Make the proxy to report the number of clients to the broker

So the assignment of proxies is based on the load. The number of clients
is ronded down to 8. Existing proxies that doesn't report the number
of clients will be distributed equaly to new proxies until they get 8
clients, that is okish as the existing proxies do have a maximum
capacity of 10.

Fixes #40048

broker/broker.go

@@ -124,16 +124,18 @@ type ProxyPoll struct {
 	id           string
 	proxyType    string
 	natType      string
+	clients      int
 	offerChannel chan *ClientOffer
 }
 
 // Registers a Snowflake and waits for some Client to send an offer,
 // as part of the polling logic of the proxy handler.
-func (ctx *BrokerContext) RequestOffer(id string, proxyType string, natType string) *ClientOffer {
+func (ctx *BrokerContext) RequestOffer(id string, proxyType string, natType string, clients int) *ClientOffer {
 	request := new(ProxyPoll)
 	request.id = id
 	request.proxyType = proxyType
 	request.natType = natType
+	request.clients = clients
 	request.offerChannel = make(chan *ClientOffer)
 	ctx.proxyPolls <- request
 	// Block until an offer is available, or timeout which sends a nil offer.
@@ -146,7 +148,7 @@ func (ctx *BrokerContext) RequestOffer(id string, proxyType string, natType stri
 // client offer or nil on timeout / none are available.
 func (ctx *BrokerContext) Broker() {
 	for request := range ctx.proxyPolls {
-		snowflake := ctx.AddSnowflake(request.id, request.proxyType, request.natType)
+		snowflake := ctx.AddSnowflake(request.id, request.proxyType, request.natType, request.clients)
 		// Wait for a client to avail an offer to the snowflake.
 		go func(request *ProxyPoll) {
 			select {
@@ -174,10 +176,10 @@ func (ctx *BrokerContext) Broker() {
 // Create and add a Snowflake to the heap.
 // Required to keep track of proxies between providing them
 // with an offer and awaiting their second POST with an answer.
-func (ctx *BrokerContext) AddSnowflake(id string, proxyType string, natType string) *Snowflake {
+func (ctx *BrokerContext) AddSnowflake(id string, proxyType string, natType string, clients int) *Snowflake {
 	snowflake := new(Snowflake)
 	snowflake.id = id
-	snowflake.clients = 0
+	snowflake.clients = clients
 	snowflake.proxyType = proxyType
 	snowflake.natType = natType
 	snowflake.offerChannel = make(chan *ClientOffer)
@@ -205,7 +207,7 @@ func proxyPolls(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	sid, proxyType, natType, err := messages.DecodePollRequest(body)
+	sid, proxyType, natType, clients, err := messages.DecodePollRequest(body)
 	if err != nil {
 		w.WriteHeader(http.StatusBadRequest)
 		return
@@ -222,7 +224,7 @@ func proxyPolls(ctx *BrokerContext, w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Wait for a client to avail an offer to the snowflake, or timeout if nil.
-	offer := ctx.RequestOffer(sid, proxyType, natType)
+	offer := ctx.RequestOffer(sid, proxyType, natType, clients)
 	var b []byte
 	if nil == offer {
 		ctx.metrics.lock.Lock()

broker/snowflake-broker_test.go

@@ -32,7 +32,7 @@ func TestBroker(t *testing.T) {
 		Convey("Adds Snowflake", func() {
 			So(ctx.snowflakes.Len(), ShouldEqual, 0)
 			So(len(ctx.idToSnowflake), ShouldEqual, 0)
-			ctx.AddSnowflake("foo", "", NATUnrestricted)
+			ctx.AddSnowflake("foo", "", NATUnrestricted, 0)
 			So(ctx.snowflakes.Len(), ShouldEqual, 1)
 			So(len(ctx.idToSnowflake), ShouldEqual, 1)
 		})
@@ -59,7 +59,7 @@ func TestBroker(t *testing.T) {
 		Convey("Request an offer from the Snowflake Heap", func() {
 			done := make(chan *ClientOffer)
 			go func() {
-				offer := ctx.RequestOffer("test", "", NATUnrestricted)
+				offer := ctx.RequestOffer("test", "", NATUnrestricted, 0)
 				done <- offer
 			}()
 			request := <-ctx.proxyPolls
@@ -84,7 +84,7 @@ func TestBroker(t *testing.T) {
 			Convey("with a proxy answer if available.", func() {
 				done := make(chan bool)
 				// Prepare a fake proxy to respond with.
-				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted)
+				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
 				go func() {
 					clientOffers(ctx, w, r)
 					done <- true
@@ -102,7 +102,7 @@ func TestBroker(t *testing.T) {
 					return
 				}
 				done := make(chan bool)
-				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted)
+				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
 				go func() {
 					clientOffers(ctx, w, r)
 					// Takes a few seconds here...
@@ -132,7 +132,7 @@ func TestBroker(t *testing.T) {
 			Convey("with a proxy answer if available.", func() {
 				done := make(chan bool)
 				// Prepare a fake proxy to respond with.
-				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted)
+				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
 				go func() {
 					clientOffers(ctx, w, r)
 					done <- true
@@ -150,7 +150,7 @@ func TestBroker(t *testing.T) {
 					return
 				}
 				done := make(chan bool)
-				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted)
+				snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
 				go func() {
 					clientOffers(ctx, w, r)
 					// Takes a few seconds here...
@@ -201,7 +201,7 @@ func TestBroker(t *testing.T) {
 		})
 
