feat: resolve LB-type Service hostname to create A/AAAA instead of CNAME

charts/external-dns/README.md

@@ -83,16 +83,17 @@ The following table lists the configurable parameters of the _ExternalDNS_ chart
 | `secretConfiguration.mountPath`    | Mount path of secret configuration secret (this can be templated).                                                                                                                                                                                                                                                    | `""`                                        |
 | `secretConfiguration.data`         | Secret configuration secret data. Could be used to store DNS provider credentials.                                                                                                                                                                                                                                    | `{}`                                        |
 | `secretConfiguration.subPath`      | Sub-path of secret configuration secret (this can be templated).                                                                                                                                                                                                                                                      | `""`                                        |
+| `resolveLoadBalancerHostname`      | Resolve the hostname of LoadBalancer-type Service object to IP addresses in order to create DNS A/AAAA records instead of CNAMEs | `false`                                        |
 
 ## Namespaced scoped installation
 
-external-dns supports running on a namespaced only scope, too. 
+external-dns supports running on a namespaced only scope, too.
 If `namespaced=true` is defined, the helm chart will setup `Roles` and `RoleBindings` instead `ClusterRoles` and `ClusterRoleBindings`.
 
 ### Limited supported
 Not all sources are supported in namespaced scope, since some sources depends on cluster-wide resources.
 For example: Source `node` isn't supported, since `kind: Node` has scope `Cluster`.
-Sources like `istio-virtualservice` only work, if all resources like `Gateway` and `VirtualService` are present in the same 
+Sources like `istio-virtualservice` only work, if all resources like `Gateway` and `VirtualService` are present in the same
 namespaces as `external-dns`.
 
 The annotation `external-dns.alpha.kubernetes.io/endpoints-type: NodeExternalIP` is not supported.

charts/external-dns/templates/deployment.yaml

@@ -96,6 +96,9 @@ spec:
             - --domain-filter={{ . }}
             {{- end }}
             - --provider={{ tpl .Values.provider $ }}
+            {{- if .Values.resolveLoadBalancerHostname }}
+            - --resolve-load-balancer-hostname
+            {{- end }}
           {{- range .Values.extraArgs }}
             - {{ tpl . $ }}
           {{- end }}

charts/external-dns/values.yaml

@@ -15,6 +15,8 @@ fullnameOverride: ""
 
 commonLabels: {}
 
+resolveLoadBalancerHostname: false
+
 serviceAccount:
   # Specifies whether a service account should be created
   create: true

main.go

@@ -141,6 +141,7 @@ func main() {
 		DefaultTargets:                 cfg.DefaultTargets,
 		OCPRouterName:                  cfg.OCPRouterName,
 		UpdateEvents:                   cfg.UpdateEvents,
+		ResolveLoadBalancerHostname:    cfg.ResolveLoadBalancerHostname,
 	}
 
 	// Lookup all the selected sources by names and pass them the desired configuration.

pkg/apis/externaldns/types.go

@@ -166,6 +166,7 @@ type Config struct {
 	CFAPIEndpoint                     string
 	CFUsername                        string
 	CFPassword                        string
+	ResolveLoadBalancerHostname       bool
 	RFC2136Host                       string
 	RFC2136Port                       int
 	RFC2136Zone                       string
@@ -390,6 +391,7 @@ func (cfg *Config) ParseFlags(args []string) error {
 	app.Flag("server", "The Kubernetes API server to connect to (default: auto-detect)").Default(defaultConfig.APIServerURL).StringVar(&cfg.APIServerURL)
 	app.Flag("kubeconfig", "Retrieve target cluster configuration from a Kubernetes configuration file (default: auto-detect)").Default(defaultConfig.KubeConfig).StringVar(&cfg.KubeConfig)
 	app.Flag("request-timeout", "Request timeout when calling Kubernetes APIs. 0s means no timeout").Default(defaultConfig.RequestTimeout.String()).DurationVar(&cfg.RequestTimeout)
+	app.Flag("resolve-lb-hostname", "Resolve the hostname of LoadBalancer-type Service object to IP addresses in order to create DNS A/AAAA records instead of CNAMEs").BoolVar(&cfg.ResolveLoadBalancerHostname)
 
 	// Flags related to cloud foundry
 	app.Flag("cf-api-endpoint", "The fully-qualified domain name of the cloud foundry instance you are targeting").Default(defaultConfig.CFAPIEndpoint).StringVar(&cfg.CFAPIEndpoint)

source/service.go

@@ -19,6 +19,7 @@ package source
 import (
 	"context"
 	"fmt"
+	"net"
 	"sort"
 	"strings"
 	"text/template"
@@ -57,6 +58,7 @@ type serviceSource struct {
 	publishInternal                bool
 	publishHostIP                  bool
 	alwaysPublishNotReadyAddresses bool
+	resolveLoadBalancerHostname    bool
 	serviceInformer                coreinformers.ServiceInformer
 	endpointsInformer              coreinformers.EndpointsInformer
 	podInformer                    coreinformers.PodInformer
@@ -66,7 +68,7 @@ type serviceSource struct {
 }
 
