Merge pull request #209 from iamqizhao/master

Make Dial nonblocking by default. Add a DialOption to enable blocking operation if needed.

clientconn.go

@@ -61,6 +61,7 @@ var (
 // values passed to Dial.
 type dialOptions struct {
 	codec Codec
+	block bool
 	copts transport.ConnectOptions
 }
 
@@ -74,6 +75,15 @@ func WithCodec(c Codec) DialOption {
 	}
 }
 
+// WithBlock returns a DialOption which makes caller of Dial blocks until the underlying
+// connection is up. Without this, Dial returns immediately and connecting the server
+// happens in background.
+func WithBlock() DialOption {
+	return func(o *dialOptions) {
+		o.block = true
+	}
+}
+
 // WithTransportCredentials returns a DialOption which configures a
 // connection level security credentials (e.g., TLS/SSL).
 func WithTransportCredentials(creds credentials.TransportAuthenticator) DialOption {
@@ -112,7 +122,8 @@ func Dial(target string, opts ...DialOption) (*ClientConn, error) {
 		return nil, ErrUnspecTarget
 	}
 	cc := &ClientConn{
-		target: target,
+		target:       target,
+		shutdownChan: make(chan struct{}),
 	}
 	for _, opt := range opts {
 		opt(&cc.dopts)
@@ -126,12 +137,22 @@ func Dial(target string, opts ...DialOption) (*ClientConn, error) {
 		// Set the default codec.
 		cc.dopts.codec = protoCodec{}
 	}
-	if err := cc.resetTransport(false); err != nil {
-		return nil, err
+	if cc.dopts.block {
+		if err := cc.resetTransport(false); err != nil {
+			return nil, err
+		}
+		// Start to monitor the error status of transport.
+		go cc.transportMonitor()
+	} else {
+		// Start a goroutine connecting to the server asynchronously.
+		go func() {
+			if err := cc.resetTransport(false); err != nil {
+				grpclog.Printf("Failed to dial %s: %v; please retry.", target, err)
+				return
+			}
+			go cc.transportMonitor()
+		}()
 	}
-	cc.shutdownChan = make(chan struct{})
-	// Start to monitor the error status of transport.
-	go cc.transportMonitor()
 	return cc, nil
 }
 

test/end2end_test.go

@@ -205,7 +205,7 @@ func (s *testServer) HalfDuplexCall(stream testpb.TestService_HalfDuplexCallServ
 const tlsDir = "testdata/"
 
 func TestDialTimeout(t *testing.T) {
-	conn, err := grpc.Dial("Non-Existent.Server:80", grpc.WithTimeout(time.Millisecond))
+	conn, err := grpc.Dial("Non-Existent.Server:80", grpc.WithTimeout(time.Millisecond), grpc.WithBlock())
 	if err == nil {
 		conn.Close()
 	}
@@ -219,7 +219,7 @@ func TestTLSDialTimeout(t *testing.T) {
 	if err != nil {
 		t.Fatalf("Failed to create credentials %v", err)
 	}
-	conn, err := grpc.Dial("Non-Existent.Server:80", grpc.WithTransportCredentials(creds), grpc.WithTimeout(time.Millisecond))
+	conn, err := grpc.Dial("Non-Existent.Server:80", grpc.WithTransportCredentials(creds), grpc.WithTimeout(time.Millisecond), grpc.WithBlock())
 	if err == nil {
 		conn.Close()
 	}
@@ -238,7 +238,7 @@ func TestReconnectTimeout(t *testing.T) {
 		t.Fatalf("Failed to parse listener address: %v", err)
 	}
 	addr := "localhost:" + port
-	conn, err := grpc.Dial(addr, grpc.WithTimeout(5*time.Second))
+	conn, err := grpc.Dial(addr, grpc.WithTimeout(5*time.Second), grpc.WithBlock())
 	if err != nil {
 		t.Fatalf("Failed to dial to the server %q: %v", addr, err)
 	}