Statefulset

stateless App

분산목적으로 app 실패 후 재생성 과정에서
app3 -> app4 변경 가능
하나의 볼륨 공유 가능

stateful App

각각 app마다 고유 지정 역할이 있기 때문에
각 volume 존재 , app1 -> app1 재생성 규칙

1. StatefulSet Controller

1-1) ReplicaSet

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: replica-web
spec:
  replicas: 1
  selector:
    matchLabels:
      type: web
  template:
    metadata:
      labels:
        type: web
    spec:
      containers:
      - name: container
        image: kubetm/app
      terminationGracePeriodSeconds: 10

1-2) StatefulSet

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: stateful-db
spec:
  replicas: 1
  selector:
    matchLabels:
      type: db
  template:
    metadata:
      labels:
        type: db
    spec:
      containers:
      - name: container
        image: kubetm/app
      terminationGracePeriodSeconds: 10

2. PersistentVolumeClaim

2-1) PersistentVolumeClaim

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: replica-pvc1
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 1G
  storageClassName: "fast"
  

2-2) ReplicaSet

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: replica-pvc
spec:
  replicas: 1
  selector:
    matchLabels:
      type: web2
  template:
    metadata:
      labels:
        type: web2
    spec:
      nodeSelector:
        kubernetes.io/hostname: k8s-node1
      containers:
      - name: container
        image: kubetm/init
        volumeMounts:
        - name: storageos
          mountPath: /applog
      volumes:
      - name: storageos
        persistentVolumeClaim:
          claimName: replica-pvc1
      terminationGracePeriodSeconds: 10
      

touch /applog/server.log

2-3) StatefulSet

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: stateful-pvc
spec:
  replicas: 1
  selector:
    matchLabels:
      type: db2
  serviceName: "stateful-headless"
  template: 
    metadata:
      labels:
        type: db2
    spec:
      containers:
      - name: container
        image: kubetm/app
        volumeMounts:
        - name: volume
          mountPath: /applog
      terminationGracePeriodSeconds: 10
  volumeClaimTemplates:
  - metadata:
      name: volume
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 1G
      storageClassName: "fast"
      
      

3. Headless Service

3-1) Service (Headless)

apiVersion: v1
kind: Service
metadata:
  name: stateful-headless
spec:
  selector:
    type: db2
  ports:
    - port: 80
      targetPort: 8080    
  clusterIP: None
  

3-2) Pod

apiVersion: v1
kind: Pod
metadata:
  name: request-pod
spec:
  containers:
  - name: container
    image: kubetm/init
    

nslookup stateful-headless

curl stateful-pvc-0.stateful-headless:8080/hostname