Validate control-plane quorum only on OpenShift

Assert if cluster was installed on OpenShift, since only there a quorum PDB exists, otherwise we have nothing to assert

Dockerfile

@@ -18,6 +18,7 @@ RUN export GO_VERSION=$(grep -E "go [[:digit:]]\.[[:digit:]][[:digit:]]" go.mod
 # Copy the go source
 COPY api/ api/
 COPY controllers/ controllers/
+COPY pkg/ pkg/
 COPY hack/ hack/
 COPY main.go main.go
 COPY vendor/ vendor/

api/v1beta1/nodemaintenance_webhook.go

@@ -32,6 +32,8 @@ import (
 	logf "sigs.k8s.io/controller-runtime/pkg/log"
 	"sigs.k8s.io/controller-runtime/pkg/webhook"
 	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
+
+	"github.com/medik8s/node-maintenance-operator/pkg/utils"
 )
 
 const (
@@ -163,7 +165,12 @@ func (v *NodeMaintenanceValidator) validateNoNodeMaintenanceExists(nodeName stri
 }
 
 func (v *NodeMaintenanceValidator) validateControlPlaneQuorum(nodeName string) error {
-	// check if the node is a control-plane node
+	if !utils.IsOpenshiftSupported {
+		// etcd quorum PDB is only installed in OpenShift
+		nodemaintenancelog.Info("Cluster does not have etcd quorum PDB, thus we can't asses control-plane quorum violation")
+		return nil
+	}
+	// check if the node is a control-plane node on OpenShift
 	node, err := getNode(nodeName, v.client)
 	if err != nil {
 		return fmt.Errorf("could not get node for master/control-plane quorum validation, please try again: %v", err)
@@ -174,11 +181,13 @@ func (v *NodeMaintenanceValidator) validateControlPlaneQuorum(nodeName string) e
 		// not a control-plane node, nothing to do
 		return nil
 	}
-	canDisrupt, err := etcd.IsEtcdDisruptionAllowed(context.Background(), v.client, nodemaintenancelog, node)
+	// The node is a control-plane node on OpenShift
+	// now we check if adding nm CR for this node will disrupt control-plane quorum
+	isDisruptionAllowed, err := etcd.IsEtcdDisruptionAllowed(context.Background(), v.client, nodemaintenancelog, node)
 	if err != nil {
 		return err
 	}
-	if !canDisrupt {
+	if !isDisruptionAllowed {
 		return fmt.Errorf(ErrorControlPlaneQuorumViolation, nodeName)
 	}
 	return nil

api/v1beta1/nodemaintenance_webhook_test.go

@@ -11,6 +11,8 @@ import (
 	policyv1 "k8s.io/api/policy/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"sigs.k8s.io/controller-runtime/pkg/client"
+
+	"github.com/medik8s/node-maintenance-operator/pkg/utils"
 )
 
 var _ = Describe("NodeMaintenance Validation", func() {
@@ -91,6 +93,10 @@ var _ = Describe("NodeMaintenance Validation", func() {
 				node = getTestNode(existingNodeName, true)
 				err := k8sClient.Create(context.Background(), node)
 				Expect(err).ToNot(HaveOccurred())
+				// mock IsOpenshiftSupported value and set it true for the quorum violation check
+				orgValue := utils.IsOpenshiftSupported
+				utils.IsOpenshiftSupported = true
+				DeferCleanup(func() { utils.IsOpenshiftSupported = orgValue })
 			})
 
 			AfterEach(func() {

main.go

@@ -43,6 +43,7 @@ import (
 
 	nodemaintenancev1beta1 "github.com/medik8s/node-maintenance-operator/api/v1beta1"
 	"github.com/medik8s/node-maintenance-operator/controllers"
+	"github.com/medik8s/node-maintenance-operator/pkg/utils"
 	"github.com/medik8s/node-maintenance-operator/version"
 	//+kubebuilder:scaffold:imports
 )
@@ -110,6 +111,13 @@ func main() {
 		setupLog.Error(err, "unable to set up lease Manager", "lease", "NodeMaintenance")
 		os.Exit(1)
 	}
+
+	if err := utils.ValidateIsOpenshift(mgr.GetConfig()); err != nil {
+		setupLog.Error(err, "failed to check if we run on Openshift")
+		os.Exit(1)
+	}
+	setupLog.Info("NMO was installed on Openshift cluster")
+
 
 	if err = (&controllers.NodeMaintenanceReconciler{
 		Client:       cl,

pkg/utils/validation.go

@@ -0,0 +1,33 @@
+package utils
+
+import (
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/rest"
+)
+
+// IsOpenshiftSupported will be set to true in case the operator was installed on OpenShift cluster
+var	IsOpenshiftSupported bool
+
+// ValidateIsOpenshift returns true if the cluster has the openshift config group
+func ValidateIsOpenshift(config *rest.Config) error {
+	dc, err := discovery.NewDiscoveryClientForConfig(config)
+	if err != nil {
+		return err
+	}
+	apiGroups, err := dc.ServerGroups()
+	if err != nil {
+		return err
+	}
+
+	kind := schema.GroupVersionKind{Group: "config.openshift.io", Version: "v1", Kind: "ClusterVersion"}
+	for _, apiGroup := range apiGroups.Groups {
+		for _, supportedVersion := range apiGroup.Versions {
+			if supportedVersion.GroupVersion == kind.GroupVersion().String() {
+				IsOpenshiftSupported = true
+				return nil
+			}
+		}
+	}
+	return nil
+}