refactor(core): Use type-safe event emitters (no-changelog) (#10234)

packages/cli/src/TypedEmitter.ts

@@ -0,0 +1,48 @@
+import { EventEmitter } from 'node:events';
+import debounce from 'lodash/debounce';
+
+type Payloads<ListenerMap> = {
+	[E in keyof ListenerMap]: unknown;
+};
+
+type Listener<Payload> = (payload: Payload) => void;
+
+export class TypedEmitter<ListenerMap extends Payloads<ListenerMap>> extends EventEmitter {
+	private debounceWait = 300; // milliseconds
+
+	override on<EventName extends keyof ListenerMap & string>(
+		eventName: EventName,
+		listener: Listener<ListenerMap[EventName]>,
+	) {
+		return super.on(eventName, listener);
+	}
+
+	override once<EventName extends keyof ListenerMap & string>(
+		eventName: EventName,
+		listener: Listener<ListenerMap[EventName]>,
+	) {
+		return super.once(eventName, listener);
+	}
+
+	override off<EventName extends keyof ListenerMap & string>(
+		eventName: EventName,
+		listener: Listener<ListenerMap[EventName]>,
+	) {
+		return super.off(eventName, listener);
+	}
+
+	override emit<EventName extends keyof ListenerMap & string>(
+		eventName: EventName,
+		payload?: ListenerMap[EventName],
+	): boolean {
+		return super.emit(eventName, payload);
+	}
+
+	protected debouncedEmit = debounce(
+		<EventName extends keyof ListenerMap & string>(
+			eventName: EventName,
+			payload?: ListenerMap[EventName],
+		) => super.emit(eventName, payload),
+		this.debounceWait,
+	);
+}

packages/cli/src/WebhookHelpers.ts

@@ -360,11 +360,10 @@ export async function executeWebhook(
 				NodeExecuteFunctions,
 				executionMode,
 			);
-			Container.get(WorkflowStatisticsService).emit(
-				'nodeFetchedData',
-				workflow.id,
-				workflowStartNode,
-			);
+			Container.get(WorkflowStatisticsService).emit('nodeFetchedData', {
+				workflowId: workflow.id,
+				node: workflowStartNode,
+			});
 		} catch (err) {
 			// Send error response to webhook caller
 			const errorMessage = 'Workflow Webhook Error: Workflow could not be started!';

packages/cli/src/WorkflowExecuteAdditionalData.ts

@@ -525,17 +525,16 @@ function hookFunctionsSave(): IWorkflowExecuteHooks {
 						);
 					}
 				} finally {
-					workflowStatisticsService.emit(
-						'workflowExecutionCompleted',
-						this.workflowData,
+					workflowStatisticsService.emit('workflowExecutionCompleted', {
+						workflowData: this.workflowData,
 						fullRunData,
-					);
+					});
 				}
 			},
 		],
 		nodeFetchedData: [
 			async (workflowId: string, node: INode) => {
-				workflowStatisticsService.emit('nodeFetchedData', workflowId, node);
+				workflowStatisticsService.emit('nodeFetchedData', { workflowId, node });
 			},
 		],
 	};
@@ -636,11 +635,10 @@ function hookFunctionsSaveWorker(): IWorkflowExecuteHooks {
 						this.retryOf,
 					);
 				} finally {
-					workflowStatisticsService.emit(
-						'workflowExecutionCompleted',
-						this.workflowData,
+					workflowStatisticsService.emit('workflowExecutionCompleted', {
+						workflowData: this.workflowData,
 						fullRunData,
-					);
+					});
 				}
 			},
 			async function (this: WorkflowHooks, runData: IRun): Promise<void> {
@@ -676,7 +674,7 @@ function hookFunctionsSaveWorker(): IWorkflowExecuteHooks {
 		],
 		nodeFetchedData: [
 			async (workflowId: string, node: INode) => {
-				workflowStatisticsService.emit('nodeFetchedData', workflowId, node);
+				workflowStatisticsService.emit('nodeFetchedData', { workflowId, node });
 			},
 		],
 	};

packages/cli/src/concurrency/concurrency-control.service.ts

@@ -53,20 +53,20 @@ export class ConcurrencyControlService {
 
 		this.isEnabled = true;
 
