OCM Stateful application samples, including Ramen resources.
Clone this git repository to get started:
git clone https://github.com/RamenDR/ocm-ramen-samples.git
cd ocm-ramen-samples
Switch kubeconfig to point to the OCM Hub cluster
kubectl config use-context hub
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
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
In the workloads directory provides samples that can be deployed on Kubernetes and OpenShift.
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.
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
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
To undeploy an application delete the subscription overlay used to deploy the application:
kubectl delete -k subscription/deployment-k8s-regional-rbd
Change the Placement to be reconciled by Ramen
kubectl annotate placement placement -n deployment-rbd \
cluster.open-cluster-management.io/experimental-scheduling-disable=true
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.
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.
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.