kops/pkg/model/awsmodel/api_loadbalancer.go

665 lines
21 KiB
Go

/*
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 awsmodel
import (
"fmt"
"sort"
"time"
elbv2types "github.com/aws/aws-sdk-go-v2/service/elasticloadbalancingv2/types"
"k8s.io/apimachinery/pkg/util/sets"
"k8s.io/klog/v2"
"k8s.io/kops/pkg/apis/kops"
"k8s.io/kops/pkg/wellknownports"
"k8s.io/kops/pkg/wellknownservices"
"k8s.io/kops/upup/pkg/fi"
"k8s.io/kops/upup/pkg/fi/cloudup/awstasks"
)
// LoadBalancerDefaultIdleTimeout is the default idle time for the ELB
const LoadBalancerDefaultIdleTimeout = 5 * time.Minute
// APILoadBalancerBuilder builds a LoadBalancer for accessing the API
type APILoadBalancerBuilder struct {
*AWSModelContext
Lifecycle fi.Lifecycle
SecurityLifecycle fi.Lifecycle
}
var _ fi.CloudupModelBuilder = &APILoadBalancerBuilder{}
// Build is responsible for building the KubeAPI tasks for the aws model
func (b *APILoadBalancerBuilder) Build(c *fi.CloudupModelBuilderContext) error {
// Configuration where an ELB fronts the API
if !b.UseLoadBalancerForAPI() {
return nil
}
lbSpec := b.Cluster.Spec.API.LoadBalancer
if lbSpec == nil {
// Skipping API ELB creation; not requested in Spec
return nil
}
switch lbSpec.Type {
case kops.LoadBalancerTypeInternal, kops.LoadBalancerTypePublic:
// OK
default:
return fmt.Errorf("unhandled LoadBalancer type %q", lbSpec.Type)
}
var elbSubnets []*awstasks.Subnet
var nlbSubnetMappings []*awstasks.SubnetMapping
if len(lbSpec.Subnets) != 0 {
// Subnets have been explicitly set
for _, subnet := range lbSpec.Subnets {
for _, clusterSubnet := range b.Cluster.Spec.Networking.Subnets {
if subnet.Name == clusterSubnet.Name {
elbSubnet := b.LinkToSubnet(&clusterSubnet)
elbSubnets = append(elbSubnets, elbSubnet)
nlbSubnetMapping := &awstasks.SubnetMapping{
Subnet: elbSubnet,
}
if subnet.PrivateIPv4Address != nil {
nlbSubnetMapping.PrivateIPv4Address = subnet.PrivateIPv4Address
}
if subnet.AllocationID != nil {
nlbSubnetMapping.AllocationID = subnet.AllocationID
}
nlbSubnetMappings = append(nlbSubnetMappings, nlbSubnetMapping)
break
}
}
}
} else {
// Compute the subnets - only one per zone, and then break ties based on chooseBestSubnetForELB
subnetsByZone := make(map[string][]*kops.ClusterSubnetSpec)
for i := range b.Cluster.Spec.Networking.Subnets {
subnet := &b.Cluster.Spec.Networking.Subnets[i]
switch subnet.Type {
case kops.SubnetTypePublic, kops.SubnetTypeUtility:
if lbSpec.Type != kops.LoadBalancerTypePublic {
continue
}
case kops.SubnetTypeDualStack, kops.SubnetTypePrivate:
if lbSpec.Type != kops.LoadBalancerTypeInternal {
continue
}
default:
return fmt.Errorf("subnet %q had unknown type %q", subnet.Name, subnet.Type)
}
subnetsByZone[subnet.Zone] = append(subnetsByZone[subnet.Zone], subnet)
}
for zone, subnets := range subnetsByZone {
subnet := b.chooseBestSubnetForELB(zone, subnets)
elbSubnet := b.LinkToSubnet(subnet)
elbSubnets = append(elbSubnets, elbSubnet)
nlbSubnetMappings = append(nlbSubnetMappings, &awstasks.SubnetMapping{Subnet: elbSubnet})
}
}
var clb *awstasks.ClassicLoadBalancer
var nlb *awstasks.NetworkLoadBalancer
{
idleTimeout := LoadBalancerDefaultIdleTimeout
if lbSpec.IdleTimeoutSeconds != nil {
idleTimeout = time.Second * time.Duration(*lbSpec.IdleTimeoutSeconds)
}
listeners := map[string]*awstasks.ClassicLoadBalancerListener{
"443": {InstancePort: 443},
}
var nlbListeners []*awstasks.NetworkLoadBalancerListener
if lbSpec.SSLCertificate == "" {
listener443 := &awstasks.NetworkLoadBalancerListener{
Name: fi.PtrTo(b.NLBListenerName("api", 443)),
Lifecycle: b.Lifecycle,
NetworkLoadBalancer: b.LinkToNLB("api"),
Port: 443,
TargetGroup: b.LinkToTargetGroup("tcp"),
}
nlbListeners = append(nlbListeners, listener443)
} else {
// When using a custom certificate, we create a secondary listener on 8443, which does _not_ use the custom certificate.
