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Use kubectl to run a Kubernetes stateful application with StorageClass on your Azure Stack Edge Pro GPU device

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APPLIES TO: Yes for Pro GPU SKUAzure Stack Edge Pro - GPUYes for Pro 2 SKUAzure Stack Edge Pro 2Yes for Pro R SKUAzure Stack Edge Pro RYes for Mini R SKUAzure Stack Edge Mini R                  

This article shows you how to deploy a single-instance stateful application in Kubernetes using a StorageClass to dynamically provision storage and a deployment. The deployment uses kubectl commands on an existing Kubernetes cluster and deploys the MySQL application.

This procedure is intended for those who have reviewed the Kubernetes storage on Azure Stack Edge Pro device and are familiar with the concepts of Kubernetes storage.

Prerequisites

Before you can deploy the stateful application, complete the following prerequisites on your device and the client that you will use to access the device:

For device

  • You have sign-in credentials to a 1-node Azure Stack Edge Pro device.

For client accessing the device

  • You have a Windows client system that will be used to access the Azure Stack Edge Pro device.

    • The client is running Windows PowerShell 5.0 or later. To download the latest version of Windows PowerShell, go to Install Windows PowerShell.

    • You can have any other client with a Supported operating system as well. This article describes the procedure when using a Windows client.

    • You have completed the procedure described in Access the Kubernetes cluster on Azure Stack Edge Pro device. You have:

      • Created a userns1 namespace via the New-HcsKubernetesNamespace command.
      • Created a user user1 via the New-HcsKubernetesUser command.
      • Granted the user1 access to userns1 via the Grant-HcsKubernetesNamespaceAccess command.
      • Installed kubectl on the client and saved the kubeconfig file with the user configuration to C:\Users\<username>\.kube.

    • Make sure that the kubectl client version is skewed no more than one version from the Kubernetes master version running on your Azure Stack Edge Pro device.

      • Use kubectl version to check the version of kubectl running on the client. Make a note of the full version.
      • In the local UI of your Azure Stack Edge Pro device, go to Overview and note the Kubernetes software number.
      • Verify these two versions for compatibility from the mapping provided in the Supported Kubernetes version.

You are ready to deploy a stateful application on your Azure Stack Edge Pro device.

Deploy MySQL

You will now run a stateful application by creating a Kubernetes Deployment and connecting it to the built-in StorageClass using a PersistentVolumeClaim (PVC).

All kubectl commands you use to create and manage stateful application deployments need to specify the namespace associated with the configuration. To specify the namespace in a kubectl command, use kubectl <command> -n <your-namespace>.

  1. Get a list of the pods running on your Kubernetes cluster in your namespace. A pod is an application container, or process, running on your Kubernetes cluster.

    kubectl get pods -n <your-namespace>

    Here's an example of command usage:

     C:\Users\user>kubectl get pods -n "userns1"
 No resources found in userns1 namespace.    
 C:\Users\user>

    The output should state that no resources (pods) are found because there are no applications running on your cluster.

  2. You will use the following YAML files. The mysql-deployment.yml file describes a deployment that runs MySQL and references the PVC. The file defines a volume mount for /var/lib/mysql, and then creates a PVC that looks for a 20-GB volume. A dynamic PV is provisioned and the PVC is bound to this PV.

    Copy and save the following mysql-deployment.yml file to a folder on the Windows client that you are using to access the Azure Stack Edge Pro device.

    apiVersion: v1
kind: Service
metadata:
  name: mysql
spec:
  ports:
  - port: 3306
  selector:
    app: mysql
  clusterIP: None
---
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
  name: mysql
spec:
  selector:
    matchLabels:
      app: mysql
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
      - image: mysql:5.6
        name: mysql
        env:
          # Use secret in real usage
        - name: MYSQL_ROOT_PASSWORD
          value: password
        ports:
        - containerPort: 3306
          name: mysql
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pv-claim-sc

  3. Copy and save as a mysql-pvc.yml file to the same folder where you saved the mysql-deployment.yml. To use the builtin StorageClass that Azure Stack Edge Pro device on an attached data disk, set the storageClassName field in the PVC object to ase-node-local and accessModes should be ReadWriteOnce.

    Note

    Make sure that the YAML files have correct indentation. You can check with YAML lint to validate and then save.

    apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim-sc
spec:
  storageClassName: ase-node-local
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi

  4. Deploy the mysql-pvc.yaml file.

    kubectl apply -f <URI path to the mysql-pv.yml file> -n <your-user-namespace>

    Here's a sample output of the deployment.

    C:\Users\user>kubectl apply -f "C:\stateful-application\mysql-pvc.yml" -n userns1
persistentvolumeclaim/mysql-pv-claim-sc created
C:\Users\user>

    Note the name of the PVC created - in this example, mysql-pv-claim-sc. You will use it in a later step.

  5. Deploy the contents of the mysql-deployment.yml file.

    kubectl apply -f <URI path to mysql-deployment.yml file> -n <your-user-namespace>

    Here's a sample output of the deployment.