 // NewServiceSource creates a new serviceSource with the given config.
-func NewServiceSource(ctx context.Context, kubeClient kubernetes.Interface, namespace, annotationFilter string, fqdnTemplate string, combineFqdnAnnotation bool, compatibility string, publishInternal bool, publishHostIP bool, alwaysPublishNotReadyAddresses bool, serviceTypeFilter []string, ignoreHostnameAnnotation bool, labelSelector labels.Selector) (Source, error) {
+func NewServiceSource(ctx context.Context, kubeClient kubernetes.Interface, namespace, annotationFilter string, fqdnTemplate string, combineFqdnAnnotation bool, compatibility string, publishInternal bool, publishHostIP bool, alwaysPublishNotReadyAddresses bool, serviceTypeFilter []string, ignoreHostnameAnnotation bool, labelSelector labels.Selector, resolveLoadBalancerHostname bool) (Source, error) {
 	tmpl, err := parseTemplate(fqdnTemplate)
 	if err != nil {
 		return nil, err
@@ -137,6 +139,7 @@ func NewServiceSource(ctx context.Context, kubeClient kubernetes.Interface, name
 		nodeInformer:                   nodeInformer,
 		serviceTypeFilter:              serviceTypes,
 		labelSelector:                  labelSelector,
+		resolveLoadBalancerHostname:    resolveLoadBalancerHostname,
 	}, nil
 }
 
@@ -480,7 +483,7 @@ func (sc *serviceSource) generateEndpoints(svc *v1.Service, hostname string, pro
 		if useClusterIP {
 			targets = append(targets, extractServiceIps(svc)...)
 		} else {
-			targets = append(targets, extractLoadBalancerTargets(svc)...)
+			targets = append(targets, extractLoadBalancerTargets(svc, sc.resolveLoadBalancerHostname)...)
 		}
 	case v1.ServiceTypeClusterIP:
 		if sc.publishInternal {
@@ -540,7 +543,7 @@ func extractServiceExternalName(svc *v1.Service) endpoint.Targets {
 	return endpoint.Targets{svc.Spec.ExternalName}
 }
 
-func extractLoadBalancerTargets(svc *v1.Service) endpoint.Targets {
+func extractLoadBalancerTargets(svc *v1.Service, resolveLoadBalancerHostname bool) endpoint.Targets {
 	var (
 		targets     endpoint.Targets
 		externalIPs endpoint.Targets
@@ -552,7 +555,18 @@ func extractLoadBalancerTargets(svc *v1.Service) endpoint.Targets {
 			targets = append(targets, lb.IP)
 		}
 		if lb.Hostname != "" {
-			targets = append(targets, lb.Hostname)
+			if resolveLoadBalancerHostname {
+				ips, err := net.LookupIP(lb.Hostname)
+				if err != nil {
+					log.Errorf("Unable to resolve %q: %v", lb.Hostname, err)
+					continue
+				}
+				for _, ip := range ips {
+					targets = append(targets, ip.String())
+				}
+			} else {
+				targets = append(targets, lb.Hostname)
+			}
 		}
 	}
 

source/service_test.go

@@ -78,6 +78,7 @@ func (suite *ServiceSuite) SetupTest() {
 		[]string{},
 		false,
 		labels.Everything(),
+		false,
 	)
 	suite.NoError(err, "should initialize service source")
 }
@@ -158,6 +159,7 @@ func testServiceSourceNewServiceSource(t *testing.T) {
 				ti.serviceTypesFilter,
 				false,
 				labels.Everything(),
+				false,
 			)
 
 			if ti.expectError {
@@ -174,25 +176,26 @@ func testServiceSourceEndpoints(t *testing.T) {
 	t.Parallel()
 
