Add config setting to control udp sockets count

config/config.sample.toml

@@ -88,6 +88,14 @@ turn.static_auth_secret = ""
 # The expiration, in minutes, of the short-lived credentials generated for TURN servers.
 turn.credentials_expiration_minutes = 1440
 
+# udp_sockets_count controls the number of listening UDP sockets used for each local
+# network address. A larger number can improve performance by reducing contention
+# over a few file descriptors. At the same time, it will cause more file descriptors
+# to be open. The default is a dynamic value that scales with the number of available CPUs with
+# a constant multiplier of 100. E.g. On a 4 CPUs node, 400 sockets per local
+# network address will be open.
+# udp_sockets_count =
+
 [store]
 # A path to a directory the service will use to store persistent data such as registered client IDs and hashed credentials.
 data_source = "/tmp/rtcd_db"
@@ -109,4 +117,3 @@ file_level = "DEBUG"
 file_location = "rtcd.log"
 # A boolean controlling whether to display colors when logging to the console.
 enable_color = true
-

docs/env_config.md

@@ -20,6 +20,7 @@ RTCD_RTC_ICESERVERS                                 Comma-separated list of
 RTCD_RTC_TURNCONFIG_STATICAUTHSECRET                String
 RTCD_RTC_TURNCONFIG_CREDENTIALSEXPIRATIONMINUTES    Integer
 RTCD_RTC_ENABLEIPV6                                 True or False
+RTCD_RTC_UDPSOCKETSCOUNT                            Integer
 RTCD_STORE_DATASOURCE                               String
 RTCD_LOGGER_ENABLECONSOLE                           True or False
 RTCD_LOGGER_CONSOLEJSON                             True or False

service/config.go

@@ -83,6 +83,7 @@ func (c *Config) SetDefaults() {
 	c.RTC.ICEPortUDP = 8443
 	c.RTC.ICEPortTCP = 8443
 	c.RTC.TURNConfig.CredentialsExpirationMinutes = 1440
+	c.RTC.UDPSocketsCount = rtc.GetDefaultUDPListeningSocketsCount()
 	c.Store.DataSource = "/tmp/rtcd_db"
 	c.Logger.EnableConsole = true
 	c.Logger.ConsoleJSON = false

service/helper_test.go

@@ -81,8 +81,9 @@ func MakeDefaultCfg(tb testing.TB) *Config {
 			},
 		},
 		RTC: rtc.ServerConfig{
-			ICEPortUDP: 30444,
-			ICEPortTCP: 30444,
+			ICEPortUDP:      30444,
+			ICEPortTCP:      30444,
+			UDPSocketsCount: rtc.GetDefaultUDPListeningSocketsCount(),
 		},
 		Store: StoreConfig{
 			DataSource: dbDir,

service/rtc/config.go

@@ -31,6 +31,13 @@ type ServerConfig struct {
 	TURNConfig TURNConfig `toml:"turn"`
 	// EnableIPv6 specifies whether or not IPv6 should be used.
 	EnableIPv6 bool `toml:"enable_ipv6"`
+	// UDPSocketsCount controls the number of listening UDP sockets used for each local
+	// network address. A larger number can improve performance by reducing contention
+	// over a few file descriptors. At the same time, it will cause more file descriptors
+	// to be open. The default is a dynamic value that scales with the number of available CPUs with
+	// a constant multiplier of 100. E.g. On a 4 CPUs node, 400 sockets per local
+	// network address will be open.
+	UDPSocketsCount int `toml:"udp_sockets_count"`
 }
 
 func (c ServerConfig) IsValid() error {
@@ -62,6 +69,10 @@ func (c ServerConfig) IsValid() error {
 		return fmt.Errorf("invalid ICEHostPortOverride value: %w", err)
 	}
 
+	if c.UDPSocketsCount <= 0 {
+		return fmt.Errorf("invalid UDPSocketsCount value: should be greater than 0")
+	}
+
 	return nil
 }
 

service/rtc/config_test.go

@@ -95,12 +95,22 @@ func TestServerConfigIsValid(t *testing.T) {
 		})
 	})
 
