ServiceBackend interface (#369)

* Add ServiceBackend interface

This adds a ServiceBackend interface that is shared between etcd/etcd3
(later) and kubernetes, leading to a massive reduction in code. When
returning the specific records from their backend.

Fixes #273

middleware/kubernetes/handler.go

@@ -23,6 +23,8 @@ func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.M
 	m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
 
 	// TODO: find an alternative to this block
+	// TODO(miek): Why is this even here, why does the path Etcd takes not work?
+	// Should be a "case PTR" below. I would also like to use middleware.PTR for this.
 	ip := dnsutil.ExtractAddressFromReverse(state.Name())
 	if ip != "" {
 		records := k.getServiceRecordForIP(ip, state.Name())
@@ -54,41 +56,38 @@ func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.M
 	)
 	switch state.Type() {
 	case "A":
-		records, err = k.A(zone, state, nil)
+		records, _, err = middleware.A(&k, zone, state, nil, middleware.Options{}) // Hmm wrt to '&k'
 	case "AAAA":
-		records, err = k.AAAA(zone, state, nil)
+		records, _, err = middleware.AAAA(&k, zone, state, nil, middleware.Options{})
 	case "TXT":
-		records, err = k.TXT(zone, state)
-		// TODO: change lookup to return appropriate error. Then add code below
-		// this switch to check for the error and return not implemented.
-		//return dns.RcodeNotImplemented, nil
+		records, _, err = middleware.TXT(&k, zone, state, middleware.Options{})
 	case "CNAME":
-		records, err = k.CNAME(zone, state)
+		records, _, err = middleware.CNAME(&k, zone, state, middleware.Options{})
 	case "MX":
-		records, extra, err = k.MX(zone, state)
+		records, extra, _, err = middleware.MX(&k, zone, state, middleware.Options{})
 	case "SRV":
-		records, extra, err = k.SRV(zone, state)
+		records, extra, _, err = middleware.SRV(&k, zone, state, middleware.Options{})
 	case "SOA":
-		records = []dns.RR{k.SOA(zone, state)}
+		records, _, err = middleware.SOA(&k, zone, state, middleware.Options{})
 	case "NS":
 		if state.Name() == zone {
-			records, extra, err = k.NS(zone, state)
+			records, extra, _, err = middleware.NS(&k, zone, state, middleware.Options{})
 			break
 		}
 		fallthrough
 	default:
 		// Do a fake A lookup, so we can distinguish between NODATA and NXDOMAIN
-		_, err = k.A(zone, state, nil)
+		_, _, err = middleware.A(&k, zone, state, nil, middleware.Options{})
 	}
-	if isKubernetesNameError(err) {
-		return k.Err(zone, dns.RcodeNameError, state)
+	if k.IsNameError(err) {
+		return middleware.BackendError(&k, zone, dns.RcodeNameError, state, nil /*debug*/, err, middleware.Options{})
 	}
 	if err != nil {
 		return dns.RcodeServerFailure, err
 	}
 
 	if len(records) == 0 {
-		return k.Err(zone, dns.RcodeSuccess, state)
+		return middleware.BackendError(&k, zone, dns.RcodeSuccess, state, nil /*debug*/, nil, middleware.Options{})
 	}
 
 	m.Answer = append(m.Answer, records...)
@@ -103,13 +102,3 @@ func (k Kubernetes) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.M
 
 // Name implements the Handler interface.
 func (k Kubernetes) Name() string { return "kubernetes" }
-
-// Err writes an error response back to the client.
-func (k Kubernetes) Err(zone string, rcode int, state request.Request) (int, error) {
-	m := new(dns.Msg)
-	m.SetRcode(state.Req, rcode)
-	m.Ns = []dns.RR{k.SOA(zone, state)}
-	state.SizeAndDo(m)
-	state.W.WriteMsg(m)
-	return rcode, nil
-}

middleware/kubernetes/kubernetes.go

@@ -3,6 +3,7 @@ package kubernetes
 
 import (
 	"errors"
+	"fmt"
 	"log"
 	"strings"
 	"time"
@@ -11,8 +12,9 @@ import (
 	"github.com/miekg/coredns/middleware/etcd/msg"
 	"github.com/miekg/coredns/middleware/kubernetes/nametemplate"
 	"github.com/miekg/coredns/middleware/pkg/dnsutil"
-	dns_strings "github.com/miekg/coredns/middleware/pkg/strings"
+	dnsstrings "github.com/miekg/coredns/middleware/pkg/strings"
 	"github.com/miekg/coredns/middleware/proxy"
+	"github.com/miekg/coredns/request"
 
