Creating a StatefulSet Mounted with an OBS Volume

Scenario

CCE allows you to use an existing OBS volume to create a StatefulSet through a PVC.

Prerequisites

You have created a CCE cluster and installed the CSI plug-in (everest) in the cluster.

Notes and Constraints

The following configuration example applies to clusters of Kubernetes 1.15 or later.

Procedure

Create an OBS volume by referring to PersistentVolumeClaims (PVCs) and obtain the PVC name.
Use kubectl to connect to the cluster. For details, see Connecting to a Cluster Using kubectl.

Create a YAML file for creating the workload. Assume that the file name is obs-statefulset-example.yaml.

touch obs-statefulset-example.yaml

vi obs-statefulset-example.yaml

Configuration example:

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: obs-statefulset-example
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app: obs-statefulset-example
  template:
    metadata:
      labels:
        app: obs-statefulset-example
    spec:
      volumes: 
      - name: pvc-obs-example 
        persistentVolumeClaim:
          claimName: pvc-obs-example     
      containers:
      - name: container-0
        image: 'nginx:latest'
        volumeMounts:
          - name: pvc-obs-example
            mountPath: /tmp
      restartPolicy: Always
      imagePullSecrets:
      - name: default-secret 
  serviceName: obs-statefulset-example-headless    # Name of the headless Service

**Table 1** Key parameters
Parameter	Description
replicas	Number of pods.
name	Name of the new workload.
image	Image used by the workload.
mountPath	Mount path of a container.
serviceName	Service corresponding to the workload. For details about how to create a Service, see Creating a StatefulSet.
claimName	Name of an existing PVC.

Example of mounting an OBS volume to a StatefulSet (PVC template-based, dedicated volume):

Example YAML:

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: obs-statefulset-example
  namespace: default
spec:
  replicas: 1
  selector:
    matchLabels:
      app: obs-statefulset-example
  template:
    metadata:
      labels:
        app: obs-statefulset-example
    spec:
      containers:
        - name: container-0
          image: 'nginx:latest'
          volumeMounts:
            - name: pvc-obs-auto-example
              mountPath: /tmp
      restartPolicy: Always
      imagePullSecrets:
        - name: default-secret
  volumeClaimTemplates:
    - metadata:
        name: pvc-obs-auto-example
        namespace: default
        annotations:
          everest.io/obs-volume-type: STANDARD
      spec:
        accessModes:
          - ReadWriteMany
        resources:
          requests:
            storage: 1Gi
        storageClassName: csi-obs  
  serviceName: obs-statefulset-example-headless

Create a StatefulSet.

kubectl create -f obs-statefulset-example.yaml

Verifying Persistent Storage of an OBS Volume

Query the pod and OBS volume of the deployed workload (for example, obs-statefulset-example).
1. Run the following command to query the pod name of the workload:
```
kubectl get po | grep obs-statefulset-example
```
  Expected outputs:
```
obs-statefulset-example-0   1/1     Running   0          2m5s
```
2. Run the following command to check whether an OBS volume is mounted to the /tmp directory:
```
kubectl exec obs-statefulset-example-0 -- mount|grep /tmp
```
  Expected outputs:
```
s3fs on /tmp type fuse.s3fs (rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other)
```
Run the following command to create a file named test in the /tmp directory:
```
kubectl exec obs-statefulset-example-0 -- touch /tmp/test
```

Run the following command to view the file in the /tmp directory:

kubectl exec obs-statefulset-example-0 -- ls -l /tmp

Expected outputs:

-rw-r--r-- 1 root root     0 Jun  1 02:50 test

Run the following command to delete the pod named obs-statefulset-example-0:
```
kubectl delete po obs-statefulset-example-0
```
Check whether the file still exists after the pod is rebuilt.
1. Run the following command to query the name of the rebuilt pod:
```
kubectl get po
```
  Expected outputs:
```
obs-statefulset-example-0   1/1     Running   0          2m
```
2. Run the following command to view the file in the /tmp directory:
```
kubectl exec obs-statefulset-example-0 -- ls -l /tmp
```
  Expected outputs:
```
-rw-r--r-- 1 root root     0 Jun  1 02:50 test
```
3. The test file still exists after the pod is rebuilt, indicating that the data in the OBS volume can be persistently stored.