fix: websocket timeouts after around 50-60 seconds

server/websocket.go

@@ -13,8 +13,9 @@ import (
 )
 
 type wsConnection struct {
-	conn    *websocket.Conn
-	writeMu sync.Mutex
+	conn       *websocket.Conn
+	writeMu    sync.Mutex
+	handlerSem chan struct{}
 }
 
 type validationError struct {
@@ -24,10 +25,11 @@ type validationError struct {
 }
 
 const (
-	wsMaxMessageSize = 64 * 1024
-	wsWriteWait      = 10 * time.Second
-	wsPongWait       = 60 * time.Second
-	wsPingPeriod     = (wsPongWait * 9) / 10
+	wsMaxMessageSize        = 64 * 1024
+	wsWriteWait             = 10 * time.Second
+	wsPongWait              = 60 * time.Second
+	wsPingPeriod            = (wsPongWait * 9) / 10
+	wsMaxConcurrentHandlers = 4
 
 	jsonRPCVersion        = "2.0"
 	errMsgParseError      = "expecting jsonrpc payload"
@@ -131,7 +133,7 @@ func NewWebSocketHandler(enableCORS bool) http.HandlerFunc {
 		}
 		defer conn.Close()
 
-		wsConn := &wsConnection{conn: conn}
+		wsConn := &wsConnection{conn: conn, handlerSem: make(chan struct{}, wsMaxConcurrentHandlers)}
 		configureConnection(conn)
 		stopPing := startPingRoutine(wsConn)
 		defer stopPing()
@@ -207,14 +209,28 @@ func handleWSMethodCall(wsConn *wsConnection, req JSONRPCRequest) {
 		return
 	}
 
-	result, err := handler(req.Params)
-	if err != nil {
-		log.Printf("Error executing method %s: %v", req.Method, err)
-		wsConn.sendError(req.ID, ErrCodeServerError, "Server error", err.Error())
+	// non-blocking acquire; reject immediately when all slots are taken
+	select {
+	case wsConn.handlerSem <- struct{}{}:
+	default:
+		wsConn.sendError(req.ID, ErrCodeServerError, "Server error", "too many concurrent requests")
 		return
 	}
 
-	wsConn.sendResponse(req.ID, result)
+	// run in a goroutine so the read loop stays unblocked and can process
+	// pong frames — without this, long-running handlers cause the read
+	// deadline to expire and the connection closes with 1006
+	go func() {
+		defer func() { <-wsConn.handlerSem }()
+		result, err := handler(req.Params)
+		if err != nil {
+			log.Printf("Error executing method %s: %v", req.Method, err)
+			wsConn.sendError(req.ID, ErrCodeServerError, "Server error", err.Error())
+			return
+		}
+
+		wsConn.sendResponse(req.ID, result)
+	}()
 }
 
 func (wsc *wsConnection) sendResponse(id any, result any) error {
@@ -242,5 +258,8 @@ func (wsc *wsConnection) sendError(id any, code int, message string, data any) e
 func (wsc *wsConnection) sendJSON(v any) error {
 	wsc.writeMu.Lock()
 	defer wsc.writeMu.Unlock()
+	if err := wsc.conn.SetWriteDeadline(time.Now().Add(wsWriteWait)); err != nil {
+		return err
+	}
 	return wsc.conn.WriteJSON(v)
 }