Merge pull request #7882 from heyitsanthony/srv-priority

gateway: DNS SRV priority

Author: Anthony Romano

client/discover.go

@@ -14,8 +14,27 @@
 
 package client
 
+import (
+	"github.com/coreos/etcd/pkg/srv"
+)
+
 // Discoverer is an interface that wraps the Discover method.
 type Discoverer interface {
 	// Discover looks up the etcd servers for the domain.
 	Discover(domain string) ([]string, error)
 }
+
+type srvDiscover struct{}
+
+// NewSRVDiscover constructs a new Discoverer that uses the stdlib to lookup SRV records.
+func NewSRVDiscover() Discoverer {
+	return &srvDiscover{}
+}
+
+func (d *srvDiscover) Discover(domain string) ([]string, error) {
+	srvs, err := srv.GetClient("etcd-client", domain)
+	if err != nil {
+		return nil, err
+	}
+	return srvs.Endpoints, nil
+}

client/srv.go

@@ -22,10 +22,10 @@ import (
 	"net/url"
 	"strings"
 
-	"github.com/coreos/etcd/discovery"
 	"github.com/coreos/etcd/etcdserver"
 	"github.com/coreos/etcd/pkg/cors"
 	"github.com/coreos/etcd/pkg/netutil"
+	"github.com/coreos/etcd/pkg/srv"
 	"github.com/coreos/etcd/pkg/transport"
 	"github.com/coreos/etcd/pkg/types"
 
@@ -321,11 +321,15 @@ func (cfg *Config) PeerURLsMapAndToken(which string) (urlsmap types.URLsMap, tok
 		urlsmap[cfg.Name] = cfg.APUrls
 		token = cfg.Durl
 	case cfg.DNSCluster != "":
-		var clusterStr string
-		clusterStr, err = discovery.SRVGetCluster(cfg.Name, cfg.DNSCluster, cfg.APUrls)
-		if err != nil {
-			return nil, "", err
+		clusterStrs, cerr := srv.GetCluster("etcd-server", cfg.Name, cfg.DNSCluster, cfg.APUrls)
+		if cerr != nil {
+			plog.Errorf("couldn't resolve during SRV discovery (%v)", cerr)
+			return nil, "", cerr
+		}
+		for _, s := range clusterStrs {
+			plog.Noticef("got bootstrap from DNS for etcd-server at %s", s)
 		}
+		clusterStr := strings.Join(clusterStrs, ",")
 		if strings.Contains(clusterStr, "https://") && cfg.PeerTLSInfo.CAFile == "" {
 			cfg.PeerTLSInfo.ServerName = cfg.DNSCluster
 		}

client/srv_test.go

@@ -91,17 +91,28 @@ func stripSchema(eps []string) []string {
 
 	return endpoints
 }
-func startGateway(cmd *cobra.Command, args []string) {
-	endpoints := gatewayEndpoints
 
-	if eps := discoverEndpoints(gatewayDNSCluster, gatewayCA, gatewayInsecureDiscovery); len(eps) != 0 {
-		endpoints = eps
+func startGateway(cmd *cobra.Command, args []string) {
+	srvs := discoverEndpoints(gatewayDNSCluster, gatewayCA, gatewayInsecureDiscovery)
+	if len(srvs.Endpoints) == 0 {
+		// no endpoints discovered, fall back to provided endpoints
+		srvs.Endpoints = gatewayEndpoints
 	}
-
 	// Strip the schema from the endpoints because we start just a TCP proxy
-	endpoints = stripSchema(endpoints)
+	srvs.Endpoints = stripSchema(srvs.Endpoints)
+	if len(srvs.SRVs) == 0 {
+		for _, ep := range srvs.Endpoints {
+			h, p, err := net.SplitHostPort(ep)
+			if err != nil {
+				plog.Fatalf("error parsing endpoint %q", ep)
+			}
+			var port uint16
+			fmt.Sscanf(p, "%d", &port)
+			srvs.SRVs = append(srvs.SRVs, &net.SRV{Target: h, Port: port})
+		}
+	}
 
-	if len(endpoints) == 0 {
+	if len(srvs.Endpoints) == 0 {
 		plog.Fatalf("no endpoints found")
 	}
 
@@ -113,7 +124,7 @@ func startGateway(cmd *cobra.Command, args []string) {
 
 	tp := tcpproxy.TCPProxy{
 		Listener:        l,
-		Endpoints:       endpoints,
+		Endpoints:       srvs.SRVs,
 		MonitorInterval: getewayRetryDelay,
 	}
 

embed/config.go

@@ -106,8 +106,9 @@ func startGRPCProxy(cmd *cobra.Command, args []string) {
 		os.Exit(1)
 	}
 
-	if eps := discoverEndpoints(grpcProxyDNSCluster, grpcProxyCA, grpcProxyInsecureDiscovery); len(eps) != 0 {
-		grpcProxyEndpoints = eps
+	srvs := discoverEndpoints(grpcProxyDNSCluster, grpcProxyCA, grpcProxyInsecureDiscovery)
+	if len(srvs.Endpoints) != 0 {
+		grpcProxyEndpoints = srvs.Endpoints
 	}
 
 	l, err := net.Listen("tcp", grpcProxyListenAddr)

etcdmain/gateway.go

@@ -18,22 +18,23 @@ import (
 	"fmt"
 	"os"
 
-	"github.com/coreos/etcd/client"
+	"github.com/coreos/etcd/pkg/srv"
 	"github.com/coreos/etcd/pkg/transport"
 )
 
-func discoverEndpoints(dns string, ca string, insecure bool) (endpoints []string) {
+func discoverEndpoints(dns string, ca string, insecure bool) (s srv.SRVClients) {
 	if dns == "" {
-		return nil
+		return s
 	}
-	endpoints, err := client.NewSRVDiscover().Discover(dns)
+	srvs, err := srv.GetClient("etcd-client", dns)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
 	}
+	endpoints := srvs.Endpoints
 	plog.Infof("discovered the cluster %s from %s", endpoints, dns)
 	if insecure {
-		return endpoints
+		return *srvs
 	}
 	// confirm TLS connections are good
 	tlsInfo := transport.TLSInfo{
@@ -46,5 +47,19 @@ func discoverEndpoints(dns string, ca string, insecure bool) (endpoints []string
 		plog.Warningf("%v", err)
 	}
 	plog.Infof("using discovered endpoints %v", endpoints)
-	return endpoints
+
+	// map endpoints back to SRVClients struct with SRV data
+	eps := make(map[string]struct{})
+	for _, ep := range endpoints {
+		eps[ep] = struct{}{}
+	}
+	for i := range srvs.Endpoints {
+		if _, ok := eps[srvs.Endpoints[i]]; !ok {
+			continue
+		}
+		s.Endpoints = append(s.Endpoints, srvs.Endpoints[i])
+		s.SRVs = append(s.SRVs, srvs.SRVs[i])
+	}
+
+	return s
 }