Occasionally, when you’re moving between major versions of Kubernetes or Red Hat OpenShift, you’ll want to migrate your applications between clusters. Or, if you’re moving between two clouds, you’ll want an easy way to migrate your workloads from one platform to another.
The Crane operator from the open source Konveyor project automates this migration process for you. The Konveyor site offers a selection of helpful projects to administer your cluster. Crane is designed to automate migration from one cluster to another and is surprisingly easy to get working.
This tutorial shows you how we moved a default sample application from an OpenShift cluster hosted on AWS to an OpenShift cluster hosted on IBM Cloud. To see how it’s done, watch this video or read the steps below.
Install the Crane operator
First, log into the cluster console where your original application is hosted and also log into the console of the destination where you want to migrate your application. In our example, we logged into the OpenShift Service on AWS as our origin console and, in another tab, logged into the Red Hat OpenShift on IBM Cloud console as our destination console.
From the Operator Hub in both consoles, search for “Crane Operator” and follow the default prompts to install the operator.
Set up your sample application
From your origin cluster, choose the Developer profile and then click +Add to add a project where you will deploy your application into.
Choose a sample app to play with. In our example, we chose the Python application.
Name the sample app and then click Create. It will pull the source information from GitHub and build an image, deploy the image, and expose it as a PHP endpoint.
Change back from a Developer profile to the Admin profile to confirm your operator has installed correctly.
Create a migration (MIG) controller
Now it’s time to create your migration controller.
Go to your migration cluster (in this example, our IBM console), select the Crane operator, and select Create migration controller. Do the same on the origin cluster (in our example, AWS).
Switch to the
Update the host MIG controller.
apiVersion: migration.openshift.io/v1alpha1 kind: MigCluster metadata: name: host namespace: openshift-migration spec: isHostCluster: true
Then you can apply your migration cluster.
kubectl apply -f origin-migcluster.yaml
NOTE: Run only this following command on the remote cluster
Save your service account secret for the destination cluster.
oc sa get-token migration-controller -n openshift-migration | base64 -w 0
Write this into
sa-secret-remote.yamlon your origin cluster:
apiVersion: v1 kind: Secret metadata: name: sa-token-remote namespace: openshift-config type: Opaque data: # [!] Change saToken to contain a base64 encoded SA token with cluster-admin # privileges on the remote cluster. # `oc sa get-token migration-controller -n openshift-migration | base64 -w 0` saToken: <your-base64-encoded-aws-sa-token-here>
kubectl apply -f sa-secret-remote.yaml
Add your destination cluster:
apiVersion: migration.openshift.io/v1alpha1 kind: MigCluster metadata: name: src-ocp-3-cluster namespace: openshift-migration spec: insecure: true isHostCluster: false serviceAccountSecretRef: name: sa-token-remote namespace: openshift-config url: 'https://master.ocp3.mycluster.com/'
kubectl apply -f dest-migcluster.yaml
Configure s3 credentials to host migration storage. Included here is the correct access key for my files. You’ll need to have that handy.
apiVersion: v1 kind: Secret metadata: namespace: openshift-config name: migstorage-creds type: Opaque data: aws-access-key-id: aGVsbG8K aws-secret-access-key: aGVsbG8K
kubectl apply -f mig-storage-creds.yaml
Configure MIG storage to use s3
apiVersion: migration.openshift.io/v1alpha1 kind: MigStorage metadata: name: aws-s3 namespace: openshift-migration spec: backupStorageConfig: awsBucketName: konveyor-jj-migration # You need to change this for your s3 bucket credsSecretRef: name: migstorage-creds namespace: openshift-config backupStorageProvider: aws volumeSnapshotConfig: credsSecretRef: name: migstorage-creds namespace: openshift-config volumeSnapshotProvider: aws
kubectl apply -f migstorage.yaml
Create the migration plan. THe plan is essentially saying: “This is what I want”. The plan says what namespace you want to move. In this example, it’s
project-aas referenced below.
apiVersion: migration.openshift.io/v1alpha1 kind: MigPlan metadata: name: migrate-project-a namespace: openshift-migration spec: destMigClusterRef: name: destination namespace: openshift-migration indirectImageMigration: true indirectVolumeMigration: true srcMigClusterRef: name: host namespace: openshift-migration migStorageRef: name: aws-s3 namespace: openshift-migration namespaces: - project-a # notice this is where you'd add other projects persistentVolumes: 
kubectl apply -f migplan.yaml
Execute your migration plan.
apiVersion: migration.openshift.io/v1alpha1 kind: MigMigration metadata: name: migrate-project-a-execute namespace: openshift-migration spec: migPlanRef: name: migrate-project-a namespace: openshift-migration quiescePods: true stage: false
kubectl apply -f migplanexecute.yaml
Watch the magic
Back in your original console, you can find the correct namespace and see that things have moved.
Go back to the origin OpenShift console (AWS in our example). Bring up the migration GUI from the openshift-migration namespace. Check through the migration plans which show you the migration or watch the logs to see the migration happening.
Or, watch the progress via the CLI if you prefer.
kubectl logs -f migration-log-reader-<hash> color
You can also open your destination console (Red Hat OpenShift on IBM Cloud in our example) and see if the new cluster has migrated.
Hopefully walking through these steps has helped you understand the power that Crane can offer you when migrating workloads between clusters. This was only a sample application. With a little work and testing, you should be able to leverage Crane for your applications. If you have any questions or thoughts, come around to #konveyor on the Kubernetes public Slack channel, and the team would me more then willing to help advise you.
Happy migrating your apps!