feat(metrics): add Prometheus metrics to all backends

- Add metrics module to calendar, chat, clock, contacts backends
- Add metrics module to mana-core-auth service
- Expose /metrics endpoint for Prometheus scraping
- Track HTTP requests, response times, and custom business metrics

Co-Authored-By: Claude <noreply@anthropic.com>

apps/clock/apps/backend/package.json

@@ -31,6 +31,7 @@
 		"drizzle-kit": "^0.30.2",
 		"drizzle-orm": "^0.38.3",
 		"postgres": "^3.4.5",
+		"prom-client": "^15.1.0",
 		"reflect-metadata": "^0.2.2",
 		"rxjs": "^7.8.1"
 	},

apps/clock/apps/backend/src/app.module.ts

@@ -7,6 +7,7 @@ import { AlarmModule } from './alarm/alarm.module';
 import { TimerModule } from './timer/timer.module';
 import { WorldClockModule } from './world-clock/world-clock.module';
 import { PresetModule } from './preset/preset.module';
+import { MetricsModule } from './metrics';
 
 @Module({
 	imports: [
@@ -15,6 +16,7 @@ import { PresetModule } from './preset/preset.module';
 			envFilePath: '.env',
 		}),
 		ScheduleModule.forRoot(),
+		MetricsModule,
 		DatabaseModule,
 		HealthModule,
 		AlarmModule,

apps/clock/apps/backend/src/main.ts

@@ -1,10 +1,48 @@
 import { NestFactory } from '@nestjs/core';
 import { ValidationPipe } from '@nestjs/common';
+import { Request, Response, NextFunction } from 'express';
 import { AppModule } from './app.module';
+import { MetricsService } from './metrics/metrics.service';
+
+// Normalize route paths to prevent high cardinality
+function normalizeRoute(path: string): string {
+	return path
+		.replace(/[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}/gi, ':id')
+		.replace(/\/\d+/g, '/:id');
+}
 
 async function bootstrap() {
 	const app = await NestFactory.create(AppModule);
 
+	// Get MetricsService for request tracking
+	const metricsService = app.get(MetricsService);
+
+	// Global Express middleware to track ALL HTTP requests
+	app.use((req: Request, res: Response, next: NextFunction) => {
+		if (req.path === '/metrics') {
+			return next();
+		}
+
+		const startTime = Date.now();
+		const method = req.method;
+		const route = normalizeRoute(req.path);
+
+		res.once('finish', () => {
+			const duration = (Date.now() - startTime) / 1000;
+			metricsService.httpRequestsTotal.inc({
+				method,
+				route,
+				status: res.statusCode.toString(),
+			});
+			metricsService.httpRequestDuration.observe(
+				{ method, route, status: res.statusCode.toString() },
+				duration
+			);
+		});
+
+		next();
+	});
+
 	// Enable CORS for mobile and web apps
 	const corsOrigins = process.env.CORS_ORIGINS?.split(',').map((origin) => origin.trim()) || [
 		'http://localhost:3000',
@@ -30,8 +68,10 @@ async function bootstrap() {
 		})
 	);
 
-	// Set global prefix for API routes
-	app.setGlobalPrefix('api/v1');
+	// Set global prefix for API routes (exclude metrics endpoint)
+	app.setGlobalPrefix('api/v1', {
+		exclude: ['metrics', 'health'],
+	});
 
 	const port = process.env.PORT || 3017;
 	await app.listen(port);

apps/clock/apps/backend/src/metrics/index.ts

@@ -0,0 +1,3 @@
+export * from './metrics.module';
+export * from './metrics.service';
+export * from './metrics.controller';

apps/clock/apps/backend/src/metrics/metrics.controller.ts

@@ -0,0 +1,13 @@
+import { Controller, Get, Header } from '@nestjs/common';
+import { MetricsService } from './metrics.service';
+
+@Controller()
+export class MetricsController {
+	constructor(private readonly metricsService: MetricsService) {}
+
+	@Get('metrics')
+	@Header('Content-Type', 'text/plain; version=0.0.4; charset=utf-8')
+	async getMetrics(): Promise<string> {
+		return this.metricsService.getMetrics();
+	}
+}

apps/clock/apps/backend/src/metrics/metrics.module.ts

@@ -0,0 +1,11 @@
+import { Module, Global } from '@nestjs/common';
+import { MetricsService } from './metrics.service';
+import { MetricsController } from './metrics.controller';
+
+@Global()
+@Module({
+	controllers: [MetricsController],
+	providers: [MetricsService],
+	exports: [MetricsService],
+})
+export class MetricsModule {}

apps/clock/apps/backend/src/metrics/metrics.service.ts

@@ -0,0 +1,50 @@
+import { Injectable, OnModuleInit } from '@nestjs/common';
+import * as client from 'prom-client';
+
+@Injectable()
+export class MetricsService implements OnModuleInit {
+	private readonly register: client.Registry;
+
+	// HTTP metrics
+	readonly httpRequestsTotal: client.Counter<string>;
+	readonly httpRequestDuration: client.Histogram<string>;
+
+	constructor() {
+		this.register = new client.Registry();
+
+		// Add default metrics (CPU, memory, event loop, etc.)
+		client.collectDefaultMetrics({
+			register: this.register,
+			prefix: 'clock_',
+		});
+
+		// HTTP request counter
+		this.httpRequestsTotal = new client.Counter({
+			name: 'http_requests_total',
+			help: 'Total number of HTTP requests',
+			labelNames: ['method', 'route', 'status'],
+			registers: [this.register],
+		});
+
+		// HTTP request duration histogram
+		this.httpRequestDuration = new client.Histogram({
+			name: 'http_request_duration_seconds',
+			help: 'Duration of HTTP requests in seconds',
+			labelNames: ['method', 'route', 'status'],
+			buckets: [0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 2, 5],
+			registers: [this.register],
+		});
+	}
+
+	onModuleInit() {
+		// Metrics are ready
+	}
+
+	async getMetrics(): Promise<string> {
+		return this.register.metrics();
+	}
+
+	getContentType(): string {
+		return this.register.contentType;
+	}
+}