    C:\Users\user>kubectl apply -f "C:\stateful-application\mysql-deployment.yml" -n userns1
service/mysql created
deployment.apps/mysql created
C:\Users\user>

  6. Display information about the deployment.

    kubectl describe deployment <app-label> -n <your-user-namespace>

    C:\Users\user>kubectl describe deployment mysql -n userns1
Name:               mysql
Namespace:          userns1
CreationTimestamp:  Thu, 20 Aug 2020 11:14:25 -0700
Labels:             <none>
Annotations:        deployment.kubernetes.io/revision: 1
                    kubectl.kubernetes.io/last-applied-configuration:
                      {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"name":"mysql","namespace":"userns1"},"spec":{"selector":{"matchL...
Selector:           app=mysql
Replicas:           1 desired | 1 updated | 1 total | 1 available | 0 unavailable
StrategyType:       Recreate
MinReadySeconds:    0
Pod Template:
  Labels:  app=mysql
  Containers:
   mysql:
    Image:      mysql:5.6
    Port:       3306/TCP
    Host Port:  0/TCP
    Environment:
      MYSQL_ROOT_PASSWORD:  password
    Mounts:
      /var/lib/mysql from mysql-persistent-storage (rw)
  Volumes:
   mysql-persistent-storage:
    Type:       PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
    ClaimName:  mysql-pv-claim-sc
    ReadOnly:   false
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   mysql-695c4d9dcd (1/1 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  24s   deployment-controller  Scaled up replica set mysql-695c4d9dcd to 1
C:\Users\user>

  7. List the pods created by the deployment.

    kubectl get pods -l <app=label> -n <your-user-namespace>

    Here's a sample output.

    C:\Users\user>kubectl get pods -l app=mysql -n userns1
NAME                     READY   STATUS    RESTARTS   AGE
mysql-695c4d9dcd-rvzff   1/1     Running   0          40s
C:\Users\user>

  8. Inspect the PersistentVolumeClaim.

    kubectl describe pvc <your-pvc-name>

    Here's a sample output.

    C:\Users\user>kubectl describe pvc mysql-pv-claim-sc -n userns1
Name:          mysql-pv-claim-sc
Namespace:     userns1
StorageClass:  ase-node-local
Status:        Bound
Volume:        pvc-dc48253c-82dc-42a4-a7c6-aaddc97c9b8a
Labels:        <none>
Annotations:   kubectl.kubernetes.io/last-applied-configuration:
                 {"apiVersion":"v1","kind":"PersistentVolumeClaim","metadata":{"annotations":{},"name":"mysql-pv-claim-sc","namespace":"userns1"},"spec":{"...
               pv.kubernetes.io/bind-completed: yes
               pv.kubernetes.io/bound-by-controller: yes
               volume.beta.kubernetes.io/storage-provisioner: rancher.io/local-path
               volume.kubernetes.io/selected-node: k8s-3q7lhq2cl-3q7lhq2
Finalizers:    [kubernetes.io/pvc-protection]
Capacity:      20Gi
Access Modes:  RWO
VolumeMode:    Filesystem
Mounted By:    mysql-695c4d9dcd-rvzff
Events:
  Type    Reason                 Age                From                                                                                                Message
  ----    ------                 ----               ----                                                                                                -------
  Normal  WaitForFirstConsumer   71s (x2 over 77s)  persistentvolume-controller                                                                         waiting for first consumer to be created before binding
  Normal  ExternalProvisioning   62s                persistentvolume-controller                                                                         waiting for a volume to be created, either by external provisioner "rancher.io/local-path" or manually created by system administrator
  Normal  Provisioning           62s                rancher.io/local-path_local-path-provisioner-6b84988bf9-tx8mz_1896d824-f862-4cbf-912a-c8cc0ca05574  External provisioner is provisioning volume for claim "userns1/mysql-pv-claim-sc"
  Normal  ProvisioningSucceeded  60s                rancher.io/local-path_local-path-provisioner-6b84988bf9-tx8mz_1896d824-f862-4cbf-912a-c8cc0ca05574  Successfully provisioned volume pvc-dc48253c-82dc-42a4-a7c6-aaddc97c9b8a
C:\Users\user>

Verify MySQL is running

To verify that the application is running, type:

kubectl exec <your-pod-with-the-app> -i -t -n <your-namespace> -- mysql -p

When prompted, provide the password. The password is in your mysql-deployment file.

Here's a sample output.

C:\Users\user>kubectl exec mysql-695c4d9dcd-rvzff -i -t -n userns1 -- mysql -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.49 MySQL Community Server (GPL)

Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>

Delete a deployment

To delete the deployment, delete the deployed objects by name. These objects include deployment, service, and PVC.

kubectl delete deployment <deployment-name>,svc <service-name> -n <your-namespace>
kubectl delete pvc <your-pvc-name> -n <your-namespace>

Here's sample output of when you delete the deployment and the service.

C:\Users\user>kubectl delete deployment,svc mysql -n userns1
deployment.apps "mysql" deleted
service "mysql" deleted
C:\Users\user>

Here's sample output of when you delete the PVC.

C:\Users\user>kubectl delete pvc mysql-pv-claim-sc -n userns1
persistentvolumeclaim "mysql-pv-claim-sc" deleted
C:\Users\user>

Next steps

To understand how to configure networking via kubectl, see Deploy a stateless application on an Azure Stack Edge Pro device