[Kubernetes]How to use Label and Selector - Example

Example - How to use label and selector

create deployment, service with labels and selector

deployment(nginx-label01~04)에 label(app,environment,release)을 작성한다.

• deployment-nginx-label01 ~04.yaml 작성
• 위 표에 맞게 라벨을 작성한다.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-label01 # deployment별로 label01~04로 설정
  labels:
    app: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels: # labels 항목, 3개의 labels
        app: nginx
        environment: develop
        release: beta
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80

service(develop, stable)에 selector(environment: develop, release: stable) 를 작성한다.

• labe-service01~02.yaml 작성
• 위 표에 맞게 selector를 작성

apiVersion: v1
kind: Service
metadata:
  name: label-develop-service
spec:
  type: ClusterIP
  selector:
    environment: develop
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80

apiVersion: v1
kind: Service
metadata:
  name: label-stable-service
spec:
  type: ClusterIP
  selector:
    release: stable
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80

deployment, service apply

[dewble@instance-1 labels]$ kubectl apply -f .
deployment.apps/nginx-label01 created
deployment.apps/nginx-label02 created
deployment.apps/nginx-label03 created
deployment.apps/nginx-label04 created
service/label-develop-service created
service/label-stable-service created

작성한 label과 selector에 맞게 서비스가 연결되었는지 확인해본다.

What is the result that I expect

develop-service → deployment01,03

stable-service→ deployment03,04

배포한 deploy의 pod가 어떤 IP를 가지고 만들어 졌는지 확인

[dewble@instance-1 labels]$ kubectl get pods -o wide | grep label
nginx-label01-58f576c6f4-gnp7h                1/1     Running            0          2m6s    10.233.118.39    instance-5   <none>           <none>
nginx-label02-657ccdb46-pjvjg                 1/1     Running            0          2m6s    10.233.125.120   instance-4   <none>           <none>
nginx-label03-686d484df7-vhj2z                1/1     Running            0          2m6s    10.233.125.138   instance-4   <none>           <none>
nginx-label04-6ff7b6c8bf-xmhpw                1/1     Running            0          2m6s    10.233.125.113   instance-4   <none>           <none>

pod	IP
nginx-label01	10.233.118.39
nginx-label02	10.233.125.120
nginx-label03	10.233.125.138
nginx-label04	10.233.125.113

서비스가 어떤 셀렉터를 가지고 만들어졌는지 확인

[dewble@instance-1 labels]$ kubectl get svc -o wide | grep label
label-develop-service       ClusterIP      10.233.9.113    <none>        80/TCP                   2m37s   environment=develop
label-stable-service        ClusterIP      10.233.41.156   <none>        80/TCP                   2m37s   release=stable

service	label
label-develop-service	environment=develop
label-stable-service	release=stable

서비스가 설정한 파드를 선택했는지 확인

[dewble@instance-1 labels]$ kubectl describe svc
Name:              label-develop-service
Namespace:         kube-system
Labels:            <none>
Annotations:       <none>
Selector:          environment=develop
Type:              ClusterIP
IP:                10.233.9.113
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         10.233.118.39:80,10.233.125.138:80
Session Affinity:  None
Events:            <none>

Name:              label-stable-service
Namespace:         kube-system
Labels:            <none>
Annotations:       <none>
Selector:          release=stable
Type:              ClusterIP
IP:                10.233.41.156
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         10.233.125.113:80,10.233.125.138:80
Session Affinity:  None
Events:            <none>

service	Endpoints
nginx-label01	10.233.118.39
nginx-label02	10.233.125.120
nginx-label03	10.233.125.138
nginx-label04	10.233.125.113

service	label	pod IP
label-develop-service	environment=develop	nginx-label01 10.233.118.39 nginx-label03 10.233.125.138
label-stable-service	release=stable	nginx-label03 10.233.125.138 nginx-label04 10.233.125.113

• 예상했던 대로 service의 Endpoints에 각 label에 맞는 pod의 IP가 할당된 것을 알 수 있다.

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Example - How to use selector in command

[dewble@instance-1 labels]$ kubectl get pods -l app=nginx
NAME                             READY   STATUS    RESTARTS   AGE
nginx-label01-58f576c6f4-gnp7h   1/1     Running   0          6m17s
nginx-label02-657ccdb46-pjvjg    1/1     Running   0          6m17s
nginx-label03-686d484df7-vhj2z   1/1     Running   0          6m17s
nginx-label04-6ff7b6c8bf-xmhpw   1/1     Running   0          6m17s

[dewble@instance-1 labels]$ kubectl get pods -l environment=develop,release=stable
NAME                             READY   STATUS    RESTARTS   AGE
nginx-label03-686d484df7-vhj2z   1/1     Running   0          7m30s

[dewble@instance-1 labels]$ kubectl get pods -l "app=nginx,environment notin (develop)"
NAME                             READY   STATUS    RESTARTS   AGE
nginx-label02-657ccdb46-pjvjg    1/1     Running   0          8m5s
nginx-label04-6ff7b6c8bf-xmhpw   1/1     Running   0          8m5s

[dewble@instance-1 labels]$ kubectl get pods -l release!=stable
NAME                                          READY   STATUS             RESTARTS   AGE
nginx-label01-58f576c6f4-gnp7h                1/1     Running            0          10m
nginx-label02-657ccdb46-pjvjg                 1/1     Running            0          10m

[dewble@instance-1 labels]$ kubectl get pods -l release!=stable
NAME                                          READY   STATUS             RESTARTS   AGE
nginx-label01-58f576c6f4-gnp7h                1/1     Running            0          10m
nginx-label02-657ccdb46-pjvjg                 1/1     Running            0          10m

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2022.05.01 - [리뷰/도서] - [도서]쿠버네티스 입문