// This is because client certificates cannot be used in conjunction with custom certificates on NLBs.
listener8443 := &awstasks.NetworkLoadBalancerListener{
Name: fi.PtrTo(b.NLBListenerName("api", 8443)),
Lifecycle: b.Lifecycle,
NetworkLoadBalancer: b.LinkToNLB("api"),
Port: 8443,
TargetGroup: b.LinkToTargetGroup("tcp"),
}
nlbListeners = append(nlbListeners, listener8443)
// The primary listener _does_ use the custom certificate.
listeners["443"].SSLCertificateID = lbSpec.SSLCertificate
listener443 := &awstasks.NetworkLoadBalancerListener{
Name: fi.PtrTo(b.NLBListenerName("api", 443)),
Lifecycle: b.Lifecycle,
NetworkLoadBalancer: b.LinkToNLB("api"),
Port: 443,
TargetGroup: b.LinkToTargetGroup("tls"),
SSLCertificateID: lbSpec.SSLCertificate,
}
if lbSpec.SSLPolicy != nil {
listener443.SSLPolicy = *lbSpec.SSLPolicy
} else {
listener443.SSLPolicy = "ELBSecurityPolicy-2016-08" // The AWS default
}
nlbListeners = append(nlbListeners, listener443)
}
if b.Cluster.UsesNoneDNS() {
nlbListener := &awstasks.NetworkLoadBalancerListener{
Name: fi.PtrTo(b.NLBListenerName("api", wellknownports.KopsControllerPort)),
Lifecycle: b.Lifecycle,
NetworkLoadBalancer: b.LinkToNLB("api"),
Port: wellknownports.KopsControllerPort,
TargetGroup: b.LinkToTargetGroup("kops-controller"),
}
nlbListeners = append(nlbListeners, nlbListener)
}
if lbSpec.SecurityGroupOverride != nil {
klog.V(1).Infof("WARNING: You are overwriting the Load Balancers, Security Group. When this is done you are responsible for ensure the correct rules!")
}
tags := b.CloudTags("", false)
for k, v := range b.Cluster.Spec.CloudLabels {
tags[k] = v
}
// Override the returned name to be the expected ELB name
tags["Name"] = "api." + b.ClusterName()
nlb = &awstasks.NetworkLoadBalancer{
Name: fi.PtrTo(b.NLBName("api")),
Lifecycle: b.Lifecycle,
LoadBalancerBaseName: fi.PtrTo(b.LBName32("api")),
CLBName: fi.PtrTo("api." + b.ClusterName()),
SecurityGroups: []*awstasks.SecurityGroup{
b.LinkToELBSecurityGroup("api"),
},
SubnetMappings: nlbSubnetMappings,
Tags: tags,
WellKnownServices: []wellknownservices.WellKnownService{wellknownservices.KubeAPIServer},
VPC: b.LinkToVPC(),
Type: elbv2types.LoadBalancerTypeEnumNetwork,
}
// Wait for all load balancer components to be created (including network interfaces needed for NoneDNS).
