Migrate applications to an ACK cluster

Procedure

1. Set up the environment
2. Back up the application in the self-managed Kubernetes cluster
3. Restore the application in the ACK cluster
4. Update application configurations
5. Debug and start the application.

Set up the environment

1. Install the Velero client.
   Download Velero. Run the following command to install Velero and verify the result:

   curl -o /usr/bin/velero https://public-bucket-1.oss-cn-hangzhou.aliyuncs.com/velero && chmod +x /usr/bin/velero 

2. Create an Object Storage Service (OSS) bucket. For more information, see Create buckets.
   You must first create an OSS bucket to store data of the application and PVs. We recommend that you create an OSS bucket for each self-managed Kubernetes cluster.
   1. Log on to the OSS console.
   2. On the Overview page, click Create Bucket on the right side. You can also click the Create icon (+) next to Storage Capacity on the left side.
   3. In the Create Bucket panel, set parameters for the bucket.
      In this example, the OSS bucket is named ls-velero and deployed in the China (Hangzhou) region.
3. Create a Resource Access Management (RAM) user and generate an AccessKey pair. For more information, see Create a RAM user.
   If you use the AccessKey pair of an Alibaba Cloud account, skip this step.

   {
       "Version": "1",
       "Statement": [
           {
               "Action": [
                   "ecs:DescribeSnapshots",
                   "ecs:CreateSnapshot",
                   "ecs:DeleteSnapshot",
                   "ecs:DescribeDisks",
                   "ecs:CreateDisk",
                   "ecs:Addtags",
                   "oss:PutObject",
                   "oss:GetObject",
                   "oss:DeleteObject",
                   "oss:GetBucket",
                   "oss:ListObjects"
               ],
               "Resource": [
                   "*"
               ],
               "Effect": "Allow"
           }
       ]
   }

4. Deploy the Velero server.
   1. Add the AccessKey pair generated in Step 3 to the credentials-velero deployment file of Velero.

      ALIBABA_CLOUD_ACCESS_KEY_ID=<access_key_id>
      ALIBABA_CLOUD_ACCESS_KEY_SECRET=<access_key_secret>

   2. Run the following command to deploy Velero:

      velero install --provider alibabacloud --image registry.cn-hangzhou.aliyuncs.com/haoshuwei24/velero:v1.2.0 --bucket ls-velero --secret-file ./credentials-velero --use-volume-snapshots=false --backup-location-config region=cn-hangzhou --use-restic --plugins registry.cn-hangzhou.aliyuncs.com/acs/velero-plugin-alibabacloud:v1.2 --wait

   Run the following command to query the pod status:

   kubectl -n velero get po

   Expected output:

   NAME                      READY   STATUS    RESTARTS   AGE
   restic-fqwsc              1/1     Running   0          41s
   restic-kfzqt              1/1     Running   0          41s
   restic-klxhc              1/1     Running   0          41s
   restic-ql2kr              1/1     Running   0          41s
   restic-qrsrn              1/1     Running   0          41s
   restic-srjmm              1/1     Running   0          41s
   velero-67b975f5cb-68nj4   1/1     Running   0          41s

Back up the application in the self-managed Kubernetes cluster

• If you want to back up only the WordPress application, run the following command:

  velero backup create wordpress-backup-without-pv --include-namespaces wordpress

  Expected output:

  Backup request "wordpress-backup-without-pv" submitted successfully.
  Run `velero backup describe wordpress-backup-without-pv` or `velero backup logs wordpress-backup-without-pv` for more details.

  Run the following command to back up the application:

  velero backup get

  Expected output:

  NAME                          STATUS      CREATED                         EXPIRES   STORAGE LOCATION   SELECTOR
  wordpress-backup-without-pv   Completed   2019-12-12 14:08:24 +0800 CST   29d       default            <none>

• If you want to back up the data of the WordPress application and PVs, run the following commands:

  1. # Annotate the pods to which PVs are attached. In this example, the WordPress application runs on the wordpress-7cf5849f47-mbvx4 and mysql-74dddbdcc8-h2tls pods.
     kubectl -n wordpress annotate pod/wordpress-7cf5849f47-mbvx4 backup.velero.io/backup-volumes=wordpress-persistent-storage
     pod/wordpress-7cf5849f47-mbvx4 annotated

  2. # The PV attached to the wordpress-7cf5849f47-mbvx4 pod is mysql-persistent-storage. The PV attached to the mysql-74dddbdcc8-h2tls pod is wordpress-persistent-storage. Run the following commands to annotate the pods:
     kubectl -n wordpress annotate pod/mysql-74dddbdcc8-h2tls backup.velero.io/backup-volumes=mysql-persistent-storage
     pod/mysql-74dddbdcc8-h2tls annotated

  3. # Back up the WordPress application.
     velero backup create wordpress-backup-with-pv --include-namespaces wordpress

     Expected output:

     Backup request "wordpress-backup-with-pv" submitted successfully.
     Run `velero backup describe wordpress-backup-with-pv` or `velero backup logs wordpress-backup-with-pv` for more details.

  4. velero backup get

     Expected output:

     NAME                          STATUS      CREATED                         EXPIRES   STORAGE LOCATION   SELECTOR
     wordpress-backup-with-pv      Completed   2019-12-12 14:23:40 +0800 CST   29d       default            <none>
     wordpress-backup-without-pv   Completed   2019-12-12 14:08:24 +0800 CST   29d       default            <none>

In the OSS console, you can view the files that have been backed up in the OSS bucket.

Restore the application in the ACK cluster

In the self-managed Kubernetes cluster, the WordPress application uses NFS PVs. In the ACK cluster, you can configure Apsara File Storage NAS volumes to store data of the WordPress application. In this example, a StorageClass named nfs is created for the WordPress application, and Alibaba Cloud SSDs are used as backend storage.