+	t.Run("invalid UDPSocketsCount", func(t *testing.T) {
+		var cfg ServerConfig
+		cfg.ICEPortUDP = 8443
+		cfg.ICEPortTCP = 8443
+		cfg.UDPSocketsCount = 0
+		err := cfg.IsValid()
+		require.EqualError(t, err, "invalid UDPSocketsCount value: should be greater than 0")
+	})
+
 	t.Run("valid", func(t *testing.T) {
 		var cfg ServerConfig
 		cfg.ICEAddressUDP = "127.0.0.1"
 		cfg.ICEPortUDP = 8443
 		cfg.ICEPortTCP = 8443
 		cfg.TURNConfig.CredentialsExpirationMinutes = 1440
+		cfg.UDPSocketsCount = 1
 		err := cfg.IsValid()
 		require.NoError(t, err)
 	})

service/rtc/net.go

@@ -23,7 +23,7 @@ const (
 	tcpSocketWriteBufferSize = 1024 * 1024 * 4 // 4MB
 )
 
-func getUDPListeningSocketsCount() int {
+func GetDefaultUDPListeningSocketsCount() int {
 	// Originally we used runtime.NumCPU() but increased it as a result of v1 ceiling tests.
 	// The reason is that having just a few sockets caused significant lock contentions on
 	// the underlying file descriptors (at WriteToInet4 in internal/poll/fd_unix.go).
@@ -78,10 +78,10 @@ func getSystemIPs(log mlog.LoggerIFace, dualStack bool) ([]netip.Addr, error) {
 	return ips, nil
 }
 
-func createUDPConnsForAddr(log mlog.LoggerIFace, network, listenAddress string) ([]net.PacketConn, error) {
+func createUDPConnsForAddr(log mlog.LoggerIFace, network, listenAddress string, socketsCount int) ([]net.PacketConn, error) {
 	var conns []net.PacketConn
 
-	for i := 0; i < getUDPListeningSocketsCount(); i++ {
+	for i := 0; i < socketsCount; i++ {
 		listenConfig := net.ListenConfig{
 			Control: func(_, _ string, c syscall.RawConn) error {
 				return c.Control(func(fd uintptr) {

service/rtc/net_test.go

@@ -71,9 +71,9 @@ func TestCreateUDPConnsForAddr(t *testing.T) {
 		require.NotEmpty(t, ips)
 
 		for _, ip := range ips {
-			conns, err := createUDPConnsForAddr(log, "udp4", netip.AddrPortFrom(ip, 30443).String())
+			conns, err := createUDPConnsForAddr(log, "udp4", netip.AddrPortFrom(ip, 30443).String(), 45)
 			require.NoError(t, err)
-			require.Len(t, conns, getUDPListeningSocketsCount())
+			require.Len(t, conns, 45)
 			for _, conn := range conns {
 				require.NoError(t, conn.Close())
 			}
@@ -91,9 +91,9 @@ func TestCreateUDPConnsForAddr(t *testing.T) {
 		require.NotEmpty(t, ips)
 
 		for _, ip := range ips {
-			conns, err := createUDPConnsForAddr(log, "udp", netip.AddrPortFrom(ip, 30443).String())
+			conns, err := createUDPConnsForAddr(log, "udp", netip.AddrPortFrom(ip, 30443).String(), 45)
 			require.NoError(t, err)
-			require.Len(t, conns, getUDPListeningSocketsCount())
+			require.Len(t, conns, 45)
 			for _, conn := range conns {
 				require.NoError(t, conn.Close())
 			}

service/rtc/server.go

@@ -298,7 +298,7 @@ func (s *Server) initUDP(localIPs []netip.Addr, network string) error {
 	var udpMuxes []ice.UDPMux
 
 	initUDPMux := func(addr string) error {
-		conns, err := createUDPConnsForAddr(s.log, network, addr)
+		conns, err := createUDPConnsForAddr(s.log, network, addr, s.cfg.UDPSocketsCount)
 		if err != nil {
 			return fmt.Errorf("failed to create UDP connections: %w", err)
 		}