// Limiting this to clusters using NoneDNS because load balancer creation is quite slow.
if b.Cluster.UsesNoneDNS() {
nlb.SetWaitForLoadBalancerReady(true)
}
clb = &awstasks.ClassicLoadBalancer{
Name: fi.PtrTo("api." + b.ClusterName()),
Lifecycle: b.Lifecycle,
LoadBalancerName: fi.PtrTo(b.LBName32("api")),
SecurityGroups: []*awstasks.SecurityGroup{
b.LinkToELBSecurityGroup("api"),
},
Subnets: elbSubnets,
Listeners: listeners,
// Configure fast-recovery health-checks
HealthCheck: &awstasks.ClassicLoadBalancerHealthCheck{
Target: fi.PtrTo("SSL:443"),
Timeout: fi.PtrTo(int64(5)),
Interval: fi.PtrTo(int64(10)),
HealthyThreshold: fi.PtrTo(int64(2)),
UnhealthyThreshold: fi.PtrTo(int64(2)),
},
ConnectionSettings: &awstasks.ClassicLoadBalancerConnectionSettings{
IdleTimeout: fi.PtrTo(int64(idleTimeout.Seconds())),
},
ConnectionDraining: &awstasks.ClassicLoadBalancerConnectionDraining{
Enabled: fi.PtrTo(true),
Timeout: fi.PtrTo(int64(300)),
},
Tags: tags,
WellKnownServices: []wellknownservices.WellKnownService{wellknownservices.KubeAPIServer},
}
if b.Cluster.UsesNoneDNS() {
lbSpec.CrossZoneLoadBalancing = fi.PtrTo(true)
} else if lbSpec.CrossZoneLoadBalancing == nil {
lbSpec.CrossZoneLoadBalancing = fi.PtrTo(false)
}
clb.CrossZoneLoadBalancing = &awstasks.ClassicLoadBalancerCrossZoneLoadBalancing{
Enabled: lbSpec.CrossZoneLoadBalancing,
}
nlb.CrossZoneLoadBalancing = lbSpec.CrossZoneLoadBalancing
switch lbSpec.Type {
case kops.LoadBalancerTypeInternal:
clb.Scheme = fi.PtrTo("internal")
nlb.Scheme = elbv2types.LoadBalancerSchemeEnumInternal
case kops.LoadBalancerTypePublic:
clb.Scheme = nil
nlb.Scheme = elbv2types.LoadBalancerSchemeEnumInternetFacing
default:
return fmt.Errorf("unknown load balancer Type: %q", lbSpec.Type)
}
if lbSpec.AccessLog != nil {
clb.AccessLog = &awstasks.ClassicLoadBalancerAccessLog{
EmitInterval: fi.PtrTo(int64(lbSpec.AccessLog.Interval)),
Enabled: fi.PtrTo(true),
S3BucketName: lbSpec.AccessLog.Bucket,
S3BucketPrefix: lbSpec.AccessLog.BucketPrefix,
}
nlb.AccessLog = &awstasks.NetworkLoadBalancerAccessLog{
Enabled: fi.PtrTo(true),
S3BucketName: lbSpec.AccessLog.Bucket,
S3BucketPrefix: lbSpec.AccessLog.BucketPrefix,
}
} else {
clb.AccessLog = &awstasks.ClassicLoadBalancerAccessLog{
Enabled: fi.PtrTo(false),
}
nlb.AccessLog = &awstasks.NetworkLoadBalancerAccessLog{
Enabled: fi.PtrTo(false),
}
}
if b.APILoadBalancerClass() == kops.LoadBalancerClassClassic {
c.AddTask(clb)
} else if b.APILoadBalancerClass() == kops.LoadBalancerClassNetwork {
groupAttrs := map[string]string{
awstasks.TargetGroupAttributeDeregistrationDelayConnectionTerminationEnabled: "true",
awstasks.TargetGroupAttributeDeregistrationDelayTimeoutSeconds: "30",
}
{
groupName := b.NLBTargetGroupName("tcp")
groupTags := b.CloudTags(groupName, false)
// Override the returned name to be the expected NLB TG name
groupTags["Name"] = groupName
tg := &awstasks.TargetGroup{
Name: fi.PtrTo(groupName),
Lifecycle: b.Lifecycle,
VPC: b.LinkToVPC(),
