mongoose.js

'use strict';

var mongoose = require('mongoose');

const MAILER_MONGO_USER = process.env.MAILER_MONGO_USER || "";
const MAILER_MONGO_PASSWORD = process.env.MAILER_MONGO_PASSWORD || "";
const MAILER_MONGO_DATABASE = process.env.MAILER_MONGO_DATABASE || "mails";
const MAILER_MONGO_ADDR = process.env.MONGO_PORT_27017_TCP_ADDR || "localhost";
const MAILER_MONGO_PORT = process.env.MONGO_PORT_27017_TCP_PORT || "27017";

const MAILER_MONGO_HOST = `${MAILER_MONGO_ADDR}:${MAILER_MONGO_PORT}`;

const URL = buildMongoUrl(MAILER_MONGO_USER, MAILER_MONGO_PASSWORD, MAILER_MONGO_DATABASE, MAILER_MONGO_HOST);

// Build connection URL dependent on whether a user is specified or not
function buildMongoUrl(user, password, database, host) {
    if (user == "") {
        return `mongodb://${host}/${database}`;
    } else {
        return `mongodb://${user}:${password}@${host}/${database}`;
    }
}

/**
 * Code in this File is taken from http://stackoverflow.com/a/33139673
 *
 * Created By: Gil SH (https://stackoverflow.com/users/880223/gil-sh)
 * License is cc by-sa 3.0
 */
var db = mongoose.connection;
var lastReconnectAttempt; //saves the timestamp of the last reconnect attempt

var opt = {
    // user: 'admin',
    // pass: 'pass',
    // auth: {
    //     authdb: 'admin'
    // },
    autoReconnect: true,
    useNewUrlParser: true
};

console.log('mongoose connect', URL, opt);
mongoose.createConnection(URL, opt);

db.on('error', function (error) {
    console.error('Error in MongoDb connection: ' + error);
    mongoose.disconnect();
});

db.on('disconnected', function () {
    console.log('MongoDB disconnected!');
    var now = new Date().getTime();
    // check if the last reconnection attempt was too early
    if (lastReconnectAttempt && now - lastReconnectAttempt < 5000) {
        // if it does, delay the next attempt
        var delay = 5000 - (now - lastReconnectAttempt);
        console.log('reconnecting to MongoDB in ' + delay + "mills");
        setTimeout(function () {
            console.log('reconnecting to MongoDB');
            lastReconnectAttempt = new Date().getTime();
            mongoose.createConnection(URL, opt);
        }, delay);
    }
    else {
        console.log('reconnecting to MongoDB');
        lastReconnectAttempt = now;
        mongoose.createConnection(URL, opt);
    }
});

module.exports = {
    mongoose: mongoose
};