Merge pull request #17747 from ethersphere/max-stream-peer-servers

Add stream peer servers limit

10 files changed, 276 insertions, 75 deletions

diff --git a/cmd/swarm/config.go b/cmd/swarm/config.go
index c2f885d25..9d6fe41a7 100644
--- a/cmd/swarm/config.go
+++ b/cmd/swarm/config.go
@@ -59,27 +59,28 @@ var (
 
 //constants for environment variables
 const (
-	SWARM_ENV_CHEQUEBOOK_ADDR      = "SWARM_CHEQUEBOOK_ADDR"
-	SWARM_ENV_ACCOUNT              = "SWARM_ACCOUNT"
-	SWARM_ENV_LISTEN_ADDR          = "SWARM_LISTEN_ADDR"
-	SWARM_ENV_PORT                 = "SWARM_PORT"
-	SWARM_ENV_NETWORK_ID           = "SWARM_NETWORK_ID"
-	SWARM_ENV_SWAP_ENABLE          = "SWARM_SWAP_ENABLE"
-	SWARM_ENV_SWAP_API             = "SWARM_SWAP_API"
-	SWARM_ENV_SYNC_DISABLE         = "SWARM_SYNC_DISABLE"
-	SWARM_ENV_SYNC_UPDATE_DELAY    = "SWARM_ENV_SYNC_UPDATE_DELAY"
-	SWARM_ENV_LIGHT_NODE_ENABLE    = "SWARM_LIGHT_NODE_ENABLE"
-	SWARM_ENV_DELIVERY_SKIP_CHECK  = "SWARM_DELIVERY_SKIP_CHECK"
-	SWARM_ENV_ENS_API              = "SWARM_ENS_API"
-	SWARM_ENV_ENS_ADDR             = "SWARM_ENS_ADDR"
-	SWARM_ENV_CORS                 = "SWARM_CORS"
-	SWARM_ENV_BOOTNODES            = "SWARM_BOOTNODES"
-	SWARM_ENV_PSS_ENABLE           = "SWARM_PSS_ENABLE"
-	SWARM_ENV_STORE_PATH           = "SWARM_STORE_PATH"
-	SWARM_ENV_STORE_CAPACITY       = "SWARM_STORE_CAPACITY"
-	SWARM_ENV_STORE_CACHE_CAPACITY = "SWARM_STORE_CACHE_CAPACITY"
-	SWARM_ACCESS_PASSWORD          = "SWARM_ACCESS_PASSWORD"
-	GETH_ENV_DATADIR               = "GETH_DATADIR"
+	SWARM_ENV_CHEQUEBOOK_ADDR         = "SWARM_CHEQUEBOOK_ADDR"
+	SWARM_ENV_ACCOUNT                 = "SWARM_ACCOUNT"
+	SWARM_ENV_LISTEN_ADDR             = "SWARM_LISTEN_ADDR"
+	SWARM_ENV_PORT                    = "SWARM_PORT"
+	SWARM_ENV_NETWORK_ID              = "SWARM_NETWORK_ID"
+	SWARM_ENV_SWAP_ENABLE             = "SWARM_SWAP_ENABLE"
+	SWARM_ENV_SWAP_API                = "SWARM_SWAP_API"
+	SWARM_ENV_SYNC_DISABLE            = "SWARM_SYNC_DISABLE"
+	SWARM_ENV_SYNC_UPDATE_DELAY       = "SWARM_ENV_SYNC_UPDATE_DELAY"
+	SWARM_ENV_MAX_STREAM_PEER_SERVERS = "SWARM_ENV_MAX_STREAM_PEER_SERVERS"
+	SWARM_ENV_LIGHT_NODE_ENABLE       = "SWARM_LIGHT_NODE_ENABLE"
+	SWARM_ENV_DELIVERY_SKIP_CHECK     = "SWARM_DELIVERY_SKIP_CHECK"
+	SWARM_ENV_ENS_API                 = "SWARM_ENS_API"
+	SWARM_ENV_ENS_ADDR                = "SWARM_ENS_ADDR"
+	SWARM_ENV_CORS                    = "SWARM_CORS"
+	SWARM_ENV_BOOTNODES               = "SWARM_BOOTNODES"
+	SWARM_ENV_PSS_ENABLE              = "SWARM_PSS_ENABLE"
+	SWARM_ENV_STORE_PATH              = "SWARM_STORE_PATH"
+	SWARM_ENV_STORE_CAPACITY          = "SWARM_STORE_CAPACITY"
+	SWARM_ENV_STORE_CACHE_CAPACITY    = "SWARM_STORE_CACHE_CAPACITY"
+	SWARM_ACCESS_PASSWORD             = "SWARM_ACCESS_PASSWORD"
+	GETH_ENV_DATADIR                  = "GETH_DATADIR"
 )
 