The CSI plug-in is used in this example. For more information, see Provision Alibaba Cloud disks as dynamic PVs.

1. Create a StorageClass.
   If you back up only the WordPress application, skip this step.

   cat nfs.yaml

   The following code block shows a sample template:

   # Output
   apiVersion: storage.k8s.io/v1
   kind: StorageClass
   metadata:
      name: nfs
   provisioner: diskplugin.csi.alibabacloud.com
   parameters:
       type: cloud_ssd
   reclaimPolicy: Retain

   Run the following command to deploy the application:

   kubectl apply -f nfs.yaml

   Expected output:

   storageclass.storage.k8s.io/nfs created

2. Restore the WordPress application.
   Use Velero to restore the WordPress application in the ACK cluster. This completes the migration process.

   velero restore create --from-backup wordpress-backup-with-pv
   velero restore get

   Expected output:

   NAME                                      BACKUP                     STATUS       WARNINGS   ERRORS   CREATED                         SELECTOR
   wordpress-backup-with-pv-20191212152745   wordpress-backup-with-pv   InProgress   0          0        2019-12-12 15:27:45 +0800 CST   <none>

   Run the following command to check the status of the WordPress application. An error is returned to indicate that the container images cannot be pulled.

   $ kubectl -n wordpress get po

   Expected output:

   NAME                         READY   STATUS         RESTARTS   AGE
   mysql-669b4666cd-trsnz       0/1     ErrImagePull   0          19m
   mysql-74dddbdcc8-h2tls       0/1     Init:0/1       0          19m
   wordpress-7cf5849f47-mbvx4   0/1     Init:0/1       0          19m
   wordpress-bb5d74d95-xcjxw    0/1     ErrImagePull   0          19m

Update application configurations

Application configurations include the image address, service exposure method, and the mount point of the storage disks used by the application. In this example, only the image address is updated.

1. Log on to the Container Service for Kubernetes (ACK) console.
2. In the left-side navigation pane, Choose Applications > Deployments. Select the cluster and namespace to which the application is migrated.
3. Find the WordPress application, and choose More > View in Yaml in the Actions column.
4. In the Edit YAML dialog box, change the image field to the address of the application image after migration and click Update.
   Note You can obtain the address of the application image after migration from the Prerequisites section in this topic.
   Run the following command to check the status of the WordPress application:

   kubectl -n wordpress get po

   Expected output:

   NAME                         READY   STATUS    RESTARTS   AGE
   mysql-678b5d8499-vckfd       1/1     Running   0          100s
   wordpress-8566f5f7d8-7shk6   1/1     Running   0          3m18s

Debug and start the application.

# 1. Create a StorageClass named nfs.
cat nfs-sc.yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: nfs
provisioner: helm.default/nfs
reclaimPolicy: Delete
kubectl apply -f  nfs-sc.yaml

# 2. Create a Secret to store the password of the MySQL component. For example, if the password is mysql, run the echo -n "mysql" |base64 command to query the Base64-encoded string of the password.
cat secret.yaml
apiVersion: v1
kind: Secret
metadata:
  name: mysql
type: Opaque
data:
  password: bXlzcWw=
kubectl apply -f secret.yaml

# 3. Create a Service, a persistent volume claim (PVC), and a Deployment for the MySQL component.
cat mysql.yaml
apiVersion: v1
kind: Service
metadata:
  name: mysql
  labels:
    app: mysql
spec:
  type: ClusterIP
  ports:
    - port: 3306
  selector:
    app: mysql
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-volumeclaim
  annotations:
    volume.beta.kubernetes.io/storage-class: "nfs"
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: mysql
  labels:
    app: mysql
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mysql
  template:
    metadata:
      labels:
        app: mysql
    spec:
      securityContext:
        runAsUser: 999
        runAsGroup: 999
        fsGroup: 999
      containers:
        - image: registry.api.paas.com:5000/admin/mysql:8
          name: mysql
          args:
            - "--default-authentication-plugin=mysql_native_password"
          env:
            - name: MYSQL_ROOT_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: mysql
                  key: password
          ports:
            - containerPort: 3306
              name: mysql
          volumeMounts:
            - name: mysql-persistent-storage
              mountPath: /var/lib/mysql
      volumes:
        - name: mysql-persistent-storage
          persistentVolumeClaim:
            claimName: mysql-volumeclaim
kubectl apply -f mysql.yaml

 # 4. Create a PVC, a Deployment, and a Service for the WordPress component.
cat wordpress.yaml
apiVersion: v1
kind: Service
metadata:
  labels:
    app: wordpress
  name: wordpress
spec:
  ports:
    - port: 80
      targetPort: 80
      protocol: TCP
      nodePort: 31570
  selector:
    app: wordpress
  type: NodePort
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: wordpress-volumeclaim
  annotations:
    volume.beta.kubernetes.io/storage-class: "nfs"
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: wordpress
  labels:
    app: wordpress
spec:
  replicas: 1
  selector:
    matchLabels:
      app: wordpress
  template:
    metadata:
      labels:
        app: wordpress
    spec:
      containers:
        - image: registry.api.paas.com:5000/admin/wordpress
          name: wordpress
          env:
          - name: WORDPRESS_DB_HOST
            value: mysql:3306
          - name: WORDPRESS_DB_PASSWORD
            valueFrom:
              secretKeyRef:
                name: mysql
                key: password
          ports:
            - containerPort: 80
              name: wordpress
          volumeMounts:
            - name: wordpress-persistent-storage
              mountPath: /var/www/html
      volumes:
        - name: wordpress-persistent-storage
          persistentVolumeClaim:
            claimName: wordpress-volumeclaim
 kubectl apply -f wordpress.yaml