feat: add new flag to allow configuring per pod FQDNs for service source.

docs/flags.md

@@ -180,5 +180,6 @@
 | `--webhook-provider-read-timeout=5s` | The read timeout for the webhook provider in duration format (default: 5s) |
 | `--webhook-provider-write-timeout=10s` | The write timeout for the webhook provider in duration format (default: 10s) |
 | `--[no-]webhook-server` | When enabled, runs as a webhook server instead of a controller. (default: false). |
+| `--service-per-pod-fqdn=` | enables/disables to create per pod FQDNs for headless services. (default: 'true' for pods with non empty Hostnames, 'false' otherwise). |
 | `--provider=provider` | The DNS provider where the DNS records will be created (required, options: akamai, alibabacloud, aws, aws-sd, azure, azure-dns, azure-private-dns, civo, cloudflare, coredns, digitalocean, dnsimple, exoscale, gandi, godaddy, google, inmemory, linode, ns1, oci, ovh, pdns, pihole, plural, rfc2136, scaleway, skydns, transip, webhook) |
 | `--source=source` | The resource types that are queried for endpoints; specify multiple times for multiple sources (required, options: service, ingress, node, pod, fake, connector, gateway-httproute, gateway-grpcroute, gateway-tlsroute, gateway-tcproute, gateway-udproute, istio-gateway, istio-virtualservice, cloudfoundry, contour-httpproxy, gloo-proxy, crd, empty, skipper-routegroup, openshift-route, ambassador-host, kong-tcpingress, f5-virtualserver, f5-transportserver, traefik-proxy) |

pkg/apis/externaldns/types.go

@@ -217,6 +217,7 @@ type Config struct {
 	ExcludeUnschedulable                          bool
 	EmitEvents                                    []string
 	ForceDefaultTargets                           bool
+	ServicePerPodFqdn                             string
 }
 
 var defaultConfig = &Config{
@@ -382,6 +383,7 @@ var defaultConfig = &Config{
 	WebhookServer:                false,
 	ZoneIDFilter:                 []string{},
 	ForceDefaultTargets:          false,
+	ServicePerPodFqdn:            "",
 }
 
 var providerNames = []string{
@@ -804,6 +806,7 @@ func bindFlags(b FlagBinder, cfg *Config) {
 	b.DurationVar("webhook-provider-read-timeout", "The read timeout for the webhook provider in duration format (default: 5s)", defaultConfig.WebhookProviderReadTimeout, &cfg.WebhookProviderReadTimeout)
 	b.DurationVar("webhook-provider-write-timeout", "The write timeout for the webhook provider in duration format (default: 10s)", defaultConfig.WebhookProviderWriteTimeout, &cfg.WebhookProviderWriteTimeout)
 	b.BoolVar("webhook-server", "When enabled, runs as a webhook server instead of a controller. (default: false).", defaultConfig.WebhookServer, &cfg.WebhookServer)
+	b.EnumVar("service-per-pod-fqdn", "enables/disables to create per pod FQDNs for headless services. (default: 'true' for pods with non empty Hostnames, 'false' otherwise).", defaultConfig.ServicePerPodFqdn, &cfg.ServicePerPodFqdn, "true", "false", "")
 }
 
 func App(cfg *Config) *kingpin.Application {

source/service.go

@@ -75,6 +75,7 @@ type serviceSource struct {
 	alwaysPublishNotReadyAddresses bool
 	resolveLoadBalancerHostname    bool
 	listenEndpointEvents           bool
+	servicePerPodFqdn              *bool
 	serviceInformer                coreinformers.ServiceInformer
 	endpointSlicesInformer         discoveryinformers.EndpointSliceInformer
 	podInformer                    coreinformers.PodInformer
@@ -97,7 +98,7 @@ func NewServiceSource(
 	ignoreHostnameAnnotation bool,
 	labelSelector labels.Selector,
 	resolveLoadBalancerHostname,
-	listenEndpointEvents, exposeInternalIPv6 bool,
+	listenEndpointEvents, exposeInternalIPv6 bool, servicePerPodFqdn *bool,
 ) (Source, error) {
 	tmpl, err := fqdn.ParseTemplate(fqdnTemplate)
 	if err != nil {
@@ -223,6 +224,7 @@ func NewServiceSource(
 		resolveLoadBalancerHostname:    resolveLoadBalancerHostname,
 		listenEndpointEvents:           listenEndpointEvents,
 		exposeInternalIPv6:             exposeInternalIPv6,
+		servicePerPodFqdn:              servicePerPodFqdn,
 	}, nil
 }
 
