Expose metrics for prometheus on /api/metrics

Author: lukazuljevic

apps/api/package.json

@@ -32,6 +32,7 @@
     "@nestjs/websockets": "^10.3.8",
     "@prisma/client": "^6.2.1",
     "@types/postmark": "^2.0.3",
+    "@willsoto/nestjs-prometheus": "^6.0.2",
     "bcrypt": "^5.1.1",
     "class-transformer": "^0.5.1",
     "class-validator": "0.13.2",
@@ -45,6 +46,7 @@
     "passport": "^0.7.0",
     "passport-jwt": "^4.0.1",
     "postmark": "^4.0.5",
+    "prom-client": "^15.1.3",
     "react-dropzone": "^14.2.3",
     "reflect-metadata": "^0.1.13",
     "rxjs": "^7.8.1",

apps/api/src/app.module.ts

@@ -18,6 +18,7 @@ import { FrequentlyAskedQuestionModule } from './frequently-asked-question/frequ
 import { InterestModule } from './interest/interest.module';
 import { JobModule } from './job/job.module';
 import { LeaderboardModule } from './leaderboard/leaderboard.module';
+import { MetricsModule } from './metrics/metrics.module';
 import { NotificationModule } from './notification/notification.module';
 import { PotentialSponsorModule } from './potential-sponsor/potential-sponsor.module';
 import { PrinterModule } from './printer/printer.module';
@@ -30,7 +31,6 @@ import { SponsorContractModule } from './sponsor-contract/sponsor-contract.modul
 import { SponsorMaterialsModule } from './sponsor-materials/sponsor-materials.module';
 import { SurveyQuestionModule } from './survey-question/survey-question.module';
 import { UserModule } from './user/user.module';
-
 @Module({
   imports: [
     ScheduleModule.forRoot(),
@@ -52,6 +52,7 @@ import { UserModule } from './user/user.module';
     PotentialSponsorModule,
     SponsorMaterialsModule,
     SponsorContractModule,
+    MetricsModule,
 
     ...(process.env.NODE_ENV !== 'dev'
       ? [

apps/api/src/main.ts

@@ -79,6 +79,7 @@ const run = async (app: INestApplication) => {
 
 async function bootstrap() {
   const app = await NestFactory.create(AppModule);
+
   app.setGlobalPrefix('api');
 
   setupClassValidator(app);

apps/api/src/metrics/metrics.interceptor.ts

@@ -0,0 +1,44 @@
+import {
+  CallHandler,
+  ExecutionContext,
+  Injectable,
+  NestInterceptor,
+} from '@nestjs/common';
+import { InjectMetric } from '@willsoto/nestjs-prometheus';
+import { Counter, Histogram } from 'prom-client';
+import { tap } from 'rxjs/operators';
+
+@Injectable()
+export class MetricsInterceptor implements NestInterceptor {
+  constructor(
+    @InjectMetric('http_request_duration_seconds')
+    public readonly histogram: Histogram<string>,
+
+    @InjectMetric('http_error_total')
+    public readonly errorCounter: Counter<string>,
+  ) {}
+
+  intercept(context: ExecutionContext, next: CallHandler) {
+    const start = process.hrtime();
+
+    return next.handle().pipe(
+      tap(() => {
+        const req = context.switchToHttp().getRequest();
+        const res = context.switchToHttp().getResponse();
+
+        if (!req || !res) return;
+
+        const diff = process.hrtime(start);
+        const seconds = diff[0] + diff[1] / 1e9;
+
+        this.histogram
+          .labels(
+            req.method,
+            req.route?.path ?? 'unknown',
+            String(res.statusCode),
+          )
+          .observe(seconds);
+      }),
+    );
+  }
+}

apps/api/src/metrics/metrics.module.ts

@@ -0,0 +1,29 @@
+import { Module } from '@nestjs/common';
+import { APP_INTERCEPTOR } from '@nestjs/core'; // <--- Import this
+import { PrometheusModule as WPrometheusModule } from '@willsoto/nestjs-prometheus';
+
+import { MetricsInterceptor } from './metrics.interceptor';
+import { HttpErrorCounter } from './providers/http-error.counter';
+import { HttpRequestDuration } from './providers/http-request.histogram';
+
+@Module({
+  imports: [
+    WPrometheusModule.register({
+      path: '/metrics',
+      defaultMetrics: {
+        enabled: true,
+      },
+    }),
+  ],
+  providers: [
+    HttpRequestDuration,
+    MetricsInterceptor,
+    HttpErrorCounter,
+    {
+      provide: APP_INTERCEPTOR,
+      useClass: MetricsInterceptor,
+    },
+  ],
+  exports: [WPrometheusModule, HttpRequestDuration, MetricsInterceptor],
+})
+export class MetricsModule {}

apps/api/src/metrics/providers/http-error.counter.ts

@@ -0,0 +1,7 @@
+import { makeCounterProvider } from '@willsoto/nestjs-prometheus';
+
+export const HttpErrorCounter = makeCounterProvider({
+  name: 'http_error_total',
+  help: 'Total HTTP errors',
+  labelNames: ['method', 'route', 'status'],
+});

apps/api/src/metrics/providers/http-request.histogram.ts

@@ -0,0 +1,8 @@
+import { makeHistogramProvider } from '@willsoto/nestjs-prometheus';
+
+export const HttpRequestDuration = makeHistogramProvider({
+  name: 'http_request_duration_seconds',
+  help: 'Request duration in seconds',
+  labelNames: ['method', 'route', 'status'],
+  buckets: [0.05, 0.1, 0.3, 1, 3, 5],
+});

infrastructure/ansible/playbooks/api/roles/api/tasks/main.yml

@@ -22,7 +22,7 @@
       - name: traefiknet
     labels:
       traefik.enable: 'true'
-      traefik.http.routers.api.rule: 'Host(`{{ api_domain }}`)'
+      traefik.http.routers.api.rule: 'Host(`{{ api_domain }}`) && !PathPrefix(`/api/metrics`)'
       traefik.http.middlewares.api-retry.retry.attempts: '5'
       traefik.http.middlewares.api-retry.retry.initialinterval: '100ms'
       traefik.http.middlewares.api-cors.headers.accesscontrolallowmethods: '*'

yarn.lock

@@ -1905,6 +1905,11 @@
     consola "^2.15.0"
     node-fetch "^2.6.1"
 
