🌱 workspace_reconcile_scheduling: allow for skipping a shard with a special annotation during scheduling

pkg/reconciler/tenancy/workspace/workspace_reconcile_scheduling.go

@@ -53,8 +53,13 @@ const (
 	// WorkspaceShardHashAnnotationKey keeps track on which shard LogicalCluster must be scheduled. The value
 	// is a base36(sha224) hash of the Shard name.
 	WorkspaceShardHashAnnotationKey = "internal.tenancy.kcp.io/shard"
+
 	// workspaceClusterAnnotationKey keeps track of the logical cluster on the shard.
 	workspaceClusterAnnotationKey = "internal.tenancy.kcp.io/cluster"
+
+	// unschedulableAnnotationKey is the annotation key used to indicate that a shard is unschedulable.
+	// The annotation is meant to be used by e2e tests that otherwise started a private instance of kcp server.
+	unschedulableAnnotationKey = "experimental.core.kcp.io/unschedulable"
 )
 
 type schedulingReconciler struct {
@@ -194,6 +199,10 @@ func (r *schedulingReconciler) chooseShardAndMarkCondition(logger klog.Logger, w
 		reason, message string
 	}{}
 	for _, shard := range shards {
+		if _, ok := shard.Annotations[unschedulableAnnotationKey]; ok {
+			logger.V(4).Info("Skipping a shard because it is annotated as unschedulable", "shard", shard.Name, "annotation", unschedulableAnnotationKey)
+			continue
+		}
 		if valid, reason, message := isValidShard(shard); valid {
 			validShards = append(validShards, shard)
 		} else {

pkg/reconciler/tenancy/workspace/workspace_reconcile_scheduling_test.go

@@ -253,6 +253,32 @@ func TestReconcileScheduling(t *testing.T) {
 			},
 			expectedStatus: reconcileStatusStopAndRequeue,
 		},
+		{
+			name: "only an unschedulable shard is available, the ws is unscheduled",
+			initialShards: []*corev1alpha1.Shard{func() *corev1alpha1.Shard {
+				s := shard("amber")
+				s.Annotations[unschedulableAnnotationKey] = "true"
+				return s
+			}()},
+			targetWorkspace:      workspace("foo"),
+			targetLogicalCluster: &corev1alpha1.LogicalCluster{},
+			validateWorkspace: func(t *testing.T, initialWS, wsAfterReconciliation *tenancyv1alpha1.Workspace) {
+				t.Helper()
+
+				clearLastTransitionTimeOnWsConditions(wsAfterReconciliation)
+				initialWS.Status.Conditions = append(initialWS.Status.Conditions, conditionsapi.Condition{
+					Type:     tenancyv1alpha1.WorkspaceScheduled,
+					Severity: conditionsapi.ConditionSeverityError,
+					Status:   corev1.ConditionFalse,
+					Reason:   tenancyv1alpha1.WorkspaceReasonUnschedulable,
+					Message:  "No available shards to schedule the workspace",
+				})
+				if !equality.Semantic.DeepEqual(wsAfterReconciliation, initialWS) {
+					t.Fatal(fmt.Errorf("unexpected Workspace:\n%s", cmp.Diff(wsAfterReconciliation, initialWS)))
+				}
+			},
+			expectedStatus: reconcileStatusContinue,
+		},
 	}
 	for _, scenario := range scenarios {
 		t.Run(scenario.name, func(t *testing.T) {