Ignore topology.gke.io/zone when comparing groups

Commit bb2eed1cff introduced a new `topology.gke.io/zone` label to
GCE nodes templates, for CSI needs.

That label holds zone name, making nodeInfo templates dissimilar
for groups belonging to different zones. The CA otherwise tries to
ignore those zonal labels (ie. it ignores the standards LabelZoneRegion
and LabelZoneFailureDomain) when it looks for nodegroups similarities.

cluster-autoscaler/main.go

@@ -309,6 +309,8 @@ func buildAutoscaler() (core.Autoscaler, error) {
 		nodeInfoComparatorBuilder = nodegroupset.CreateAzureNodeInfoComparator
 	} else if autoscalingOptions.CloudProviderName == cloudprovider.AwsProviderName {
 		nodeInfoComparatorBuilder = nodegroupset.CreateAwsNodeInfoComparator
+	} else if autoscalingOptions.CloudProviderName == cloudprovider.GceProviderName {
+		nodeInfoComparatorBuilder = nodegroupset.CreateGceNodeInfoComparator
 	}
 
 	opts.Processors.NodeGroupSetProcessor = &nodegroupset.BalancingNodeGroupSetProcessor{

cluster-autoscaler/processors/nodegroupset/gce_nodegroups.go

@@ -0,0 +1,42 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package nodegroupset
+
+import (
+	schedulerframework "k8s.io/kubernetes/pkg/scheduler/framework/v1alpha1"
+)
+
+// CreateGceNodeInfoComparator returns a comparator that checks if two nodes should be considered
+// part of the same NodeGroupSet. This is true if they match usual conditions checked by IsCloudProviderNodeInfoSimilar,
+// even if they have different GCE-specific labels.
+func CreateGceNodeInfoComparator(extraIgnoredLabels []string) NodeInfoComparator {
+	gceIgnoredLabels := map[string]bool{
+		"topology.gke.io/zone": true,
+	}
+
+	for k, v := range BasicIgnoredLabels {
+		gceIgnoredLabels[k] = v
+	}
+
+	for _, k := range extraIgnoredLabels {
+		gceIgnoredLabels[k] = true
+	}
+
+	return func(n1, n2 *schedulerframework.NodeInfo) bool {
+		return IsCloudProviderNodeInfoSimilar(n1, n2, gceIgnoredLabels)
+	}
+}