 	"github.com/miekg/dns"
 	"k8s.io/kubernetes/pkg/api"
@@ -41,6 +43,28 @@ type Kubernetes struct {
 	Selector      *labels.Selector
 }
 
+// Services implements the ServiceBackend interface.
+func (k *Kubernetes) Services(state request.Request, exact bool, opt middleware.Options) ([]msg.Service, []msg.Service, error) {
+	s, e := k.Records(state.Name(), exact)
+	return s, nil, e // Haven't implemented debug queries yet.
+}
+
+// Lookup implements the ServiceBackend interface.
+func (k *Kubernetes) Lookup(state request.Request, name string, typ uint16) (*dns.Msg, error) {
+	return k.Proxy.Lookup(state, name, typ)
+}
+
+// IsNameError implements the ServiceBackend interface.
+// TODO(infoblox): implement!
+func (k *Kubernetes) IsNameError(err error) bool {
+	return false
+}
+
+// Debug implements the ServiceBackend interface.
+func (k *Kubernetes) Debug() string {
+	return "debug"
+}
+
 func (k *Kubernetes) getClientConfig() (*restclient.Config, error) {
 	// For a custom api server or running outside a k8s cluster
 	// set URL in env.KUBERNETES_MASTER or set endpoint in Corefile
@@ -73,7 +97,6 @@ func (k *Kubernetes) getClientConfig() (*restclient.Config, error) {
 }
 
 // InitKubeCache initializes a new Kubernetes cache.
-// TODO(miek): is this correct?
 func (k *Kubernetes) InitKubeCache() error {
 
 	config, err := k.getClientConfig()
@@ -83,21 +106,24 @@ func (k *Kubernetes) InitKubeCache() error {
 
 	kubeClient, err := clientset_generated.NewForConfig(config)
 	if err != nil {
-		log.Printf("[ERROR] Failed to create kubernetes notification controller: %v", err)
-		return err
+		return fmt.Errorf("Failed to create kubernetes notification controller: %v", err)
 	}
-	if k.LabelSelector == nil {
-		log.Printf("[INFO] Kubernetes middleware configured without a label selector. No label-based filtering will be performed.")
-	} else {
+
+	if k.LabelSelector != nil {
 		var selector labels.Selector
 		selector, err = unversionedapi.LabelSelectorAsSelector(k.LabelSelector)
 		k.Selector = &selector
 		if err != nil {
-			log.Printf("[ERROR] Unable to create Selector for LabelSelector '%s'.Error was: %s", k.LabelSelector, err)
-			return err
+			return fmt.Errorf("Unable to create Selector for LabelSelector '%s'.Error was: %s", k.LabelSelector, err)
 		}
+	}
+
+	if k.LabelSelector == nil {
+		log.Printf("[INFO] Kubernetes middleware configured without a label selector. No label-based filtering will be performed.")
+	} else {
 		log.Printf("[INFO] Kubernetes middleware configured with the label selector '%s'. Only kubernetes objects matching this label selector will be exposed.", unversionedapi.FormatLabelSelector(k.LabelSelector))
 	}
+
 	k.APIConn = newdnsController(kubeClient, k.ResyncPeriod, k.Selector)
 
 	return err
@@ -125,12 +151,11 @@ func (k *Kubernetes) getZoneForName(name string) (string, []string) {
 	return zone, serviceSegments
 }
 
-// Records looks up services in kubernetes.
-// If exact is true, it will lookup just
-// this name. This is used when find matches when completing SRV lookups
+// Records looks up services in kubernetes. If exact is true, it will lookup
+// just this name. This is used when find matches when completing SRV lookups
 // for instance.
 func (k *Kubernetes) Records(name string, exact bool) ([]msg.Service, error) {
-	// TODO: refector this.
+	// TODO: refactor this.
 	// Right now NamespaceFromSegmentArray do not supports PRE queries
 	ip := dnsutil.ExtractAddressFromReverse(name)
 	if ip != "" {
@@ -169,7 +194,7 @@ func (k *Kubernetes) Records(name string, exact bool) ([]msg.Service, error) {
 
