Mongoose how to be connected to many database

For a project, I need to switch between some MongoDB databases for doing some queries.

I found some exemple like that one : Mongoose and multiple database in single node.js project

His answer is perfectly working but now I'm trying to do it in a loop and unfortunally it's not work, I get this error:

events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: failed to connect to [localhost:27017]
    at null.<anonymous> (/home/user/test_many_db_mongodb/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/server.js:549:74)
    at EventEmitter.emit (events.js:106:17)
    at null.<anonymous> (/home/user/test_many_db_mongodb/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/connection_pool.js:150:15)
    at EventEmitter.emit (events.js:98:17)
    at Socket.<anonymous> (/home/user/test_many_db_mongodb/node_modules/mongoose/node_modules/mongodb/lib/mongodb/connection/connection.js:533:10)
    at Socket.EventEmitter.emit (events.js:95:17)
    at net.js:440:14
    at process._tickCallback (node.js:419:13)

And I don't understand why I get this error, if the example in the link above work my code should too:

var mongoose = require('mongoose');

for (var i = 0; i != 1000; i++) {
    var conn = mongoose.createConnection('mongodb://localhost/test' + i);

    conn.on('connected', function() {
        console.log('Mongoose connected to database');

        var Model    = conn.model('Model', new mongoose.Schema({
            title : { type : String, default : 'model in test database' }
        }));

        var newModelA = new Model();
        newModelA.save(function(err) {
            if (err)
                console.log(err);
            console.log('save A');
        });
    });
}

Thanks for your help.

Thanks for your help.

I tried both way but it didn't work on my project, probably because I didn't show you all the code. I found a way using useDb():

var amqp = require('amqp');

var MailParser = require('mailparser').MailParser;
var mailparser = new MailParser();

var mongoose = require('mongoose');
var conn = mongoose.createConnection('mongodb://localhost');

var count = 1;

var connection = amqp.createConnection({host: 'localhost'});

    connection.on('ready', function() {
        connection.queue('task_queue', {autoDelete: false,
                                        durable: true}, function(queue) {

            console.log('Waiting for emails. To exit press CTRL+C');

            queue.subscribe({ack: true, prefetchCount: 1}, function(message, headers, deliveryInfo, ack) {
                mailparser.write(message.data.toString('utf-8'));
                mailparser.end();

                ack.acknowledge();
            });
        });
    });

mailparser.on("end", function(email_object){
    var d = new Date(); // just for be sure the db name is unique for the test
    var db = conn.useDb('test_'+d.getDate()+'-'+d.getMonth()+'-'+d.getYear()+'_'+d.getHours()+'-'+d.getMinutes()+'-'+d.getSeconds()+'-'+d.getMilliseconds());

    var Model    = conn.model('Model', new mongoose.Schema({
            subject : { type : String },
            body : { type : String }
        }));
    var newEmail = new Model();
    newEmail.subject = email_object.subject;
    newEmail.body = email_object.body;
    newEmail.save(function(err) {
        if (err) console.error(err);
        console.log(count++);
    });
});