-		this.productionQueue.on('concurrency-check', ({ capacity }: { capacity: number }) => {
+		this.productionQueue.on('concurrency-check', ({ capacity }) => {
 			if (this.shouldReport(capacity)) {
 				void this.telemetry.track('User hit concurrency limit', {
 					threshold: CLOUD_TEMP_PRODUCTION_LIMIT - capacity,
 				});
 			}
 		});
 
-		this.productionQueue.on('execution-throttled', ({ executionId }: { executionId: string }) => {
+		this.productionQueue.on('execution-throttled', ({ executionId }) => {
 			this.log('Execution throttled', { executionId });
 			this.eventService.emit('execution-throttled', { executionId });
 		});
 
-		this.productionQueue.on('execution-released', async (executionId: string) => {
+		this.productionQueue.on('execution-released', async (executionId) => {
 			this.log('Execution released', { executionId });
 			await this.executionRepository.resetStartedAt(executionId);
 		});

packages/cli/src/concurrency/concurrency-queue.ts

@@ -1,9 +1,14 @@
 import { Service } from 'typedi';
-import { EventEmitter } from 'node:events';
-import debounce from 'lodash/debounce';
+import { TypedEmitter } from '@/TypedEmitter';
+
+type ConcurrencyEvents = {
+	'execution-throttled': { executionId: string };
+	'execution-released': string;
+	'concurrency-check': { capacity: number };
+};
 
 @Service()
-export class ConcurrencyQueue extends EventEmitter {
+export class ConcurrencyQueue extends TypedEmitter<ConcurrencyEvents> {
 	private readonly queue: Array<{
 		executionId: string;
 		resolve: () => void;
@@ -63,9 +68,4 @@ export class ConcurrencyQueue extends EventEmitter {
 
 		resolve();
 	}
-
-	private debouncedEmit = debounce(
-		(event: string, payload: object) => this.emit(event, payload),
-		300,
-	);
 }

packages/cli/src/eventbus/event.service.ts

@@ -1,16 +1,6 @@
-import { EventEmitter } from 'node:events';
 import { Service } from 'typedi';
+import { TypedEmitter } from '@/TypedEmitter';
 import type { Event } from './event.types';
 
 @Service()
-export class EventService extends EventEmitter {
-	emit<K extends keyof Event>(eventName: K, arg?: Event[K]) {
-		super.emit(eventName, arg);
-		return true;
-	}
-
-	on<K extends keyof Event>(eventName: K, handler: (arg: Event[K]) => void) {
-		super.on(eventName, handler);
-		return this;
-	}
-}
+export class EventService extends TypedEmitter<Event> {}

packages/cli/src/push/index.ts

@@ -1,4 +1,3 @@
-import { EventEmitter } from 'events';
 import { ServerResponse } from 'http';
 import type { Server } from 'http';
 import type { Socket } from 'net';
@@ -17,6 +16,11 @@ import { OrchestrationService } from '@/services/orchestration.service';
 import { SSEPush } from './sse.push';
 import { WebSocketPush } from './websocket.push';
 import type { PushResponse, SSEPushRequest, WebSocketPushRequest } from './types';
+import { TypedEmitter } from '@/TypedEmitter';
+
+type PushEvents = {
+	editorUiConnected: string;
+};
 
 const useWebSockets = config.getEnv('push.backend') === 'websocket';
 
