app1/node/app.js

var express = require('express');
var app = express();
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var database = 'mongodb://root:ruth@mongo:27017/admin';
var today = new Date();
var counter = 0;
var Prometheus = require("prom-client");

const libCounter = new Prometheus.Counter({
  name: 'lib_invocation_count',
  help: 'A simple counter for app access during runtime created with unofficial prometheus nodejs library'
});

const libUptime = new Prometheus.Counter({
  name: 'lib_upTime',
  help: 'uptime A counter of the application\'s uptime in seconds.'
})


// const collectDefaultMetrics = Prometheus.collectDefaultMetrics;
// Probe every 5th second.
// collectDefaultMetrics({ timeout: 5000 });

// new schema model object based on the structure of what I want to put on MongoDB collection
var testSchema = new Schema({
  color: {
    type: String
  }
},{
  collection: 'test'
});

// new object that will hold the data using model structure made above
var colors = mongoose.model('colorName', testSchema);

// Prometheus metrics
app.get('/metrics', function(req, res){
  // var now = new Date();
  // var passedTime = now - today;
  // res.writeHead(200, {'Content-Type':'text/plain'});
  // res.write('# HELP uptime A counter of the application\'s uptime in millisenconds.' + '\n');
  // res.write('# TYPE uptime counter' + '\n');
  // res.write('uptime ' + passedTime + '\n');
  // res.write('# HELP invocation_count A simple counter for app access during runtime' + '\n');
  // res.write('# TYPE invocation_count counter'+ '\n');
  // res.write('invocation_count ' + counter + '\n');
  // res.end();
  libUptime.inc(Math.floor(process.uptime()));
  res.set('Content-Type', Prometheus.register.contentType)
  res.end(Prometheus.register.metrics())
  res.end();
  libUptime.reset();
});



app.get('/', (req, res)=>{
  res.json([{message:'yes, your nodejs app is really running'}]);
  counter++;
  libCounter.inc();
});

app.get('/info', function(req, res){
  colors.find({}).then(function (colors) {
    res.json(colors);
  });
});

app.get('/info/:name', function(req, res){
  colors.find({color: req.params.name}).then(function(colors){
    res.json(colors);
  });
});

app.get('/colors', function(req, res){
  colors.find({}).then(function (colors) {
    res.json(colors);
  });
});

app.get('/colors/query/:name', function(req, res){
  res.send('color is ' + req.params.name);
});

app.post('/colors/add/:name', function(req, res){
  var item = {color: req.params.name};
  var data = new colors(item);
  data.save();
  res.send('color ' + req.params.name + ' added to database');
});

// database connection (with retries)
const options = {
  autoIndex: false, // Don't build indexes
  reconnectTries:30, // Retry up to 30 times
  reconnectInterval: 500, // Reconnect every 500ms
  poolSize: 10, // Maintain up to 10 socket connections
  // If not connected, return errors immediately rather than waiting for reconnect
  bufferMaxEntries: 0,
  useNewUrlParser: true
}

const connectWithRetry = () => {
  console.log('MongoDB connection with retry')
  mongoose.connect(database, options).then(()=>{
    console.log('MongoDB is connected')
  }).catch(err=>{
    console.log('MongoDB connection unsuccessful, retry after 5 seconds.')
    setTimeout(connectWithRetry, 5000)
  })
}

connectWithRetry();

app.listen(3001, () => {
 console.log('Server running on port 3001');
});

// var today = new Date();
//
//
// setInterval(()=>{
//   // console.log('process.uptime(): ' + process.uptime());
//   var now = new Date();
//   var passed = now - today;
//   console.log('# HELP uptime A summary of the application\'s uptime.')
//   console.log('# TYPE uptime summary')
//   console.log('uptime ' + passed);
// }, 1000)