first commit

src/index.js

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+'use strict'
+
+const express = require('express')
+const promClient = require('prom-client')
+
+const app = express()
+const PORT = process.env.PORT || 3000
+
+// Prometheus metrics
+const collectDefaultMetrics = promClient.collectDefaultMetrics
+collectDefaultMetrics({ prefix: 'nodejs_app_' })
+
+const httpRequestDuration = new promClient.Histogram({
+  name: 'http_request_duration_seconds',
+  help: 'Duration of HTTP requests in seconds',
+  labelNames: ['method', 'route', 'status'],
+  buckets: [0.01, 0.05, 0.1, 0.5, 1, 5],
+})
+
+const httpRequestTotal = new promClient.Counter({
+  name: 'http_requests_total',
+  help: 'Total number of HTTP requests',
+  labelNames: ['method', 'route', 'status'],
+})
+
+// Metrics middleware
+app.use((req, res, next) => {
+  const end = httpRequestDuration.startTimer()
+  res.on('finish', () => {
+    const route = req.route ? req.route.path : req.path
+    const labels = { method: req.method, route, status: res.statusCode }
+    end(labels)
+    httpRequestTotal.inc(labels)
+  })
+  next()
+})
+
+app.use(express.json())
+
+app.get('/metrics', async (_req, res) => {
+  res.set('Content-Type', promClient.register.contentType)
+  res.end(await promClient.register.metrics())
+})
+
+app.get('/health', (_req, res) => {
+  res.json({ status: 'ok' })
+})
+
+app.get('/', (_req, res) => {
+  res.json({
+    message: 'Hello from Node.js!',
+    env: process.env.NODE_ENV || 'development',
+    version: process.env.APP_VERSION || 'unknown',
+  })
+})
+
+app.listen(PORT, '0.0.0.0', () => {
+  console.log(`Server listening on port ${PORT}`)
+})
+
+// Graceful shutdown — important for Nomad rolling deploys
+process.on('SIGTERM', () => {
+  console.log('SIGTERM received, shutting down gracefully')
+  process.exit(0)
+})