plugin/etcdv3: Add etcd v3 plugin (#1702)

* Update dependencies and add etcdv3 client

* Update etcd plugin to support etcd v3 clients

Fixes #341

5 files changed, 64 insertions, 70 deletions

diff --git a/plugin/etcd/README.md b/plugin/etcd/README.md
index 2306729b2..e60292a6d 100644
--- a/plugin/etcd/README.md
+++ b/plugin/etcd/README.md
@@ -2,11 +2,11 @@
 
 ## Name
 
-*etcd* - enables reading zone data from an etcd instance.
+*etcd* - enables reading zone data from an etcd version 3 instance.
 
 ## Description
 
-The data in etcd has to be encoded as
+The data in etcd instance has to be encoded as
 a [message](https://github.com/skynetservices/skydns/blob/2fcff74cdc9f9a7dd64189a447ef27ac354b725f/msg/service.go#L26)
 like [SkyDNS](https://github.com/skynetservices/skydns). It should also work just like SkyDNS.
 
@@ -21,7 +21,7 @@ etcd [ZONES...]
 
 * **ZONES** zones etcd should be authoritative for.
 
-The path will default to `/skydns` the local etcd proxy (http://localhost:2379). If no zones are
+The path will default to `/skydns` the local etcd3 proxy (http://localhost:2379). If no zones are
 specified the block's zone will be used as the zone.
 
