Support for multi-target domains

This commit adds ability to have several endpoints for single domain
name with CoreDNS by adding random to the DNS name and setting
TargetStrip to 1 so that it will be stripped upon read. When TXT
record is encountered, it is merged with the first available A
record, if any available. Otherwise dedicated record is created.

provider/coredns.go

@@ -19,7 +19,10 @@ package provider
 import (
 	"container/list"
 	"encoding/json"
+	"fmt"
+	"math/rand"
 	"strings"
+	"time"
 
 	log "github.com/Sirupsen/logrus"
 	etcd "github.com/coreos/etcd/client"
@@ -29,6 +32,10 @@ import (
 	"github.com/kubernetes-incubator/external-dns/plan"
 )
 
+func init() {
+	rand.Seed(time.Now().UnixNano())
+}
+
 // skyDNSClient is an interface to work with SkyDNS service records in etcd
 type skyDNSClient interface {
 	GetServices(prefix string) ([]*Service, error)
@@ -160,22 +167,26 @@ func (p coreDNSProvider) Records() ([]*endpoint.Endpoint, error) {
 	for _, service := range services {
 		domains := strings.Split(strings.TrimPrefix(service.Key, "/skydns/"), "/")
 		reverse(domains)
+		dnsName := strings.Join(domains[service.TargetStrip:], ".")
+		prefix := strings.Join(domains[:service.TargetStrip], ".")
 		if service.Host != "" {
 			ep := endpoint.NewEndpoint(
-				strings.Join(domains, "."),
+				dnsName,
 				service.Host,
 				"",
 			)
 			ep.RecordType = suitableType(ep)
 			ep.Labels["originalText"] = service.Text
+			ep.Labels["prefix"] = prefix
 			result = append(result, ep)
 		}
 		if service.Text != "" {
 			ep := endpoint.NewEndpoint(
-				strings.Join(domains, "."),
+				dnsName,
 				service.Text,
 				"TXT",
 			)
+			ep.Labels["prefix"] = prefix
 			result = append(result, ep)
 		}
 	}
@@ -192,28 +203,47 @@ func (p coreDNSProvider) ApplyChanges(changes *plan.Changes) error {
 		grouped[ep.DNSName] = append(grouped[ep.DNSName], ep)
 	}
 	for dnsName, group := range grouped {
-		service := Service{}
+		var services []Service
 		for _, ep := range group {
-			recType := suitableType(ep)
-			switch recType {
-			case "A", "AAAA":
-				service.Host = ep.Target
-			case "CNAME":
-				if service.Host == "" {
-					service.Host = ep.Target
-				}
-			case "TXT":
-				service.Text = ep.Target
-			default:
-				log.Error("Unsupported record type", recType)
+			if ep.RecordType == "TXT" {
+				continue
+			}
+			prefix := ep.Labels["prefix"]
+			if prefix == "" {
+				prefix = fmt.Sprintf("%08x", rand.Int31())
+			}
+			service := Service{
+				Host:        ep.Target,
+				Text:        ep.Labels["originalText"],
+				Key:         etcdKeyFor(prefix + "." + dnsName),
+				TargetStrip: strings.Count(prefix, ".") + 1,
+			}
+			services = append(services, service)
+		}
+		index := 0
+		for _, ep := range group {
+			if ep.RecordType != "TXT" {
 				continue
 			}
-			if service.Text == "" {
-				service.Text = ep.Labels["originalText"]
+			if index >= len(services) {
+				prefix := ep.Labels["prefix"]
+				if prefix == "" {
+					prefix = fmt.Sprintf("%08x", rand.Int31())
+				}
+				services = append(services, Service{
+					Key:         etcdKeyFor(prefix + "." + dnsName),
+					TargetStrip: strings.Count(prefix, ".") + 1,
+				})
 			}
+			services[index].Text = ep.Target
+			index++
 		}
-		if service.Host != "" || service.Text != "" {
-			service.Key = etcdKeyFor(dnsName)
+
+		for i := index; index > 0 && i < len(services); i++ {
+			services[i].Text = ""
+		}
+
+		for _, service := range services {
 			log.Infof("Add/set key %s to Host=%s, Text=%s", service.Key, service.Host, service.Text)
 			if !p.dryRun {
 				err := p.client.SaveService(&service)
@@ -225,7 +255,11 @@ func (p coreDNSProvider) ApplyChanges(changes *plan.Changes) error {
 	}
 
 	for _, ep := range changes.Delete {
-		key := etcdKeyFor(ep.DNSName)
+		dnsName := ep.DNSName
+		if ep.Labels["prefix"] != "" {
+			dnsName = ep.Labels["prefix"] + "." + dnsName
+		}
+		key := etcdKeyFor(dnsName)
 		log.Infof("Delete key %s", key)
 		if !p.dryRun {
 			err := p.client.DeleteService(key)

provider/coredns_test.go

@@ -235,15 +235,15 @@ func TestCoreDNSApplyChanges(t *testing.T) {
 	}
 	validateServices(client.services, expectedServices1, t, 1)
 
-	updatedEp := endpoint.NewEndpoint("domain1.local", "6.6.6.6", "A")
-	updatedEp.Labels["originalText"] = "string1"
 	changes2 := &plan.Changes{
 		Create: []*endpoint.Endpoint{
 			endpoint.NewEndpoint("domain3.local", "7.7.7.7", ""),
 		},
-		UpdateNew: []*endpoint.Endpoint{updatedEp},
+		UpdateNew: []*endpoint.Endpoint{
+			endpoint.NewEndpoint("domain1.local", "6.6.6.6", "A"),
+		},
 	}
-	coredns.ApplyChanges(changes2)
+	applyServiceChanges(coredns, changes2)
 
 	expectedServices2 := map[string]*Service{
 		"/skydns/local/domain1": {Host: "6.6.6.6", Text: "string1"},
@@ -260,20 +260,36 @@ func TestCoreDNSApplyChanges(t *testing.T) {
 		},
 	}
 
-	coredns.ApplyChanges(changes3)
+	applyServiceChanges(coredns, changes3)
 
 	expectedServices3 := map[string]*Service{
 		"/skydns/local/domain2": {Host: "site.local"},
 	}
 	validateServices(client.services, expectedServices3, t, 3)
 }
 
+func applyServiceChanges(provider coreDNSProvider, changes *plan.Changes) {
+	records, _ := provider.Records()
+	for _, col := range [][]*endpoint.Endpoint{changes.Create, changes.UpdateNew, changes.Delete} {
+		for _, record := range col {
+			for _, existingRecord := range records {
+				if existingRecord.DNSName == record.DNSName && existingRecord.RecordType == suitableType(record) {
+					record.MergeLabels(existingRecord.Labels)
+				}
+			}
+		}
+	}
+	provider.ApplyChanges(changes)
+}
+
 func validateServices(services, expectedServices map[string]*Service, t *testing.T, step int) {
 	if len(services) != len(expectedServices) {
 		t.Errorf("wrong number of records on step %d: %d != %d", step, len(services), len(expectedServices))
 	}
 	for key, value := range services {
-		expectedService := expectedServices[key]
+		keyParts := strings.Split(key, "/")
+		expectedKey := strings.Join(keyParts[:len(keyParts)-value.TargetStrip], "/")
+		expectedService := expectedServices[expectedKey]
 		if expectedService == nil {
 			t.Errorf("unexpected service %s", key)
 			continue