Tags: groupTags,
Protocol: elbv2types.ProtocolEnumTcp,
Port: fi.PtrTo(int32(443)),
Attributes: groupAttrs,
Interval: fi.PtrTo(int32(10)),
HealthyThreshold: fi.PtrTo(int32(2)),
UnhealthyThreshold: fi.PtrTo(int32(2)),
Shared: fi.PtrTo(false),
}
tg.CreateNewRevisionsWith(nlb)
c.AddTask(tg)
}
if b.Cluster.UsesNoneDNS() {
groupName := b.NLBTargetGroupName("kops-controller")
groupTags := b.CloudTags(groupName, false)
// Override the returned name to be the expected NLB TG name
groupTags["Name"] = groupName
tg := &awstasks.TargetGroup{
Name: fi.PtrTo(groupName),
Lifecycle: b.Lifecycle,
VPC: b.LinkToVPC(),
Tags: groupTags,
Protocol: elbv2types.ProtocolEnumTcp,
Port: fi.PtrTo(int32(wellknownports.KopsControllerPort)),
Attributes: groupAttrs,
Interval: fi.PtrTo(int32(10)),
HealthyThreshold: fi.PtrTo(int32(2)),
UnhealthyThreshold: fi.PtrTo(int32(2)),
Shared: fi.PtrTo(false),
}
tg.CreateNewRevisionsWith(nlb)
c.AddTask(tg)
}
if lbSpec.SSLCertificate != "" {
tlsGroupName := b.NLBTargetGroupName("tls")
tlsGroupTags := b.CloudTags(tlsGroupName, false)
// Override the returned name to be the expected NLB TG name
tlsGroupTags["Name"] = tlsGroupName
secondaryTG := &awstasks.TargetGroup{
Name: fi.PtrTo(tlsGroupName),
Lifecycle: b.Lifecycle,
VPC: b.LinkToVPC(),
Tags: tlsGroupTags,
Protocol: elbv2types.ProtocolEnumTls,
Port: fi.PtrTo(int32(443)),
Attributes: groupAttrs,
Interval: fi.PtrTo(int32(10)),
HealthyThreshold: fi.PtrTo(int32(2)),
UnhealthyThreshold: fi.PtrTo(int32(2)),
Shared: fi.PtrTo(false),
}
secondaryTG.CreateNewRevisionsWith(nlb)
c.AddTask(secondaryTG)
}
for _, nlbListener := range nlbListeners {
c.AddTask(nlbListener)
}
c.AddTask(nlb)
}
}
var lbSG *awstasks.SecurityGroup
{
lbSG = &awstasks.SecurityGroup{
Name: fi.PtrTo(b.ELBSecurityGroupName("api")),
Lifecycle: b.SecurityLifecycle,
Description: fi.PtrTo("Security group for api ELB"),
RemoveExtraRules: []string{"port=443"},
VPC: b.LinkToVPC(),
}
lbSG.Tags = b.CloudTags(*lbSG.Name, false)
if lbSpec.SecurityGroupOverride != nil {
lbSG.ID = fi.PtrTo(*lbSpec.SecurityGroupOverride)
lbSG.Shared = fi.PtrTo(true)
}
c.AddTask(lbSG)
}
// Allow traffic from ELB to egress freely
{
{
t := &awstasks.SecurityGroupRule{
Name: fi.PtrTo("ipv4-api-elb-egress"),
Lifecycle: b.SecurityLifecycle,
CIDR: fi.PtrTo("0.0.0.0/0"),
Egress: fi.PtrTo(true),
SecurityGroup: lbSG,
}
AddDirectionalGroupRule(c, t)
}
{
t := &awstasks.SecurityGroupRule{
Name: fi.PtrTo("ipv6-api-elb-egress"),
Lifecycle: b.SecurityLifecycle,
IPv6CIDR: fi.PtrTo("::/0"),
Egress: fi.PtrTo(true),
SecurityGroup: lbSG,
}
AddDirectionalGroupRule(c, t)
}
}
// Allow traffic into the ELB from KubernetesAPIAccess CIDRs
{
for _, cidr := range b.Cluster.Spec.API.Access {
{
t := &awstasks.SecurityGroupRule{
Name: fi.PtrTo("https-api-elb-" + cidr),
Lifecycle: b.SecurityLifecycle,
FromPort: fi.PtrTo(int64(443)),
Protocol: fi.PtrTo("tcp"),
SecurityGroup: lbSG,
ToPort: fi.PtrTo(int64(443)),
}
t.SetCidrOrPrefix(cidr)
AddDirectionalGroupRule(c, t)