 		Convey("Responds to proxy answers...", func() {
-			s := ctx.AddSnowflake("test", "", NATUnrestricted)
+			s := ctx.AddSnowflake("test", "", NATUnrestricted, 0)
 			w := httptest.NewRecorder()
 			data := bytes.NewReader([]byte(`{"Version":"1.0","Sid":"test","Answer":"test"}`))
 
@@ -314,7 +314,7 @@ func TestBroker(t *testing.T) {
 			// Manually do the Broker goroutine action here for full control.
 			p := <-ctx.proxyPolls
 			So(p.id, ShouldEqual, "ymbcCMto7KHNGYlp")
-			s := ctx.AddSnowflake(p.id, "", NATUnrestricted)
+			s := ctx.AddSnowflake(p.id, "", NATUnrestricted, 0)
 			go func() {
 				offer := <-s.offerChannel
 				p.offerChannel <- offer
@@ -593,7 +593,7 @@ func TestMetrics(t *testing.T) {
 			So(err, ShouldBeNil)
 
 			// Prepare a fake proxy to respond with.
-			snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted)
+			snowflake := ctx.AddSnowflake("fake", "", NATUnrestricted, 0)
 			go func() {
 				clientOffers(ctx, w, r)
 				done <- true

common/messages/messages_test.go

@@ -15,6 +15,7 @@ func TestDecodeProxyPollRequest(t *testing.T) {
 			sid       string
 			proxyType string
 			natType   string
+			clients   int
 			data      string
 			err       error
 		}{
@@ -23,6 +24,7 @@ func TestDecodeProxyPollRequest(t *testing.T) {
 				"ymbcCMto7KHNGYlp",
 				"",
 				"unknown",
+				0,
 				`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.0"}`,
 				nil,
 			},
@@ -31,6 +33,7 @@ func TestDecodeProxyPollRequest(t *testing.T) {
 				"ymbcCMto7KHNGYlp",
 				"standalone",
 				"unknown",
+				0,
 				`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.1","Type":"standalone"}`,
 				nil,
 			},
@@ -39,14 +42,25 @@ func TestDecodeProxyPollRequest(t *testing.T) {
 				"ymbcCMto7KHNGYlp",
 				"standalone",
 				"restricted",
+				0,
 				`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.2","Type":"standalone", "NAT":"restricted"}`,
 				nil,
 			},
+			{
+				//Version 1.2 proxy message with clients
+				"ymbcCMto7KHNGYlp",
+				"standalone",
+				"restricted",
+				24,
+				`{"Sid":"ymbcCMto7KHNGYlp","Version":"1.2","Type":"standalone", "NAT":"restricted","Clients":24}`,
+				nil,
+			},
 			{
 				//Version 0.X proxy message:
 				"",
 				"",
 				"",
+				0,
 				"",
 				&json.SyntaxError{},
 			},
@@ -54,6 +68,7 @@ func TestDecodeProxyPollRequest(t *testing.T) {
 				"",
 				"",
 				"",
+				0,
 				`{"Sid":"ymbcCMto7KHNGYlp"}`,
 				fmt.Errorf(""),
 			},
@@ -61,6 +76,7 @@ func TestDecodeProxyPollRequest(t *testing.T) {
 				"",
 				"",
 				"",
+				0,
 				"{}",
 				fmt.Errorf(""),
 			},
@@ -68,6 +84,7 @@ func TestDecodeProxyPollRequest(t *testing.T) {
 				"",
 				"",
 				"",
+				0,
 				`{"Version":"1.0"}`,
 				fmt.Errorf(""),
 			},
@@ -75,14 +92,16 @@ func TestDecodeProxyPollRequest(t *testing.T) {
 				"",
 				"",
 				"",
+				0,
 				`{"Version":"2.0"}`,
 				fmt.Errorf(""),
 			},
 		} {
-			sid, proxyType, natType, err := DecodePollRequest([]byte(test.data))
+			sid, proxyType, natType, clients, err := DecodePollRequest([]byte(test.data))
 			So(sid, ShouldResemble, test.sid)
 			So(proxyType, ShouldResemble, test.proxyType)
 			So(natType, ShouldResemble, test.natType)
+			So(clients, ShouldEqual, test.clients)
 			So(err, ShouldHaveSameTypeAs, test.err)
 		}
 