 // These settings ensure that TOML keys use the same names as Go struct fields.
@@ -207,6 +208,9 @@ func cmdLineOverride(currentConfig *bzzapi.Config, ctx *cli.Context) *bzzapi.Con
 		currentConfig.SyncUpdateDelay = d
 	}
 
+	// any value including 0 is acceptable
+	currentConfig.MaxStreamPeerServers = ctx.GlobalInt(SwarmMaxStreamPeerServersFlag.Name)
+
 	if ctx.GlobalIsSet(SwarmLightNodeEnabled.Name) {
 		currentConfig.LightNodeEnabled = true
 	}
@@ -308,6 +312,14 @@ func envVarsOverride(currentConfig *bzzapi.Config) (config *bzzapi.Config) {
 		}
 	}
 
+	if max := os.Getenv(SWARM_ENV_MAX_STREAM_PEER_SERVERS); max != "" {
+		m, err := strconv.Atoi(max)
+		if err != nil {
+			utils.Fatalf("invalid environment variable %s: %v", SWARM_ENV_MAX_STREAM_PEER_SERVERS, err)
+		}
+		currentConfig.MaxStreamPeerServers = m
+	}
+
 	if lne := os.Getenv(SWARM_ENV_LIGHT_NODE_ENABLE); lne != "" {
 		if lightnode, err := strconv.ParseBool(lne); err != nil {
 			currentConfig.LightNodeEnabled = lightnode
diff --git a/cmd/swarm/main.go b/cmd/swarm/main.go
index 4c9ce931e..71d707c2b 100644
--- a/cmd/swarm/main.go
+++ b/cmd/swarm/main.go
@@ -116,6 +116,12 @@ var (
 		Usage:  "Duration for sync subscriptions update after no new peers are added (default 15s)",
 		EnvVar: SWARM_ENV_SYNC_UPDATE_DELAY,
 	}
+	SwarmMaxStreamPeerServersFlag = cli.IntFlag{
+		Name:   "max-stream-peer-servers",
+		Usage:  "Limit of Stream peer servers, 0 denotes unlimited",
+		EnvVar: SWARM_ENV_MAX_STREAM_PEER_SERVERS,
+		Value:  10000, // A very large default value is possible as stream servers have very small memory footprint
+	}
 	SwarmLightNodeEnabled = cli.BoolFlag{
 		Name:   "lightnode",
 		Usage:  "Enable Swarm LightNode (default false)",
@@ -542,6 +548,7 @@ pv(1) tool to get a progress bar:
 		SwarmSwapAPIFlag,
 		SwarmSyncDisabledFlag,
 		SwarmSyncUpdateDelay,
+		SwarmMaxStreamPeerServersFlag,
 		SwarmLightNodeEnabled,
 		SwarmDeliverySkipCheckFlag,
 		SwarmListenAddrFlag,
diff --git a/swarm/api/config.go b/swarm/api/config.go
index e753890e4..be7385408 100644
--- a/swarm/api/config.go
+++ b/swarm/api/config.go
@@ -50,26 +50,27 @@ type Config struct {
 	Swap *swap.LocalProfile
 	Pss  *pss.PssParams
 	//*network.SyncParams
-	Contract          common.Address
-	EnsRoot           common.Address
-	EnsAPIs           []string
-	Path              string
-	ListenAddr        string
-	Port              string
-	PublicKey         string
-	BzzKey            string
-	NodeID            string
-	NetworkID         uint64
-	SwapEnabled       bool
-	SyncEnabled       bool
-	SyncingSkipCheck  bool
-	DeliverySkipCheck bool
-	LightNodeEnabled  bool
-	SyncUpdateDelay   time.Duration
-	SwapAPI           string
-	Cors              string
-	BzzAccount        string
-	privateKey        *ecdsa.PrivateKey
+	Contract             common.Address
+	EnsRoot              common.Address
+	EnsAPIs              []string
+	Path                 string
+	ListenAddr           string
+	Port                 string
+	PublicKey            string
+	BzzKey               string
+	NodeID               string
+	NetworkID            uint64
+	SwapEnabled          bool
+	SyncEnabled          bool
+	SyncingSkipCheck     bool
+	DeliverySkipCheck    bool
+	MaxStreamPeerServers int
+	LightNodeEnabled     bool
+	SyncUpdateDelay      time.Duration
+	SwapAPI              string
+	Cors                 string
+	BzzAccount           string
+	privateKey           *ecdsa.PrivateKey
 }
 
