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In this article, I will show you the experiments on pv and pvc storage in k8s, so as to help you further understand the storage part of k8s.

Theme of my blog: I hope everyone can make experiments with my blog, first do the experiments, and then understand the technical points in a deeper level in combination with theoretical knowledge, so as to have fun and motivation in learning. Moreover, the content steps of my blog are very complete. I also share the source code and the software used in the experiment. I hope I can make progress with you!

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Introduction to basic knowledge

Experimental environment

Experimental environment:
1,win10,vmwrokstation Virtual machine;
2,k8s Cluster: 3 sets centos7.6 1810 Virtual machine, 1 master node,2 individual node node
   k8s version: v1.21
   CONTAINER-RUNTIME: docker://20.10.7

Special note: nfs storage services should be pre configured here!

See another blog post on how to configure nfs storage classes:

https://www.onlyonexl.cn/2021/09/21/36%20%E5%AE%9E%E6%88%98%EF%BC%9A%E7%BD%91%E7%BB%9C%E5%AD%98%E5%82%A8%E5%8D%B7NFS%E5%AE%9E%E9%AA%8C%E6%BC%94%E7%A4%BA(%E6%88%90%E5%8A%9F%E6%B5%8B%E8%AF%95-%E5%8D%9A%E5%AE%A2%E8%BE%93%E5%87%BA)-20210921/

1. Copy the official sample code and modify it

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

Official Code:

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: k8s.gcr.io/nginx-slim:0.8
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: www
    spec:
      accessModes: [ "ReadWriteOnce" ]
      storageClassName: "my-storage-class"
      resources:
        requests:
          storage: 1Gi

Create statful.yaml: (modified code)

[root@k8s-master ~]#vim stateful.yaml
apiVersion: v1
kind: Service
metadata:
  name: sts-nginx
  labels:
    app: nginx
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None #Pay attention here
  selector:
    app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: sts-web
spec:
  selector:
    matchLabels:
      app: nginx # has to match .spec.template.metadata.labels
  serviceName: "sts-nginx" #Pay attention here
  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
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: www
    spec:
      accessModes: [ "ReadWriteOnce" ] #Create a separate pv for each pod
      storageClassName: "managed-nfs-storage"
      resources:
        requests:
          storage: 1Gi

2. apply and view

[root@k8s-master ~]# kubectl apply -f stateful.yaml
service/sts-nginx created
statefulset.apps/sts-web created

Check PV and PVC:

[root@k8s-master ~]#kubectl get pv,pvc

3. Verify

1. Correspondence between sts number and pvc; sts number mark start sequence; sts number - host name;

Check PV and PVC:

[root@k8s-master ~]#kubectl get pv,pvc

2. Verify whether the next pod is shared storage? = > Each pod has its own unique storage.

Go to sts-web-0 pod, write a web0 file, store it at the back end, and observe the directory where the test file will appear:

Then create the test file web1.html in the sts-web-1 back-end storage directory, and then go to the other two back-end storage directories to see if it will appear in their directories? = > can't.

Then go to the sts-web1 pod website to see if web1.html exists? = > existence

Note the host name of the pod:

End of test.

3.sts number and network authentication

Create busybox test image:

[root@k8s-master ~]#kubectl run dns-test --image=busybox:1.28.4 -- sleep 24h
pod/dns-test created

Delete all current pod s and clear the test environment:

[root@k8s-master ~]#kubectl delete -f .

[root@k8s-master ~]#kubectl create deployment web --image=nginx #Start an nginx pod
[root@k8s-master ~]#kubectl expose deployment web --port=80 --target-port=80 --type=NodePort

Check that the label of the current pod is different and meets the needs of the experiment:

[root@k8s-master ~]#kubectl get pod --show-labels

Expand the web application to three copies:

[root@k8s-master ~]#kubectl scale deployment web --replicas=3
deployment.apps/web scaled

apply stateful.yaml:

[root@k8s-master ~]#kubectl apply -f stateful.yaml
service/sts-nginx created
statefulset.apps/sts-web created
[root@k8s-master ~]#

Now it is equivalent to two applications: one web and one STS web, with three copies each.

[root@k8s-master ~]#kubectl get pod --show-labels

Let's now look at the differences between the two applications?

Now go to the DNS test test container and test with the nslookup command: the conclusion is as follows

This is the end of the experiment.

summary

Well, that's all for the stateful application deployment StatefulSet workload controller experiment. Thank you for reading. See you next time!