From 9346463c6bd353e50ed769a8fc633042b434b85f Mon Sep 17 00:00:00 2001
From: RomanDavydchuk <roman.davydchuk@n8n.io>
Date: Mon, 23 Jun 2025 13:30:42 +0300
Subject: [PATCH] fix(MongoDB Atlas Vector Store Node): Old credentials used
 even after credentials are updated/changed (#16471)

---
 .../VectorStoreMongoDBAtlas.node.test.ts      | 78 +++++++++++++++++++
 .../VectorStoreMongoDBAtlas.node.ts           | 23 ++++--
 2 files changed, 94 insertions(+), 7 deletions(-)
 create mode 100644 packages/@n8n/nodes-langchain/nodes/vector_store/VectorStoreMongoDBAtlas/VectorStoreMongoDBAtlas.node.test.ts

diff --git a/packages/@n8n/nodes-langchain/nodes/vector_store/VectorStoreMongoDBAtlas/VectorStoreMongoDBAtlas.node.test.ts b/packages/@n8n/nodes-langchain/nodes/vector_store/VectorStoreMongoDBAtlas/VectorStoreMongoDBAtlas.node.test.ts
new file mode 100644
index 0000000000..ba3dda5eea
--- /dev/null
+++ b/packages/@n8n/nodes-langchain/nodes/vector_store/VectorStoreMongoDBAtlas/VectorStoreMongoDBAtlas.node.test.ts
@@ -0,0 +1,78 @@
+import { MongoClient } from 'mongodb';
+
+import { getMongoClient, mongoConfig } from './VectorStoreMongoDBAtlas.node';
+
+jest.mock('mongodb', () => ({
+	MongoClient: jest.fn(),
+}));
+
+describe('VectorStoreMongoDBAtlas -> getMongoClient', () => {
+	const mockContext = {
+		getCredentials: jest.fn(),
+	};
+	const mockClient1 = {
+		connect: jest.fn().mockResolvedValue(undefined),
+		close: jest.fn().mockResolvedValue(undefined),
+	};
+	const mockClient2 = {
+		connect: jest.fn().mockResolvedValue(undefined),
+		close: jest.fn().mockResolvedValue(undefined),
+	};
+	const MockMongoClient = MongoClient as jest.MockedClass<typeof MongoClient>;
+
+	beforeEach(() => {
+		jest.resetAllMocks();
+		mongoConfig.client = null;
+		mongoConfig.connectionString = '';
+	});
+
+	it('should reuse the same client when connection string is unchanged', async () => {
+		MockMongoClient.mockImplementation(() => mockClient1 as unknown as MongoClient);
+		mockContext.getCredentials.mockResolvedValue({
+			connectionString: 'mongodb://localhost:27017',
+		});
+
+		const client1 = await getMongoClient(mockContext);
+		const client2 = await getMongoClient(mockContext);
+
+		expect(MockMongoClient).toHaveBeenCalledTimes(1);
+		expect(MockMongoClient).toHaveBeenCalledWith('mongodb://localhost:27017', {
+			appName: 'devrel.integration.n8n_vector_integ',
+		});
+		expect(mockClient1.connect).toHaveBeenCalledTimes(1);
+		expect(mockClient1.close).not.toHaveBeenCalled();
+		expect(mockClient2.connect).not.toHaveBeenCalled();
+		expect(client1).toBe(mockClient1);
+		expect(client2).toBe(mockClient1);
+	});
+
+	it('should create new client when connection string changes', async () => {
+		MockMongoClient.mockImplementationOnce(
+			() => mockClient1 as unknown as MongoClient,
+		).mockImplementationOnce(() => mockClient2 as unknown as MongoClient);
+		mockContext.getCredentials
+			.mockResolvedValueOnce({
+				connectionString: 'mongodb://localhost:27017',
+			})
+			.mockResolvedValueOnce({
+				connectionString: 'mongodb://different-host:27017',
+			});
+
+		const client1 = await getMongoClient(mockContext);
+		const client2 = await getMongoClient(mockContext);
+
+		expect(MockMongoClient).toHaveBeenCalledTimes(2);
+		expect(MockMongoClient).toHaveBeenNthCalledWith(1, 'mongodb://localhost:27017', {
+			appName: 'devrel.integration.n8n_vector_integ',
+		});
+		expect(MockMongoClient).toHaveBeenNthCalledWith(2, 'mongodb://different-host:27017', {
+			appName: 'devrel.integration.n8n_vector_integ',
+		});
+		expect(mockClient1.connect).toHaveBeenCalledTimes(1);
+		expect(mockClient1.close).toHaveBeenCalledTimes(1);
+		expect(mockClient2.connect).toHaveBeenCalledTimes(1);
+		expect(mockClient2.close).not.toHaveBeenCalled();
+		expect(client1).toBe(mockClient1);
+		expect(client2).toBe(mockClient2);
+	});
+});
diff --git a/packages/@n8n/nodes-langchain/nodes/vector_store/VectorStoreMongoDBAtlas/VectorStoreMongoDBAtlas.node.ts b/packages/@n8n/nodes-langchain/nodes/vector_store/VectorStoreMongoDBAtlas/VectorStoreMongoDBAtlas.node.ts
index 0918a08977..fb016226f0 100644
--- a/packages/@n8n/nodes-langchain/nodes/vector_store/VectorStoreMongoDBAtlas/VectorStoreMongoDBAtlas.node.ts
+++ b/packages/@n8n/nodes-langchain/nodes/vector_store/VectorStoreMongoDBAtlas/VectorStoreMongoDBAtlas.node.ts
@@ -103,17 +103,26 @@ const insertFields: INodeProperties[] = [
 	},
 ];
 
-let mongoClient: MongoClient | null = null;
+export const mongoConfig = {
+	client: null as MongoClient | null,
+	connectionString: '',
+};
 
-async function getMongoClient(context: any) {
-	if (!mongoClient) {
-		const credentials = await context.getCredentials('mongoDb');
-		mongoClient = new MongoClient(credentials.connectionString as string, {
+export async function getMongoClient(context: any) {
+	const credentials = await context.getCredentials('mongoDb');
+	const connectionString = credentials.connectionString as string;
+	if (!mongoConfig.client || mongoConfig.connectionString !== connectionString) {
+		if (mongoConfig.client) {
+			await mongoConfig.client.close();
+		}
+
+		mongoConfig.connectionString = connectionString;
+		mongoConfig.client = new MongoClient(connectionString, {
 			appName: 'devrel.integration.n8n_vector_integ',
 		});
-		await mongoClient.connect();
+		await mongoConfig.client.connect();
 	}
-	return mongoClient;
+	return mongoConfig.client;
 }
 
 async function mongoClientAndDatabase(context: any) {