feat(MCP Server Trigger Node): Cleanup MCP server management, use sanitized trigger node's name as name for the MCP server (#15751)

packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpServer.ts

@@ -38,8 +38,9 @@ function wasToolCall(body: string) {
 }
 
 /**
- * Extracts the request ID from a JSONRPC message
+ * Extracts the request ID from a JSONRPC message (for example for tool calls).
- * Returns undefined if the message doesn't have an ID or can't be parsed
+ * Returns undefined if the message doesn't have an ID (for example on a tool list request)
+ *
  */
 function getRequestId(body: string): string | undefined {
 	try {
@@ -51,25 +52,56 @@ function getRequestId(body: string): string | undefined {
 	}
 }
 
-export class McpServer {
+/**
+ * This singleton is shared across the instance, making sure it is the one
+ * keeping account of MCP servers.
+ * It needs to stay in memory to keep track of the long-lived connections.
+ * It requires a logger at first creation to set everything up.
+ */
+export class McpServerManager {
+	static #instance: McpServerManager;
+
 	servers: { [sessionId: string]: Server } = {};
 
 	transports: { [sessionId: string]: FlushingSSEServerTransport } = {};
 
-	logger: Logger;
-
 	private tools: { [sessionId: string]: Tool[] } = {};
 
 	private resolveFunctions: { [callId: string]: CallableFunction } = {};
 
-	constructor(logger: Logger) {
+	logger: Logger;
+
+	private constructor(logger: Logger) {
 		this.logger = logger;
 		this.logger.debug('MCP Server created');
 	}
 
-	async connectTransport(postUrl: string, resp: CompressionResponse): Promise<void> {
+	static instance(logger: Logger): McpServerManager {
+		if (!McpServerManager.#instance) {
+			McpServerManager.#instance = new McpServerManager(logger);
+			logger.debug('Created singleton MCP manager');
+		}
+
+		return McpServerManager.#instance;
+	}
+
+	async createServerAndTransport(
+		serverName: string,
+		postUrl: string,
+		resp: CompressionResponse,
+	): Promise<void> {
 		const transport = new FlushingSSEServerTransport(postUrl, resp);
-		const server = this.setUpServer();
+		const server = new Server(
+			{
+				name: serverName,
+				version: '0.1.0',
+			},
+			{
+				capabilities: { tools: {} },
+			},
+		);
+
+		this.setUpHandlers(server);
 		const { sessionId } = transport;
 		this.transports[sessionId] = transport;
 		this.servers[sessionId] = server;
@@ -123,17 +155,7 @@ export class McpServer {
 		return wasToolCall(req.rawBody.toString());
 	}
 
-	setUpServer(): Server {
+	setUpHandlers(server: Server) {
-		const server = new Server(
-			{
-				name: 'n8n-mcp-server',
-				version: '0.1.0',
-			},
-			{
-				capabilities: { tools: {} },
-			},
-		);
-
 		server.setRequestHandler(
 			ListToolsRequestSchema,
 			async (_, extra: RequestHandlerExtra<ServerRequest, ServerNotification>) => {
@@ -203,34 +225,5 @@ export class McpServer {
 		server.onerror = (error: unknown) => {
 			this.logger.error(`MCP Error: ${error}`);
 		};
-		return server;
-	}
-}
-
-/**
- * This singleton is shared across the instance, making sure we only have one server to worry about.
- * It needs to stay in memory to keep track of the long-lived connections.
- * It requires a logger at first creation to set everything up.
- */
-export class McpServerSingleton {
-	static #instance: McpServerSingleton;
-
-	private _serverData: McpServer;
-
-	private constructor(logger: Logger) {
-		this._serverData = new McpServer(logger);
-	}
-
-	static instance(logger: Logger): McpServer {
-		if (!McpServerSingleton.#instance) {
-			McpServerSingleton.#instance = new McpServerSingleton(logger);
-			logger.debug('Created singleton for MCP Servers');
-		}
-
-		return McpServerSingleton.#instance.serverData;
-	}
-
-	get serverData() {
-		return this._serverData;
 	}
 }

packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpTrigger.node.ts

@@ -3,11 +3,10 @@ import { validateWebhookAuthentication } from 'n8n-nodes-base/dist/nodes/Webhook
 import type { INodeTypeDescription, IWebhookFunctions, IWebhookResponseData } from 'n8n-workflow';
 import { NodeConnectionTypes, Node } from 'n8n-workflow';
 
