Setting up singleton connection with node.js and mongo

Question

Previously I used mongodb with php and to query a database I was using a singleton. This way I instantiated connection only once and then reused it:

class MD         


        

Answer 1

Here's one way to do it. You can put your database connection details in a small module, initialize it when your app starts up, then use that module from any other modules that need a database connection. Here's the code I've been using and has been working for me in a rather simple internal application.

file: DataAccessAdapter.js

var Db = require('mongodb').Db;
var Server = require('mongodb').Server;
var dbPort = 27017;
var dbHost = 'localhost';
var dbName = 'CatDatabase';

var DataBase = function () {
};

module.exports = DataBase;

DataBase.GetDB = function () {
    if (typeof DataBase.db === 'undefined') {
        DataBase.InitDB();
    }
    return DataBase.db;
}

DataBase.InitDB = function () {
    DataBase.db = new Db(dbName, new Server(dbHost, dbPort, {}, {}), { safe: false, auto_reconnect: true });

    DataBase.db.open(function (e, d) {
        if (e) {
            console.log(e);
        } else {
            console.log('connected to database :: ' + dbName);
        }
    });
}

DataBase.Disconnect = function () {
    if (DataBase.db) {
        DataBase.db.close();
    }
}

DataBase.BsonIdFromString = function (id) {
    var mongo = require('mongodb');
    var BSON = mongo.BSONPure;
    return new BSON.ObjectID(id);
}

Then from server.js, when your application is starting up:

// Startup database connection
require('./DataAccessAdapter').InitDB();

And when you need to use the database, for example in your "Cat.js" file, you could do something like this:

var dataAccessAdapter = require('./DataAccessAdapter');

var Cat = function () {
    if (!Cat.db) {
        console.log('Initializing my Cat database');
        Cat.db = dataAccessAdapter.GetDB();
    }
    if (!Cat.CatCollection) {
            console.log('Initializing cats collection');
        Cat.CatCollection = Cat.db.collection('Cats'); // Name of collection in mongo
    }
    return Cat;
}

module.exports = Cat;

Cat.Name = null;
Cat.HasFur = false;

Cat.Read = function (catId, callback) {
    var o_id = dataAccessAdapter.BsonIdFromString(catId);
    Cat.CatCollection.findOne({ '_id': o_id }, function (err, document) {
        if (!document) {
            var msg = "This cat is not in the database";
            console.warn(msg);
            callback(null, msg);
        }
        else {
            callback(document);
        }
    });
}

I hope this is at least a little helpful in seeing a different approach. I don't claim to be an expert and am open to some SO feedback on this, but this solution has worked well for me so far.