Add support for port reuse by implementing multiplexing listener

config/configgrpc/configgrpc.go

@@ -235,9 +235,47 @@ func validateBalancerName(balancerName string) bool {
 	return false
 }
 
-// ToListener returns the net.Listener constructed from the settings.
+// muxListeners is a map of Endpoint to multiplexing listener
+var muxListeners = make(map[string]net.Listener)
+
+// ToListener creates a new net.Listener when it is called at the first time. After that,
+// whenever the same Endpoint is passed in, that listener will be returned.
 func (gss *GRPCServerSettings) ToListener() (net.Listener, error) {
-	return gss.NetAddr.Listen()
+	var addr net.Addr
+	var err error
+
+	// Get the network address according to the protocol type and the given endpoint.
+	switch gss.NetAddr.Transport {
+	case "tcp", "tcp4", "tcp6":
+		addr, err = net.ResolveTCPAddr(gss.NetAddr.Transport, gss.NetAddr.Endpoint)
+	case "udp", "udp4", "udp6":
+		addr, err = net.ResolveUDPAddr(gss.NetAddr.Transport, gss.NetAddr.Endpoint)
+	case "ip", "ip4", "ip6":
+		addr, err = net.ResolveIPAddr(gss.NetAddr.Transport, gss.NetAddr.Endpoint)
+	case "unix", "unixgram", "unixpacket":
+		addr, err = net.ResolveUnixAddr(gss.NetAddr.Transport, gss.NetAddr.Endpoint)
+	default:
+		return nil, fmt.Errorf("unknown network protocol")
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	// If the Endpoint is in use (i.e. it corresponds to a listener), use the existing
+	// listener. Otherwise, get a new listener.
+	if muxLs, ok := muxListeners[addr.String()]; ok {
+		return muxLs, nil
+	}
+
+	listener, err := gss.NetAddr.Listen()
+	if err != nil {
+		return nil, err
+	}
+
+	// Set the multiplexing listener.
+	muxListeners[addr.String()] = listener
+
+	return listener, nil
 }
 
 // ToServerOption maps configgrpc.GRPCServerSettings to a slice of server options for gRPC

config/configgrpc/configgrpc_test.go

@@ -536,3 +536,25 @@ func tempSocketName(t *testing.T) string {
 	require.NoError(t, os.Remove(socket))
 	return socket
 }
+
+func TestGRPCPortReuse(t *testing.T) {
+	endpoint := "localhost: 2873"
+	t.Run("", func(t *testing.T) {
+		settings1 := createGRPCServerSettings(endpoint)
+		muxListener1, err := settings1.ToListener()
+		assert.NoError(t, err)
+		settings2 := createGRPCServerSettings(endpoint)
+		muxListener2, err := settings2.ToListener()
+		assert.NoError(t, err)
+		assert.Equal(t, muxListener1, muxListener2)
+	})
+}
+
+func createGRPCServerSettings(endpoint string) GRPCServerSettings {
+	return GRPCServerSettings{
+		NetAddr: confignet.NetAddr{
+			Endpoint: endpoint,
+			Transport: "tcp",
+		},
+	}
+}

config/confighttp/confighttp.go

@@ -125,13 +125,33 @@ type HTTPServerSettings struct {
 	CorsHeaders []string `mapstructure:"cors_allowed_headers"`
 }
 
-// ToListener creates a net.Listener.
+// muxListeners is a map of Endpoint to multiplexing listener
+var muxListeners = make(map[string]net.Listener)
+
+// ToListener creates a new net.Listener when it is called at the first time. After that,
+// whenever the same Endpoint is passed in, that listener will be returned.
 func (hss *HTTPServerSettings) ToListener() (net.Listener, error) {
-	listener, err := net.Listen("tcp", hss.Endpoint)
+	var listener net.Listener
+	var addr net.Addr
+	var err error
+
+	// Get the tcp address according to the given endpoint.
+	addr, err = net.ResolveTCPAddr("tcp", hss.Endpoint)
 	if err != nil {
 		return nil, err
 	}
 
+	// If the Endpoint is in use (i.e. it corresponds to a listener), use the existing
+	// listener. Otherwise, get a new listener.
+	if muxLs, ok := muxListeners[addr.String()]; ok {
+		listener = muxLs
+	} else {
+		listener, err = net.Listen("tcp", hss.Endpoint)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	if hss.TLSSetting != nil {
 		var tlsCfg *tls.Config
 		tlsCfg, err = hss.TLSSetting.LoadTLSConfig()
@@ -140,6 +160,10 @@ func (hss *HTTPServerSettings) ToListener() (net.Listener, error) {
 		}
 		listener = tls.NewListener(listener, tlsCfg)
 	}
+
+	// Set the multiplexing listener.
+	muxListeners[addr.String()] = listener
+
 	return listener, nil
 }
 

config/confighttp/confighttp_test.go

@@ -482,3 +482,22 @@ func TestHttpHeaders(t *testing.T) {
 		})
 	}
 }
+
+func TestHTTPPortReuse(t *testing.T) {
+	endpoint := "localhost: 6489"
+	t.Run("", func(t *testing.T) {
+		settings1 := createHTTPServerSettings(endpoint)
+		muxListener1, err := settings1.ToListener()
+		assert.NoError(t, err)
+		settings2 := createHTTPServerSettings(endpoint)
+		muxListener2, err := settings2.ToListener()
+		assert.NoError(t, err)
+		assert.Equal(t, muxListener1, muxListener2)
+	})
+}
+
+func createHTTPServerSettings(endpoint string) HTTPServerSettings {
+	return HTTPServerSettings{
+		Endpoint: endpoint,
+	}
+}