Implement clusterset IP in the CoredDNS plugin

Modify the resolver to return the ServiceImport's IP if it's
set and a specific cluster name wasn't requested. If the latter
then return the cluster's DNS record info as it normally does.

Signed-off-by: Tom Pantelis <[email protected]>

coredns/plugin/handler_test.go

@@ -77,6 +77,7 @@ var _ = Describe("Lighthouse DNS plugin Handler", func() {
 	Context("Headless services", testHeadlessService)
 	Context("Local services", testLocalService)
 	Context("Service with multiple ports", testSRVMultiplePorts)
+	Context("Service with clusterset IP", testClusterSetIP)
 })
 
 type FailingResponseWriter struct {
@@ -959,6 +960,58 @@ func testSRVMultiplePorts() {
 	})
 }
 
+func testClusterSetIP() {
+	const clusterSetIP = "243.1.0.1"
+
+	qname := fmt.Sprintf("%s.%s.svc.clusterset.local.", service1, namespace1)
+
+	var (
+		rec *dnstest.Recorder
+		t   *handlerTestDriver
+	)
+
+	BeforeEach(func() {
+		t = newHandlerTestDriver()
+
+		si := newServiceImport(namespace1, service1, mcsv1a1.ClusterSetIP)
+		si.Spec.IPs = []string{clusterSetIP}
+		si.Spec.Ports = []mcsv1a1.ServicePort{port1, port2}
+
+		t.lh.Resolver.PutServiceImport(si)
+
+		t.lh.Resolver.PutEndpointSlices(newEndpointSlice(namespace1, service1, clusterID, []mcsv1a1.ServicePort{port1},
+			newEndpoint(serviceIP, "", true)))
+
+		t.lh.Resolver.PutEndpointSlices(newEndpointSlice(namespace1, service1, clusterID2, []mcsv1a1.ServicePort{port2},
+			newEndpoint(serviceIP2, "", true)))
+
+		rec = dnstest.NewRecorder(&test.ResponseWriter{})
+	})
+
+	Specify("DNS query of Type A record should succeed and write an A record response", func() {
+		t.executeTestCase(rec, test.Case{
+			Qname: qname,
+			Qtype: dns.TypeA,
+			Rcode: dns.RcodeSuccess,
+			Answer: []dns.RR{
+				test.A(fmt.Sprintf("%s    5    IN    A    %s", qname, clusterSetIP)),
+			},
+		})
+	})
+
+	Specify("DNS query of Type SRV should succeed and write an SRV record response", func() {
+		t.executeTestCase(rec, test.Case{
+			Qname: qname,
+			Qtype: dns.TypeSRV,
+			Rcode: dns.RcodeSuccess,
+			Answer: []dns.RR{
+				test.SRV(fmt.Sprintf("%s    5    IN    SRV 0 50 %d %s", qname, port2.Port, qname)),
+				test.SRV(fmt.Sprintf("%s    5    IN    SRV 0 50 %d %s", qname, port1.Port, qname)),
+			},
+		})
+	})
+}
+
 type handlerTestDriver struct {
 	mockCs *fakecs.ClusterStatus
 	lh     *lighthouse.Lighthouse

coredns/resolver/clusterip_service_test.go

@@ -32,6 +32,7 @@ var _ = Describe("GetDNSRecords", func() {
 		When("a service is present in one cluster", testClusterIPServiceInOneCluster)
 		When("a service is present in two clusters", testClusterIPServiceInTwoClusters)
 		When("a service is present in three clusters", testClusterIPServiceInThreeClusters)
+		Context("with a clusterset IP", testClusterSetIP)
 
 		testClusterIPServiceMisc()
 	})
@@ -441,3 +442,39 @@ func testClusterIPServiceMisc() {
 		})
 	})
 }
+
+func testClusterSetIP() {
+	const clusterSetIP = "243.1.0.1"
+
+	t := newTestDriver()
+
+	BeforeEach(func() {
+		si := newAggregatedServiceImport(namespace1, service1)
+		si.Spec.IPs = []string{clusterSetIP}
+		si.Spec.Ports = []mcsv1a1.ServicePort{port1, port2}
+
+		t.resolver.PutServiceImport(si)
+
+		t.putEndpointSlice(newClusterIPEndpointSlice(namespace1, service1, clusterID1, serviceIP1, true, port1))
+		t.putEndpointSlice(newClusterIPEndpointSlice(namespace1, service1, clusterID2, serviceIP2, true, port2))
+	})
+
+	Context("and no specific cluster is requested", func() {
+		It("should return the clusterset IP DNS record", func() {
+			t.assertDNSRecordsFound(namespace1, service1, "", "", false, resolver.DNSRecord{
+				IP:    clusterSetIP,
+				Ports: []mcsv1a1.ServicePort{port1, port2},
+			})
+		})
+	})
+
+	Context("and a cluster is requested", func() {
+		It("should return its DNS record", func() {
+			t.assertDNSRecordsFound(namespace1, service1, clusterID1, "", false, resolver.DNSRecord{
+				IP:          serviceIP1,
+				Ports:       []mcsv1a1.ServicePort{port1},
+				ClusterName: clusterID1,
+			})
+		})
+	})
+}