 //create a default config with all parameters to set to defaults
@@ -80,20 +81,21 @@ func NewConfig() (c *Config) {
 		FileStoreParams:  storage.NewFileStoreParams(),
 		HiveParams:       network.NewHiveParams(),
 		//SyncParams:    network.NewDefaultSyncParams(),
-		Swap:              swap.NewDefaultSwapParams(),
-		Pss:               pss.NewPssParams(),
-		ListenAddr:        DefaultHTTPListenAddr,
-		Port:              DefaultHTTPPort,
-		Path:              node.DefaultDataDir(),
-		EnsAPIs:           nil,
-		EnsRoot:           ens.TestNetAddress,
-		NetworkID:         network.DefaultNetworkID,
-		SwapEnabled:       false,
-		SyncEnabled:       true,
-		SyncingSkipCheck:  false,
-		DeliverySkipCheck: true,
-		SyncUpdateDelay:   15 * time.Second,
-		SwapAPI:           "",
+		Swap:                 swap.NewDefaultSwapParams(),
+		Pss:                  pss.NewPssParams(),
+		ListenAddr:           DefaultHTTPListenAddr,
+		Port:                 DefaultHTTPPort,
+		Path:                 node.DefaultDataDir(),
+		EnsAPIs:              nil,
+		EnsRoot:              ens.TestNetAddress,
+		NetworkID:            network.DefaultNetworkID,
+		SwapEnabled:          false,
+		SyncEnabled:          true,
+		SyncingSkipCheck:     false,
+		MaxStreamPeerServers: 10000,
+		DeliverySkipCheck:    true,
+		SyncUpdateDelay:      15 * time.Second,
+		SwapAPI:              "",
 	}
 
 	return
diff --git a/swarm/network/stream/common_test.go b/swarm/network/stream/common_test.go
index deb7e9815..72fdb2bd9 100644
--- a/swarm/network/stream/common_test.go
+++ b/swarm/network/stream/common_test.go
@@ -84,7 +84,7 @@ func createGlobalStore() (string, *mockdb.GlobalStore, error) {
 	return globalStoreDir, globalStore, nil
 }
 
-func newStreamerTester(t *testing.T) (*p2ptest.ProtocolTester, *Registry, *storage.LocalStore, func(), error) {
+func newStreamerTester(t *testing.T, registryOptions *RegistryOptions) (*p2ptest.ProtocolTester, *Registry, *storage.LocalStore, func(), error) {
 	// setup
 	addr := network.RandomAddr() // tested peers peer address
 	to := network.NewKademlia(addr.OAddr, network.NewKadParams())
@@ -114,7 +114,7 @@ func newStreamerTester(t *testing.T) (*p2ptest.ProtocolTester, *Registry, *stora
 
 	delivery := NewDelivery(to, netStore)
 	netStore.NewNetFetcherFunc = network.NewFetcherFactory(delivery.RequestFromPeers, true).New
-	streamer := NewRegistry(addr.ID(), delivery, netStore, state.NewInmemoryStore(), nil)
+	streamer := NewRegistry(addr.ID(), delivery, netStore, state.NewInmemoryStore(), registryOptions)
 	teardown := func() {
 		streamer.Close()
 		removeDataDir()
diff --git a/swarm/network/stream/delivery_test.go b/swarm/network/stream/delivery_test.go
index 9fb90eeba..b021b8771 100644
--- a/swarm/network/stream/delivery_test.go
+++ b/swarm/network/stream/delivery_test.go
@@ -39,7 +39,7 @@ import (
 )
 
