Container Service for Kubernetes (ACK) allows you to back up and restore stateful applications deployed in an ACK cluster. This is an all-in-one solution to achieve crash consistency, application consistency, and cross-region disaster recovery for stateful applications in ACK clusters. This topic describes how to migrate applications across clusters by using the application backup feature or Velero.

Prerequisites

Two Kubernetes clusters of the same version are created. For more information, see Create a managed Kubernetes cluster.

Introduction

In this example, a cluster named Cluster_A and a cluster named Cluster_B are used. The following example shows how to back up an application in Cluster_A and restore the application to Cluster_B.
Notice Make sure that the two clusters run the same Kubernetes version. Otherwise, you cannot migrate the application to the specified cluster.
Architecture

Method 1: Migrate an application by using the application backup feature

  1. Grant the required Object Storage Service (OSS) permissions to Cluster_A and Cluster_B. For more information, see Configure OSS permissions.
  2. Install the application backup component in Cluster_A and Cluster_B. For more information, see Install the application backup component.
  3. Create backup vaults for Cluster_A and Cluster_B. When you create backup vaults for Cluster_A and Cluster_B, select the same OSS bucket and set Network Type to Public Network. For more information, see Create a backup vault.
  4. Create a backup task in Cluster_A. For more information, see Create a backup task.
    After you create the backup task in Cluster_A, you can log on to Cluster_B to view the backup task on the Backups tab of the Application Backup page.
  5. On the Application Backup page, click the Restore tab and create a restoration task based on the backup task that is created in Cluster_A. For more information, see Create a restoration task.

Method 2: Migrate an application by using Velero

This example shows how to migrate an application in the nginx-examples namespace from Cluster_A to Cluster_B. To migrate the application, perform the following steps:

  1. Install the Velero client and the application backup component in Cluster_A. Then, configure and connect to the OSS bucket named mybackups. For more information, see velero and Install the application backup component.
  2. Install the Velero client and migrate-controller in Cluster_B. Then, configure and connect to the OSS bucket named mybackups.
  3. Back up applications in the nginx-examples namespace in Cluster_A and specify the name of the backup file, for example, nginx-backup.
  4. Use the backup file named nginx-backup in Cluster_B to restore the applications. This operation migrates the applications from Cluster_A to Cluster_B.

In this example, an application in Cluster_A is backed up and then restored to Cluster_B. This way, the application is migrated from Cluster_A to Cluster_B. Before you back up and restore the application, you must complete the operations in Step 1 and Step 2. The following example shows how to back up and restore the application:

  1. Deploy the sample application named nginx-app-with-pv in Cluster_A.
    1. Create a file named nginx-app-with-pv.yaml and copy the following content to the file: 
      ---
apiVersion: v1
kind: Namespace
metadata:
  name: nginx-example
  labels:
    app: nginx

---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: nginx-logs
  namespace: nginx-example
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
  storageClassName: alicloud-disk-ssd

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  namespace: nginx-example
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: nginx
      annotations:
        pre.hook.backup.velero.io/container: fsfreeze
        pre.hook.backup.velero.io/command: '["/sbin/fsfreeze", "--freeze", "/var/log/nginx"]'
        post.hook.backup.velero.io/container: fsfreeze
        post.hook.backup.velero.io/command: '["/sbin/fsfreeze", "--unfreeze", "/var/log/nginx"]'
    spec:
      volumes:
        - name: nginx-logs
          persistentVolumeClaim:
           claimName: nginx-logs
      containers:
      - image: nginx:1.7.9
        name: nginx
        ports:
        - containerPort: 80
        volumeMounts:
          - mountPath: "/var/log/nginx"
            name: nginx-logs
            readOnly: false
      # sync from gcr.io/heptio-images/fsfreeze-pause:latest
      - image: registry.cn-hangzhou.aliyuncs.com/acs/fsfreeze-pause:latest
        name: fsfreeze
        securityContext:
          privileged: true
        volumeMounts:
          - mountPath: "/var/log/nginx"
            name: nginx-logs
            readOnly: false
    2. Run the following command to deploy the application to Cluster_A: 
      kubectl apply -f nginx-app-with-pv.yam
  2. Run the following commands to view information about the application.
    • Run the following command to query the Deployment: 
      kubectl -n nginx-example get deployment

      Expected output:

      NAME                                     READY   UP-TO-DATE   AVAILABLE   AGE
deployment.extensions/nginx-deployment   1/1     1            1           108s
    • Run the following command to view the pod: 
      kubectl -n nginx-example get pod

      Expected output:

      NAME                                    READY   STATUS    RESTARTS   AGE
pod/nginx-deployment-7477779c4f-rz95l   2/2     Running   0          108s
    • Run the following command to query information about the PVC: 
      kubectl -n nginx-example get pvc

      Expected output:

      NAME                               STATUS   VOLUME                   CAPACITY   ACCESS MODES   STORAGECLASS        AGE
persistentvolumeclaim/nginx-logs   Bound    d-bp1eutshfe774exa5os2   20Gi       RWO            alicloud-disk-ssd   108s
  3. Back up the namespace to which the application belongs.
    • Run the following command to back up the namespace to which the application belongs (excluding PV data): 
      velero backup create nginx-backup-without-pv --include-namespaces nginx-example
    • Run the following command to back up the namespace to which the application belongs (including PV data).
      1. Run the following command to add annotations to the pod volume that needs to be backed up: 
        kubectl -n nginx-example annotate pod/nginx-deployment-7477779c4f-rz95l backup.velero.io/backup-volumes=nginx-logs
      2. Run the following command to back up the application: 
        velero backup create nginx-backup-with-pv --include-namespaces nginx-example
  4. Optional:Run the following command to view information about the backup file: 
    velero backup get

    Expected output (excluding PV data):

    NAME                      STATUS      ERRORS   WARNINGS   CREATED                         EXPIRES   STORAGE LOCATION   SELECTOR
nginx-backup-without-pv   Completed   0        0          2020-09-18 14:43:13 +0800 CST   29d       default            <none>
    The output indicates that a backup file is created for the application.
  5. Run the following command to restore the application to Cluster_B (excluding PV data): 
    velero restore create --from-backup nginx-backup-without-pv