awesome-compose/react-express-mongodb/server/db/index.js

/**
 * Created by Syed Afzal
 */
const mongoose = require('mongoose');
const {log} = require('../utils/helpers/logger');

exports.connect = (app) => {
    const options = {
        useNewUrlParser: true,
        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
    }

    const connectWithRetry = () => {
        mongoose.Promise = global.Promise;
        console.log('MongoDB connection with retry')
        mongoose.connect(process.env.MONGODB_URI, options).then(()=>{
            console.log('MongoDB is connected');
            app.emit('ready');
        }).catch(err=>{
            console.log('MongoDB connection unsuccessful, retry after 2 seconds.')
            setTimeout(connectWithRetry, 2000)
        })
    }
    connectWithRetry();
};