 	// Abort if the namespace does not contain a wildcard, and namespace is not published per CoreFile
 	// Case where namespace contains a wildcard is handled in Get(...) method.
-	if (!nsWildcard) && (len(k.Namespaces) > 0) && (!dns_strings.StringInSlice(namespace, k.Namespaces)) {
+	if (!nsWildcard) && (len(k.Namespaces) > 0) && (!dnsstrings.StringInSlice(namespace, k.Namespaces)) {
 		return nil, nil
 	}
 
@@ -219,7 +244,7 @@ func (k *Kubernetes) Get(namespace string, nsWildcard bool, servicename string,
 		if symbolMatches(namespace, item.Namespace, nsWildcard) && symbolMatches(servicename, item.Name, serviceWildcard) {
 			// If namespace has a wildcard, filter results against Corefile namespace list.
 			// (Namespaces without a wildcard were filtered before the call to this function.)
-			if nsWildcard && (len(k.Namespaces) > 0) && (!dns_strings.StringInSlice(item.Namespace, k.Namespaces)) {
+			if nsWildcard && (len(k.Namespaces) > 0) && (!dnsstrings.StringInSlice(item.Namespace, k.Namespaces)) {
 				continue
 			}
 			resultItems = append(resultItems, item)
@@ -242,11 +267,6 @@ func symbolMatches(queryString string, candidateString string, wildcard bool) bo
 	return result
 }
 
-// kubernetesNameError checks if the error is ErrorCodeKeyNotFound from kubernetes.
-func isKubernetesNameError(err error) bool {
-	return false
-}
-
 func (k *Kubernetes) getServiceRecordForIP(ip, name string) []msg.Service {
 	svcList, err := k.APIConn.svcLister.List(labels.Everything())
 	if err != nil {

middleware/kubernetes/lookup.go

@@ -2,11 +2,8 @@ package kubernetes
 
 import (
 	"fmt"
-	"math"
 	"net"
-	"time"
 
-	"github.com/miekg/coredns/middleware"
 	"github.com/miekg/coredns/middleware/etcd/msg"
 	"github.com/miekg/coredns/middleware/pkg/dnsutil"
 	"github.com/miekg/coredns/request"
@@ -19,278 +16,10 @@ func (k Kubernetes) records(state request.Request, exact bool) ([]msg.Service, e
 	if err != nil {
 		return nil, err
 	}
-	// TODO: Do we want to support the SkyDNS (hacky) Group feature?
 	services = msg.Group(services)
 	return services, nil
 }
 