-import { getConnectedTools } from '@utils/helpers';
+import { getConnectedTools, nodeNameToToolName } from '@utils/helpers';
 
 import type { CompressionResponse } from './FlushingSSEServerTransport';
-import { McpServerSingleton } from './McpServer';
+import { McpServerManager } from './McpServer';
-import type { McpServer } from './McpServer';
 
 const MCP_SSE_SETUP_PATH = 'sse';
 const MCP_SSE_MESSAGES_PATH = 'messages';
@@ -21,7 +20,7 @@ export class McpTrigger extends Node {
 			dark: 'file:../mcp.dark.svg',
 		},
 		group: ['trigger'],
-		version: 1,
+		version: [1, 1.1],
 		description: 'Expose n8n tools as an MCP Server endpoint',
 		activationMessage: 'You can now connect your MCP Clients to the SSE URL.',
 		defaults: {
@@ -143,8 +142,11 @@ export class McpTrigger extends Node {
 			}
 			throw error;
 		}
+		const node = context.getNode();
+		// Get a url/tool friendly name for the server, based on the node name
+		const serverName = node.typeVersion > 1 ? nodeNameToToolName(node) : 'n8n-mcp-server';
 
-		const mcpServer: McpServer = McpServerSingleton.instance(context.logger);
+		const mcpServerManager: McpServerManager = McpServerManager.instance(context.logger);
 
 		if (webhookName === 'setup') {
 			// Sets up the transport and opens the long-lived connection. This resp
@@ -153,7 +155,7 @@ export class McpTrigger extends Node {
 				new RegExp(`/${MCP_SSE_SETUP_PATH}$`),
 				`/${MCP_SSE_MESSAGES_PATH}`,
 			);
-			await mcpServer.connectTransport(postUrl, resp);
+			await mcpServerManager.createServerAndTransport(serverName, postUrl, resp);
 
 			return { noWebhookResponse: true };
 		} else if (webhookName === 'default') {
@@ -162,7 +164,7 @@ export class McpTrigger extends Node {
 			// 'setup' call
 			const connectedTools = await getConnectedTools(context, true);
 
-			const wasToolCall = await mcpServer.handlePostMessage(req, resp, connectedTools);
+			const wasToolCall = await mcpServerManager.handlePostMessage(req, resp, connectedTools);
 
 			if (wasToolCall) return { noWebhookResponse: true, workflowData: [[{ json: {} }]] };
 			return { noWebhookResponse: true };

packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/__test__/McpServer.test.ts

@@ -6,7 +6,7 @@ import { captor, mock } from 'jest-mock-extended';
 
 import type { CompressionResponse } from '../FlushingSSEServerTransport';
 import { FlushingSSEServerTransport } from '../FlushingSSEServerTransport';
-import { McpServer } from '../McpServer';
+import { McpServerManager } from '../McpServer';
 
 const sessionId = 'mock-session-id';
 const mockServer = mock<Server>();
@@ -28,20 +28,18 @@ describe('McpServer', () => {
 	const mockResponse = mock<CompressionResponse>();
 	const mockTool = mock<Tool>({ name: 'mockTool' });
 
-	let mcpServer: McpServer;
+	const mcpServerManager = McpServerManager.instance(mock());
 
 	beforeEach(() => {
 		jest.clearAllMocks();
 		mockResponse.status.mockReturnThis();
-
-		mcpServer = new McpServer(mock());
 	});
 
 	describe('connectTransport', () => {
 		const postUrl = '/post-url';
 
 		it('should set up a transport and server', async () => {
-			await mcpServer.connectTransport(postUrl, mockResponse);
+			await mcpServerManager.createServerAndTransport('mcpServer', postUrl, mockResponse);
 
 			// Check that FlushingSSEServerTransport was initialized with correct params
 			expect(FlushingSSEServerTransport).toHaveBeenCalledWith(postUrl, mockResponse);
@@ -50,18 +48,18 @@ describe('McpServer', () => {
 			expect(Server).toHaveBeenCalled();
 
 			// Check that transport and server are stored
-			expect(mcpServer.transports[sessionId]).toBeDefined();
+			expect(mcpServerManager.transports[sessionId]).toBeDefined();
-			expect(mcpServer.servers[sessionId]).toBeDefined();
+			expect(mcpServerManager.servers[sessionId]).toBeDefined();
 
 			// Check that connect was called on the server
-			expect(mcpServer.servers[sessionId].connect).toHaveBeenCalled();
+			expect(mcpServerManager.servers[sessionId].connect).toHaveBeenCalled();
 
 			// Check that flush was called if available
 			expect(mockResponse.flush).toHaveBeenCalled();
 		});
 
 		it('should set up close handler that cleans up resources', async () => {
-			await mcpServer.connectTransport(postUrl, mockResponse);
+			await mcpServerManager.createServerAndTransport('mcpServer', postUrl, mockResponse);
 
