: web
        ports:
        - containerPort: 80

kubectl apply -f nginx-deployment-exam.yaml

kubectl set image deploy app-deploy web=nginx:1.15 --record
를 실행하면 1.15버전으로 새로 생성된 pod들이 등장한다.
(하나씩 순차적으로 생성하고 기존 pod를 하나씩 삭제함)
❗ rs는 그대로 있음!

rollout 관련 명령

	- 상태 확인
kubectl rollout status deployment app-deploy

	- 배포를 잠시 미룸
kubectl rollout pause deployment app-deploy

	- 미뤄둔 배포를 진행
kubectl rollout resume deployment app-deploy

	- 명령 확인
kubectl rollout history deployment app-deploy

	- 방금 명령 취소
kubectl rollout undo deployment app-deploy

<ex.2>

cat > nginx-deployment-exam2.yaml

>
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deploy-nginx
  annotations:
    kubernetes.io/change-cause: version 1.14
spec:
  progressDeadlineSeconds: 600
  revisionHistoryLimit: 10
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate
  replicas: 3
  selector:
    matchLabels:
      app: webui
  template:
    metadata:
      labels:
        app: webui
    spec:
      containers:
      - name: web
        image: nginx:1.14
        ports:
        - containerPort: 80

kubectl apply -f nginx-deployment-exam2.yaml

vi 에디터에서

kubernetes.io/change-cause: version 1.15
image: nginx:1.15

로 버전을 바꾸고

kubectl apply -f nginx-deployment-exam2.yaml
하면 버전이 바뀌는 것을 확인할 수 있다

undo도 가능하다.
kubectl rollout undo deployment deploy-nginx
(--to-revision=3)도 붙여서 버전에 따른 undo가 가능

연습문제

cat > deb-lab.yaml

>
apiVersion: apps/v1
kind: Deployment
metadata:
  name: dep-mainui
  annotations:
    kubernetes.io/change-cause: version 2.2
spec:
  replicas: 2
  selector:
    matchLabels:
      app: main
  template:
    metadata:
      labels:
        app: main
        rel: stable
    spec:
      containers:
      - name: apache
        image: httpd:2.2
        ports:
        - containerPort: 80

---

Daemonset

cat > nginx-daemonset.yaml

>
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: daemonset-nginx
spec:
  selector:
    matchLabels:
      app: webui
  template:
    metadata:
      name: nginx-pod
      labels:
        app: webui
    spec:
      containers:
      - name: nginx-container
        image: nginx:1.14

kubectl apply -f nginx-daemonset.yaml

kubectl delete pod [pod 이름]
하면 pod가 다시 생성됨

node 별로 pod가 하나씩 생성

kubectl edit daemonset daemonset-nginx
에서 container의 이미지 버전을 변경해주면 pod가 삭제되고 새로 만들어짐

kubectl rollout undo daemonset daemonset-nginx
을 하면 이미지 버전이 변경되기 전으로 돌아감

---

Stateful sets

cat > nginx-stateful.yaml

>
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: sf-nginx
spec:
  replicas: 3
  serviceName: sf-service
#  podManagementPolicy: OrderedReady
  podManagementPolicy: Parallel
  selector:
    matchLabels:
      app: webui
  template:
    metadata:
      name: nginx-pod
      labels:
        app: webui
    spec:
      containers:
      - name: nginx-container
        image: nginx:1.14

replicaset과 다른 특이점은 serviceName이 들어가는 부분이다.

kubectl apply -f nginx-stateful.yaml
kubectl get statefulsets.apps

kubectl delete pod sf-nginx-1
하면 해당 pod가 삭제됐다가 똑같이 다시 살아남

scale-out, scale-in 가능
kubectl scale statefulset sf-nginx --replicas=5

rollback도 가능

kubectl edit statefulsets.apps sf-nginx
kubectl rollout undo statefulset sf-nginx

---

Job

cat > nginx-job.yaml

>
apiVersion: batch/v1
kind: Job
metadata:
  name: centos-job
spec:
#  completions: 5 # 총 몇개를 돌지
#  parallelism: 2 # 동시에 몇개까지 돌지 (마지막엔 나머지만// 여기서는 1)
  activeDeadlineSeconds: 5
  template:
    spec:
      containers:
      - name: centos-container
        image: centos:7
        command: ["bash"]
        args:
        - "-c"
        - "echo 'Hello World'; sleep 25; echo 'Bye'"
      restartPolicy: Never # 성공할 때까지 돌아라
#      restartPolicy: OnFailure # 실패해도 종료해라
#  backoffLimit: 3 # 3번까지 돌아라

kubectl apply -f nginx-job.yaml
한 번 실행되고 나서 Terminating 된다.

kubectl get jobs.batch centos-job
으로 보면 job의 COMPLETIONS 내용을 볼 수 있음

---

Cronjob

: 일정한 주기로 반복함

cat > cronjob-exam.yaml

>
apiVersion: batch/v1
kind: CronJob
metadata:
  name: cronjob-exam
spec:
  schedule: "* * * * *"
  startingDeadlineSeconds: 500
#  concurrencyPolicy: Allow
  concurrencyPolicy: Forbid
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: hello
            image: busybox
            args:
            - /bin/sh
            - -c
            - echo Hello; sleep 10; echo Bye
          restartPolicy: Never

job과 비교해 schedule과 jobTemplate이 추가 되었음.

kubectl apply -f cronjob-exam.yaml
kubectl get cronjobs.batch -o yaml 로 확인

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