 If you want to `round robin` A and AAAA responses look at the `loadbalance` plugin.
@@ -169,7 +169,3 @@ dig +short skydns.local AAAA @localhost
 2003::8:1
 2003::8:2
 ~~~
-
-## Bugs
-
-Only the etcdv2 protocol is supported.
diff --git a/plugin/etcd/etcd.go b/plugin/etcd/etcd.go
index fc4542bfe..493764f0b 100644
--- a/plugin/etcd/etcd.go
+++ b/plugin/etcd/etcd.go
@@ -1,9 +1,10 @@
-// Package etcd provides the etcd backend plugin.
+// Package etcd provides the etcd version 3 backend plugin.
 package etcd
 
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"strings"
 	"time"
@@ -15,10 +16,19 @@ import (
 	"github.com/coredns/coredns/request"
 
 	"github.com/coredns/coredns/plugin/pkg/upstream"
-	etcdc "github.com/coreos/etcd/client"
+	etcdcv3 "github.com/coreos/etcd/clientv3"
+	"github.com/coreos/etcd/mvcc/mvccpb"
 	"github.com/miekg/dns"
 )
 
+const (
+	priority    = 10  // default priority when nothing is set
+	ttl         = 300 // default ttl when nothing is set
+	etcdTimeout = 5 * time.Second
+)
+
+var errKeyNotFound = errors.New("Key not found")
+
 // Etcd is a plugin talks to an etcd cluster.
 type Etcd struct {
 	Next       plugin.Handler
@@ -26,7 +36,7 @@ type Etcd struct {
 	Zones      []string
 	PathPrefix string
 	Upstream   upstream.Upstream // Proxy for looking up names during the resolution process
-	Client     etcdc.KeysAPI
+	Client     *etcdcv3.Client
 	Ctx        context.Context
 	Stubmap    *map[string]proxy.Proxy // list of proxies for stub resolving.
 
@@ -56,10 +66,7 @@ func (e *Etcd) Lookup(state request.Request, name string, typ uint16) (*dns.Msg,
 
 // IsNameError implements the ServiceBackend interface.
 func (e *Etcd) IsNameError(err error) bool {
-	if ee, ok := err.(etcdc.Error); ok && ee.Code == etcdc.ErrorCodeKeyNotFound {
-		return true
-	}
-	return false
+	return err == errKeyNotFound
 }
 
 // Records looks up records in etcd. If exact is true, it will lookup just this
@@ -73,51 +80,50 @@ func (e *Etcd) Records(state request.Request, exact bool) ([]msg.Service, error)
 		return nil, err
 	}
 	segments := strings.Split(msg.Path(name, e.PathPrefix), "/")
-	switch {
-	case exact && r.Node.Dir:
-		return nil, nil
-	case r.Node.Dir:
-		return e.loopNodes(r.Node.Nodes, segments, star, nil)
-	default:
-		return e.loopNodes([]*etcdc.Node{r.Node}, segments, false, nil)
-	}
+	return e.loopNodes(r.Kvs, segments, star)
 }
 
-// get is a wrapper for client.Get
-func (e *Etcd) get(path string, recursive bool) (*etcdc.Response, error) {
+func (e *Etcd) get(path string, recursive bool) (*etcdcv3.GetResponse, error) {
 	ctx, cancel := context.WithTimeout(e.Ctx, etcdTimeout)
 	defer cancel()
-	r, err := e.Client.Get(ctx, path, &etcdc.GetOptions{Sort: false, Recursive: recursive})
+	if recursive == true {
+		if !strings.HasSuffix(path, "/") {
+			path = path + "/"
+		}
+		r, err := e.Client.Get(ctx, path, etcdcv3.WithPrefix())
+		if err != nil {
+			return nil, err
+		}
+		if r.Count == 0 {
+			path = strings.TrimSuffix(path, "/")
+			r, err = e.Client.Get(ctx, path)
+			if err != nil {
+				return nil, err
+			}
+			if r.Count == 0 {
+				return nil, errKeyNotFound
+			}
+		}
+		return r, nil
+	}
+
+	r, err := e.Client.Get(ctx, path)
 	if err != nil {
 		return nil, err
 	}
+	if r.Count == 0 {
+		return nil, errKeyNotFound
+	}
 	return r, nil
 }
 
-// skydns/local/skydns/east/staging/web
-// skydns/local/skydns/west/production/web
-//
-// skydns/local/skydns/*/*/web
-// skydns/local/skydns/*/web
-
-// loopNodes recursively loops through the nodes and returns all the values. The nodes' keyname
-// will be match against any wildcards when star is true.
-func (e *Etcd) loopNodes(ns []*etcdc.Node, nameParts []string, star bool, bx map[msg.Service]bool) (sx []msg.Service, err error) {
-	if bx == nil {
-		bx = make(map[msg.Service]bool)
-	}
+func (e *Etcd) loopNodes(kv []*mvccpb.KeyValue, nameParts []string, star bool) (sx []msg.Service, err error) {
+	bx := make(map[msg.Service]bool)
 Nodes:
-	for _, n := range ns {
-		if n.Dir {
-			nodes, err := e.loopNodes(n.Nodes, nameParts, star, bx)
-			if err != nil {
-				return nil, err
-			}
-			sx = append(sx, nodes...)
-			continue
-		}