 			// Get the close callback and execute it
 			const closeCallbackCaptor = captor<() => Promise<void>>();
@@ -69,8 +67,8 @@ describe('McpServer', () => {
 			await closeCallbackCaptor.value();
 
 			// Check that resources were cleaned up
-			expect(mcpServer.transports[sessionId]).toBeUndefined();
+			expect(mcpServerManager.transports[sessionId]).toBeUndefined();
-			expect(mcpServer.servers[sessionId]).toBeUndefined();
+			expect(mcpServerManager.servers[sessionId]).toBeUndefined();
 		});
 	});
 
@@ -78,11 +76,11 @@ describe('McpServer', () => {
 		it('should call transport.handlePostMessage when transport exists', async () => {
 			mockTransport.handlePostMessage.mockImplementation(async () => {
 				// @ts-expect-error private property `resolveFunctions`
-				mcpServer.resolveFunctions[`${sessionId}_123`]();
+				mcpServerManager.resolveFunctions[`${sessionId}_123`]();
 			});
 
 			// Add the transport directly
-			mcpServer.transports[sessionId] = mockTransport;
+			mcpServerManager.transports[sessionId] = mockTransport;
 
 			mockRequest.rawBody = Buffer.from(
 				JSON.stringify({
@@ -94,7 +92,9 @@ describe('McpServer', () => {
 			);
 
 			// Call the method
-			const result = await mcpServer.handlePostMessage(mockRequest, mockResponse, [mockTool]);
+			const result = await mcpServerManager.handlePostMessage(mockRequest, mockResponse, [
+				mockTool,
+			]);
 
 			// Verify that transport's handlePostMessage was called
 			expect(mockTransport.handlePostMessage).toHaveBeenCalledWith(
@@ -119,11 +119,11 @@ describe('McpServer', () => {
 					? `${sessionId}_${firstId}`
 					: `${sessionId}_${secondId}`;
 				// @ts-expect-error private property `resolveFunctions`
-				mcpServer.resolveFunctions[requestKey]();
+				mcpServerManager.resolveFunctions[requestKey]();
 			});
 
 			// Add the transport directly
-			mcpServer.transports[sessionId] = mockTransport;
+			mcpServerManager.transports[sessionId] = mockTransport;
 
 			// First tool call
 			mockRequest.rawBody = Buffer.from(
@@ -136,7 +136,9 @@ describe('McpServer', () => {
 			);
 
 			// Handle first tool call
-			const firstResult = await mcpServer.handlePostMessage(mockRequest, mockResponse, [mockTool]);
+			const firstResult = await mcpServerManager.handlePostMessage(mockRequest, mockResponse, [
+				mockTool,
+			]);
 			expect(firstResult).toBe(true);
 			expect(mockTransport.handlePostMessage).toHaveBeenCalledWith(
 				mockRequest,
@@ -155,7 +157,9 @@ describe('McpServer', () => {
 			);
 
 			// Handle second tool call
-			const secondResult = await mcpServer.handlePostMessage(mockRequest, mockResponse, [mockTool]);
+			const secondResult = await mcpServerManager.handlePostMessage(mockRequest, mockResponse, [
+				mockTool,
+			]);
 			expect(secondResult).toBe(true);
 
 			// Verify transport's handlePostMessage was called twice
@@ -166,8 +170,22 @@ describe('McpServer', () => {
 		});
 
 		it('should return 401 when transport does not exist', async () => {
-			// Call without setting up transport
+			// Set up request with rawBody and ensure sessionId is properly set
-			await mcpServer.handlePostMessage(mockRequest, mockResponse, [mockTool]);
+			const testRequest = mock<Request>({
+				query: { sessionId: 'non-existent-session' },
+				path: '/sse',
+			});
+			testRequest.rawBody = Buffer.from(
+				JSON.stringify({
+					jsonrpc: '2.0',
+					method: 'tools/call',
+					id: 123,
+					params: { name: 'mockTool' },
+				}),
+			);
+
+			// Call without setting up transport for this sessionId
+			await mcpServerManager.handlePostMessage(testRequest, mockResponse, [mockTool]);
 
 			// Verify error status was set
 			expect(mockResponse.status).toHaveBeenCalledWith(401);

packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/__test__/McpTrigger.node.test.ts

@@ -2,20 +2,20 @@ import { jest } from '@jest/globals';
 import type { Tool } from '@langchain/core/tools';
 import type { Request, Response } from 'express';
 import { mock } from 'jest-mock-extended';
-import type { IWebhookFunctions } from 'n8n-workflow';
+import type { INode, IWebhookFunctions } from 'n8n-workflow';
 
