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

1. Create an OBS volume by referring to PersistentVolumeClaims (PVCs) and obtain the PVC name.
2. Use kubectl to connect to the cluster. For details, see Connecting to a Cluster Using kubectl.
3. 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

4. Create a StatefulSet.

   kubectl create -f obs-statefulset-example.yaml

Verifying Persistent Storage of an OBS Volume

1. 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)

2. Run the following command to create a file named test in the /tmp directory:

   kubectl exec obs-statefulset-example-0 -- touch /tmp/test

3. 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

4. Run the following command to delete the pod named obs-statefulset-example-0:

   kubectl delete po obs-statefulset-example-0

5. 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.