Chapter 11. Creating a sample application

Procedure

1. Create a namespace or project on the Hub cluster for a busybox sample application.

   $ oc new-project busybox-sample

   Note

   A different project name other than busybox-sample can be used if desired. Make sure when deploying the sample application via the Advanced Cluster Manager console to use the same project name as what is created in this step.

2. Create DRPlacementControl resource

   DRPlacementControl is an API available after the OpenShift DR Hub Operator is installed on the Hub cluster. It is broadly an Advanced Cluster Manager PlacementRule reconciler that orchestrates placement decisions based on data availability across clusters that are part of a DRPolicy.

   1. On the Hub cluster, navigate to Installed Operators in the busybox-sample project and click on OpenShift DR Hub Operator. You should see two available APIs, DRPolicy and DRPlacementControl.
   2. Create an instance for DRPlacementControl and then go to the YAML view. Make sure the busybox-sample project is selected.

   3. Copy and save the following YAML to filename busybox-drpc.yaml after replacing <cluster1> with the correct name of your managed cluster in Advanced Cluster Manager.

      apiVersion: ramendr.openshift.io/v1alpha1
      kind: DRPlacementControl
      metadata:
        labels:
          app: busybox-sample
        name: busybox-drpc
      spec:
        drPolicyRef:
          name: odr-policy
        placementRef:
          kind: PlacementRule
          name: busybox-placement
        preferredCluster: <cluster1>
        pvcSelector:
          matchLabels:
            appname: busybox

   4. Copy the contents of your unique busybox-drpc.yaml file into the YAML view (completely replacing original content).

   5. Click Create on the YAML view screen.

      You can also create this resource using the following CLI command:

      $ oc create -f busybox-drpc.yaml -n busybox-sample

      Example output:

      drplacementcontrol.ramendr.openshift.io/busybox-drpc created

      Important

      This resource must be created in the busybox-sample namespace (or whatever namespace you created earlier).

3. Create Placement Rule resource that defines the target clusters where resource templates can be deployed. Use placement rules to facilitate the multicluster deployment of your applications.

   1. Copy and save the following YAML to filename busybox-placementrule.yaml.

      apiVersion: apps.open-cluster-management.io/v1
      kind: PlacementRule
      metadata:
        labels:
          app: busybox-sample
        name: busybox-placement
      spec:
        clusterConditions:
        - status: "True"
          type: ManagedClusterConditionAvailable
        clusterReplicas: 1
        schedulerName: ramen

   2. Create the Placement Rule resource for the busybox-sample application.

      $ oc create -f busybox-placementrule.yaml -n busybox-sample

      Example output:

      placementrule.apps.open-cluster-management.io/busybox-placement created

      Important

      This resource must be created in the busybox-sample namespace (or whatever namespace you created earlier).

4. Create sample application using RHACM console

   1. Log in to the RHACM console using your OpenShift credentials if not already logged in.

      $ oc get route multicloud-console -n open-cluster-management -o jsonpath --template="https://{.spec.host}/multicloud/applications{'\n'}"

      Example Output:

      https://multicloud-console.apps.perf3.example.com/multicloud/applications

   2. Navigate to Applications and click Create application.
   3. Select type as Subscription.
   4. Enter your application Name (for example, busybox) and Namespace (for example, busybox-sample).
   5. In Repository location for resources section, select Repository type Git.

   6. Enter the Git repository URL for the sample application, the github Branch and Path where the resources busybox Pod and PVC will be created.

      Use the sample application repository as https://github.com/RamenDR/ocm-ramen-samples where the Branch is main and Path is busybox-odr-metro.

   7. Scroll down the form to the section Select clusters to deploy to and click Select an existing placement configuration.
   8. Select an Existing Placement Rule (for example, busybox-placement) from the drop-down list.

   9. Click Save.

      On the follow-on screen scroll to the bottom. You should see that there are all Green checkmarks on the application topology.

      Note

      To get more information, click on any of the topology elements and a window will appear on the right of the topology view.

5. Validating the sample application deployment and replication.

   Now that the busybox application has been deployed to your preferred Cluster (specified in the DRPlacementControl) the deployment can be validated.

   1. Login to your managed cluster where busybox was deployed by RHACM.

      $ oc get pods,pvc -n busybox-sample

      Example output:

      NAME          READY   STATUS    RESTARTS   AGE
      pod/busybox   1/1     Running   0          6m
      
      NAME                                STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS                  AGE
      persistentvolumeclaim/busybox-pvc   Bound    pvc-a56c138a-a1a9-4465-927f-af02afbbff37   1Gi        RWO            ocs-storagecluster-ceph-rbd   6m

   2. Verify that the replication resources are also created for the busybox PVC.

      $ oc get volumereplicationgroup -n busybox-sample

      Example output:

      NAME                                                       AGE
      volumereplicationgroup.ramendr.openshift.io/busybox-drpc   6m