+	for _, n := range kv {
 		if star {
-			keyParts := strings.Split(n.Key, "/")
+			s := string(n.Key)
+			keyParts := strings.Split(s, "/")
 			for i, n := range nameParts {
 				if i > len(keyParts)-1 {
 					// name is longer than key
@@ -132,16 +138,16 @@ Nodes:
 			}
 		}
 		serv := new(msg.Service)
-		if err := json.Unmarshal([]byte(n.Value), serv); err != nil {
+		if err := json.Unmarshal(n.Value, serv); err != nil {
 			return nil, fmt.Errorf("%s: %s", n.Key, err.Error())
 		}
-		b := msg.Service{Host: serv.Host, Port: serv.Port, Priority: serv.Priority, Weight: serv.Weight, Text: serv.Text, Key: n.Key}
+		b := msg.Service{Host: serv.Host, Port: serv.Port, Priority: serv.Priority, Weight: serv.Weight, Text: serv.Text, Key: string(n.Key)}
 		if _, ok := bx[b]; ok {
 			continue
 		}
 		bx[b] = true
 
-		serv.Key = n.Key
+		serv.Key = string(n.Key)
 		serv.TTL = e.TTL(n, serv)
 		if serv.Priority == 0 {
 			serv.Priority = priority
@@ -153,8 +159,8 @@ Nodes:
 
 // TTL returns the smaller of the etcd TTL and the service's
 // TTL. If neither of these are set (have a zero value), a default is used.
-func (e *Etcd) TTL(node *etcdc.Node, serv *msg.Service) uint32 {
-	etcdTTL := uint32(node.TTL)
+func (e *Etcd) TTL(kv *mvccpb.KeyValue, serv *msg.Service) uint32 {
+	etcdTTL := uint32(kv.Lease)
 
 	if etcdTTL == 0 && serv.TTL == 0 {
 		return ttl
@@ -170,9 +176,3 @@ func (e *Etcd) TTL(node *etcdc.Node, serv *msg.Service) uint32 {
 	}
 	return serv.TTL
 }
-
-const (
-	priority    = 10  // default priority when nothing is set
-	ttl         = 300 // default ttl when nothing is set
-	etcdTimeout = 5 * time.Second
-)
diff --git a/plugin/etcd/handler.go b/plugin/etcd/handler.go
index 8520680d8..b70684165 100644
--- a/plugin/etcd/handler.go
+++ b/plugin/etcd/handler.go
@@ -65,8 +65,7 @@ func (e *Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 		// Do a fake A lookup, so we can distinguish between NODATA and NXDOMAIN
 		_, err = plugin.A(e, zone, state, nil, opt)
 	}
-
-	if e.IsNameError(err) {
+	if err != nil && e.IsNameError(err) {
 		if e.Fall.Through(state.Name()) {
 			return plugin.NextOrFailure(e.Name(), e.Next, ctx, w, r)
 		}
diff --git a/plugin/etcd/lookup_test.go b/plugin/etcd/lookup_test.go
index 51e4b954b..68f654d34 100644
--- a/plugin/etcd/lookup_test.go
+++ b/plugin/etcd/lookup_test.go
@@ -15,7 +15,6 @@ import (
 	"github.com/coredns/coredns/plugin/proxy"
 	"github.com/coredns/coredns/plugin/test"
 
-	etcdc "github.com/coreos/etcd/client"
 	"github.com/miekg/dns"
 )
 
@@ -300,12 +299,12 @@ func set(t *testing.T, e *Etcd, k string, ttl time.Duration, m *msg.Service) {
 		t.Fatal(err)
 	}
 	path, _ := msg.PathWithWildcard(k, e.PathPrefix)
-	e.Client.Set(ctxt, path, string(b), &etcdc.SetOptions{TTL: ttl})
+	e.Client.KV.Put(ctxt, path, string(b))
 }
 
 func delete(t *testing.T, e *Etcd, k string) {
 	path, _ := msg.PathWithWildcard(k, e.PathPrefix)
-	e.Client.Delete(ctxt, path, &etcdc.DeleteOptions{Recursive: false})
+	e.Client.Delete(ctxt, path)
 }
 
 func TestLookup(t *testing.T) {
diff --git a/plugin/etcd/setup.go b/plugin/etcd/setup.go
index 0cc8b0553..7e03acf0d 100644
--- a/plugin/etcd/setup.go
+++ b/plugin/etcd/setup.go
@@ -11,7 +11,7 @@ import (
 	"github.com/coredns/coredns/plugin/pkg/upstream"
 	"github.com/coredns/coredns/plugin/proxy"
 
-	etcdc "github.com/coreos/etcd/client"
+	etcdcv3 "github.com/coreos/etcd/clientv3"
 	"github.com/mholt/caddy"
 )
 
@@ -124,22 +124,22 @@ func etcdParse(c *caddy.Controller) (*Etcd, bool, error) {
 		}
 		etc.Client = client
 		etc.endpoints = endpoints
-
+		
 		return &etc, stubzones, nil
 	}
 	return &Etcd{}, false, nil
 }
 
-func newEtcdClient(endpoints []string, cc *tls.Config) (etcdc.KeysAPI, error) {
-	etcdCfg := etcdc.Config{
+func newEtcdClient(endpoints []string, cc *tls.Config) (*etcdcv3.Client, error) {
+	etcdCfg := etcdcv3.Config{
 		Endpoints: endpoints,
-		Transport: mwtls.NewHTTPSTransport(cc),
+		TLS:       cc,
 	}
-	cli, err := etcdc.New(etcdCfg)
+	cli, err := etcdcv3.New(etcdCfg)
 	if err != nil {
 		return nil, err
 	}
-	return etcdc.NewKeysAPI(cli), nil
+	return cli, nil
 }
 
 const defaultEndpoint = "http://localhost:2379"