-import type { McpServer } from '../McpServer';
+import * as helpers from '@utils/helpers';
+
+import type { McpServerManager } from '../McpServer';
 import { McpTrigger } from '../McpTrigger.node';
 
 const mockTool = mock<Tool>({ name: 'mockTool' });
-jest.mock('@utils/helpers', () => ({
+jest.spyOn(helpers, 'getConnectedTools').mockResolvedValue([mockTool]);
-	getConnectedTools: jest.fn().mockImplementation(() => [mockTool]),
-}));
 
-const mockServer = mock<McpServer>();
+const mockServerManager = mock<McpServerManager>();
 jest.mock('../McpServer', () => ({
-	McpServerSingleton: {
+	McpServerManager: {
-		instance: jest.fn().mockImplementation(() => mockServer),
+		instance: jest.fn().mockImplementation(() => mockServerManager),
 	},
 }));
 
@@ -30,9 +30,12 @@ describe('McpTrigger Node', () => {
 		jest.clearAllMocks();
 
 		mcpTrigger = new McpTrigger();
-
 		mockContext.getRequestObject.mockReturnValue(mockRequest);
 		mockContext.getResponseObject.mockReturnValue(mockResponse);
+		mockContext.getNode.mockReturnValue({
+			name: 'McpTrigger',
+			typeVersion: 1.1,
+		} as INode);
 	});
 
 	describe('webhook method', () => {
@@ -44,7 +47,8 @@ describe('McpTrigger Node', () => {
 			const result = await mcpTrigger.webhook(mockContext);
 
 			// Verify that the connectTransport method was called with correct URL
-			expect(mockServer.connectTransport).toHaveBeenCalledWith(
+			expect(mockServerManager.createServerAndTransport).toHaveBeenCalledWith(
+				'McpTrigger',
 				'/custom-path/messages',
 				mockResponse,
 			);
@@ -58,13 +62,13 @@ describe('McpTrigger Node', () => {
 			mockContext.getWebhookName.mockReturnValue('default');
 
 			// Mock that the server executes a tool and returns true
-			mockServer.handlePostMessage.mockResolvedValueOnce(true);
+			mockServerManager.handlePostMessage.mockResolvedValueOnce(true);
 
 			// Call the webhook method
 			const result = await mcpTrigger.webhook(mockContext);
 
 			// Verify that handlePostMessage was called with request, response and tools
-			expect(mockServer.handlePostMessage).toHaveBeenCalledWith(mockRequest, mockResponse, [
+			expect(mockServerManager.handlePostMessage).toHaveBeenCalledWith(mockRequest, mockResponse, [
 				mockTool,
 			]);
 
@@ -80,7 +84,7 @@ describe('McpTrigger Node', () => {
 			mockContext.getWebhookName.mockReturnValue('default');
 
 			// Mock that the server doesn't execute a tool and returns false
-			mockServer.handlePostMessage.mockResolvedValueOnce(false);
+			mockServerManager.handlePostMessage.mockResolvedValueOnce(false);
 
 			// Call the webhook method
 			const result = await mcpTrigger.webhook(mockContext);
@@ -88,5 +92,42 @@ describe('McpTrigger Node', () => {
 			// Verify the returned result when no tool was called
 			expect(result).toEqual({ noWebhookResponse: true });
 		});
+
+		it('should pass the correct server name to McpServerSingleton.instance for version > 1', async () => {
+			// Configure node with version > 1 and custom name
+			mockContext.getNode.mockReturnValue({
+				name: 'My custom MCP server!',
+				typeVersion: 1.1,
+			} as INode);
+			mockContext.getWebhookName.mockReturnValue('setup');
+
+			// Call the webhook method
+			await mcpTrigger.webhook(mockContext);
+
+			// Verify that connectTransport was called with the sanitized server name
+			expect(mockServerManager.createServerAndTransport).toHaveBeenCalledWith(
+				'My_custom_MCP_server_',
+				'/custom-path/messages',
+				mockResponse,
+			);
+		});
+
+		it('should use default server name for version 1', async () => {
+			// Configure node with version 1
+			mockContext.getNode.mockReturnValue({
+				typeVersion: 1,
+			} as INode);
+			mockContext.getWebhookName.mockReturnValue('setup');
+
+			// Call the webhook method
+			await mcpTrigger.webhook(mockContext);
+
+			// Verify that connectTransport was called with the default server name
+			expect(mockServerManager.createServerAndTransport).toHaveBeenCalledWith(
+				'n8n-mcp-server',
+				'/custom-path/messages',
+				mockResponse,
+			);
+		});
 	});
 });