docker-development-youtube-series/prometheus-monitoring/nodejs-application/src/server.js

'use strict';

const express = require('express');

// Constants
const PORT = 5000;
const HOST = '0.0.0.0';

// App
const client = require('prom-client');
const collectDefaultMetrics = client.collectDefaultMetrics;
// Probe every 5th second.
collectDefaultMetrics({ timeout: 5000 });

const counter = new client.Counter({
  name: 'node_request_operations_total',
  help: 'The total number of processed requests'
});

const histogram = new client.Histogram({
  name: 'node_request_duration_seconds',
  help: 'Histogram for the duration in seconds.',
  buckets: [1, 2, 5, 6, 10]
});

const app = express();
app.get('/', (req, res) => {

  //Simulate a sleep
  var start = new Date()
  var simulateTime = 1000

  setTimeout(function(argument) {
    // execution time simulated with setTimeout function
    var end = new Date() - start
    histogram.observe(end / 1000); //convert to seconds
  }, simulateTime)

  counter.inc();
  
  res.send('Hello world\n');
});


// Metrics endpoint
app.get('/metrics', (req, res) => {
  res.set('Content-Type', client.register.contentType)
  res.end(client.register.metrics())
})

app.listen(PORT, HOST);
console.log(`Running on http://${HOST}:${PORT}`);