}
// If we have opened a secondary listener on 8443, allow it also
if b.APILoadBalancerClass() == kops.LoadBalancerClassNetwork && b.Cluster.Spec.API.LoadBalancer != nil && b.Cluster.Spec.API.LoadBalancer.SSLCertificate != "" {
t := &awstasks.SecurityGroupRule{
Name: fi.PtrTo("https-api-elb-8443-" + cidr),
Lifecycle: b.SecurityLifecycle,
FromPort: fi.PtrTo(int64(8443)),
ToPort: fi.PtrTo(int64(8443)),
Protocol: fi.PtrTo("tcp"),
SecurityGroup: lbSG,
}
lbSG.RemoveExtraRules = append(lbSG.RemoveExtraRules, "port=8443")
t.SetCidrOrPrefix(cidr)
AddDirectionalGroupRule(c, t)
}
// Allow ICMP traffic required for PMTU discovery
{
t := &awstasks.SecurityGroupRule{
Name: fi.PtrTo("icmpv6-pmtu-api-elb-" + cidr),
Lifecycle: b.SecurityLifecycle,
FromPort: fi.PtrTo(int64(-1)),
Protocol: fi.PtrTo("icmpv6"),
SecurityGroup: lbSG,
ToPort: fi.PtrTo(int64(-1)),
}
t.SetCidrOrPrefix(cidr)
if t.CIDR == nil {
c.AddTask(t)
}
}
{
t := &awstasks.SecurityGroupRule{
Name: fi.PtrTo("icmp-pmtu-api-elb-" + cidr),
Lifecycle: b.SecurityLifecycle,
FromPort: fi.PtrTo(int64(3)),
Protocol: fi.PtrTo("icmp"),
SecurityGroup: lbSG,
ToPort: fi.PtrTo(int64(4)),
}
t.SetCidrOrPrefix(cidr)
if t.IPv6CIDR == nil {
c.AddTask(t)
}
}
}
}
if b.Cluster.UsesNoneDNS() {
nodeGroups, err := b.GetSecurityGroups(kops.InstanceGroupRoleNode)
if err != nil {
return err
}
for _, nodeGroup := range nodeGroups {
suffix := nodeGroup.Suffix
t := &awstasks.SecurityGroupRule{
Name: fi.PtrTo(fmt.Sprintf("node%s-to-elb", suffix)),
Lifecycle: b.SecurityLifecycle,
SecurityGroup: lbSG,
SourceGroup: nodeGroup.Task,
}
c.AddTask(t)
}
}
masterGroups, err := b.GetSecurityGroups(kops.InstanceGroupRoleControlPlane)
if err != nil {
return err
}
if b.APILoadBalancerClass() == kops.LoadBalancerClassNetwork && b.Cluster.Spec.API.LoadBalancer != nil && b.Cluster.Spec.API.LoadBalancer.SSLCertificate != "" {
for _, masterGroup := range masterGroups {
suffix := masterGroup.Suffix
// Allow access to control plane on secondary port through NLB
t := &awstasks.SecurityGroupRule{
Name: fi.PtrTo(fmt.Sprintf("tcp-api-cp%s", suffix)),
Lifecycle: b.SecurityLifecycle,
FromPort: fi.PtrTo(int64(8443)),
Protocol: fi.PtrTo("tcp"),
SecurityGroup: masterGroup.Task,
SourceGroup: lbSG,
ToPort: fi.PtrTo(int64(8443)),
}
c.AddTask(t)
}
}
// Add precreated additional security groups to the ELB
{
for _, id := range b.Cluster.Spec.API.LoadBalancer.AdditionalSecurityGroups {
t := &awstasks.SecurityGroup{
Name: fi.PtrTo(id),
Lifecycle: b.SecurityLifecycle,
ID: fi.PtrTo(id),
Shared: fi.PtrTo(true),
}
c.EnsureTask(t)
clb.SecurityGroups = append(clb.SecurityGroups, t)
nlb.SecurityGroups = append(nlb.SecurityGroups, t)
}
}
// Allow HTTPS to the control-plane instances from the ELB
{
for _, masterGroup := range masterGroups {
suffix := masterGroup.Suffix
c.AddTask(&awstasks.SecurityGroupRule{
Name: fi.PtrTo(fmt.Sprintf("https-elb-to-master%s", suffix)),
Lifecycle: b.SecurityLifecycle,
FromPort: fi.PtrTo(int64(443)),
