fix(webhook): fix cspi node selector label in scale down operation (o…

…penebs-archive#122)

While scaling down a pool by removing a pool spec
from the CSPC, there was nil pool list getting initialized due to 
additional node-selector labels get added in pool list label-selector not
matches with existing CSPI labels, causing the webhook failures 

Signed-off-by: Ashutosh Kumar <ashutosh.kumar@mayadata.io>

pkg/webhook/cspc.go

@@ -28,7 +28,7 @@ import (
 	openebsapis "github.com/openebs/api/pkg/apis/openebs.io/v1alpha1"
 	"github.com/openebs/api/pkg/apis/types"
 	clientset "github.com/openebs/api/pkg/client/clientset/versioned"
-	util "github.com/openebs/api/pkg/util"
+	"github.com/openebs/api/pkg/util"
 	"github.com/pkg/errors"
 	"k8s.io/api/admission/v1beta1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -519,6 +519,7 @@ func (wh *webhook) validateCSPCUpdateRequest(req *v1beta1.AdmissionRequest, getC
 // that is being scaled down
 func (p *PoolOperations) ValidateScaledown() (bool, string) {
 	removedPools := []string{}
+
 	for _, oldPool := range p.OldCSPC.Spec.Pools {
 		found := false
 		for _, newPool := range p.NewCSPC.Spec.Pools {
@@ -528,10 +529,26 @@ func (p *PoolOperations) ValidateScaledown() (bool, string) {
 			}
 		}
 		if !found && p.IsScaledownCase(oldPool) {
+			var nodeName string
+			if v, ok := oldPool.NodeSelector[types.HostNameLabelKey]; ok {
+				nodeName = v
+			} else {
+				gotNodeName, err := GetHostNameFromLabelSelector(oldPool.NodeSelector, p.kubeClient)
+				if err != nil {
+					return false, fmt.Sprintf("Could not list node for node selectors {%v}", oldPool.NodeSelector)
+				}
+				nodeName = gotNodeName
+			}
+
+			ls := &metav1.LabelSelector{
+				MatchLabels: map[string]string{
+					types.CStorPoolClusterLabelKey: p.OldCSPC.Name,
+					types.HostNameLabelKey:         nodeName,
+				},
+			}
 			cspi, err := p.clientset.CstorV1().CStorPoolInstances(p.OldCSPC.Namespace).
 				List(metav1.ListOptions{
-					LabelSelector: labels.SelectorFromSet(oldPool.NodeSelector).String() + "," +
-						types.CStorPoolClusterLabelKey + "=" + p.OldCSPC.Name,
+					LabelSelector: labels.Set(ls.MatchLabels).String(),
 				})
 			if err != nil {
 				return false, fmt.Sprintf("Could not list cspi for cspc %s: %s", p.OldCSPC.Name, err.Error())