test(core): Add tests for Prometheus metrics service (no-changelog) (#10050)

packages/cli/src/Server.ts

@@ -168,8 +168,8 @@ export class Server extends AbstractServer {
 
 	async configure(): Promise<void> {
 		if (config.getEnv('endpoints.metrics.enable')) {
-			const { MetricsService } = await import('@/services/metrics.service');
-			await Container.get(MetricsService).configureMetrics(this.app);
+			const { PrometheusMetricsService } = await import('@/metrics/prometheus-metrics.service');
+			await Container.get(PrometheusMetricsService).configureMetrics(this.app);
 		}
 
 		const { frontendService } = this;

packages/cli/src/metrics/__tests__/prometheus-metrics.service.test.ts

@@ -0,0 +1,123 @@
+import config from '@/config';
+import promClient from 'prom-client';
+import promBundle from 'express-prom-bundle';
+import { mock } from 'jest-mock-extended';
+import { PrometheusMetricsService } from '../prometheus-metrics.service';
+import type express from 'express';
+import type { MessageEventBus } from '@/eventbus/MessageEventBus/MessageEventBus';
+
+const mockMiddleware = (
+	_req: express.Request,
+	_res: express.Response,
+	next: express.NextFunction,
+) => next();
+
+jest.mock('prom-client');
+jest.mock('express-prom-bundle', () => jest.fn(() => mockMiddleware));
+
+describe('PrometheusMetricsService', () => {
+	beforeEach(() => {
+		config.load(config.default);
+	});
+
+	describe('configureMetrics', () => {
+		it('should set up `n8n_version_info`', async () => {
+			const service = new PrometheusMetricsService(mock(), mock(), mock());
+
+			await service.configureMetrics(mock<express.Application>());
+
+			expect(promClient.Gauge).toHaveBeenCalledWith({
+				name: 'n8n_version_info',
+				help: 'n8n version info.',
+				labelNames: ['version', 'major', 'minor', 'patch'],
+			});
+		});
+
+		it('should set up default metrics collection with `prom-client`', async () => {
+			const service = new PrometheusMetricsService(mock(), mock(), mock());
+
+			await service.configureMetrics(mock<express.Application>());
+
+			expect(promClient.collectDefaultMetrics).toHaveBeenCalled();
+		});
+
+		it('should set up `n8n_cache_hits_total`', async () => {
+			config.set('endpoints.metrics.includeCacheMetrics', true);
+			const service = new PrometheusMetricsService(mock(), mock(), mock());
+
+			await service.configureMetrics(mock<express.Application>());
+
+			expect(promClient.Counter).toHaveBeenCalledWith({
+				name: 'n8n_cache_hits_total',
+				help: 'Total number of cache hits.',
+				labelNames: ['cache'],
+			});
+			expect(service.counters.cacheHitsTotal?.inc).toHaveBeenCalledWith(0);
+		});
+
+		it('should set up `n8n_cache_misses_total`', async () => {
+			config.set('endpoints.metrics.includeCacheMetrics', true);
+			const service = new PrometheusMetricsService(mock(), mock(), mock());
+
+			await service.configureMetrics(mock<express.Application>());
+
+			expect(promClient.Counter).toHaveBeenCalledWith({
+				name: 'n8n_cache_misses_total',
+				help: 'Total number of cache misses.',
+				labelNames: ['cache'],
+			});
+			expect(service.counters.cacheMissesTotal?.inc).toHaveBeenCalledWith(0);
+		});
+
+		it('should set up `n8n_cache_updates_total`', async () => {
+			config.set('endpoints.metrics.includeCacheMetrics', true);
+			const service = new PrometheusMetricsService(mock(), mock(), mock());
+
+			await service.configureMetrics(mock<express.Application>());
+
+			expect(promClient.Counter).toHaveBeenCalledWith({
+				name: 'n8n_cache_updates_total',
+				help: 'Total number of cache updates.',
+				labelNames: ['cache'],
+			});
+			expect(service.counters.cacheUpdatesTotal?.inc).toHaveBeenCalledWith(0);
+		});
+
+		it('should set up API metrics with `express-prom-bundle`', async () => {
+			config.set('endpoints.metrics.includeApiEndpoints', true);
+			config.set('endpoints.metrics.includeApiPathLabel', true);
+			config.set('endpoints.metrics.includeApiMethodLabel', true);
+			config.set('endpoints.metrics.includeApiStatusCodeLabel', true);
+			const service = new PrometheusMetricsService(mock(), mock(), mock());
+
+			const app = mock<express.Application>();
+
+			await service.configureMetrics(app);
+
+			expect(promBundle).toHaveBeenCalledWith({
+				autoregister: false,
+				includeUp: false,
+				includePath: true,
+				includeMethod: true,
+				includeStatusCode: true,
+			});
+
+			expect(app.use).toHaveBeenCalledWith(
+				['/rest/', '/webhook/', 'webhook-test/', '/api/'],
+				expect.any(Function),
+			);
+		});
+
+		it('should set up event bus metrics', async () => {
+			const eventBus = mock<MessageEventBus>();
+			const service = new PrometheusMetricsService(mock(), mock(), eventBus);
+
+			await service.configureMetrics(mock<express.Application>());
+
+			expect(eventBus.on).toHaveBeenCalledWith(
+				'metrics.messageEventBus.Event',
+				expect.any(Function),
+			);
+		});
+	});
+});

