StatefulSet特性：

  • 部署有状态应用

  • 解决Pod独立生命周期，保持Pod启动顺序和唯一性

    1、稳定，唯一的网络标识符，持久存储

    2、有序，优雅的部署和扩展、删除和终止

    3、有序，滚动更新

  • 稳定得网络ID

    使用Headless Service（相比普通得Service只是将spec.clusterIP定义为Node）来维护Pod网络身份；

    DNS解析名称：...svc.cluster.local

  • 稳定的存储

    Statefulset得存储卷使用VolumeClaimTemplate创建，成为卷申请模板，当statefulset使用VolumeClaimTemplate创建一个PersistentVolume时，同样也会为每个Pod分配并创建一个编号得PVC；

StatefulSet-Pod部署

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[root@pool1 k8s_yaml]# vi statefulset.yaml
apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None
  selector:
    app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  selector:
    matchLabels:
      app: nginx # has to match .spec.template.metadata.labels
  serviceName: "nginx"
  replicas: 3 # by default is 1
  template:
    metadata:
      labels:
        app: nginx # has to match .spec.selector.matchLabels
    spec:
      terminationGracePeriodSeconds: 10
      containers:
      - name: nginx
        image: nginx:1.20
        imagePullPolicy: IfNotPresent 
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:	# StatefuSet特有的存储机制
  - metadata:
      name: www
    spec:
      accessModes: [ "ReadWriteOnce" ]	# 访问模式
      storageClassName: "managed-nfs-storage"  # 动态PV名称
      resources:
        requests:
          storage: 1Gi
[root@pool1 k8s_yaml]# kubectl apply -f statefulset.yaml 
service/nginx created
statefulset.apps/web created

[root@pool1 k8s_yaml]# kubectl get pod | grep web
web-0                                     1/1     Running   0          22m
web-1                                     1/1     Running   0          22m
web-2                                     1/1     Running   0          22m

获取pod得DNS域名解析

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[root@pool1 k8s_yaml]# kubectl run -it test --image=busybox:1.28.4 -- sh
/ # nslookup nginx
Server:    10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local

Name:      nginx
Address 1: 10.244.206.14 web-0.nginx.default.svc.cluster.local
Address 2: 10.244.52.201 web-2.nginx.default.svc.cluster.local
Address 3: 10.244.206.15 web-1.nginx.default.svc.cluster.local
/ # ping web-0.nginx.default.svc.cluster.local
PING web-0.nginx.default.svc.cluster.local (10.244.206.14): 56 data bytes
64 bytes from 10.244.206.14: seq=0 ttl=62 time=0.689 ms
^C
--- web-0.nginx.default.svc.cluster.local ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 0.689/0.689/0.689 ms
/ # ping web-2.nginx.default.svc.cluster.local
PING web-2.nginx.default.svc.cluster.local (10.244.52.201): 56 data bytes
64 bytes from 10.244.52.201: seq=0 ttl=62 time=0.354 ms
64 bytes from 10.244.52.201: seq=1 ttl=62 time=0.391 ms
^C
--- web-2.nginx.default.svc.cluster.local ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.354/0.372/0.391 ms
/ # ping web-1.nginx.default.svc.cluster.local
PING web-1.nginx.default.svc.cluster.local (10.244.206.15): 56 data bytes
64 bytes from 10.244.206.15: seq=0 ttl=62 time=0.851 ms
64 bytes from 10.244.206.15: seq=1 ttl=62 time=1.290 ms
^C
--- web-1.nginx.default.svc.cluster.local ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.851/1.070/1.290 ms

# 这时可以通过nslookup解析的域名来让其他服务进行关联，保证每个Pod都有唯一联系地址；而不是通过svc来实现服务发现及负载均衡；