@@ -91,12 +110,13 @@ func TestDecodeProxyPollRequest(t *testing.T) {
 
 func TestEncodeProxyPollRequests(t *testing.T) {
 	Convey("Context", t, func() {
-		b, err := EncodePollRequest("ymbcCMto7KHNGYlp", "standalone", "unknown")
+		b, err := EncodePollRequest("ymbcCMto7KHNGYlp", "standalone", "unknown", 16)
 		So(err, ShouldEqual, nil)
-		sid, proxyType, natType, err := DecodePollRequest(b)
+		sid, proxyType, natType, clients, err := DecodePollRequest(b)
 		So(sid, ShouldEqual, "ymbcCMto7KHNGYlp")
 		So(proxyType, ShouldEqual, "standalone")
 		So(natType, ShouldEqual, "unknown")
+		So(clients, ShouldEqual, 16)
 		So(err, ShouldEqual, nil)
 	})
 }

common/messages/proxy.go

@@ -17,8 +17,9 @@ const version = "1.2"
 {
   Sid: [generated session id of proxy],
   Version: 1.2,
-  Type: ["badge"|"webext"|"standalone"]
+  Type: ["badge"|"webext"|"standalone"],
-  NAT: ["unknown"|"restricted"|"unrestricted"]
+  NAT: ["unknown"|"restricted"|"unrestricted"],
+  Clients: [number of current clients, rounded down to multiples of 8]
 }
 
 == ProxyPollResponse ==
@@ -79,43 +80,48 @@ type ProxyPollRequest struct {
 	Version string
 	Type    string
 	NAT     string
+	Clients int
 }
 
-func EncodePollRequest(sid string, proxyType string, natType string) ([]byte, error) {
+func EncodePollRequest(sid string, proxyType string, natType string, clients int) ([]byte, error) {
 	return json.Marshal(ProxyPollRequest{
 		Sid:     sid,
 		Version: version,
 		Type:    proxyType,
 		NAT:     natType,
+		Clients: clients,
 	})
 }
 
 // Decodes a poll message from a snowflake proxy and returns the
-// sid and proxy type of the proxy on success and an error if it failed
+// sid, proxy type, nat type and clients of the proxy on success
-func DecodePollRequest(data []byte) (string, string, string, error) {
+// and an error if it failed
+func DecodePollRequest(data []byte) (sid string, proxyType string, natType string, clients int, err error) {
 	var message ProxyPollRequest
 
-	err := json.Unmarshal(data, &message)
+	err = json.Unmarshal(data, &message)
 	if err != nil {
-		return "", "", "", err
+		return
 	}
 
 	majorVersion := strings.Split(message.Version, ".")[0]
 	if majorVersion != "1" {
-		return "", "", "", fmt.Errorf("using unknown version")
+		err = fmt.Errorf("using unknown version")
+		return
 	}
 
 	// Version 1.x requires an Sid
 	if message.Sid == "" {
-		return "", "", "", fmt.Errorf("no supplied session id")
+		err = fmt.Errorf("no supplied session id")
+		return
 	}
 
-	natType := message.NAT
+	natType = message.NAT
 	if natType == "" {
 		natType = "unknown"
 	}
 
-	return message.Sid, message.Type, natType, nil
+	return message.Sid, message.Type, natType, message.Clients, nil
 }
 