@@ -28,7 +32,7 @@ const useWebSockets = config.getEnv('push.backend') === 'websocket';
  * @emits message when a message is received from a client
  */
 @Service()
-export class Push extends EventEmitter {
+export class Push extends TypedEmitter<PushEvents> {
 	private backend = useWebSockets ? Container.get(WebSocketPush) : Container.get(SSEPush);
 
 	constructor(private readonly orchestrationService: OrchestrationService) {
@@ -37,7 +41,6 @@ export class Push extends EventEmitter {
 
 	handleRequest(req: SSEPushRequest | WebSocketPushRequest, res: PushResponse) {
 		const {
-			user,
 			ws,
 			query: { pushRef },
 		} = req;

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

@@ -1,5 +1,3 @@
-import EventEmitter from 'node:events';
-
 import Container, { Service } from 'typedi';
 import { caching } from 'cache-manager';
 import { ApplicationError, jsonStringify } from 'n8n-workflow';
@@ -10,14 +8,20 @@ import { MalformedRefreshValueError } from '@/errors/cache-errors/malformed-refr
 import type {
 	TaggedRedisCache,
 	TaggedMemoryCache,
-	CacheEvent,
 	MaybeHash,
 	Hash,
 } from '@/services/cache/cache.types';
 import { TIME } from '@/constants';
+import { TypedEmitter } from '@/TypedEmitter';
+
+type CacheEvents = {
+	'metrics.cache.hit': never;
+	'metrics.cache.miss': never;
+	'metrics.cache.update': never;
+};
 
 @Service()
-export class CacheService extends EventEmitter {
+export class CacheService extends TypedEmitter<CacheEvents> {
 	private cache: TaggedRedisCache | TaggedMemoryCache;
 
 	async init() {
@@ -66,10 +70,6 @@ export class CacheService extends EventEmitter {
 		await this.cache.store.reset();
 	}
 
-	emit(event: CacheEvent, ...args: unknown[]) {
-		return super.emit(event, ...args);
-	}
-
 	isRedis() {
 		return this.cache.kind === 'redis';
 	}

packages/cli/src/services/cache/cache.types.ts

@@ -8,5 +8,3 @@ export type TaggedMemoryCache = MemoryCache & { kind: 'memory' };
 export type Hash<T = unknown> = Record<string, T>;
 
 export type MaybeHash<T> = Hash<T> | undefined;
-
-export type CacheEvent = `metrics.cache.${'hit' | 'miss' | 'update'}`;

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

@@ -1,14 +1,19 @@
-import { EventEmitter } from 'node:events';
 import config from '@/config';
 import { Service } from 'typedi';
 import { TIME } from '@/constants';
 import { ErrorReporterProxy as EventReporter } from 'n8n-workflow';
 import { Logger } from '@/Logger';
 import { RedisServicePubSubPublisher } from '@/services/redis/RedisServicePubSubPublisher';
 import { RedisClientService } from '@/services/redis/redis-client.service';
+import { TypedEmitter } from '@/TypedEmitter';
+
+type MultiMainEvents = {
+	'leader-stepdown': never;
+	'leader-takeover': never;
+};
 
 @Service()
-export class MultiMainSetup extends EventEmitter {
+export class MultiMainSetup extends TypedEmitter<MultiMainEvents> {
 	constructor(
 		private readonly logger: Logger,
 		private readonly redisPublisher: RedisServicePubSubPublisher,

packages/cli/src/services/workflow-statistics.service.ts

@@ -1,29 +1,48 @@
-import { EventEmitter } from 'events';
-import { Container, Service } from 'typedi';
+import { Service } from 'typedi';
 import type { INode, IRun, IWorkflowBase } from 'n8n-workflow';
 import { StatisticsNames } from '@db/entities/WorkflowStatistics';
 import { WorkflowStatisticsRepository } from '@db/repositories/workflowStatistics.repository';
 import { UserService } from '@/services/user.service';
 import { Logger } from '@/Logger';
 import { OwnershipService } from './ownership.service';
+import { TypedEmitter } from '@/TypedEmitter';
+
+type WorkflowStatisticsEvents = {
+	nodeFetchedData: { workflowId: string; node: INode };
+	workflowExecutionCompleted: { workflowData: IWorkflowBase; fullRunData: IRun };
+	'telemetry.onFirstProductionWorkflowSuccess': {
+		project_id: string;
+		workflow_id: string;
+		user_id: string;
+	};
+	'telemetry.onFirstWorkflowDataLoad': {
+		user_id: string;
+		project_id: string;
+		workflow_id: string;
+		node_type: string;
+		node_id: string;
+	};
+};
 
