Graceful start & Shutdown of NodeJS application

Graceful start & Graceful shutdown.js

// Graceful start & Graceful shutdown of application to prevent errors with ongoing requests on restarting https://pm2.io/doc/en/runtime/best-practices/graceful-shutdown/?utm_source=pm2&utm_medium=website&utm_campaign=rebranding
const server = http.createServer(app)
mongoose.connect(process.env.MONGO_URL)
  .then(db => {
    console.log('connected to mongo successfully')
    server.listen(port, err => {
      if (err) {
        console.log('something bad happened', err)
      } else {
        process.send = process.send || function () { }
        process.send('ready')
        console.log(`server is listening on ${port}`)
      }
    })
  })
  .catch(err => console.log('Mongo connection error', err))

// If the Node process ends, close the Mongoose connection
const sigs = ['SIGINT', 'SIGTERM', 'SIGQUIT']
sigs.forEach(sig => {
  process.on(sig, () => {
    // Stops the server from accepting new connections and finishes existing connections.
    server.close(function (err) {
      if (err) {
        console.error(err)
        process.exit(1)
      }
      // close your database connection and exit with success (0 code)
      // for example with mongoose
      mongoose.connection.close(function () {
        console.log('Mongoose connection disconnected')
        process.exit(0)
      })
    })
  })
})