 	for _, tc := range []struct {
-		title                    string
+		title                       string
-		targetNamespace          string
+		targetNamespace             string
-		annotationFilter         string
+		annotationFilter            string
-		svcNamespace             string
+		svcNamespace                string
-		svcName                  string
+		svcName                     string
-		svcType                  v1.ServiceType
+		svcType                     v1.ServiceType
-		compatibility            string
+		compatibility               string
-		fqdnTemplate             string
+		fqdnTemplate                string
-		combineFQDNAndAnnotation bool
+		combineFQDNAndAnnotation    bool
-		ignoreHostnameAnnotation bool
+		ignoreHostnameAnnotation    bool
-		labels                   map[string]string
+		labels                      map[string]string
-		annotations              map[string]string
+		annotations                 map[string]string
-		clusterIP                string
+		clusterIP                   string
-		externalIPs              []string
+		externalIPs                 []string
-		lbs                      []string
+		lbs                         []string
-		serviceTypesFilter       []string
+		serviceTypesFilter          []string
-		expected                 []*endpoint.Endpoint
+		expected                    []*endpoint.Endpoint
-		expectError              bool
+		expectError                 bool
-		serviceLabelSelector     string
+		serviceLabelSelector        string
+		resolveLoadBalancerHostname bool
 	}{
 		{
 			title:              "no annotated services return no endpoints",
@@ -389,6 +392,24 @@ func testServiceSourceEndpoints(t *testing.T) {
 				{DNSName: "foo.example.org", RecordType: endpoint.RecordTypeCNAME, Targets: endpoint.Targets{"lb.example.com"}},
 			},
 		},
+		{
+			title:        "annotated services return an endpoint with hostname then resolve hostname",
+			svcNamespace: "testing",
+			svcName:      "foo",
+			svcType:      v1.ServiceTypeLoadBalancer,
+			labels:       map[string]string{},
+			annotations: map[string]string{
+				hostnameAnnotationKey: "foo.example.org.",
+			},
+			externalIPs:                 []string{},
+			lbs:                         []string{"example.com"}, // Use a resolvable hostname for testing.
+			serviceTypesFilter:          []string{},
+			resolveLoadBalancerHostname: true,
+			expected: []*endpoint.Endpoint{
+				{DNSName: "foo.example.org", RecordType: endpoint.RecordTypeA, Targets: endpoint.Targets{"93.184.216.34"}},
+				{DNSName: "foo.example.org", RecordType: endpoint.RecordTypeAAAA, Targets: endpoint.Targets{"2606:2800:220:1:248:1893:25c8:1946"}},
+			},
+		},
 		{
 			title:        "annotated services can omit trailing dot",
 			svcNamespace: "testing",
@@ -1086,6 +1107,7 @@ func testServiceSourceEndpoints(t *testing.T) {
 				tc.serviceTypesFilter,
 				tc.ignoreHostnameAnnotation,
 				sourceLabel,
+				tc.resolveLoadBalancerHostname,
 			)
 
 			require.NoError(t, err)
@@ -1275,6 +1297,7 @@ func testMultipleServicesEndpoints(t *testing.T) {
 				tc.serviceTypesFilter,
 				tc.ignoreHostnameAnnotation,
 				labels.Everything(),
+				false,
 			)
 			require.NoError(t, err)
 
@@ -1440,6 +1463,7 @@ func TestClusterIpServices(t *testing.T) {
 				[]string{},
 				tc.ignoreHostnameAnnotation,
 				labelSelector,
+				false,
 			)
 			require.NoError(t, err)
 
@@ -2010,6 +2034,7 @@ func TestServiceSourceNodePortServices(t *testing.T) {
 				[]string{},
 				tc.ignoreHostnameAnnotation,
 				labels.Everything(),
+				false,
 			)
 			require.NoError(t, err)
 
@@ -2483,6 +2508,7 @@ func TestHeadlessServices(t *testing.T) {
 				[]string{},
 				tc.ignoreHostnameAnnotation,
 				labels.Everything(),
+				false,
 			)
 			require.NoError(t, err)
 
@@ -2840,6 +2866,7 @@ func TestHeadlessServicesHostIP(t *testing.T) {
 				[]string{},
 				tc.ignoreHostnameAnnotation,
 				labels.Everything(),
+				false,
 			)
 			require.NoError(t, err)
 
@@ -2952,6 +2979,7 @@ func TestExternalServices(t *testing.T) {
 				[]string{},
 				tc.ignoreHostnameAnnotation,
 				labels.Everything(),
+				false,
 			)
 			require.NoError(t, err)
 
@@ -3006,6 +3034,7 @@ func BenchmarkServiceEndpoints(b *testing.B) {
 		[]string{},
 		false,
 		labels.Everything(),
+		false,
 	)
 	require.NoError(b, err)
 

source/store.go

@@ -73,6 +73,7 @@ type Config struct {
 	DefaultTargets                 []string
 	OCPRouterName                  string
 	UpdateEvents                   bool
+	ResolveLoadBalancerHostname    bool
 }
 
 // ClientGenerator provides clients
@@ -215,7 +216,7 @@ func BuildWithConfig(ctx context.Context, source string, p ClientGenerator, cfg
 		if err != nil {
 			return nil, err
 		}
-		return NewServiceSource(ctx, client, cfg.Namespace, cfg.AnnotationFilter, cfg.FQDNTemplate, cfg.CombineFQDNAndAnnotation, cfg.Compatibility, cfg.PublishInternal, cfg.PublishHostIP, cfg.AlwaysPublishNotReadyAddresses, cfg.ServiceTypeFilter, cfg.IgnoreHostnameAnnotation, cfg.LabelFilter)
+		return NewServiceSource(ctx, client, cfg.Namespace, cfg.AnnotationFilter, cfg.FQDNTemplate, cfg.CombineFQDNAndAnnotation, cfg.Compatibility, cfg.PublishInternal, cfg.PublishHostIP, cfg.AlwaysPublishNotReadyAddresses, cfg.ServiceTypeFilter, cfg.IgnoreHostnameAnnotation, cfg.LabelFilter, cfg.ResolveLoadBalancerHostname)
 	case "ingress":
 		client, err := p.KubeClient()
 		if err != nil {