 func TestStreamerRetrieveRequest(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -75,7 +75,7 @@ func TestStreamerRetrieveRequest(t *testing.T) {
 }
 
 func TestStreamerUpstreamRetrieveRequestMsgExchangeWithoutStore(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -127,7 +127,7 @@ func TestStreamerUpstreamRetrieveRequestMsgExchangeWithoutStore(t *testing.T) {
 // upstream request server receives a retrieve Request and responds with
 // offered hashes or delivery if skipHash is set to true
 func TestStreamerUpstreamRetrieveRequestMsgExchange(t *testing.T) {
-	tester, streamer, localStore, teardown, err := newStreamerTester(t)
+	tester, streamer, localStore, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -221,7 +221,7 @@ func TestStreamerUpstreamRetrieveRequestMsgExchange(t *testing.T) {
 }
 
 func TestStreamerDownstreamChunkDeliveryMsgExchange(t *testing.T) {
-	tester, streamer, localStore, teardown, err := newStreamerTester(t)
+	tester, streamer, localStore, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
diff --git a/swarm/network/stream/messages.go b/swarm/network/stream/messages.go
index 117f88044..74c785d58 100644
--- a/swarm/network/stream/messages.go
+++ b/swarm/network/stream/messages.go
@@ -84,11 +84,13 @@ func (p *Peer) handleSubscribeMsg(ctx context.Context, req *SubscribeMsg) (err e
 
 	defer func() {
 		if err != nil {
-			if e := p.Send(context.TODO(), SubscribeErrorMsg{
+			// The error will be sent as a subscribe error message
+			// and will not be returned as it will prevent any new message
+			// exchange between peers over p2p. Instead, error will be returned
+			// only if there is one from sending subscribe error message.
+			err = p.Send(context.TODO(), SubscribeErrorMsg{
 				Error: err.Error(),
-			}); e != nil {
-				log.Error("send stream subscribe error message", "err", err)
-			}
+			})
 		}
 	}()
 
diff --git a/swarm/network/stream/peer.go b/swarm/network/stream/peer.go
index 5fdaa7b87..ef6bbdf70 100644
--- a/swarm/network/stream/peer.go
+++ b/swarm/network/stream/peer.go
@@ -18,6 +18,7 @@ package stream
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"sync"
 	"time"
@@ -46,6 +47,10 @@ func (e *notFoundError) Error() string {
 	return fmt.Sprintf("%s not found for stream %q", e.t, e.s)
 }
 
+// ErrMaxPeerServers will be returned if peer server limit is reached.
+// It will be sent in the SubscribeErrorMsg.
+var ErrMaxPeerServers = errors.New("max peer servers")
+
 // Peer is the Peer extension for the streaming protocol
 type Peer struct {
 	*protocols.Peer
@@ -204,6 +209,11 @@ func (p *Peer) setServer(s Stream, o Server, priority uint8) (*server, error) {
 	if p.servers[s] != nil {
 		return nil, fmt.Errorf("server %s already registered", s)
 	}
+
+	if p.streamer.maxPeerServers > 0 && len(p.servers) >= p.streamer.maxPeerServers {
+		return nil, ErrMaxPeerServers
+	}
+
 	os := &server{
 		Server:   o,
 		stream:   s,
@@ -346,6 +356,7 @@ func (p *Peer) removeClient(s Stream) error {
 		return newNotFoundError("client", s)
 	}
 	client.close()
+	delete(p.clients, s)
 	return nil
 }
 
diff --git a/swarm/network/stream/stream.go b/swarm/network/stream/stream.go
index 65b8dff5a..1eda06c6a 100644
--- a/swarm/network/stream/stream.go
+++ b/swarm/network/stream/stream.go
@@ -60,6 +60,7 @@ type Registry struct {
 	delivery       *Delivery
 	intervalsStore state.Store
 	doRetrieve     bool
+	maxPeerServers int
 }
 
