mongoconnect.js

var mongoose = require('mongoose');
var isSeenConnected = false;
var connect = function() {
    var opt = { server: { auto_reconnect: true } };
    mongoose.connect('mongodb://localhost/' + 'test', opt);
};

connect();

mongoose.connection.on('error', function() {
    console.log('Could not connect to mongoDB');
});

mongoose.connection.on('open', function() {
    console.log('Open connection to mongoDB');
});

mongoose.connection.on('disconnected', function() {
    console.log('Lost mongoDB connection...');
    if (!isSeenConnected)
        connect();
});

mongoose.connection.on('connected', function() {
    isSeenConnected = true;
    console.log('Establish connection to mongoDB');
});

mongoose.connection.on('reconnected', function() {
    console.log('Reconnected to mongoDB');
});

process.on('SIGINT', function() {
    mongoose.connection.close(function() {
        console.log('Force to close the connection with mongoDB');
        process.exit(0);
    });
});