 type ProxyPollResponse struct {

doc/broker-spec.txt

@@ -141,7 +141,9 @@ POST /proxy HTTP
 {
   Sid: [generated session id of proxy],
   Version: 1.1,
-  Type: ["badge"|"webext"|"standalone"|"mobile"]
+  Type: ["badge"|"webext"|"standalone"|"mobile"],
+  NAT: ["unknown"|"restricted"|"unrestricted"],
+  Clients: [number of current clients, rounded down to multiples of 8]
 }
 ```
 

proxy/proxy-go_test.go

@@ -7,7 +7,6 @@ import (
 	"io/ioutil"
 	"net"
 	"net/http"
-	"net/url"
 	"strconv"
 	"strings"
 	"testing"
@@ -337,8 +336,9 @@ func TestBrokerInteractions(t *testing.T) {
 	const sampleAnswer = `{"type":"answer","sdp":` + sampleSDP + `}`
 
 	Convey("Proxy connections to broker", t, func() {
-		broker := new(SignalingServer)
+		broker, err := newSignalingServer("localhost", false)
-		broker.url, _ = url.Parse("localhost")
+		So(err, ShouldEqual, nil)
+		tokens = newTokens(0)
 
 		//Mock peerConnection
 		config = webrtc.Configuration{
@@ -469,17 +469,6 @@ func TestUtilityFuncs(t *testing.T) {
 			So(err, ShouldEqual, io.ErrClosedPipe)
 		})
 	})
-	Convey("Tokens", t, func() {
-		tokens = make(chan bool, 2)
-		for i := uint(0); i < 2; i++ {
-			tokens <- true
-		}
-		So(len(tokens), ShouldEqual, 2)
-		getToken()
-		So(len(tokens), ShouldEqual, 1)
-		retToken()
-		So(len(tokens), ShouldEqual, 2)
-	})
 	Convey("SessionID Generation", t, func() {
 		sid1 := genSessionID()
 		sid2 := genSessionID()

proxy/snowflake.go

@@ -55,7 +55,7 @@ const (
 )
 
 var (
-	tokens chan bool
+	tokens *tokens_t
 	config webrtc.Configuration
 	client http.Client
 )
@@ -171,14 +171,6 @@ func (c *webRTCConn) SetWriteDeadline(t time.Time) error {
 	return fmt.Errorf("SetWriteDeadline not implemented")
 }
 
-func getToken() {
-	<-tokens
-}
-
-func retToken() {
-	tokens <- true
-}
-
 func genSessionID() string {
 	buf := make([]byte, sessionIDLength)
 	_, err := rand.Read(buf)
@@ -204,6 +196,21 @@ type SignalingServer struct {
 	keepLocalAddresses bool
 }
 
+func newSignalingServer(rawURL string, keepLocalAddresses bool) (*SignalingServer, error) {
+	var err error
+	s := new(SignalingServer)
+	s.keepLocalAddresses = keepLocalAddresses
+	s.url, err = url.Parse(rawURL)
+	if err != nil {
+		return nil, fmt.Errorf("invalid broker url: %s", err)
+	}
+
+	s.transport = http.DefaultTransport.(*http.Transport)
+	s.transport.(*http.Transport).ResponseHeaderTimeout = 30 * time.Second
+
+	return s, nil
+}
+
 func (s *SignalingServer) Post(path string, payload io.Reader) ([]byte, error) {
 
 	req, err := http.NewRequest("POST", path, payload)
@@ -238,7 +245,8 @@ func (s *SignalingServer) pollOffer(sid string) *webrtc.SessionDescription {
 			timeOfNextPoll = now
 		}
 
-		body, err := messages.EncodePollRequest(sid, "standalone", currentNATType)
+		numClients := int((tokens.count() / 8) * 8) // Round down to 8
+		body, err := messages.EncodePollRequest(sid, "standalone", currentNATType, numClients)
 		if err != nil {
 			log.Printf("Error encoding poll message: %s", err.Error())
 			return nil
@@ -323,7 +331,7 @@ func CopyLoop(c1 io.ReadWriteCloser, c2 io.ReadWriteCloser) {
 // RemoteAddr). https://bugs.torproject.org/18628#comment:8
 func datachannelHandler(conn *webRTCConn, remoteAddr net.Addr) {
 	defer conn.Close()
-	defer retToken()
+	defer tokens.ret()
 
 	u, err := url.Parse(relayURL)
 	if err != nil {
@@ -494,14 +502,14 @@ func runSession(sid string) {
 	offer := broker.pollOffer(sid)
 	if offer == nil {
 		log.Printf("bad offer from broker")
-		retToken()
+		tokens.ret()
 		return
 	}
 	dataChan := make(chan struct{})
 	pc, err := makePeerConnectionFromOffer(offer, config, dataChan, datachannelHandler)
 	if err != nil {
 		log.Printf("error making WebRTC connection: %s", err)
-		retToken()
+		tokens.ret()
 		return
 	}
 	err = broker.sendAnswer(sid, pc)