@@ -410,8 +412,10 @@ func (sc *serviceSource) processHeadlessEndpointsFromSlices(
 				continue
 			}
 			headlessDomains := []string{hostname}
-			if pod.Spec.Hostname != "" {
+			if pod.Spec.Hostname != "" && (sc.servicePerPodFqdn == nil || *sc.servicePerPodFqdn) {
 				headlessDomains = append(headlessDomains, fmt.Sprintf("%s.%s", pod.Spec.Hostname, hostname))
+			} else if sc.servicePerPodFqdn != nil && *sc.servicePerPodFqdn {
+				headlessDomains = append(headlessDomains, fmt.Sprintf("%s.%s", pod.Name, hostname))
 			}
 			for _, headlessDomain := range headlessDomains {
 				targets := sc.getTargetsForDomain(pod, ep, endpointSlice, endpointsType, headlessDomain)

source/service_fqdn_test.go

@@ -745,6 +745,7 @@ func TestServiceSourceFqdnTemplatingExamples(t *testing.T) {
 				false,
 				false,
 				true,
+				nil,
 			)
 			require.NoError(t, err)
 

source/service_test.go

@@ -22,6 +22,7 @@ import (
 	"maps"
 	"math/rand"
 	"net"
+	"slices"
 	"sort"
 	"strings"
 	"testing"
@@ -38,6 +39,7 @@ import (
 	"k8s.io/apimachinery/pkg/util/intstr"
 	kubeinformers "k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes/fake"
+	"k8s.io/utils/ptr"
 	"sigs.k8s.io/external-dns/endpoint"
 	"sigs.k8s.io/external-dns/internal/testutils"
 	"sigs.k8s.io/external-dns/source/annotations"
@@ -91,6 +93,7 @@ func (suite *ServiceSuite) SetupTest() {
 		false,
 		false,
 		false,
+		nil,
 	)
 	suite.NoError(err, "should initialize service source")
 }
@@ -174,6 +177,7 @@ func testServiceSourceNewServiceSource(t *testing.T) {
 				false,
 				false,
 				false,
+				nil,
 			)
 
 			if ti.expectError {
@@ -1158,6 +1162,7 @@ func testServiceSourceEndpoints(t *testing.T) {
 				tc.resolveLoadBalancerHostname,
 				false,
 				false,
+				nil,
 			)
 
 			require.NoError(t, err)
@@ -1374,6 +1379,7 @@ func testMultipleServicesEndpoints(t *testing.T) {
 				false,
 				false,
 				false,
+				nil,
 			)
 			require.NoError(t, err)
 
@@ -1679,6 +1685,7 @@ func TestClusterIpServices(t *testing.T) {
 				false,
 				false,
 				false,
+				nil,
 			)
 			require.NoError(t, err)
 
@@ -2456,6 +2463,7 @@ func TestServiceSourceNodePortServices(t *testing.T) {
 				false,
 				false,
 				tc.exposeInternalIPv6,
+				nil,
 			)
 			require.NoError(t, err)
 
@@ -3364,6 +3372,7 @@ func TestHeadlessServices(t *testing.T) {
 				false,
 				false,
 				tc.exposeInternalIPv6,
+				nil,
 			)
 			require.NoError(t, err)
 
@@ -3500,6 +3509,7 @@ func TestMultipleServicesPointingToSameLoadBalancer(t *testing.T) {
 		false,
 		false,
 		false,
+		nil,
 	)
 	require.NoError(t, err)
 	assert.NotNil(t, src)
@@ -3866,6 +3876,7 @@ func TestMultipleHeadlessServicesPointingToPodsOnTheSameNode(t *testing.T) {
 		false,
 		false,
 		false,
+		nil,
 	)
 	require.NoError(t, err)
 	assert.NotNil(t, src)
@@ -4324,6 +4335,7 @@ func TestHeadlessServicesHostIP(t *testing.T) {
 				false,
 				false,
 				false,
+				nil,
 			)
 			require.NoError(t, err)
 
@@ -4534,6 +4546,7 @@ func TestExternalServices(t *testing.T) {
 				false,
 				false,
 				false,
+				nil,
 			)
 			require.NoError(t, err)
 
@@ -4596,6 +4609,7 @@ func BenchmarkServiceEndpoints(b *testing.B) {
 		false,
 		false,
 		false,
+		nil,
 	)
 	require.NoError(b, err)
 
