Create app.js

nodejsapp/app.js

@@ -0,0 +1,35 @@
+const express = require('express');
+const promClient = require('prom-client');
+
+const app = express();
+const port = 3000;
+
+// Create a default Registry and collect default metrics
+const register = new promClient.Registry();
+promClient.collectDefaultMetrics({ register });
+
+// Define a custom metric
+const httpRequestsTotal = new promClient.Counter({
+  name: 'http_requests_total',
+  help: 'Total number of HTTP requests',
+  labelNames: ['method', 'route', 'code']
+});
+register.registerMetric(httpRequestsTotal);
+
+app.use((req, res, next) => {
+  httpRequestsTotal.inc({ method: req.method, route: req.route ? req.route.path : '/', code: res.statusCode });
+  next();
+});
+
+app.get('/', (req, res) => {
+  res.send('Hello World!');
+});
+
+app.get('/metrics', (req, res) => {
+  res.set('Content-Type', register.contentType);
+  res.send(register.metrics());
+});
+
+app.listen(port, () => {
+  console.log(`Server running at http://localhost:${port}/`);
+});