feat(core): Add multi-main setup debug endpoint (no-changelog) (#7991)

## Summary
Provide details about your pull request and what it adds, fixes, or
changes. Photos and videos are recommended.
Adi's idea here to help diagnose:
https://n8nio.slack.com/archives/C069KJBJ8HE/p1702300349277609?thread_ts=1702299930.728029&cid=C069KJBJ8HE
...

#### How to test the change:
1. ...


## Issues fixed
Include links to Github issue or Community forum post or **Linear
ticket**:
> Important in order to close automatically and provide context to
reviewers

...


## Review / Merge checklist
- [ ] PR title and summary are descriptive. **Remember, the title
automatically goes into the changelog. Use `(no-changelog)` otherwise.**
([conventions](https://github.com/n8n-io/n8n/blob/master/.github/pull_request_title_conventions.md))
- [ ] [Docs updated](https://github.com/n8n-io/n8n-docs) or follow-up
ticket created.
- [ ] Tests included.
> A bug is not considered fixed, unless a test is added to prevent it
from happening again. A feature is not complete without tests.
  >
> *(internal)* You can use Slack commands to trigger [e2e
tests](https://www.notion.so/n8n/How-to-use-Test-Instances-d65f49dfc51f441ea44367fb6f67eb0a?pvs=4#a39f9e5ba64a48b58a71d81c837e8227)
or [deploy test
instance](https://www.notion.so/n8n/How-to-use-Test-Instances-d65f49dfc51f441ea44367fb6f67eb0a?pvs=4#f6a177d32bde4b57ae2da0b8e454bfce)
or [deploy early access version on
Cloud](https://www.notion.so/n8n/Cloudbot-3dbe779836004972b7057bc989526998?pvs=4#fef2d36ab02247e1a0f65a74f6fb534e).

packages/cli/src/ActiveWorkflowRunner.ts

@@ -108,6 +108,10 @@ export class ActiveWorkflowRunner implements IWebhookManager {
 		await this.webhookService.populateCache();
 	}
 
+	async getAllWorkflowActivationErrors() {
+		return this.activationErrorsService.getAll();
+	}
+
 	/**
 	 * Removes all the currently active workflows from memory.
 	 */

packages/cli/src/Server.ts

@@ -120,6 +120,7 @@ import { CollaborationService } from './collaboration/collaboration.service';
 import { RoleController } from './controllers/role.controller';
 import { BadRequestError } from './errors/response-errors/bad-request.error';
 import { NotFoundError } from './errors/response-errors/not-found.error';
+import { MultiMainSetup } from './services/orchestration/main/MultiMainSetup.ee';
 import { PasswordUtility } from './services/password.utility';
 
 const exec = promisify(callbackExec);
@@ -307,6 +308,11 @@ export class Server extends AbstractServer {
 			Container.get(RoleController),
 		];
 
+		if (Container.get(MultiMainSetup).isEnabled) {
+			const { DebugController } = await import('./controllers/debug.controller');
+			controllers.push(Container.get(DebugController));
+		}
+
 		if (isLdapEnabled()) {
 			const { service, sync } = LdapManager.getInstance();
 			controllers.push(new LdapController(service, sync, internalHooks));

packages/cli/src/controllers/debug.controller.ts

@@ -0,0 +1,35 @@
+import { Service } from 'typedi';
+import { Get, RestController } from '@/decorators';
+import { ActiveWorkflowRunner } from '@/ActiveWorkflowRunner';
+import { MultiMainSetup } from '@/services/orchestration/main/MultiMainSetup.ee';
+import { WorkflowRepository } from '@/databases/repositories/workflow.repository';
+import { In } from 'typeorm';
+
+@RestController('/debug')
+@Service()
+export class DebugController {
+	constructor(
+		private readonly multiMainSetup: MultiMainSetup,
+		private readonly activeWorkflowRunner: ActiveWorkflowRunner,
+		private readonly workflowRepository: WorkflowRepository,
+	) {}
+
+	@Get('/multi-main-setup')
+	async getMultiMainSetupDetails() {
+		const leaderKey = await this.multiMainSetup.fetchLeaderKey();
+
+		const activeWorkflows = await this.workflowRepository.find({
+			select: ['id', 'name'],
+			where: { id: In(this.activeWorkflowRunner.allActiveInMemory()) },
+		});
+
+		const activationErrors = await this.activeWorkflowRunner.getAllWorkflowActivationErrors();
+
+		return {
+			instanceId: this.multiMainSetup.instanceId,
+			leaderKey,
+			activeWorkflows,
+			activationErrors,
+		};
+	}
+}

packages/cli/src/services/orchestration/main/MultiMainSetup.ee.ts

@@ -28,6 +28,10 @@ export class MultiMainSetup extends SingleMainSetup {
 		return !this.isLeader;
 	}
 
