rpcsrv: make websocket client limit configurable

docs/node-configuration.md

@@ -142,6 +142,7 @@ RPC:
   MaxIteratorResultItems: 100
   MaxFindResultItems: 100
   MaxNEP11Tokens: 100
+  MaxWebSocketClients: 64
   Port: 10332
   SessionEnabled: false
   SessionExpirationTime: 15
@@ -176,6 +177,10 @@ where:
 - `MaxFindResultItems` - the maximum number of elements for `findstates` response.
 - `MaxNEP11Tokens` - limit for the number of tokens returned from
   `getnep11balances` call.
+- `MaxWebSocketClients` - the maximum simultaneous websocket client connection
+  number (64 by default). Attempts to establish additional connections will
+  lead to websocket handshake failures. Use "-1" to disable websocket
+  connections (0 will lead to using the default value).
 - `Port` is an RPC server port it should be bound to.
 - `SessionEnabled` denotes whether session-based iterator JSON-RPC API is enabled.
   If true, then all iterators got from `invoke*` calls will be stored as sessions

pkg/config/rpc_config.go

@@ -16,6 +16,7 @@ type (
 		MaxIteratorResultItems int           `yaml:"MaxIteratorResultItems"`
 		MaxFindResultItems     int           `yaml:"MaxFindResultItems"`
 		MaxNEP11Tokens         int           `yaml:"MaxNEP11Tokens"`
+		MaxWebSocketClients    int           `yaml:"MaxWebSocketClients"`
 		Port                   uint16        `yaml:"Port"`
 		SessionEnabled         bool          `yaml:"SessionEnabled"`
 		SessionExpirationTime  int           `yaml:"SessionExpirationTime"`

pkg/services/rpcsrv/server.go

@@ -183,10 +183,8 @@ const (
 	// Write deadline.
 	wsWriteLimit = wsPingPeriod / 2
 
-	// Maximum number of subscribers per Server. Each websocket client is
-	// treated like a subscriber, so technically it's a limit on websocket
-	// connections.
-	maxSubscribers = 64
+	// Default maximum number of websocket clients per Server.
+	defaultMaxWebSocketClients = 64
 
 	// Maximum number of elements for get*transfers requests.
 	maxTransfersLimit = 1000
@@ -278,6 +276,10 @@ func New(chain Ledger, conf config.RPC, coreServer *network.Server,
 			log.Info("SessionPoolSize is not set or wrong, setting default value", zap.Int("SessionPoolSize", defaultSessionPoolSize))
 		}
 	}
+	if conf.MaxWebSocketClients == 0 {
+		conf.MaxWebSocketClients = defaultMaxWebSocketClients
+		log.Info("MaxWebSocketClients is not set or wrong, setting default value", zap.Int("MaxWebSocketClients", defaultMaxWebSocketClients))
+	}
 	var oracleWrapped = new(atomic.Value)
 	if orc != nil {
 		oracleWrapped.Store(&orc)
@@ -428,7 +430,7 @@ func (s *Server) handleHTTPRequest(w http.ResponseWriter, httpRequest *http.Requ
 		s.subsLock.RLock()
 		numOfSubs := len(s.subscribers)
 		s.subsLock.RUnlock()
-		if numOfSubs >= maxSubscribers {
+		if numOfSubs >= s.config.MaxWebSocketClients {
 			s.writeHTTPErrorResponse(
 				params.NewIn(),
 				w,

pkg/services/rpcsrv/server_helper_test.go

@@ -112,7 +112,10 @@ func getTestBlocks(t *testing.T) []*block.Block {
 
 func initClearServerWithServices(t testing.TB, needOracle bool, needNotary bool, disableIteratorsSessions bool) (*core.Blockchain, *Server, *httptest.Server) {
 	chain, orc, cfg, logger := getUnitTestChain(t, needOracle, needNotary, disableIteratorsSessions)
+	return wrapUnitTestChain(t, chain, orc, cfg, logger)
+}
 
+func wrapUnitTestChain(t testing.TB, chain *core.Blockchain, orc *oracle.Oracle, cfg config.Config, logger *zap.Logger) (*core.Blockchain, *Server, *httptest.Server) {
 	serverConfig := network.NewServerConfig(cfg)
 	serverConfig.UserAgent = fmt.Sprintf(config.UserAgentFormat, "0.98.6-test")
 	serverConfig.Port = 0
@@ -128,6 +131,11 @@ func initClearServerWithServices(t testing.TB, needOracle bool, needNotary bool,
 	return chain, &rpcServer, srv
 }
 
+func initClearServerWithCustomConfig(t testing.TB, ccfg func(configuration *config.Config)) (*core.Blockchain, *Server, *httptest.Server) {
+	chain, orc, cfg, logger := getUnitTestChainWithCustomConfig(t, false, false, ccfg)
+	return wrapUnitTestChain(t, chain, orc, cfg, logger)
+}
+
 func initClearServerWithInMemoryChain(t testing.TB) (*core.Blockchain, *Server, *httptest.Server) {
 	return initClearServerWithServices(t, false, false, false)
 }

pkg/services/rpcsrv/subscription_test.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/gorilla/websocket"
 	"github.com/nspcc-dev/neo-go/internal/testchain"
+	"github.com/nspcc-dev/neo-go/pkg/config"
 	"github.com/nspcc-dev/neo-go/pkg/core"
 	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
 	"github.com/nspcc-dev/neo-go/pkg/neorpc"
@@ -534,20 +535,30 @@ func doSomeWSRequest(t *testing.T, ws *websocket.Conn) {
 }
 
 func TestWSClientsLimit(t *testing.T) {
-	chain, rpcSrv, httpSrv := initClearServerWithInMemoryChain(t)
+	for tname, limit := range map[string]int{"default": 0, "8": 8, "disabled": -1} {
+		effectiveClients := limit
+		if limit == 0 {
+			effectiveClients = defaultMaxWebSocketClients
+		} else if limit < 0 {
+			effectiveClients = 0
+		}
+		t.Run(tname, func(t *testing.T) {
+			chain, rpcSrv, httpSrv := initClearServerWithCustomConfig(t, func(cfg *config.Config) {
+				cfg.ApplicationConfiguration.RPC.MaxWebSocketClients = limit
+			})
 			defer chain.Close()
 			defer rpcSrv.Shutdown()
 
 			dialer := websocket.Dialer{HandshakeTimeout: time.Second}
 			url := "ws" + strings.TrimPrefix(httpSrv.URL, "http") + "/ws"
-	wss := make([]*websocket.Conn, maxSubscribers)
+			wss := make([]*websocket.Conn, effectiveClients)
 
 			for i := 0; i < len(wss)+1; i++ {
 				ws, r, err := dialer.Dial(url, nil)
 				if r != nil && r.Body != nil {
 					defer r.Body.Close()
 				}
-		if i < maxSubscribers {
+				if i < effectiveClients {
 					require.NoError(t, err)
 					wss[i] = ws
 					// Check that it's completely ready.
@@ -561,6 +572,8 @@ func TestWSClientsLimit(t *testing.T) {
 			for i := 0; i < len(wss); i++ {
 				doSomeWSRequest(t, wss[i])
 			}
+		})
+	}
 }
 
 // The purpose of this test is to overflow buffers on server side to