Changing interceptor to not be global for prom metrics and exposing prom metrics on /metrics

src/main.ts

@@ -3,7 +3,6 @@ import { ConfigService } from '@nestjs/config'
 import { NestFactory } from '@nestjs/core'
 
 import { AppModule } from './app.module'
-import { CustomResponseTransformInterceptor } from './common/customResponse'
 import { setDefaults } from './common/dayjs'
 
 async function bootstrap() {
@@ -15,7 +14,6 @@ async function bootstrap() {
 	const port = config.get('PORT', 3000)
 	app.enableShutdownHooks()
 	app.useGlobalPipes(new ValidationPipe({ transform: true }))
-	app.useGlobalInterceptors(new CustomResponseTransformInterceptor())
 	setDefaults()
 	await app.listen(port, () => console.log(`Listening on port ${port}`))
 }

src/members/controller.ts

@@ -1,8 +1,10 @@
-import { Controller, Get, Inject, Query } from '@nestjs/common'
+import { Controller, Get, Inject, Query, UseInterceptors } from '@nestjs/common'
 
+import { CustomResponseTransformInterceptor } from '../common/customResponse'
 import { MembersService } from './service'
 
 @Controller('members')
+@UseInterceptors(CustomResponseTransformInterceptor)
 export class MembersController {
 	constructor(
 		@Inject(MembersService)

src/prometheus/controller.ts

@@ -0,0 +1,16 @@
+import { Controller, Get, Inject } from '@nestjs/common'
+
+import { PrometheusProvider } from './provider'
+
+@Controller('metrics')
+export class PrometheusController {
+	constructor(
+		@Inject(PrometheusProvider)
+		private readonly promProvider: PrometheusProvider,
+	) {}
+
+	@Get('/')
+	async getMetrics() {
+		return await this.promProvider.getMetrics()
+	}
+}

src/prometheus/module.ts

@@ -1,8 +1,10 @@
 import { Module } from '@nestjs/common'
 
+import { PrometheusController } from './controller'
 import { PrometheusProvider } from './provider'
 
 @Module({
+	controllers: [PrometheusController],
 	providers: [PrometheusProvider],
 })
 export class PrometheusModule {}

src/prometheus/provider.ts

@@ -1,11 +1,13 @@
 import { OnApplicationBootstrap } from '@nestjs/common'
-import { collectDefaultMetrics, Registry } from 'prom-client'
+import { collectDefaultMetrics, Counter, Registry } from 'prom-client'
 
 export class PrometheusProvider implements OnApplicationBootstrap {
 	private readonly registry: Registry
+	private readonly counters: Map<string, Counter>
 
 	constructor() {
 		this.registry = new Registry()
+		this.counters = new Map()
 	}
 
 	onApplicationBootstrap() {
@@ -15,4 +17,18 @@ export class PrometheusProvider implements OnApplicationBootstrap {
 			labels: { GIT_COMMIT: process.env.GIT_COMMIT ?? 'unknown' },
 		})
 	}
+
+	async getMetrics() {
+		return this.registry.metrics()
+	}
+
+	async count(name: string, help: string, increment = 1) {
+		let counter = this.counters.get(name)
+		if (counter == null) {
+			counter = new Counter({ name, help })
+			this.counters.set(name, counter)
+		}
+
+		counter.inc(increment)
+	}
 }

src/recurringReservations/controller.ts

@@ -20,6 +20,7 @@ import {
 	ValidateNested,
 } from 'class-validator'
 
+import { CustomResponseTransformInterceptor } from '../common/customResponse'
 import { DayOfWeek } from './entity'
 import { RecurringReservationsService } from './service'
 
@@ -79,7 +80,7 @@ export class UpdateRecurringReservationRequest {
 }
 
 @Controller('recurring-reservations')
-@UseInterceptors(ClassSerializerInterceptor)
+@UseInterceptors(ClassSerializerInterceptor, CustomResponseTransformInterceptor)
 export class RecurringReservationsController {
 	constructor(
 		@Inject(RecurringReservationsService)

src/reservations/controller.ts

@@ -23,6 +23,7 @@ import {
 } from 'class-validator'
 import { Dayjs } from 'dayjs'
 
+import { CustomResponseTransformInterceptor } from '../common/customResponse'
 import { DayjsTransformer } from '../common/dayjs'
 import { LoggerService } from '../logger/service.logger'
 import { RESERVATIONS_QUEUE_NAME, ReservationsQueue } from './config'
@@ -70,7 +71,7 @@ export class CreateReservationRequest {
 }
 
 @Controller('reservations')
-@UseInterceptors(ClassSerializerInterceptor)
+@UseInterceptors(ClassSerializerInterceptor, CustomResponseTransformInterceptor)
 export class ReservationsController {
 	constructor(
 		@Inject(ReservationsService)