 // RegistryOptions holds optional values for NewRegistry constructor.
@@ -68,6 +69,7 @@ type RegistryOptions struct {
 	DoSync          bool
 	DoRetrieve      bool
 	SyncUpdateDelay time.Duration
+	MaxPeerServers  int // The limit of servers for each peer in registry
 }
 
 // NewRegistry is Streamer constructor
@@ -87,6 +89,7 @@ func NewRegistry(localID enode.ID, delivery *Delivery, syncChunkStore storage.Sy
 		delivery:       delivery,
 		intervalsStore: intervalsStore,
 		doRetrieve:     options.DoRetrieve,
+		maxPeerServers: options.MaxPeerServers,
 	}
 	streamer.api = NewAPI(streamer)
 	delivery.getPeer = streamer.getPeer
diff --git a/swarm/network/stream/streamer_test.go b/swarm/network/stream/streamer_test.go
index 0390a7b9b..0bdebefa7 100644
--- a/swarm/network/stream/streamer_test.go
+++ b/swarm/network/stream/streamer_test.go
@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"context"
 	"errors"
+	"strconv"
 	"testing"
 	"time"
 
@@ -28,7 +29,7 @@ import (
 )
 
 func TestStreamerSubscribe(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -42,7 +43,7 @@ func TestStreamerSubscribe(t *testing.T) {
 }
 
 func TestStreamerRequestSubscription(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -127,7 +128,7 @@ func (self *testServer) Close() {
 }
 
 func TestStreamerDownstreamSubscribeUnsubscribeMsgExchange(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -220,7 +221,7 @@ func TestStreamerDownstreamSubscribeUnsubscribeMsgExchange(t *testing.T) {
 }
 
 func TestStreamerUpstreamSubscribeUnsubscribeMsgExchange(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -287,7 +288,7 @@ func TestStreamerUpstreamSubscribeUnsubscribeMsgExchange(t *testing.T) {
 }
 
 func TestStreamerUpstreamSubscribeUnsubscribeMsgExchangeLive(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -353,7 +354,7 @@ func TestStreamerUpstreamSubscribeUnsubscribeMsgExchangeLive(t *testing.T) {
 }
 
 func TestStreamerUpstreamSubscribeErrorMsgExchange(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -397,7 +398,7 @@ func TestStreamerUpstreamSubscribeErrorMsgExchange(t *testing.T) {
 }
 
 func TestStreamerUpstreamSubscribeLiveAndHistory(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -462,7 +463,7 @@ func TestStreamerUpstreamSubscribeLiveAndHistory(t *testing.T) {
 }
 
 func TestStreamerDownstreamCorruptHashesMsgExchange(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -527,7 +528,7 @@ func TestStreamerDownstreamCorruptHashesMsgExchange(t *testing.T) {
 }
 
 func TestStreamerDownstreamOfferedHashesMsgExchange(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -626,7 +627,7 @@ func TestStreamerDownstreamOfferedHashesMsgExchange(t *testing.T) {
 }
 
