ocm-ramen-samples

OCM Stateful application samples, including Ramen resources.

Initial setup

1. Clone this git repository to get started:

   git clone https://github.com/RamenDR/ocm-ramen-samples.git
   cd ocm-ramen-samples
   

2. Switch kubeconfig to point to the OCM Hub cluster

   kubectl config use-context hub
   

3. Create DRClusters and DRPolicy

   When using the ramen testing environment this is not needed, but if you are using your own Kubernetes clusters you need to create the resources.

   Modify the DRCluster and DRpolicy resources in the ramen directory to match the actual cluster names in your environment, and apply the kustomization:

   kubectl apply -k ramen
   

   This creates DRPolicy and DRCluster resources in the cluster namespace that can be viewed using:

   kubectl get drcluster,drpolicy
   

4. Setup the common OCM channel resources on the hub:

   kubectl apply -k channel
   

   This creates a Channel resource in the ramen-samples namespace and can be viewed using:

   kubectl get channel ramen-gitops -n ramen-samples
   

Sample applications

In the workloads directory provides samples that can be deployed on Kubernetes and OpenShift.

• deployment - busybox deployment
• kubevirt
  • vm-pvc - PVC based VM
  • vm-dv - DataVolume based VM
  • vm-dvt - DataVolumeTemplate based VM

Deploying a sample application

In the example we use the busybox deployment for Kubernetes regional DR environment using RBD storage:

subscription/deployment-k8s-regional-rbd

This application is deployed in the deployment-rbd namespace on the hub and managed clusters.

You can use other overlays to deploy on other cluster types or use different storage class. You can also create your own overlays based on the examples.

1. Deploy an OCM application subscription on hub:

   kubectl apply -k subscription/deployment-k8s-regional-rbd
   

   This creates the required Subscription, Placement, and ManagedClusterSetBinding resources for the deployment in the deployment-rbd namespace and can be viewed using:

   kubectl get subscription,placement -n deployment-rbd
   

2. Inspect subscribed resources from the channel created in the same namespace on the ManagedCluster selected by the Placement.

   The busybox deployment Placement status can be viewed on the hub using:

   kubectl get placement placement -n deployment-rbd
   

   The Busybox deployment subscribed resources, like the pod and the PVC can be viewed on the ManagedCluster using (example ManagedCluster dr1):

   kubectl get pod,pvc -n deployment-rbd --context dr1
   

Undeploying a sample application

To undeploy an application delete the subscription overlay used to deploy the application:

kubectl delete -k subscription/deployment-k8s-regional-rbd

Enable DR for a deployed application

1. Change the Placement to be reconciled by Ramen

   kubectl annotate placement placement -n deployment-rbd \
      cluster.open-cluster-management.io/experimental-scheduling-disable=true
   

2. Deploy a DRPlacementControl resource for the OCM application on the hub, for example:

   kubectl apply -k dr/deployment-k8s-regional-rbd
   

   This creates a DRPlacementControl resource for the busybox deployment in the deployment-rbd namespace and can be viewed using:

   kubectl get drpc -n deployment-rbd
   

   At this point the placement of the application is managed by Ramen.

Disable DR for a DR enabled application

1. Delete the drpc resource for the OCM application on the hub:

   kubectl delete -k dr/deployment-k8s-regional-rbd
   

   This deletes the DRPlacementControl resource for the busybox deployment, disabling replication and removing replicated data.

Important

Do not delete the Placement annotation cluster.open-cluster-management.io/experimental-scheduling-disable to ensure that OCM will not change the placement of the application, which can result in data loss.

Optional: enabling OCM scheduling for the application

It is not recommended to enable OCM scheduling on after disabling DR, since OCM does not support moving workload storage between clusters. If the placement point to wrong cluster, OCM will delete the application and its storage from the current cluster, and deploy the application with new storage on the cluster selected by the placement.

Find the current placement of the application:

kubectl get placementdecisions -n deployment-rbd --context hub \
    -o jsonpath='{.items[0].status.decisions[0].clusterName}{"\n"}'

Ensure that the Placement predicates is pointing to the cluster where the workload is currently placed. Here is example predicates selecting the cluster dr1:

spec:
  clusterSets:
  - default
  numberOfClusters: 1
  predicates:
  - requiredClusterSelector:
      claimSelector: {}
      labelSelector:
        matchExpressions:
        - key: name
          operator: In
          values:
          - dr1

Change the Placement to be reconciled by OCM:

kubectl annotate placement placement -n deployment-rbd \
    cluster.open-cluster-management.io/experimental-scheduling-disable-

At this point the application is managed again by OCM.