Merge pull request #774 from neilalexander/neilalexander/inprocessconn

In-process connections

nats.go

@@ -283,6 +283,10 @@ type CustomDialer interface {
 	Dial(network, address string) (net.Conn, error)
 }
 
+type InProcessConnProvider interface {
+	InProcessConn() (net.Conn, error)
+}
+
 // Options can be used to create a customized connection.
 type Options struct {
 
@@ -291,6 +295,11 @@ type Options struct {
 	// then becomes the first server in the Servers array.
 	Url string
 
+	// InProcessServer represents a NATS server running within the
+	// same process. If this is set then we will attempt to connect
+	// to the server directly rather than using external TCP conns.
+	InProcessServer InProcessConnProvider
+
 	// Servers is a configured set of servers which this client
 	// will use when attempting to connect.
 	Servers []string
@@ -783,6 +792,15 @@ func Name(name string) Option {
 	}
 }
 
+// InProcessServer is an Option that will try to establish a direction to a NATS server
+// running within the process instead of dialing via TCP.
+func InProcessServer(server InProcessConnProvider) Option {
+	return func(o *Options) error {
+		o.InProcessServer = server
+		return nil
+	}
+}
+
 // Secure is an Option to enable TLS secure connections that skip server verification by default.
 // Pass a TLS Configuration for proper TLS.
 // NOTE: This should NOT be used in a production setting.
@@ -1749,6 +1767,18 @@ func (nc *Conn) createConn() (err error) {
 		return ErrNoServers
 	}
 
+	// If we have a reference to an in-process server then establish a
+	// connection using that.
+	if nc.Opts.InProcessServer != nil {
+		conn, err := nc.Opts.InProcessServer.InProcessConn()
+		if err != nil {
+			return fmt.Errorf("failed to get in-process connection: %w", err)
+		}
+		nc.conn = conn
+		nc.bindToNewConn()
+		return nil
+	}
+
 	// We will auto-expand host names if they resolve to multiple IPs
 	hosts := []string{}
 	u := nc.current.url

nats_test.go

@@ -2883,3 +2883,25 @@ func TestRespInbox(t *testing.T) {
 		t.Fatalf("Error: %s", resp.Data)
 	}
 }
+
+func TestInProcessConn(t *testing.T) {
+	s := RunServerOnPort(-1)
+	defer s.Shutdown()
+
+	nc, err := Connect("", InProcessServer(s))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer nc.Close()
+
+	// Status should be connected.
+	if nc.Status() != CONNECTED {
+		t.Fatal("should be status CONNECTED")
+	}
+
+	// The server should respond to a request.
+	if _, err := nc.RTT(); err != nil {
+		t.Fatal(err)
+	}
+}