Exercise

Exercise: Storage

1. Setting up the default StorageClass

   SKS defines a StorageClass to provision storage dynamically, it is named exoscale-sbs. This StorageClass is not set as the default one, run the following command to do so:

   kubectl patch storageclass exoscale-sbs -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "true"}}}'
   

2. In a file named pvc-redis.yaml, define the specification for a PersistentVolumeClaim with the following characteristics:

   • name: redis
   • ReadWriteOnce mode
   • request for 1OG storage

   Warning

   10Gi if the minimum capacity we can require on Exoscale

   Then modify the redis Deployment specification by adding a volume based on this PersistentVolumeClaim, and use the volumeMounts instruction to ensure that the associated PersistentVolume is mounted in the /data directory of the redis container.

3. In a file named pvc-db.yaml containing the specification for a PersistentVolumeClaim with the following characteristics:

   • name: db
   • ReadWriteOnce mode
   • request for 10G of storage

   Then modify the db Deployment specification by adding a volume based on this PersistentVolumeClaim, and use the volumeMounts instruction to ensure that the associated PersistentVolume is mounted in the /var/lib/postgresql/data directory of the postgres container.

4. Deploy the application defined in these specifications and verify that it is working correctly.

5. List the PersistentVolumeClaim resources. What do you observe?

6. Delete the application.

Tip

1. already done

2. The specification to define the PersistentVolumeClaim named redis:

   pvc-redis.yaml

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata: 
     name: redis
   spec: 
     accessModes:
       - ReadWriteOnce
     resources:
       requests: 
         storage: 10Gi
   

   The redis Deployment is modified as follows:

   deploy-redis.yaml

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: redis
     name: redis
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: redis
     template:
       metadata:
         labels:
           app: redis
       spec:
         containers:
           - image: redis:7.0.8-alpine3.17
             name: redis
             volumeMounts:
             - name: data
               mountPath: /data
         volumes:
         - name: data
           persistentVolumeClaim:
             claimName: redis
   

3. The specification to define the PersistentVolumeClaim named db:

   pvc-db.yaml

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata: 
     name: db
   spec: 
     accessModes:
       - ReadWriteOnce
     resources:
       requests: 
         storage: 10Gi
   

   The db Deployment is modified as follows:

   deploy-db.yaml

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     labels:
       app: db
     name: db
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: db
     template:
       metadata:
         labels:
           app: db
       spec:
         containers:
           - image: postgres:15.1-alpine3.17
             name: postgres
             env:
               - name: POSTGRES_PASSWORD
                 valueFrom:
                   secretKeyRef:
                     name: db
                     key: password
             volumeMounts:
             - name: data
               mountPath: /var/lib/postgresql/data
             ports:
               - containerPort: 5432
                 name: postgres
         volumes:
         - name: data
           persistentVolumeClaim: 
             claimName: db
   

4. Deploy the application using the following command from the manifests directory:

   kubectl apply -f .
   

   Using the IP address of one of the cluster nodes, you can access the vote and result interfaces via ports 31000 and 31001 respectively.

5. You can list the PersistentVolumeClaim resources and observe that a PersistentVolume has been created for each of the 2 PVCs.

   List of PersistentVolumeClaims:

   $ kubectl get pvc
   NAME                          STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
   persistentvolumeclaim/redis   Bound    pvc-789e3c5c-4402-4b96-b09d-ee441e8ade1d   10Gi       RWO            local-path     39s
   persistentvolumeclaim/db      Bound    pvc-75b9a32c-eab5-4452-a9b8-12d41dd74e7a   10Gi       RWO            local-path     39s
   

   List of PersistentVolumes:

   $ kubectl get pv
   NAME                                                        CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM           STORAGECLASS   REASON   AGE
   persistentvolume/pvc-789e3c5c-4402-4b96-b09d-ee441e8ade1d   10Gi       RWO            Delete           Bound    default/redis   local-path              32s
   persistentvolume/pvc-75b9a32c-eab5-4452-a9b8-12d41dd74e7a   10Gi       RWO            Delete           Bound    default/db      local-path              32s
   

   The volumes can be listed from the Exoscale console

   

6. Delete the application using the following command from the manifests directory:

   kubectl delete -f .