+	get instanceId() {
+		return this.id;
+	}
+
 	setLicensed(newState: boolean) {
 		this.isLicensed = newState;
 	}
@@ -140,4 +144,8 @@ export class MultiMainSetup extends SingleMainSetup {
 			payload,
 		});
 	}
+
+	async fetchLeaderKey() {
+		return this.redisPublisher.get(this.leaderKey);
+	}
 }

packages/cli/test/integration/debug.controller.test.ts

@@ -0,0 +1,48 @@
+import { WorkflowRepository } from '@/databases/repositories/workflow.repository';
+import { ActiveWorkflowRunner } from '@/ActiveWorkflowRunner';
+import { mockInstance } from '../shared/mocking';
+import { randomName } from './shared/random';
+import { generateNanoId } from '@/databases/utils/generators';
+import type { WorkflowEntity } from '@/databases/entities/WorkflowEntity';
+import { setupTestServer } from './shared/utils';
+import type { SuperAgentTest } from 'supertest';
+import { createOwner } from './shared/db/users';
+import { MultiMainSetup } from '@/services/orchestration/main/MultiMainSetup.ee';
+
+describe('DebugController', () => {
+	const workflowRepository = mockInstance(WorkflowRepository);
+	const activeWorkflowRunner = mockInstance(ActiveWorkflowRunner);
+
+	let testServer = setupTestServer({ endpointGroups: ['debug'] });
+	let ownerAgent: SuperAgentTest;
+
+	beforeAll(async () => {
+		const owner = await createOwner();
+		ownerAgent = testServer.authAgentFor(owner);
+		testServer.license.enable('feat:multipleMainInstances');
+	});
+
+	describe('GET /debug/multi-main-setup', () => {
+		test('should return multi-main setup details', async () => {
+			const workflowId = generateNanoId();
+			const activeWorkflows = [{ id: workflowId, name: randomName() }] as WorkflowEntity[];
+			const activationErrors = { [workflowId]: 'Failed to activate' };
+			const instanceId = 'main-71JdWtq306epIFki';
+
+			workflowRepository.find.mockResolvedValue(activeWorkflows);
+			activeWorkflowRunner.allActiveInMemory.mockReturnValue([workflowId]);
+			activeWorkflowRunner.getAllWorkflowActivationErrors.mockResolvedValue(activationErrors);
+			jest.spyOn(MultiMainSetup.prototype, 'instanceId', 'get').mockReturnValue(instanceId);
+			jest.spyOn(MultiMainSetup.prototype, 'fetchLeaderKey').mockResolvedValue('some-leader-key');
+
+			const response = await ownerAgent.get('/debug/multi-main-setup').expect(200);
+
+			expect(response.body.data).toMatchObject({
+				instanceId,
+				leaderKey: 'some-leader-key',
+				activeWorkflows,
+				activationErrors,
+			});
+		});
+	});
+});

packages/cli/test/integration/shared/types.ts

@@ -32,7 +32,8 @@ type EndpointGroup =
 	| 'workflowHistory'
 	| 'binaryData'
 	| 'role'
-	| 'invitations';
+	| 'invitations'
+	| 'debug';
 
 export interface SetupProps {
 	applyAuth?: boolean;

packages/cli/test/integration/shared/utils/testServer.ts

@@ -312,6 +312,11 @@ export const setupTestServer = ({
 						const { RoleController } = await import('@/controllers/role.controller');
 						registerController(app, config, Container.get(RoleController));
 						break;
+
+					case 'debug':
+						const { DebugController } = await import('@/controllers/debug.controller');
+						registerController(app, config, Container.get(DebugController));
+						break;
 				}
 			}
 		}