fix(core): Ensure only leader handles waiting executions (#9014)

packages/cli/src/WaitTracker.ts

@@ -7,8 +7,9 @@ import { Container, Service } from 'typedi';
 import type { IExecutionsStopData, IWorkflowExecutionDataProcess } from '@/Interfaces';
 import { WorkflowRunner } from '@/WorkflowRunner';
 import { ExecutionRepository } from '@db/repositories/execution.repository';
-import { OwnershipService } from './services/ownership.service';
+import { OwnershipService } from '@/services/ownership.service';
 import { Logger } from '@/Logger';
+import { OrchestrationService } from '@/services/orchestration.service';
 
 @Service()
 export class WaitTracker {
@@ -26,7 +27,22 @@ export class WaitTracker {
 		private readonly executionRepository: ExecutionRepository,
 		private readonly ownershipService: OwnershipService,
 		private readonly workflowRunner: WorkflowRunner,
+		readonly orchestrationService: OrchestrationService,
 	) {
+		const { isLeader, isMultiMainSetupEnabled, multiMainSetup } = orchestrationService;
+
+		if (isLeader) this.startTracking();
+
+		if (isMultiMainSetupEnabled) {
+			multiMainSetup
+				.on('leader-takeover', () => this.startTracking())
+				.on('leader-stepdown', () => this.stopTracking());
+		}
+	}
+
+	startTracking() {
+		this.logger.debug('Wait tracker started tracking waiting executions');
+
 		// Poll every 60 seconds a list of upcoming executions
 		this.mainTimer = setInterval(() => {
 			void this.getWaitingExecutions();
@@ -174,7 +190,9 @@ export class WaitTracker {
 		});
 	}
 
-	shutdown() {
+	stopTracking() {
+		this.logger.debug('Wait tracker shutting down');
+
 		clearInterval(this.mainTimer);
 		Object.keys(this.waitingExecutions).forEach((executionId) => {
 			clearTimeout(this.waitingExecutions[executionId].timer);

packages/cli/src/commands/start.ts

@@ -94,7 +94,7 @@ export class Start extends BaseCommand {
 			// Stop with trying to activate workflows that could not be activated
 			this.activeWorkflowRunner.removeAllQueuedWorkflowActivations();
 
-			Container.get(WaitTracker).shutdown();
+			Container.get(WaitTracker).stopTracking();
 
 			await this.externalHooks?.run('n8n.stop', []);
 

packages/cli/src/services/orchestration.service.ts

@@ -39,6 +39,9 @@ export class OrchestrationService {
 		return config.getEnv('redis.queueModeId');
 	}
 
+	/**
+	 * Whether this instance is the leader in a multi-main setup. Always `true` in single-main setup.
+	 */
 	get isLeader() {
 		return config.getEnv('multiMainSetup.instanceType') === 'leader';
 	}

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

@@ -62,7 +62,7 @@ export class MultiMainSetup extends EventEmitter {
 			if (config.getEnv('multiMainSetup.instanceType') === 'leader') {
 				config.set('multiMainSetup.instanceType', 'follower');
 
-				this.emit('leader-stepdown'); // lost leadership - stop triggers, pollers, pruning
+				this.emit('leader-stepdown'); // lost leadership - stop triggers, pollers, pruning, wait-tracking
 
 				EventReporter.info('[Multi-main setup] Leader failed to renew leader key');
 			}
@@ -97,7 +97,7 @@ export class MultiMainSetup extends EventEmitter {
 
 			await this.redisPublisher.setExpiration(this.leaderKey, this.leaderKeyTtl);
 
-			this.emit('leader-takeover'); // gained leadership - start triggers, pollers, pruning
+			this.emit('leader-takeover'); // gained leadership - start triggers, pollers, pruning, wait-tracking
 		} else {
 			config.set('multiMainSetup.instanceType', 'follower');
 		}

packages/cli/test/unit/WaitTracker.test.ts

@@ -2,11 +2,17 @@ import { WaitTracker } from '@/WaitTracker';
 import { mock } from 'jest-mock-extended';
 import type { ExecutionRepository } from '@/databases/repositories/execution.repository';
 import type { IExecutionResponse } from '@/Interfaces';
+import type { OrchestrationService } from '@/services/orchestration.service';
+import type { MultiMainSetup } from '@/services/orchestration/main/MultiMainSetup.ee';
 
 jest.useFakeTimers();
 
 describe('WaitTracker', () => {
 	const executionRepository = mock<ExecutionRepository>();
+	const orchestrationService = mock<OrchestrationService>({
+		isLeader: true,
+		isMultiMainSetupEnabled: false,
+	});
 
 	const execution = mock<IExecutionResponse>({
 		id: '123',
@@ -21,23 +27,29 @@ describe('WaitTracker', () => {
 		it('should query DB for waiting executions', async () => {
 			executionRepository.getWaitingExecutions.mockResolvedValue([execution]);
 
