feat: quick return tool-call request, send response via SSE in goroutine

Author: CeerDecy

server/sse.go

@@ -53,15 +53,15 @@ var _ ClientSession = (*sseSession)(nil)
 // SSEServer implements a Server-Sent Events (SSE) based MCP server.
 // It provides real-time communication capabilities over HTTP using the SSE protocol.
 type SSEServer struct {
-	server          *MCPServer
-	baseURL         string
-	basePath        string
-  useFullURLForMessageEndpoint bool
-	messageEndpoint string
-	sseEndpoint     string
-	sessions        sync.Map
-	srv             *http.Server
-	contextFunc     SSEContextFunc
+	server                       *MCPServer
+	baseURL                      string
+	basePath                     string
+	useFullURLForMessageEndpoint bool
+	messageEndpoint              string
+	sseEndpoint                  string
+	sessions                     sync.Map
+	srv                          *http.Server
+	contextFunc                  SSEContextFunc
 
 	keepAlive         bool
 	keepAliveInterval time.Duration
@@ -158,12 +158,12 @@ func WithSSEContextFunc(fn SSEContextFunc) SSEOption {
 // NewSSEServer creates a new SSE server instance with the given MCP server and options.
 func NewSSEServer(server *MCPServer, opts ...SSEOption) *SSEServer {
 	s := &SSEServer{
-		server:            server,
-		sseEndpoint:       "/sse",
-		messageEndpoint:   "/message",
-    useFullURLForMessageEndpoint: true,
-		keepAlive:         false,
-		keepAliveInterval: 10 * time.Second,
+		server:                       server,
+		sseEndpoint:                  "/sse",
+		messageEndpoint:              "/message",
+		useFullURLForMessageEndpoint: true,
+		keepAlive:                    false,
+		keepAliveInterval:            10 * time.Second,
 	}
 
 	// Apply all options
@@ -293,7 +293,6 @@ func (s *SSEServer) handleSSE(w http.ResponseWriter, r *http.Request) {
 		}()
 	}
 
-
 	// Send the initial endpoint event
 	fmt.Fprintf(w, "event: endpoint\ndata: %s\r\n\r\n", s.GetMessageEndpointForClient(sessionID))
 	flusher.Flush()
@@ -356,31 +355,28 @@ func (s *SSEServer) handleMessage(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Process message through MCPServer
-	response := s.server.HandleMessage(ctx, rawMessage)
+	// quick return request, send 202 Accepted with no body, then deal the message and sent response via SSE
+	w.WriteHeader(http.StatusAccepted)
 
-	// Only send response if there is one (not for notifications)
-	if response != nil {
-		eventData, _ := json.Marshal(response)
+	go func() {
+		// Process message through MCPServer
+		response := s.server.HandleMessage(ctx, rawMessage)
 
-		// Queue the event for sending via SSE
-		select {
-		case session.eventQueue <- fmt.Sprintf("event: message\ndata: %s\n\n", eventData):
-			// Event queued successfully
-		case <-session.done:
-			// Session is closed, don't try to queue
-		default:
-			// Queue is full, could log this
-		}
+		// Only send response if there is one (not for notifications)
+		if response != nil {
+			eventData, _ := json.Marshal(response)
 
-		// Send HTTP response
-		w.Header().Set("Content-Type", "application/json")
-		w.WriteHeader(http.StatusAccepted)
-		json.NewEncoder(w).Encode(response)
-	} else {
-		// For notifications, just send 202 Accepted with no body
-		w.WriteHeader(http.StatusAccepted)
-	}
+			// Queue the event for sending via SSE
+			select {
+			case session.eventQueue <- fmt.Sprintf("event: message\ndata: %s\n\n", eventData):
+				// Event queued successfully
+			case <-session.done:
+				// Session is closed, don't try to queue
+			default:
+				// Queue is full, could log this
+			}
+		}
+	}()
 }
 
 // writeJSONRPCError writes a JSON-RPC error response with the given error details.