-// A returns A records from kubernetes or an error.
-func (k Kubernetes) A(zone string, state request.Request, previousRecords []dns.RR) (records []dns.RR, err error) {
-	services, err := k.records(state, false)
-	if err != nil {
-		return nil, err
-	}
-
-	for _, serv := range services {
-		ip := net.ParseIP(serv.Host)
-		switch {
-		case ip == nil:
-			// TODO(miek): lowercasing? Should lowercase in everything see #85
-			if middleware.Name(state.Name()).Matches(dns.Fqdn(serv.Host)) {
-				// x CNAME x is a direct loop, don't add those
-				continue
-			}
-
-			newRecord := serv.NewCNAME(state.QName(), serv.Host)
-			if len(previousRecords) > 7 {
-				// don't add it, and just continue
-				continue
-			}
-			if dnsutil.DuplicateCNAME(newRecord, previousRecords) {
-				continue
-			}
-
-			state1 := state.NewWithQuestion(serv.Host, state.QType())
-			nextRecords, err := k.A(zone, state1, append(previousRecords, newRecord))
-
-			if err == nil {
-				// Not only have we found something we should add the CNAME and the IP addresses.
-				if len(nextRecords) > 0 {
-					records = append(records, newRecord)
-					records = append(records, nextRecords...)
-				}
-				continue
-			}
-			// This means we can not complete the CNAME, try to look else where.
-			target := newRecord.Target
-			if dns.IsSubDomain(zone, target) {
-				// We should already have found it
-				continue
-			}
-			mes, err := k.Proxy.Lookup(state, target, state.QType())
-			if err != nil {
-				continue
-			}
-			// Len(mes.Answer) > 0 here is well?
-			records = append(records, newRecord)
-			records = append(records, mes.Answer...)
-			continue
-		case ip.To4() != nil:
-			records = append(records, serv.NewA(state.QName(), ip.To4()))
-		case ip.To4() == nil:
-			// nodata?
-		}
-	}
-	return records, nil
-}
-
-// AAAA returns AAAA records from kubernetes or an error.
-func (k Kubernetes) AAAA(zone string, state request.Request, previousRecords []dns.RR) (records []dns.RR, err error) {
-	services, err := k.records(state, false)
-	if err != nil {
-		return nil, err
-	}
-
-	for _, serv := range services {
-		ip := net.ParseIP(serv.Host)
-		switch {
-		case ip == nil:
-			// Try to resolve as CNAME if it's not an IP, but only if we don't create loops.
-			if middleware.Name(state.Name()).Matches(dns.Fqdn(serv.Host)) {
-				// x CNAME x is a direct loop, don't add those
-				continue
-			}
-
-			newRecord := serv.NewCNAME(state.QName(), serv.Host)
-			if len(previousRecords) > 7 {
-				// don't add it, and just continue
-				continue
-			}
-			if dnsutil.DuplicateCNAME(newRecord, previousRecords) {
-				continue
-			}
-
-			state1 := state.NewWithQuestion(serv.Host, state.QType())
-			nextRecords, err := k.AAAA(zone, state1, append(previousRecords, newRecord))
-
-			if err == nil {
-				// Not only have we found something we should add the CNAME and the IP addresses.
-				if len(nextRecords) > 0 {
-					records = append(records, newRecord)
-					records = append(records, nextRecords...)
-				}
-				continue
-			}
-			// This means we can not complete the CNAME, try to look else where.
-			target := newRecord.Target
-			if dns.IsSubDomain(zone, target) {
-				// We should already have found it
-				continue
-			}
-			m1, e1 := k.Proxy.Lookup(state, target, state.QType())
-			if e1 != nil {
-				continue
-			}
-			// Len(m1.Answer) > 0 here is well?
-			records = append(records, newRecord)
-			records = append(records, m1.Answer...)
-			continue
-			// both here again
-		case ip.To4() != nil:
-			// nada?
-		case ip.To4() == nil:
-			records = append(records, serv.NewAAAA(state.QName(), ip.To16()))
-		}
-	}
-	return records, nil
-}
-
-// SRV returns SRV records from kubernetes.
-// If the Target is not a name but an IP address, a name is created on the fly and the IP address is put in
-// the additional section.
-func (k Kubernetes) SRV(zone string, state request.Request) (records []dns.RR, extra []dns.RR, err error) {
-	services, err := k.records(state, false)
-	if err != nil {
-		return nil, nil, err
-	}
-
-	// Looping twice to get the right weight vs priority
-	w := make(map[int]int)
-	for _, serv := range services {