+"@opentelemetry/api@^1.4.0":
+  version "1.9.0"
+  resolved "https://registry.yarnpkg.com/@opentelemetry/api/-/api-1.9.0.tgz#d03eba68273dc0f7509e2a3d5cba21eae10379fe"
+  integrity sha512-3giAOQvZiH5F9bMlMiv8+GSPMeqg0dbaeo58/0SlA9sxSqZhnUtxzX9/2FzyhS9sWQf5S0GJE0AKBrFqjpeYcg==
+
 "@parcel/[email protected]":
   version "2.5.1"
   resolved "https://registry.yarnpkg.com/@parcel/watcher-android-arm64/-/watcher-android-arm64-2.5.1.tgz#507f836d7e2042f798c7d07ad19c3546f9848ac1"
@@ -3592,6 +3597,11 @@
     "@webassemblyjs/ast" "1.14.1"
     "@xtuc/long" "4.2.2"
 
+"@willsoto/nestjs-prometheus@^6.0.2":
+  version "6.0.2"
+  resolved "https://registry.yarnpkg.com/@willsoto/nestjs-prometheus/-/nestjs-prometheus-6.0.2.tgz#d603764a923848442ed092411716c0bf211de01f"
+  integrity sha512-ePyLZYdIrOOdlOWovzzMisIgviXqhPVzFpSMKNNhn6xajhRHeBsjAzSdpxZTc6pnjR9hw1lNAHyKnKl7lAPaVg==
+
 "@xtuc/ieee754@^1.2.0":
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/@xtuc/ieee754/-/ieee754-1.2.0.tgz#eef014a3145ae477a1cbc00cd1e552336dceb790"
@@ -3940,6 +3950,11 @@ binary-extensions@^2.0.0:
   resolved "https://registry.yarnpkg.com/binary-extensions/-/binary-extensions-2.3.0.tgz#f6e14a97858d327252200242d4ccfe522c445522"
   integrity sha512-Ceh+7ox5qe7LJuLHoY0feh3pHuUDHAcRUeyL2VYghZwfpkNIy/+8Ocg0a3UuSoYzavmylwuLWQOf3hl0jjMMIw==
 
+[email protected]:
+  version "1.0.2"
+  resolved "https://registry.yarnpkg.com/bintrees/-/bintrees-1.0.2.tgz#49f896d6e858a4a499df85c38fb399b9aff840f8"
+  integrity sha512-VOMgTMwjAaUG580SXn3LacVgjurrbMme7ZZNYGSSV7mmtY6QQRh0Eg3pwIcntQ77DErK1L0NxkbetjcoXzVwKw==
+
 bl@^4.1.0:
   version "4.1.0"
   resolved "https://registry.yarnpkg.com/bl/-/bl-4.1.0.tgz#451535264182bec2fbbc83a62ab98cf11d9f7b3a"
@@ -7541,6 +7556,14 @@ prisma@^6.2.1:
     "@prisma/config" "6.18.0"
     "@prisma/engines" "6.18.0"
 
+prom-client@^15.1.3:
+  version "15.1.3"
+  resolved "https://registry.yarnpkg.com/prom-client/-/prom-client-15.1.3.tgz#69fa8de93a88bc9783173db5f758dc1c69fa8fc2"
+  integrity sha512-6ZiOBfCywsD4k1BN9IX0uZhF+tJkV8q8llP64G5Hajs4JOeVLPCwpPVcpXy3BwYiUGgyJzsJJQeOIv7+hDSq8g==
+  dependencies:
+    "@opentelemetry/api" "^1.4.0"
+    tdigest "^0.1.1"
+
 prompts@^2.0.1:
   version "2.4.2"
   resolved "https://registry.yarnpkg.com/prompts/-/prompts-2.4.2.tgz#7b57e73b3a48029ad10ebd44f74b01722a4cb069"
@@ -8419,6 +8442,13 @@ tar@^6.1.11:
     mkdirp "^1.0.3"
     yallist "^4.0.0"
 
+tdigest@^0.1.1:
+  version "0.1.2"
+  resolved "https://registry.yarnpkg.com/tdigest/-/tdigest-0.1.2.tgz#96c64bac4ff10746b910b0e23b515794e12faced"
+  integrity sha512-+G0LLgjjo9BZX2MfdvPfH+MKLCrxlXSYec5DaPYP1fe6Iyhf0/fSmJ0bFiZ1F8BT6cGXl2LpltQptzjXKWEkKA==
+  dependencies:
+    bintrees "1.0.2"
+
 terser-webpack-plugin@^5.3.10:
   version "5.3.14"
   resolved "https://registry.yarnpkg.com/terser-webpack-plugin/-/terser-webpack-plugin-5.3.14.tgz#9031d48e57ab27567f02ace85c7d690db66c3e06"