-			new WaitTracker(mock(), executionRepository, mock(), mock());
+			new WaitTracker(mock(), executionRepository, mock(), mock(), orchestrationService);
 
 			expect(executionRepository.getWaitingExecutions).toHaveBeenCalledTimes(1);
 		});
 
 		it('if no executions to start, should do nothing', () => {
 			executionRepository.getWaitingExecutions.mockResolvedValue([]);
 
-			new WaitTracker(mock(), executionRepository, mock(), mock());
+			new WaitTracker(mock(), executionRepository, mock(), mock(), orchestrationService);
 
 			expect(executionRepository.findSingleExecution).not.toHaveBeenCalled();
 		});
 
 		describe('if execution to start', () => {
 			it('if not enough time passed, should not start execution', async () => {
 				executionRepository.getWaitingExecutions.mockResolvedValue([execution]);
-				const waitTracker = new WaitTracker(mock(), executionRepository, mock(), mock());
+				const waitTracker = new WaitTracker(
+					mock(),
+					executionRepository,
+					mock(),
+					mock(),
+					orchestrationService,
+				);
 
 				executionRepository.getWaitingExecutions.mockResolvedValue([execution]);
 				await waitTracker.getWaitingExecutions();
@@ -51,7 +63,13 @@ describe('WaitTracker', () => {
 
 			it('if enough time passed, should start execution', async () => {
 				executionRepository.getWaitingExecutions.mockResolvedValue([]);
-				const waitTracker = new WaitTracker(mock(), executionRepository, mock(), mock());
+				const waitTracker = new WaitTracker(
+					mock(),
+					executionRepository,
+					mock(),
+					mock(),
+					orchestrationService,
+				);
 
 				executionRepository.getWaitingExecutions.mockResolvedValue([execution]);
 				await waitTracker.getWaitingExecutions();
@@ -68,7 +86,13 @@ describe('WaitTracker', () => {
 	describe('startExecution()', () => {
 		it('should query for execution to start', async () => {
 			executionRepository.getWaitingExecutions.mockResolvedValue([]);
-			const waitTracker = new WaitTracker(mock(), executionRepository, mock(), mock());
+			const waitTracker = new WaitTracker(
+				mock(),
+				executionRepository,
+				mock(),
+				mock(),
+				orchestrationService,
+			);
 
 			executionRepository.findSingleExecution.mockResolvedValue(execution);
 			waitTracker.startExecution(execution.id);
@@ -80,4 +104,34 @@ describe('WaitTracker', () => {
 			});
 		});
 	});
+
+	describe('multi-main setup', () => {
+		it('should start tracking if leader', () => {
+			const orchestrationService = mock<OrchestrationService>({
+				isLeader: true,
+				isMultiMainSetupEnabled: true,
+				multiMainSetup: mock<MultiMainSetup>({ on: jest.fn().mockReturnThis() }),
+			});
+
+			executionRepository.getWaitingExecutions.mockResolvedValue([]);
+
+			new WaitTracker(mock(), executionRepository, mock(), mock(), orchestrationService);
+
+			expect(executionRepository.getWaitingExecutions).toHaveBeenCalledTimes(1);
+		});
+
+		it('should not start tracking if follower', () => {
+			const orchestrationService = mock<OrchestrationService>({
+				isLeader: false,
+				isMultiMainSetupEnabled: true,
+				multiMainSetup: mock<MultiMainSetup>({ on: jest.fn().mockReturnThis() }),
+			});
+
+			executionRepository.getWaitingExecutions.mockResolvedValue([]);
+
+			new WaitTracker(mock(), executionRepository, mock(), mock(), orchestrationService);
+
+			expect(executionRepository.getWaitingExecutions).not.toHaveBeenCalled();
+		});
+	});
 });