Latest KBE Blog Post - Migrating to Kubernetes with Open Source Tools

Subscribing to an Operator

Begin my creating a new namespace called myproject. Set kubectl to consider it your default namespace, so that you don't have to specify it with every command.

kubectl create namespace myproject
kubectl config set-context --current --namespace=myproject

Next, create an OperatorGroup to ensure Operators installed to this namespace will be capable of watching for Custom Resources within the myproject namespace.

cat > mariadb-operatorgroup.yaml <<EOF
apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
  name: mariadb-operatorgroup
  namespace: myproject
spec:
  targetNamespaces:
    - myproject
EOF

Create the OperatorGroup:

oc create -f mariadb-operatorgroup.yaml

Verify the OperatorGroup has been successfully created:

oc get operatorgroup mariadb-operatorgroup

Create a Subscription manifest for the MariaDB Operator. Ensure the installPlanApproval is set to Manual. This allows you to review the InstallPlan before choosing to install the Operator:

cat > mariadb-subscription.yaml <<EOF
apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  name: mariadb-operator-app
  namespace: myproject 
spec:
  channel: alpha
  installPlanApproval: Manual
  name: mariadb-operator-app
  source: operatorhubio-catalog
  sourceNamespace: olm
EOF

Create the Subscription:

kubectl create -f mariadb-subscription.yaml

And verify the Subscription was created:

kubectl get subscription

Creating the subscription triggers OLM to generate an InstallPlan:

kubectl get installplan

Fetch the InstallPlan and observe the Kubernetes objects that will be created once it is approved:

MARIADB_INSTALLPLAN=`kubectl get installplan -o jsonpath={$.items[0].metadata.name}`
kubectl get installplan $MARIADB_INSTALLPLAN -o yaml

Install the Operator by approving the InstallPlan. You can kubectl edit installplan $MARIADB_INSTALLPLAN, change the value of Approved to true, then save the file to apply the change. OR, run the following command to set Approved=true in one shot:

kubectl patch installplan $MARIADB_INSTALLPLAN --type='json' -p '[{"op": "replace", "path": "/spec/approved", "value":true}]'

Once the InstallPlan is approved, you will see the newly provisioned ClusterServiceVersion, ClusterResourceDefinition, Role and RoleBindings, Service Accounts, and MariaDB Operator Deployment.

kubectl get clusterserviceversion
kubectl get crd | grep mariadb
kubectl get serviceaccounts | grep mariadb
kubectl get roles | grep mariadb
kubectl get rolebindings | grep mariadb
kubectl get deployments

When the MariaDB Operator is running, you can observe its logs:

MARIADB_OPERATOR=`kubectl get pods -o jsonpath={$.items[0].metadata.name}`
kubectl logs $MARIADB_OPERATOR

The MariaDB Operator is now installed and running, watching for the creation of a MariaDB Custom Resource (CR) in the `myproject` namespace.