@@ -4695,6 +4709,7 @@ func TestNewServiceSourceInformersEnabled(t *testing.T) {
 				false,
 				false,
 				false,
+				nil,
 			)
 			require.NoError(t, err)
 			svcSrc, ok := svc.(*serviceSource)
@@ -4726,6 +4741,7 @@ func TestNewServiceSourceWithServiceTypeFilters_Unsupported(t *testing.T) {
 		false,
 		false,
 		false,
+		nil,
 	)
 	require.Errorf(t, err, "unsupported service type filter: \"UnknownType\". Supported types are: [\"ClusterIP\" \"NodePort\" \"LoadBalancer\" \"ExternalName\"]")
 	require.Nil(t, svc, "ServiceSource should be nil when an unsupported service type is provided")
@@ -4905,6 +4921,7 @@ func TestEndpointSlicesIndexer(t *testing.T) {
 		false,
 		false,
 		false,
+		nil,
 	)
 	require.NoError(t, err)
 	ss, ok := src.(*serviceSource)
@@ -4992,6 +5009,7 @@ func TestPodTransformerInServiceSource(t *testing.T) {
 		false,
 		false,
 		false,
+		nil,
 	)
 	require.NoError(t, err)
 	ss, ok := src.(*serviceSource)
@@ -5356,6 +5374,96 @@ func TestProcessEndpointSlices_NotReadyWithPublishNotReady(t *testing.T) {
 	assert.NotEmpty(t, result, "Not ready endpoints should be processed when publishNotReadyAddresses is true")
 }
 
+func TestProcessEndpointSlices_PerPodFQDN(t *testing.T) {
+	for _, test := range []struct {
+		title              string
+		servicePerPodFqdn  *bool
+		podName            string
+		hostName           string
+		expectedFqdnPrefix string
+	}{
+		{
+			title:              "pod's FQDN should be created if hostname is specified",
+			servicePerPodFqdn:  nil,
+			podName:            "test-pod-name",
+			hostName:           "test-pod-host-name",
+			expectedFqdnPrefix: "test-pod-host-name",
+		},
+		{
+			title:              "pod's FQDN should be created if enabled",
+			servicePerPodFqdn:  ptr.To(true),
+			podName:            "test-pod-name",
+			hostName:           "",
+			expectedFqdnPrefix: "test-pod-name",
+		},
+		{
+			title:              "pod's FQDN should not be created if hostname is specified and disabled",
+			servicePerPodFqdn:  ptr.To(false),
+			podName:            "test-pod-name",
+			hostName:           "test-pod-host-name",
+			expectedFqdnPrefix: "",
+		},
+		{
+			title:              "pod's FQDN should not be created if disabled",
+			servicePerPodFqdn:  ptr.To(false),
+			podName:            "test-pod-name",
+			hostName:           "",
+			expectedFqdnPrefix: "",
+		},
+		{
+			title:              "hostname should be used for pod's FQDN",
+			servicePerPodFqdn:  ptr.To(true),
+			podName:            "test-pod-name",
+			hostName:           "test-pod-host-name",
+			expectedFqdnPrefix: "test-pod-host-name",
+		},
+	} {
+		t.Run(test.title, func(t *testing.T) {
+			sc := &serviceSource{servicePerPodFqdn: test.servicePerPodFqdn}
+			svc := &v1.Service{
+				ObjectMeta: metav1.ObjectMeta{Name: "test-service", Namespace: "default"},
+			}
+
+			endpointSlice := &discoveryv1.EndpointSlice{
+				ObjectMeta:  metav1.ObjectMeta{Name: "slice1", Namespace: "default"},
+				AddressType: discoveryv1.AddressTypeIPv4,
+				Endpoints: []discoveryv1.Endpoint{
+					{
+						TargetRef:  &v1.ObjectReference{Kind: "Pod", Name: test.podName},
+						Conditions: discoveryv1.EndpointConditions{Ready: testutils.ToPtr(false)}, // Not ready
+						Addresses:  []string{"10.0.0.1"},
+					},
+				},
+			}
+			pods := []*v1.Pod{{
+				ObjectMeta: metav1.ObjectMeta{Name: test.podName},
+				Status:     v1.PodStatus{PodIP: "10.0.0.1"},
+				Spec:       v1.PodSpec{Hostname: test.hostName},
+			}}
+			const serviceHostname = "test-service.example.com"
+			const endpointsType = "IPv4"
+			const publishPodIPs = false
+			const publishNotReadyAddresses = true // This should allow not-ready endpoints
+
+			result := sc.processHeadlessEndpointsFromSlices(
+				svc, pods, []*discoveryv1.EndpointSlice{endpointSlice},
+				serviceHostname, endpointsType, publishPodIPs, publishNotReadyAddresses)
+			if len(test.expectedFqdnPrefix) > 0 {
+				expectedPodFqdn := test.expectedFqdnPrefix + "." + serviceHostname
+				hasPodFqdn := slices.ContainsFunc(slices.Collect(maps.Keys(result)), func(record endpoint.EndpointKey) bool {
+					return record.DNSName == expectedPodFqdn
+				})
+				assert.True(t, hasPodFqdn, "Endpoint with pod's hostname (%s) should be generated but got: %v", expectedPodFqdn, result)
+			} else {
+				hasServiceFqdn := slices.ContainsFunc(slices.Collect(maps.Keys(result)), func(record endpoint.EndpointKey) bool {
+					return record.DNSName == serviceHostname
+				})
+				assert.True(t, hasServiceFqdn && len(result) == 1, "Result should include only service endpoint (%s): %v", serviceHostname, result)
+			}
+		})
+	}
+}
+
 // Test getTargetsForDomain with empty ep.Addresses
 func TestGetTargetsForDomain_EmptyAddresses(t *testing.T) {
 	sc := &serviceSource{}