coredns/resolver/endpoint_slice.go

@@ -76,7 +76,7 @@ func (i *Interface) PutEndpointSlices(endpointSlices ...*discovery.EndpointSlice
 		return true
 	}
 
-	if !serviceInfo.isHeadless {
+	if !serviceInfo.isHeadless() {
 		return i.putClusterIPEndpointSlice(key, clusterID, endpointSlices[0], serviceInfo)
 	}
 
@@ -264,7 +264,7 @@ func (i *Interface) RemoveEndpointSlice(endpointSlice *discovery.EndpointSlice)
 
 	if len(serviceInfo.clusters) == 0 && !serviceInfo.isExported {
 		delete(i.serviceMap, key)
-	} else if !serviceInfo.isHeadless {
+	} else if !serviceInfo.isHeadless() {
 		serviceInfo.mergePorts()
 		serviceInfo.resetLoadBalancing()
 	}

coredns/resolver/resolver.go

@@ -39,7 +39,7 @@ func (i *Interface) GetDNSRecords(namespace, name, clusterID, hostname string) (
 		return nil, false, false
 	}
 
-	if !serviceInfo.isHeadless {
+	if !serviceInfo.isHeadless() {
 		record, found := i.getClusterIPRecord(serviceInfo, clusterID)
 		if record != nil {
 			return []DNSRecord{*record}, false, true
@@ -64,6 +64,13 @@ func (i *Interface) getClusterIPRecord(serviceInfo *serviceInfo, clusterID strin
 		return &clusterInfo.endpointRecords[0], true
 	}
 
+	if len(serviceInfo.spec.IPs) > 0 {
+		return &DNSRecord{
+			IP:    serviceInfo.spec.IPs[0],
+			Ports: serviceInfo.spec.Ports,
+		}, true
+	}
+
 	// If we are aware of the local cluster and we found some accessible IP, we shall return it.
 	localClusterID := i.clusterStatus.GetLocalClusterID()
 	if localClusterID != "" {

coredns/resolver/service_import.go

@@ -39,17 +39,20 @@ func (i *Interface) PutServiceImport(serviceImport *mcsv1a1.ServiceImport) {
 
 	if !found {
 		svcInfo = &serviceInfo{
-			clusters:   make(map[string]*clusterInfo),
-			balancer:   loadbalancer.NewSmoothWeightedRR(),
-			isHeadless: serviceImport.Spec.Type == mcsv1a1.Headless,
+			clusters: make(map[string]*clusterInfo),
+			balancer: loadbalancer.NewSmoothWeightedRR(),
+		}
+
+		if !isLegacy {
+			svcInfo.spec = serviceImport.Spec
 		}
 
 		i.serviceMap[key] = svcInfo
 	}
 
 	svcInfo.isExported = true
 
-	if svcInfo.isHeadless || !isLegacy {
+	if svcInfo.isHeadless() || !isLegacy {
 		return
 	}
 

coredns/resolver/service_info.go

@@ -88,3 +88,7 @@ func (si *serviceInfo) selectIP(checkCluster func(string) bool) *DNSRecord {
 
 	return nil
 }
+
+func (si *serviceInfo) isHeadless() bool {
+	return si.spec.Type == mcsv1a1.Headless
+}

coredns/resolver/types.go

@@ -55,7 +55,7 @@ type clusterInfo struct {
 type serviceInfo struct {
 	clusters   map[string]*clusterInfo
 	balancer   loadbalancer.Interface
-	isHeadless bool
 	isExported bool
 	ports      []mcsv1a1.ServicePort
+	spec       mcsv1a1.ServiceImportSpec
 }