Merge pull request kubernetes-sigs#5114 from cnmcavoy/cmcavoy/fix-subnet-sorting

🐛 Fix subnet sorting with multiple vpcs when launching an instance

Author: k8s-ci-robot

pkg/cloud/services/ec2/instances.go

@@ -370,10 +370,10 @@ func (s *Service) findSubnet(scope *scope.MachineScope) (string, error) {
 
 			filtered = append(filtered, subnet)
 		}
-		// prefer a subnet in the cluster VPC if multiple match
+		// keep AWS returned orderz stable, but prefer a subnet in the cluster VPC
 		clusterVPC := s.scope.VPC().ID
 		sort.SliceStable(filtered, func(i, j int) bool {
-			return strings.Compare(*filtered[i].VpcId, clusterVPC) > strings.Compare(*filtered[j].VpcId, clusterVPC)
+			return *filtered[i].VpcId == clusterVPC
 		})
 		if len(filtered) == 0 {
 			errMessage = fmt.Sprintf("failed to run machine %q, found %d subnets matching criteria but post-filtering failed.",

pkg/cloud/services/ec2/instances_test.go

@@ -656,17 +656,25 @@ func TestCreateInstance(t *testing.T) {
 					}})).Return(&ec2.DescribeSubnetsOutput{
 					Subnets: []*ec2.Subnet{
 						{
-							VpcId:               aws.String("vpc-bar"),
+							VpcId:               aws.String("vpc-incorrect-1"),
+							SubnetId:            aws.String("subnet-5"),
+							AvailabilityZone:    aws.String("us-east-1c"),
+							CidrBlock:           aws.String("10.0.12.0/24"),
+							MapPublicIpOnLaunch: aws.Bool(false),
+						},
+						{
+							VpcId:               aws.String("vpc-incorrect-2"),
 							SubnetId:            aws.String("subnet-4"),
 							AvailabilityZone:    aws.String("us-east-1c"),
 							CidrBlock:           aws.String("10.0.10.0/24"),
 							MapPublicIpOnLaunch: aws.Bool(false),
 						},
 						{
-							VpcId:            aws.String("vpc-foo"),
-							SubnetId:         aws.String("subnet-3"),
-							AvailabilityZone: aws.String("us-east-1c"),
-							CidrBlock:        aws.String("10.0.11.0/24"),
+							VpcId:               aws.String("vpc-foo"),
+							SubnetId:            aws.String("subnet-3"),
+							AvailabilityZone:    aws.String("us-east-1c"),
+							CidrBlock:           aws.String("10.0.11.0/24"),
+							MapPublicIpOnLaunch: aws.Bool(false),
 						},
 					},
 				}, nil)