mongoose-connection.js

const mongoose = require('mongoose')

const dbURI = 'mongodb://localhost/Loc8r'
mongoose.connect(dbURI, {
	useNewUrlParser: true,
	useUnifiedTopology: true
})

mongoose.connection.on('connected', () => {
	console.log(`Mongoose connected to ${dbURI}`)
})

mongoose.connection.on('error', err => {
	console.log(`Mongoose connection error:`, err)
})

mongoose.connection.on('disconnected', () => {
	console.log('mongoose disconnected')
})

const gracefulShutdown = (msg, cb) => {
	mongoose.connection.close(() => {
		console.log(`Mongoose disconnected through ${msg}`)
		cb()
	})
}

process.once('SIGUSR2', () => {
	gracefulShutdown('nodemon restart', () => {
		process.kill(process.pid, 'SIGUSR2')
	})
})

process.on('SIGINT', () => {
	gracefulShutdown('app termination', () => {
		process.exit(0)
	})
})

process.on('SIGTERM', () => {
	gracefulShutdown('Heroku app shutdown', () => {
		process.exit(0)
	})
})