balancer: add Authority field to balancer.BuildOptions

balancer/balancer.go

@@ -174,25 +174,32 @@ type ClientConn interface {
 
 // BuildOptions contains additional information for Build.
 type BuildOptions struct {
-	// DialCreds is the transport credential the Balancer implementation can
-	// use to dial to a remote load balancer server. The Balancer implementations
-	// can ignore this if it does not need to talk to another party securely.
+	// DialCreds is the transport credentials to use when communicating with a
+	// remote load balancer server. Balancer implementations which do not
+	// communicate with a remote load balancer server can ignore this field.
 	DialCreds credentials.TransportCredentials
-	// CredsBundle is the credentials bundle that the Balancer can use.
+	// CredsBundle is the credentials bundle to use when communicating with a
+	// remote load balancer server. Balancer implementations which do not
+	// communicate with a remote load balancer server can ignore this field.
 	CredsBundle credentials.Bundle
-	// Dialer is the custom dialer the Balancer implementation can use to dial
-	// to a remote load balancer server. The Balancer implementations
-	// can ignore this if it doesn't need to talk to remote balancer.
+	// Dialer is the custom dialer to use when communicating with a remote load
+	// balancer server. Balancer implementations which do not communicate with a
+	// remote load balancer server can ignore this field.
 	Dialer func(context.Context, string) (net.Conn, error)
-	// ChannelzParentID is the entity parent's channelz unique identification number.
+	// Authority is the server name to use as part of the authentication
+	// handshake when communicating with a remote load balancer server. Balancer
+	// implementations which do not communicate with a remote load balancer
+	// server can ignore this field.
+	Authority string
+	// ChannelzParentID is the parent ClientConn's channelz ID.
 	ChannelzParentID int64
 	// CustomUserAgent is the custom user agent set on the parent ClientConn.
 	// The balancer should set the same custom user agent if it creates a
 	// ClientConn.
 	CustomUserAgent string
-	// Target contains the parsed address info of the dial target. It is the same resolver.Target as
-	// passed to the resolver.
-	// See the documentation for the resolver.Target type for details about what it contains.
+	// Target contains the parsed address info of the dial target. It is the
+	// same resolver.Target as passed to the resolver. See the documentation for
+	// the resolver.Target type for details about what it contains.
 	Target resolver.Target
 }
 

clientconn.go

@@ -285,6 +285,7 @@ func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *
 		DialCreds:        credsClone,
 		CredsBundle:      cc.dopts.copts.CredsBundle,
 		Dialer:           cc.dopts.copts.Dialer,
+		Authority:        cc.authority,
 		CustomUserAgent:  cc.dopts.copts.UserAgent,
 		ChannelzParentID: cc.channelzID,
 		Target:           cc.parsedTarget,