Protocol: fi.PtrTo("tcp"),
SecurityGroup: masterGroup.Task,
SourceGroup: lbSG,
ToPort: fi.PtrTo(int64(443)),
})
c.AddTask(&awstasks.SecurityGroupRule{
Name: fi.PtrTo(fmt.Sprintf("icmp-pmtu-elb-to-cp%s", suffix)),
Lifecycle: b.SecurityLifecycle,
FromPort: fi.PtrTo(int64(3)),
Protocol: fi.PtrTo("icmp"),
SecurityGroup: masterGroup.Task,
SourceGroup: lbSG,
ToPort: fi.PtrTo(int64(4)),
})
c.AddTask(&awstasks.SecurityGroupRule{
Name: fi.PtrTo(fmt.Sprintf("icmp-pmtu-cp%s-to-elb", suffix)),
Lifecycle: b.SecurityLifecycle,
FromPort: fi.PtrTo(int64(3)),
Protocol: fi.PtrTo("icmp"),
SecurityGroup: lbSG,
SourceGroup: masterGroup.Task,
ToPort: fi.PtrTo(int64(4)),
})
if b.Cluster.UsesNoneDNS() {
nlb.WellKnownServices = append(nlb.WellKnownServices, wellknownservices.KopsController)
clb.WellKnownServices = append(clb.WellKnownServices, wellknownservices.KopsController)
c.AddTask(&awstasks.SecurityGroupRule{
Name: fi.PtrTo(fmt.Sprintf("kops-controller-elb-to-cp%s", suffix)),
Lifecycle: b.SecurityLifecycle,
FromPort: fi.PtrTo(int64(wellknownports.KopsControllerPort)),
Protocol: fi.PtrTo("tcp"),
SecurityGroup: masterGroup.Task,
ToPort: fi.PtrTo(int64(wellknownports.KopsControllerPort)),
SourceGroup: lbSG,
})
}
}
}
return nil
}
type scoredSubnet struct {
score int
subnet *kops.ClusterSubnetSpec
}
type ByScoreDescending []*scoredSubnet
func (a ByScoreDescending) Len() int { return len(a) }
func (a ByScoreDescending) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (a ByScoreDescending) Less(i, j int) bool {
if a[i].score != a[j].score {
// ! to sort highest score first
return !(a[i].score < a[j].score)
}
// Use name to break ties consistently
return a[i].subnet.Name < a[j].subnet.Name
}
// Choose between subnets in a zone.
// We have already applied the rules to match internal subnets to internal ELBs and vice-versa for public-facing ELBs.
// For internal ELBs: we prefer dual stack and the master subnets
// For public facing ELBs: we prefer the utility subnets
func (b *APILoadBalancerBuilder) chooseBestSubnetForELB(zone string, subnets []*kops.ClusterSubnetSpec) *kops.ClusterSubnetSpec {
if len(subnets) == 0 {
return nil
}
if len(subnets) == 1 {
return subnets[0]
}
migSubnets := sets.NewString()
for _, ig := range b.MasterInstanceGroups() {
for _, subnet := range ig.Spec.Subnets {
migSubnets.Insert(subnet)
}
}
var scoredSubnets []*scoredSubnet
for _, subnet := range subnets {
score := 0
if migSubnets.Has(subnet.Name) {
score += 1
}
if subnet.Type == kops.SubnetTypeDualStack {
score += 2
}
if subnet.Type == kops.SubnetTypeUtility {
score += 3
}
scoredSubnets = append(scoredSubnets, &scoredSubnet{
score: score,
subnet: subnet,
})
}
sort.Sort(ByScoreDescending(scoredSubnets))
if scoredSubnets[0].score == scoredSubnets[1].score {
klog.V(2).Infof("Making arbitrary choice between subnets in zone %q to attach to ELB (%q vs %q)", zone, scoredSubnets[0].subnet.Name, scoredSubnets[1].subnet.Name)
}
return scoredSubnets[0].subnet
}