理解statefulset工作原理

1 - yaml文件

 

kind: PersistentVolume  == 同上一篇,定义PV和PVC

apiVersion: v1

metadata:

  name: task-pv-volume

  labels:

    type: local

spec:

  storageClassName: manual

  capacity:

    storage: 2Gi

  accessModes:

    - ReadWriteOnce

  hostPath:

    path: "/usr/local/"

---

kind: PersistentVolumeClaim

apiVersion: v1

metadata:

  name: task-pv-claim

spec:

  storageClassName: manual

  accessModes:

    - ReadWriteOnce

  resources:

    requests:

      storage: 1Gi

---

apiVersion: v1 

kind: Service

metadata:

  name: nginx

  labels:

    app: nginx

spec:

  ports:

  - port: 80

    name: web

  clusterIP: None == 定义一个headless service

  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: k8s.gcr.io/nginx-slim:0.8

        ports:

        - containerPort: 80

          name: web

        volumeMounts:

        - name: www

          mountPath: /usr/share/nginx/html

      volumes:

        - name: www

          persistentVolumeClaim:

            claimName: task-pv-claim

 

执行完毕验证效果:

 

pod名字是statefulset的name + 一个从0开始的数字组成的。

PS C:\e\temp> kubectl get pods

NAME                           READY     STATUS    RESTARTS   AGE

web-0                          1/1       Running   0          3h

web-1                          1/1       Running   0          3h

web-2                          1/1       Running   0          3h

 

从下面的结果开一看出,这个service没有clusterIP

PS C:\e\temp> kubectl get services

NAME           TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE

kubernetes     ClusterIP   10.96.0.1                443/TCP        14d

nginx          ClusterIP   None                     80/TCP         3h

 

登录其中一个pod

apt-get update

apt-get install dnsutils ==安装nslookup

apt-get install iputils-ping ==安装ping

 

service name = nginx

namespace = default

 

#nslookup nginx

...

...

Name:   nginx.default.svc.cluster.local == $(service name).$(namespace).svc.cluster.local

Address: 10.1.0.201

Name:   nginx.default.svc.cluster.local

Address: 10.1.0.203

Name:   nginx.default.svc.cluster.local

Address: 10.1.0.204

 

对于每个pod,是上面DNS的subdomain. $(podname).$(governing service domain)

 

governing service domain = nginx.default.svc.cluster.local

 

对于pod-1来说,他的DNS就是web-1 + nginx.default.svc.cluster.local,以此类推。

 

# ping web-1.nginx.default.svc.cluster.local

PING web-1.nginx.default.svc.cluster.local (10.1.0.204) 56(84) bytes of data.

64 bytes from web-1.nginx.default.svc.cluster.local (10.1.0.204): icmp_seq=1 ttl=64 time=0.113 ms

64 bytes from web-1.nginx.default.svc.cluster.local (10.1.0.204): icmp_seq=2 ttl=64 time=0.079 ms

64 bytes from web-1.nginx.default.svc.cluster.local (10.1.0.204): icmp_seq=3 ttl=64 time=0.128 ms

 

# ping web-2.nginx.default.svc.cluster.local

PING web-2.nginx.default.svc.cluster.local (10.1.0.203) 56(84) bytes of data.

64 bytes from web-2.nginx.default.svc.cluster.local (10.1.0.203): icmp_seq=1 ttl=64 time=0.170 ms

64 bytes from web-2.nginx.default.svc.cluster.local (10.1.0.203): icmp_seq=2 ttl=64 time=0.080 ms

 

 

https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/

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