fix: pre-create namespace if doesn't exist in management cluster

Author: dkoshkin

pkg/handlers/generic/lifecycle/clusterautoscaler/strategy_crs.go

@@ -11,6 +11,7 @@ import (
 	"github.com/spf13/pflag"
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"sigs.k8s.io/cluster-api/controllers/remote"
 	runtimehooksv1 "sigs.k8s.io/cluster-api/exp/runtime/hooks/api/v1alpha1"
 	ctrlclient "sigs.k8s.io/controller-runtime/pkg/client"
 
@@ -114,7 +115,23 @@ func (s crsStrategy) apply(
 		targetCluster = cluster
 	}
 
-	if err := utils.EnsureCRSForClusterFromConfigMaps(ctx, cm.Name, s.client, targetCluster, cm); err != nil {
+	// In the case when existingManagementCluster is nil, i.e. when s.client points to a bootstrap cluster,
+	// it is possible that the namespace where the cluster will be moved to, and where the cluster-autoscaler resources
+	// will be created, does not exist yet.
+	// In that case, we need to create the namespace in the target cluster.
+	clusterKey := ctrlclient.ObjectKeyFromObject(targetCluster)
+	remoteClient, err := remote.NewClusterClient(ctx, "", s.client, clusterKey)
+	if err != nil {
+		return fmt.Errorf("error creating remote cluster client: %w", err)
+	}
+	if err = utils.EnsureNamespace(ctx, remoteClient, cluster.Namespace); err != nil {
+		return fmt.Errorf(
+			"failed to create Namespace in remote cluster: %w",
+			err,
+		)
+	}
+
+	if err = utils.EnsureCRSForClusterFromConfigMaps(ctx, cm.Name, s.client, targetCluster, cm); err != nil {
 		return fmt.Errorf(
 			"failed to apply cluster-autoscaler installation ClusterResourceSet: %w",
 			err,

pkg/handlers/generic/lifecycle/utils/utils.go

@@ -61,3 +61,28 @@ func EnsureCRSForClusterFromConfigMaps(
 
 	return nil
 }
+
+// EnsureNamespace will create the namespece if it does not exist.
+func EnsureNamespace(ctx context.Context, c ctrlclient.Client, name string) error {
+	ns := &corev1.Namespace{
+		TypeMeta: metav1.TypeMeta{
+			APIVersion: corev1.SchemeGroupVersion.String(),
+			Kind:       "Namespace",
+		},
+		ObjectMeta: metav1.ObjectMeta{
+			Name: name,
+		},
+	}
+
+	// check if namespace exists and return early if it does
+	if err := c.Get(ctx, ctrlclient.ObjectKeyFromObject(ns), ns); err == nil {
+		return nil
+	}
+
+	err := client.ServerSideApply(ctx, c, ns)
+	if err != nil {
+		return fmt.Errorf("failed to server side apply %w", err)
+	}
+
+	return nil
+}