-		weight := 100
-		if serv.Weight != 0 {
-			weight = serv.Weight
-		}
-		if _, ok := w[serv.Priority]; !ok {
-			w[serv.Priority] = weight
-			continue
-		}
-		w[serv.Priority] += weight
-	}
-	lookup := make(map[string]bool)
-	for _, serv := range services {
-		w1 := 100.0 / float64(w[serv.Priority])
-		if serv.Weight == 0 {
-			w1 *= 100
-		} else {
-			w1 *= float64(serv.Weight)
-		}
-		weight := uint16(math.Floor(w1))
-		ip := net.ParseIP(serv.Host)
-		switch {
-		case ip == nil:
-			srv := serv.NewSRV(state.QName(), weight)
-			records = append(records, srv)
-
-			if _, ok := lookup[srv.Target]; ok {
-				break
-			}
-
-			lookup[srv.Target] = true
-
-			if !dns.IsSubDomain(zone, srv.Target) {
-				m1, e1 := k.Proxy.Lookup(state, srv.Target, dns.TypeA)
-				if e1 == nil {
-					extra = append(extra, m1.Answer...)
-				}
-				m1, e1 = k.Proxy.Lookup(state, srv.Target, dns.TypeAAAA)
-				if e1 == nil {
-					// If we have seen CNAME's we *assume* that they are already added.
-					for _, a := range m1.Answer {
-						if _, ok := a.(*dns.CNAME); !ok {
-							extra = append(extra, a)
-						}
-					}
-				}
-				break
-			}
-			// Internal name, we should have some info on them, either v4 or v6
-			// Clients expect a complete answer, because we are a recursor in their view.
-			state1 := state.NewWithQuestion(srv.Target, dns.TypeA)
-			addr, e1 := k.A(zone, state1, nil)
-			if e1 == nil {
-				extra = append(extra, addr...)
-			}
-			// k.AAA(zone, state1, nil) as well...?
-		case ip.To4() != nil:
-			serv.Host = serv.Key
-			srv := serv.NewSRV(state.QName(), weight)
-
-			records = append(records, srv)
-			extra = append(extra, serv.NewA(srv.Target, ip.To4()))
-		case ip.To4() == nil:
-			serv.Host = serv.Key
-			srv := serv.NewSRV(state.QName(), weight)
-
-			records = append(records, srv)
-			extra = append(extra, serv.NewAAAA(srv.Target, ip.To16()))
-		}
-	}
-	return records, extra, nil
-}
-
-// MX returns MX records from kubernetes. Not implemented!
-func (k Kubernetes) MX(zone string, state request.Request) (records []dns.RR, extra []dns.RR, err error) {
-	return nil, nil, err
-}
-
-// CNAME returns CNAME records from kubernetes. Not implemented!
-func (k Kubernetes) CNAME(zone string, state request.Request) (records []dns.RR, err error) {
-	return nil, err
-}
-
-// TXT returns TXT records from kubernetes. Not implemented!
-func (k Kubernetes) TXT(zone string, state request.Request) (records []dns.RR, err error) {
-	return nil, err
-}
-
-// NS returns NS records from kubernetes.
-func (k Kubernetes) NS(zone string, state request.Request) (records, extra []dns.RR, err error) {
-	// NS record for this zone live in a special place, ns.dns.<zone>. Fake our lookup.
-	// only a tad bit fishy...
-	old := state.QName()
-
-	state.Clear()
-	state.Req.Question[0].Name = "ns.dns." + zone
-	services, err := k.records(state, false)
-	if err != nil {
-		return nil, nil, err
-	}
-	// ... and reset
-	state.Req.Question[0].Name = old
-
-	for _, serv := range services {
-		ip := net.ParseIP(serv.Host)
-		switch {
-		case ip == nil:
-			return nil, nil, fmt.Errorf("NS record must be an IP address: %s", serv.Host)
-		case ip.To4() != nil:
-			serv.Host = serv.Key
-			records = append(records, serv.NewNS(state.QName()))
-			extra = append(extra, serv.NewA(serv.Host, ip.To4()))
-		case ip.To4() == nil:
-			serv.Host = serv.Key
-			records = append(records, serv.NewNS(state.QName()))
-			extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
-		}
-	}
-	return records, extra, nil
-}
-
-// SOA Record returns a SOA record from kubernetes.
-func (k Kubernetes) SOA(zone string, state request.Request) *dns.SOA {
-	header := dns.RR_Header{Name: zone, Rrtype: dns.TypeSOA, Ttl: 300, Class: dns.ClassINET}
-	return &dns.SOA{Hdr: header,
-		Mbox:    "hostmaster." + zone,
-		Ns:      "ns.dns." + zone,
-		Serial:  uint32(time.Now().Unix()),
-		Refresh: 7200,
-		Retry:   1800,
-		Expire:  86400,
-		Minttl:  60,
-	}
-}
-
 // PTR Record returns PTR records from kubernetes.
 func (k Kubernetes) PTR(zone string, state request.Request) ([]dns.RR, error) {
 	reverseIP := dnsutil.ExtractAddressFromReverse(state.Name())