test/balancer_test.go

@@ -36,6 +36,7 @@ import (
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/connectivity"
 	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/credentials/insecure"
 	"google.golang.org/grpc/internal/balancer/stub"
 	"google.golang.org/grpc/internal/balancerload"
 	"google.golang.org/grpc/internal/grpcutil"
@@ -821,3 +822,127 @@ func (s) TestWaitForReady(t *testing.T) {
 		t.Fatal(err.Error())
 	}
 }
+
+// authorityOverrideTransportCreds returns the configured authority value in its
+// Info() method.
+type authorityOverrideTransportCreds struct {
+	credentials.TransportCredentials
+	authorityOverride string
+}
+
+func (ao *authorityOverrideTransportCreds) ClientHandshake(ctx context.Context, addr string, rawConn net.Conn) (net.Conn, credentials.AuthInfo, error) {
+	return rawConn, nil, nil
+}
+func (ao *authorityOverrideTransportCreds) Info() credentials.ProtocolInfo {
+	return credentials.ProtocolInfo{ServerName: ao.authorityOverride}
+}
+func (ao *authorityOverrideTransportCreds) Clone() credentials.TransportCredentials {
+	return &authorityOverrideTransportCreds{authorityOverride: ao.authorityOverride}
+}
+
+// TestAuthorityInBuildOptions tests that the Authority field in
+// balancer.BuildOptions is setup correctly from gRPC.
+func (s) TestAuthorityInBuildOptions(t *testing.T) {
+	const dialTarget = "test.server"
+
+	tests := []struct {
+		name          string
+		dopts         []grpc.DialOption
+		wantAuthority string
+	}{
+		{
+			name:          "authority from dial target",
+			dopts:         []grpc.DialOption{grpc.WithTransportCredentials(insecure.NewCredentials())},
+			wantAuthority: dialTarget,
+		},
+		{
+			name: "authority from dial option",
+			dopts: []grpc.DialOption{
+				grpc.WithTransportCredentials(insecure.NewCredentials()),
+				grpc.WithAuthority("authority-override"),
+			},
+			wantAuthority: "authority-override",
+		},
+		{
+			name:          "authority from transport creds",
+			dopts:         []grpc.DialOption{grpc.WithTransportCredentials(&authorityOverrideTransportCreds{authorityOverride: "authority-override-from-transport-creds"})},
+			wantAuthority: "authority-override-from-transport-creds",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			authorityCh := make(chan string, 1)
+			bf := stub.BalancerFuncs{
+				UpdateClientConnState: func(bd *stub.BalancerData, ccs balancer.ClientConnState) error {
+					select {
+					case authorityCh <- bd.BuildOptions.Authority:
+					default:
+					}
+
+					addrs := ccs.ResolverState.Addresses
+					if len(addrs) == 0 {
+						return nil
+					}
+
+					// Only use the first address.
+					sc, err := bd.ClientConn.NewSubConn([]resolver.Address{addrs[0]}, balancer.NewSubConnOptions{})
+					if err != nil {
+						return err
+					}
+					sc.Connect()
+					return nil
+				},
+				UpdateSubConnState: func(bd *stub.BalancerData, sc balancer.SubConn, state balancer.SubConnState) {
+					bd.ClientConn.UpdateState(balancer.State{ConnectivityState: state.ConnectivityState, Picker: &aiPicker{result: balancer.PickResult{SubConn: sc}, err: state.ConnectionError}})
+				},
+			}
+			balancerName := "stub-balancer-" + test.name
+			stub.Register(balancerName, bf)
+			t.Logf("Registered balancer %s...", balancerName)
+
+			lis, err := testutils.LocalTCPListener()
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			s := grpc.NewServer()
+			testpb.RegisterTestServiceServer(s, &testServer{})
+			go s.Serve(lis)
+			defer s.Stop()
+			t.Logf("Started gRPC server at %s...", lis.Addr().String())
+
+			r := manual.NewBuilderWithScheme("whatever")
+			t.Logf("Registered manual resolver with scheme %s...", r.Scheme())
+			r.InitialState(resolver.State{Addresses: []resolver.Address{{Addr: lis.Addr().String()}}})
+
+			dopts := append([]grpc.DialOption{
+				grpc.WithResolvers(r),
+				grpc.WithDefaultServiceConfig(fmt.Sprintf(`{ "loadBalancingConfig": [{"%v": {}}] }`, balancerName)),
+			}, test.dopts...)
+			cc, err := grpc.Dial(r.Scheme()+":///"+dialTarget, dopts...)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer cc.Close()
+			tc := testpb.NewTestServiceClient(cc)
+			t.Log("Created a ClientConn...")
+
+			ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+			defer cancel()
+			if _, err := tc.EmptyCall(ctx, &testpb.Empty{}); err != nil {
+				t.Fatalf("EmptyCall() = _, %v, want _, <nil>", err)
+			}
+			t.Log("Made an RPC which succeeded...")
+
+			select {
+			case <-ctx.Done():
+				t.Fatal("timeout when waiting for Authority in balancer.BuildOptions")
+			case gotAuthority := <-authorityCh:
+				if gotAuthority != test.wantAuthority {
+					t.Fatalf("Authority in balancer.BuildOptions is %s, want %s", gotAuthority, test.wantAuthority)
+				}
+			}
+		})
+	}
+}