@@ -510,7 +518,7 @@ func runSession(sid string) {
 		if inerr := pc.Close(); inerr != nil {
 			log.Printf("error calling pc.Close: %v", inerr)
 		}
-		retToken()
+		tokens.ret()
 		return
 	}
 	// Set a timeout on peerconnection. If the connection state has not
@@ -524,7 +532,7 @@ func runSession(sid string) {
 		if err := pc.Close(); err != nil {
 			log.Printf("error calling pc.Close: %v", err)
 		}
-		retToken()
+		tokens.ret()
 	}
 }
 
@@ -536,7 +544,7 @@ func main() {
 	var unsafeLogging bool
 	var keepLocalAddresses bool
 
-	flag.UintVar(&capacity, "capacity", 10, "maximum concurrent clients")
+	flag.UintVar(&capacity, "capacity", 0, "maximum concurrent clients")
 	flag.StringVar(&rawBrokerURL, "broker", defaultBrokerURL, "broker URL")
 	flag.StringVar(&relayURL, "relay", defaultRelayURL, "websocket relay URL")
 	flag.StringVar(&stunURL, "stun", defaultSTUNURL, "stun URL")
@@ -565,12 +573,11 @@ func main() {
 	log.Println("starting")
 
 	var err error
-	broker = new(SignalingServer)
+	broker, err = newSignalingServer(rawBrokerURL, keepLocalAddresses)
-	broker.keepLocalAddresses = keepLocalAddresses
-	broker.url, err = url.Parse(rawBrokerURL)
 	if err != nil {
-		log.Fatalf("invalid broker url: %s", err)
+		log.Fatal(err)
 	}
+
 	_, err = url.Parse(stunURL)
 	if err != nil {
 		log.Fatalf("invalid stun url: %s", err)
@@ -580,8 +587,6 @@ func main() {
 		log.Fatalf("invalid relay url: %s", err)
 	}
 
-	broker.transport = http.DefaultTransport.(*http.Transport)
-	broker.transport.(*http.Transport).ResponseHeaderTimeout = 15 * time.Second
 	config = webrtc.Configuration{
 		ICEServers: []webrtc.ICEServer{
 			{
@@ -589,17 +594,14 @@ func main() {
 			},
 		},
 	}
-	tokens = make(chan bool, capacity)
+	tokens = newTokens(capacity)
-	for i := uint(0); i < capacity; i++ {
-		tokens <- true
-	}
 
 	// use probetest to determine NAT compatability
 	checkNATType(config, defaultProbeURL)
 	log.Printf("NAT type: %s", currentNATType)
 
 	for {
-		getToken()
+		tokens.get()
 		sessionID := genSessionID()
 		runSession(sessionID)
 	}
@@ -607,12 +609,7 @@ func main() {
 
 func checkNATType(config webrtc.Configuration, probeURL string) {
 
-	var err error
+	probe, err := newSignalingServer(probeURL, false)
-
-	probe := new(SignalingServer)
-	probe.transport = http.DefaultTransport.(*http.Transport)
-	probe.transport.(*http.Transport).ResponseHeaderTimeout = 30 * time.Second
-	probe.url, err = url.Parse(probeURL)
 	if err != nil {
 		log.Printf("Error parsing url: %s", err.Error())
 	}

proxy/tokens.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"sync/atomic"
+)
+
+type tokens_t struct {
+	ch       chan struct{}
+	capacity uint
+	clients  int64
+}
+
+func newTokens(capacity uint) *tokens_t {
+	var ch chan struct{}
+	if capacity != 0 {
+		ch = make(chan struct{}, capacity)
+	}
+
+	return &tokens_t{
+		ch:       ch,
+		capacity: capacity,
+		clients:  0,
+	}
+}
+
+func (t *tokens_t) get() {
+	atomic.AddInt64(&t.clients, 1)
+
+	if t.capacity != 0 {
+		t.ch <- struct{}{}
+	}
+}
+
+func (t *tokens_t) ret() {
+	atomic.AddInt64(&t.clients, -1)
+
+	if t.capacity != 0 {
+		<-t.ch
+	}
+}
+
+func (t tokens_t) count() int64 {
+	return atomic.LoadInt64(&t.clients)
+}

proxy/tokens_test.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"testing"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestTokens(t *testing.T) {
+	Convey("Tokens", t, func() {
+		tokens := newTokens(2)
+		So(tokens.count(), ShouldEqual, 0)
+		tokens.get()
+		So(tokens.count(), ShouldEqual, 1)
+		tokens.ret()
+		So(tokens.count(), ShouldEqual, 0)
+	})
+	Convey("Tokens capacity 0", t, func() {
+		tokens := newTokens(0)
+		So(tokens.count(), ShouldEqual, 0)
+		for i := 0; i < 20; i++ {
+			tokens.get()
+		}
+		So(tokens.count(), ShouldEqual, 20)
+		tokens.ret()
+		So(tokens.count(), ShouldEqual, 19)
+	})
+}