source/store.go

@@ -21,6 +21,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"strings"
 	"sync"
 	"time"
 
@@ -33,6 +34,7 @@ import (
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
+	"k8s.io/utils/ptr"
 	gateway "sigs.k8s.io/gateway-api/pkg/client/clientset/versioned"
 
 	"sigs.k8s.io/external-dns/source/types"
@@ -101,6 +103,7 @@ type Config struct {
 	TraefikDisableNew              bool
 	ExcludeUnschedulable           bool
 	ExposeInternalIPv6             bool
+	ServicePerPodFqdn              *bool
 }
 
 func NewSourceConfig(cfg *externaldns.Config) *Config {
@@ -147,6 +150,18 @@ func NewSourceConfig(cfg *externaldns.Config) *Config {
 		TraefikDisableNew:              cfg.TraefikDisableNew,
 		ExcludeUnschedulable:           cfg.ExcludeUnschedulable,
 		ExposeInternalIPv6:             cfg.ExposeInternalIPV6,
+		ServicePerPodFqdn:              toBoolPtr(cfg.ServicePerPodFqdn),
+	}
+}
+
+func toBoolPtr(value string) *bool {
+	if len(value) == 0 {
+		return nil
+	}
+	if strings.EqualFold(value, "true") {
+		return ptr.To(true)
+	} else {
+		return ptr.To(false)
 	}
 }
 
@@ -429,7 +444,7 @@ func buildServiceSource(ctx context.Context, p ClientGenerator, cfg *Config) (So
 	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, cfg.ResolveLoadBalancerHostname, cfg.ListenEndpointEvents, cfg.ExposeInternalIPv6)
+	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, cfg.ListenEndpointEvents, cfg.ExposeInternalIPv6, cfg.ServicePerPodFqdn)
 }
 
 // buildIngressSource creates an Ingress source for exposing Kubernetes ingresses as DNS records.

source/store_test.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/cloudfoundry-community/go-cfclient"
 	openshift "github.com/openshift/client-go/route/clientset/versioned"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/suite"
 	istioclient "istio.io/client-go/pkg/clientset/versioned"
@@ -34,6 +35,7 @@ import (
 	fakeDynamic "k8s.io/client-go/dynamic/fake"
 	"k8s.io/client-go/kubernetes"
 	fakeKube "k8s.io/client-go/kubernetes/fake"
+	"k8s.io/utils/ptr"
 	"sigs.k8s.io/external-dns/source/types"
 	gateway "sigs.k8s.io/gateway-api/pkg/client/clientset/versioned"
 )
@@ -279,3 +281,9 @@ func TestBuildWithConfig_InvalidSource(t *testing.T) {
 		t.Errorf("expected ErrSourceNotFound, got: %v", err)
 	}
 }
+
+func TestToBoolPtr(t *testing.T) {
+	assert.Equal(t, ptr.To(true), toBoolPtr("true"))
+	assert.Equal(t, ptr.To(false), toBoolPtr("false"))
+	assert.Nil(t, toBoolPtr(""))
+}