[k8s] Statefulset

Statefulset이란?

• pod의 상태를 유지해주는 controller
  • pod 이름
  • pod의 볼륨(스토리지)
• daemonset처럼 node 당 pod 1개를 보장하지 않음
• definition

apiVersion: apps/v1
kind: StatefulSet                # kind 종류 확인
metadata:
  name: sf-nginx
spec:
  replicas: 3
  serviceName: sf-service        # serviceName 존재
  selector:
    matchLabels:
      app: webui
  template:
    metadata:
      name: nginx-pod
      labels:
        app: webui
    spec:
      containers:
      - name: nginx-container
        image: nginx:1.14​

 

[ Hands - on ]

• statefulset 생성

vi statefulset-exam.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

kubectl create -f statefulset-exam.yaml

nana@master:~$ kubectl get pods -o wide --watch
NAME         READY   STATUS    RESTARTS   AGE   IP                NODE                NOMINATED NODE   READINESS GATES
sf-nginx-0   1/1     Running   0          20s   192.168.178.196   node3.example.com   <none>           <none>
sf-nginx-1   1/1     Running   0          20s   192.168.221.5     node2.example.com   <none>           <none>
sf-nginx-2   1/1     Running   0          20s   192.168.11.70     node1.example.com   <none>           <none>

 

• scale out
  • 번호 순서대로 증가

kubectl scale statefulset sf-nginx --replicas=4

nana@master:~$ kubectl get pods -o wide --watch
NAME         READY   STATUS    RESTARTS   AGE     IP                NODE                NOMINATED NODE   READINESS GATES
sf-nginx-0   1/1     Running   0          3m13s   192.168.178.196   node3.example.com   <none>           <none>
sf-nginx-1   1/1     Running   0          3m13s   192.168.221.5     node2.example.com   <none>           <none>
sf-nginx-2   1/1     Running   0          3m13s   192.168.11.70     node1.example.com   <none>           <none>
sf-nginx-3   1/1     Running   0          6s      192.168.178.197   node3.example.com   <none>           <none>

• scale in
  • 번호 역순서대로 감소

kubectl scale statefulset sf-nginx --replicas=2

nana@master:~$ kubectl get pods -o wide --watch
NAME         READY   STATUS    RESTARTS   AGE     IP                NODE                NOMINATED NODE   READINESS GATES
sf-nginx-0   1/1     Running   0          4m57s   192.168.178.196   node3.example.com   <none>           <none>
sf-nginx-1   1/1     Running   0          4m57s   192.168.221.5     node2.example.com   <none>           <none>

• rolling update
  • 번호 역순서대로 update

kubectl edit statefulsets.apps sf-nginx

• rollback

kubectl rollout undo statefulset sf-nginx

 

 

참고 :

[따배쿠] 6-5. 쿠버네티스 StatefulSet