 func TestStreamerRequestSubscriptionQuitMsgExchange(t *testing.T) {
-	tester, streamer, _, teardown, err := newStreamerTester(t)
+	tester, streamer, _, teardown, err := newStreamerTester(t, nil)
 	defer teardown()
 	if err != nil {
 		t.Fatal(err)
@@ -752,3 +753,165 @@ func TestStreamerRequestSubscriptionQuitMsgExchange(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+// TestMaxPeerServersWithUnsubscribe creates a registry with a limited
+// number of stream servers, and performs a test with subscriptions and
+// unsubscriptions, checking if unsubscriptions will remove streams,
+// leaving place for new streams.
+func TestMaxPeerServersWithUnsubscribe(t *testing.T) {
+	var maxPeerServers = 6
+	tester, streamer, _, teardown, err := newStreamerTester(t, &RegistryOptions{
+		MaxPeerServers: maxPeerServers,
+	})
+	defer teardown()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	streamer.RegisterServerFunc("foo", func(p *Peer, t string, live bool) (Server, error) {
+		return newTestServer(t), nil
+	})
+
+	node := tester.Nodes[0]
+
+	for i := 0; i < maxPeerServers+10; i++ {
+		stream := NewStream("foo", strconv.Itoa(i), true)
+
+		err = tester.TestExchanges(p2ptest.Exchange{
+			Label: "Subscribe message",
+			Triggers: []p2ptest.Trigger{
+				{
+					Code: 4,
+					Msg: &SubscribeMsg{
+						Stream:   stream,
+						Priority: Top,
+					},
+					Peer: node.ID(),
+				},
+			},
+			Expects: []p2ptest.Expect{
+				{
+					Code: 1,
+					Msg: &OfferedHashesMsg{
+						Stream: stream,
+						HandoverProof: &HandoverProof{
+							Handover: &Handover{},
+						},
+						Hashes: make([]byte, HashSize),
+						From:   1,
+						To:     1,
+					},
+					Peer: node.ID(),
+				},
+			},
+		})
+
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		err = tester.TestExchanges(p2ptest.Exchange{
+			Label: "unsubscribe message",
+			Triggers: []p2ptest.Trigger{
+				{
+					Code: 0,
+					Msg: &UnsubscribeMsg{
+						Stream: stream,
+					},
+					Peer: node.ID(),
+				},
+			},
+		})
+
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+// TestMaxPeerServersWithoutUnsubscribe creates a registry with a limited
+// number of stream servers, and performs subscriptions to detect subscriptions
+// error message exchange.
+func TestMaxPeerServersWithoutUnsubscribe(t *testing.T) {
+	var maxPeerServers = 6
+	tester, streamer, _, teardown, err := newStreamerTester(t, &RegistryOptions{
+		MaxPeerServers: maxPeerServers,
+	})
+	defer teardown()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	streamer.RegisterServerFunc("foo", func(p *Peer, t string, live bool) (Server, error) {
+		return newTestServer(t), nil
+	})
+
+	node := tester.Nodes[0]
+
+	for i := 0; i < maxPeerServers+10; i++ {
+		stream := NewStream("foo", strconv.Itoa(i), true)
+
+		if i >= maxPeerServers {
+			err = tester.TestExchanges(p2ptest.Exchange{
+				Label: "Subscribe message",
+				Triggers: []p2ptest.Trigger{
+					{
+						Code: 4,
+						Msg: &SubscribeMsg{
+							Stream:   stream,
+							Priority: Top,
+						},
+						Peer: node.ID(),
+					},
+				},
+				Expects: []p2ptest.Expect{
+					{
+						Code: 7,
+						Msg: &SubscribeErrorMsg{
+							Error: ErrMaxPeerServers.Error(),
+						},
+						Peer: node.ID(),
+					},
+				},
+			})
+
+			if err != nil {
+				t.Fatal(err)
+			}
+			continue
+		}
+
+		err = tester.TestExchanges(p2ptest.Exchange{
+			Label: "Subscribe message",
+			Triggers: []p2ptest.Trigger{
+				{
+					Code: 4,
+					Msg: &SubscribeMsg{
+						Stream:   stream,
+						Priority: Top,
+					},
+					Peer: node.ID(),
+				},
+			},
+			Expects: []p2ptest.Expect{
+				{
+					Code: 1,
+					Msg: &OfferedHashesMsg{
+						Stream: stream,
+						HandoverProof: &HandoverProof{
+							Handover: &Handover{},
+						},
+						Hashes: make([]byte, HashSize),
+						From:   1,
+						To:     1,
+					},
+					Peer: node.ID(),
+				},
+			},
+		})
+
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+}
diff --git a/swarm/swarm.go b/swarm/swarm.go
index 8b2661529..0cd56d4eb 100644
--- a/swarm/swarm.go
+++ b/swarm/swarm.go
@@ -180,6 +180,7 @@ func NewSwarm(config *api.Config, mockStore *mock.NodeStore) (self *Swarm, err e
 		DoSync:          config.SyncEnabled,
 		DoRetrieve:      true,
 		SyncUpdateDelay: config.SyncUpdateDelay,
+		MaxPeerServers:  config.MaxStreamPeerServers,
 	})
 
 	// Swarm Hash Merklised Chunking for Arbitrary-length Document/File storage