feat(core): Introduce worker metrics (#10850)

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

@@ -2,6 +2,7 @@ import { GlobalConfig } from '@n8n/config';
 import type express from 'express';
 import promBundle from 'express-prom-bundle';
 import { mock } from 'jest-mock-extended';
+import type { InstanceSettings } from 'n8n-core';
 import promClient from 'prom-client';
 
 import config from '@/config';
@@ -43,11 +44,13 @@ describe('PrometheusMetricsService', () => {
 	const app = mock<express.Application>();
 	const eventBus = mock<MessageEventBus>();
 	const eventService = mock<EventService>();
+	const instanceSettings = mock<InstanceSettings>({ instanceType: 'main' });
 	const prometheusMetricsService = new PrometheusMetricsService(
 		mock(),
 		eventBus,
 		globalConfig,
 		eventService,
+		instanceSettings,
 	);
 
 	afterEach(() => {
@@ -64,6 +67,7 @@ describe('PrometheusMetricsService', () => {
 				mock(),
 				customGlobalConfig,
 				mock(),
+				instanceSettings,
 			);
 
 			await customPrometheusMetricsService.init(app);
@@ -204,5 +208,18 @@ describe('PrometheusMetricsService', () => {
 			expect(promClient.Counter).toHaveBeenCalledTimes(0); // cache metrics
 			expect(eventService.on).not.toHaveBeenCalled();
 		});
+
+		it('should not set up queue metrics if enabled and on scaling mode but instance is not main', async () => {
+			config.set('executions.mode', 'queue');
+			prometheusMetricsService.enableMetric('queue');
+			// @ts-expect-error private field
+			instanceSettings.instanceType = 'worker';
+
+			await prometheusMetricsService.init(app);
+
+			expect(promClient.Gauge).toHaveBeenCalledTimes(1); // version metric
+			expect(promClient.Counter).toHaveBeenCalledTimes(0); // cache metrics
+			expect(eventService.on).not.toHaveBeenCalled();
+		});
 	});
 });

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

@@ -1,6 +1,7 @@
 import { GlobalConfig } from '@n8n/config';
 import type express from 'express';
 import promBundle from 'express-prom-bundle';
+import { InstanceSettings } from 'n8n-core';
 import { EventMessageTypeNames } from 'n8n-workflow';
 import promClient, { type Counter, type Gauge } from 'prom-client';
 import semverParse from 'semver/functions/parse';
@@ -22,6 +23,7 @@ export class PrometheusMetricsService {
 		private readonly eventBus: MessageEventBus,
 		private readonly globalConfig: GlobalConfig,
 		private readonly eventService: EventService,
+		private readonly instanceSettings: InstanceSettings,
 	) {}
 
 	private readonly counters: { [key: string]: Counter<string> | null } = {};
@@ -227,7 +229,13 @@ export class PrometheusMetricsService {
 	}
 
 	private initQueueMetrics() {
-		if (!this.includes.metrics.queue || config.getEnv('executions.mode') !== 'queue') return;
+		if (
+			!this.includes.metrics.queue ||
+			config.getEnv('executions.mode') !== 'queue' ||
+			this.instanceSettings.instanceType !== 'main'
+		) {
+			return;
+		}
 
 		this.gauges.waiting = new promClient.Gauge({
 			name: this.prefix + 'scaling_mode_queue_jobs_waiting',