Telling Mongoose which database to use - in a node.js Express application

Question

I have an Node.js Express web app running.

I have two database connections, the system_db is created with "Mongoose.connect", the user_db is created with "Mongoose.createConnection". This seems to make them separate and have different connection pools. Although this could be the crux of the problem.

I have code dealing with with a Mongoose model

in the model file I have:

var authSchema = mongoose.Schema({
    teamName: String,
    league: String,
    players: []

});


var Team = module.exports = mongoose.model('teams',authSchema);

in my main file I have two connections:

one is a system database

connection_uri = "mongodb://localhost:27017/";
system_db = mongoose.connect(connection_uri.concat("sparks"), {
    native_parser : true
}, function(err){
    if (err) throw err;
});

the other is a user database

 user_db = mongoose.createConnection(connection_uri.concat(user_id));

then I have this piece of code in my main file which finds a Team object based off id:

app.param('team_id', function(req, res, next, team_id) {

    Team.findOne(team_id, function(err, team) {

        if (err) {
            return next(err);
        }
        if (!team) {
            throw new Error("no team matched");
        }
        req.team = team;
        next();
    });
});

the problem is that the app.param function above is not finding any matches for teams, even though they exist in a collection in the user_db database. this means, that I am thinking my model is pointing to the wrong database somehow? Somehow it must be pointing to this system_db instead of the user_db. Could this be right? How would I fix that?

BatScream · Accepted Answer · 2014-11-20 09:23:54Z

7

The below method opens a connection to the system_db and is binded to the mongoose object,.i.e the current mongoose object is modified. The return type is not a Connection.

system_db = mongoose.connect(connection_uri.concat("sparks")...

Now when you again do:

user_db = mongoose.createConnection(connection_uri.concat(user_id));

This creates a new Connection to the user database and returns a connection, but does not modify the mongoose instance. The mongoose instance is still binded to the system_db database connection.

Since Team model is obtained from the same mongoose instance,

var Team = mongoose.model('teams',authSchema);

whatever operation is done on this model effectively occurs in the connection that the mongoose instance holds, and that is of the system_db database.

So you need to obtain the model from the user_db connection :

var user_db = mongoose.createConnection(..);
// retrieve the Team model
var Team= user_db.model('teams'); // not from mongoose instance.

use createConnection wherever you want to obtain a connection.

edited Nov 20, 2014 at 9:23

answered Nov 19, 2014 at 23:46

BatScream

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6 Comments

Alexander Mills Over a year ago

hmmm, thanks, this is discouraging. I want to be able to load that file (with Team defined in it) before the user_db variable is defined...

Alexander Mills Over a year ago

furthermore, if the user logs out, and logs in as a different user, the user_db variable would be redefined.

Alexander Mills Over a year ago

in an ideal universe, I could pass the save method the database variable, so it would be var team = new Team({}); team.save(user_db); you know what I am sayin'?

BatScream Over a year ago

Why are you maintaining a different database for each user? You should make your database queries specific to the user rather than maintaining a database for each user. That way the Model Team will be common to all the users.

Alexander Mills Over a year ago

turns out having each user in a different DB is a bad idea

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