packages/cli/src/metrics/prometheus-metrics.service.ts

@@ -14,7 +14,7 @@ import { Logger } from '@/Logger';
 import { EventMessageTypeNames } from 'n8n-workflow';
 
 @Service()
-export class MetricsService extends EventEmitter {
+export class PrometheusMetricsService extends EventEmitter {
 	constructor(
 		private readonly logger: Logger,
 		private readonly cacheService: CacheService,

packages/cli/test/integration/metrics.test.ts

@@ -4,7 +4,7 @@ import request from 'supertest';
 
 import config from '@/config';
 import { N8N_VERSION } from '@/constants';
-import { MetricsService } from '@/services/metrics.service';
+import { PrometheusMetricsService } from '@/metrics/prometheus-metrics.service';
 import { ExecutionRecoveryService } from '@/executions/execution-recovery.service';
 
 import { setupTestServer } from './shared/utils';
@@ -42,7 +42,7 @@ describe('Metrics', () => {
 
 	it('should return cache metrics when enabled', async () => {
 		config.set('endpoints.metrics.includeCacheMetrics', true);
-		await Container.get(MetricsService).configureMetrics(testServer.app);
+		await Container.get(PrometheusMetricsService).configureMetrics(testServer.app);
 		const lines = await getMetricsResponseAsLines();
 		expect(lines).toContain('n8n_test_cache_hits_total 0');
 		expect(lines).toContain('n8n_test_cache_misses_total 0');
@@ -67,7 +67,7 @@ describe('Metrics', () => {
 
 	it('should return default metrics', async () => {
 		config.set('endpoints.metrics.includeDefaultMetrics', true);
-		await Container.get(MetricsService).configureMetrics(testServer.app);
+		await Container.get(PrometheusMetricsService).configureMetrics(testServer.app);
 		const lines = await getMetricsResponseAsLines();
 		expect(lines).toContain('nodejs_heap_space_size_total_bytes{space="read_only"} 0');
 		config.set('endpoints.metrics.includeDefaultMetrics', false);
@@ -75,7 +75,7 @@ describe('Metrics', () => {
 
 	it('should not return default metrics only when disabled', async () => {
 		config.set('endpoints.metrics.includeDefaultMetrics', false);
-		await Container.get(MetricsService).configureMetrics(testServer.app);
+		await Container.get(PrometheusMetricsService).configureMetrics(testServer.app);
 		const lines = await getMetricsResponseAsLines();
 		expect(lines).not.toContain('nodejs_heap_space_size_total_bytes{space="read_only"} 0');
 		config.set('endpoints.metrics.includeDefaultMetrics', true);

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

@@ -145,8 +145,10 @@ export const setupTestServer = ({
 						break;
 
 					case 'metrics':
-						const { MetricsService } = await import('@/services/metrics.service');
-						await Container.get(MetricsService).configureMetrics(app);
+						const { PrometheusMetricsService } = await import(
+							'@/metrics/prometheus-metrics.service'
+						);
+						await Container.get(PrometheusMetricsService).configureMetrics(app);
 						break;
 
 					case 'eventBus':