 @Service()
-export class WorkflowStatisticsService extends EventEmitter {
+export class WorkflowStatisticsService extends TypedEmitter<WorkflowStatisticsEvents> {
 	constructor(
 		private readonly logger: Logger,
 		private readonly repository: WorkflowStatisticsRepository,
 		private readonly ownershipService: OwnershipService,
+		private readonly userService: UserService,
 	) {
 		super({ captureRejections: true });
 		if ('SKIP_STATISTICS_EVENTS' in process.env) return;
 
 		this.on(
 			'nodeFetchedData',
-			async (workflowId, node) => await this.nodeFetchedData(workflowId, node),
+			async ({ workflowId, node }) => await this.nodeFetchedData(workflowId, node),
 		);
 		this.on(
 			'workflowExecutionCompleted',
-			async (workflowData, runData) => await this.workflowExecutionCompleted(workflowData, runData),
+			async ({ workflowData, fullRunData }) =>
+				await this.workflowExecutionCompleted(workflowData, fullRunData),
 		);
 	}
 
@@ -49,18 +68,18 @@ export class WorkflowStatisticsService extends EventEmitter {
 			const upsertResult = await this.repository.upsertWorkflowStatistics(name, workflowId);
 
 			if (name === StatisticsNames.productionSuccess && upsertResult === 'insert') {
-				const project = await Container.get(OwnershipService).getWorkflowProjectCached(workflowId);
+				const project = await this.ownershipService.getWorkflowProjectCached(workflowId);
 				if (project.type === 'personal') {
-					const owner = await Container.get(OwnershipService).getProjectOwnerCached(project.id);
+					const owner = await this.ownershipService.getProjectOwnerCached(project.id);
 
 					const metrics = {
 						project_id: project.id,
 						workflow_id: workflowId,
-						user_id: owner?.id,
+						user_id: owner!.id,
 					};
 
 					if (owner && !owner.settings?.userActivated) {
-						await Container.get(UserService).updateSettings(owner.id, {
+						await this.userService.updateSettings(owner.id, {
 							firstSuccessfulWorkflowId: workflowId,
 							userActivated: true,
 							userActivatedAt: runData.startedAt.getTime(),
@@ -90,7 +109,7 @@ export class WorkflowStatisticsService extends EventEmitter {
 		const owner = await this.ownershipService.getProjectOwnerCached(project.id);
 
 		let metrics = {
-			user_id: owner?.id,
+			user_id: owner!.id,
 			project_id: project.id,
 			workflow_id: workflowId,
 			node_type: node.type,
@@ -111,29 +130,3 @@ export class WorkflowStatisticsService extends EventEmitter {
 		this.emit('telemetry.onFirstWorkflowDataLoad', metrics);
 	}
 }
-
-export declare interface WorkflowStatisticsService {
-	on(
-		event: 'nodeFetchedData',
-		listener: (workflowId: string | undefined | null, node: INode) => void,
-	): this;
-	on(
-		event: 'workflowExecutionCompleted',
-		listener: (workflowData: IWorkflowBase, runData: IRun) => void,
-	): this;
-	on(
-		event: 'telemetry.onFirstProductionWorkflowSuccess',
-		listener: (metrics: { user_id: string; workflow_id: string }) => void,
-	): this;
-	on(
-		event: 'telemetry.onFirstWorkflowDataLoad',
-		listener: (metrics: {
-			user_id: string;
-			workflow_id: string;
-			node_type: string;
-			node_id: string;
-			credential_type?: string;
-			credential_id?: string;
-		}) => void,
-	): this;
-}