Mongoose multiple connections - node.js

Question

Currently I have this code for my connection mongoose.js:
var mongoose = require('mongoose');
var uriUtil = require('mongodb-uri');
var mongodbUri = 'mongodb://localhost/db_name';
var mongooseUri = uriUtil.formatMongoose(mongodbUri);
mongoose.connect(mongooseUri);
module.exports = mongoose;
File that requires the connection is test.js:
var mongoose = require('../model/mongoose');
var schema = mongoose.Schema({...});
How can I update mongoose.js to use multiple connections with mongoose.createConnection(...) function?
I start with changes only for one connection when I do changes like that:
var mongoose = require('mongoose');
mongoose.createConnection('mongodb://localhost/db_name');
mongoose.open('localhost');
module.exports = mongoose;
I get "undefined is not a function".
If I use this code:
var mongoose = require('mongoose');
db = mongoose.createConnection('mongodb://localhost/db_name');
db.open('localhost');
module.exports = mongoose;
I get "Error: Trying to open unclosed connection"
Any advice?

Answer 1

Mongoose handling connections via connections pool
http://mongoosejs.com/docs/connections.html
You can use server: {poolSize: 5} option for increase/decrease pool (number of parallel connections)
If you need connections to different databases look here
Mongoose and multiple database in single node.js project
Example of multiple connections:
var mongoose = require('mongoose')
var conn = mongoose.createConnection('mongodb://localhost/db1');
var conn2 = mongoose.createConnection('mongodb://localhost/db2');
var Schema = new mongoose.Schema({})
var model1 = conn.model('User', Schema);
var model2 = conn2.model('Item', Schema);
model1.find({}, function() {
console.log("this will print out last");
});
model2.find({}, function() {
console.log("this will print out first");
});

Answer 2

OK. With your example I found a solution that fit my needs.
mongoose.js
var mongoose = require('mongoose');
mongoose.main_conn = mongoose.createConnection('mongodb://localhost/main');
mongoose.admin_conn = mongoose.createConnection('mongodb://localhost/admin');
module.exports = mongoose;
content.js
var mongoose = require('../model/mongoose');
var schema = mongoose.Schema({...});
/// functions here
schema.statics.func_a(){...};
schema.statics.func_b(){...};
// And finaly updated only one line
//exports.Content = mongoose.model('Content', schema);
exports.Content = mongoose.main_conn.model('Content', schema);
The only thing, is it OK to add connection objects to mongoose object or may be there is more elegant solution.

Answer 3

config.js
module.exports = {
default: 'main',
main: 'mongodb://localhost/main',
admin: 'mongodb://localhost/admin',
};
connection.js
const mongoose = require('mongoose');
const config = require('./config');
mongoose.Promise = global.Promise;
function createConnection(name) {
return mongoose.createConnection(config[name]);
}
module.exports = createConnection(config[config.default]);
module.exports.on = createConnection;
model.js (custom class)
const connection = require('./connection');
class Model {
constructor(name, data) {
this.data = data;
return this.connection().model(name, data.schema);
}
connection() {
if (this.data.connection) {
return connection.on(this.data.connection);
}
return connection;
}
}
module.exports = Model;
user.js
const Schema = require('mongoose').Schema;
const conn = require('./connection');
const Model = require('./model');
const userSchema = new Schema({
name: String,
email: String,
password: String
});
// USING MONGOOSE MODEL
// default connection
const UserM1 = conn.model('User', userSchema);
// admin connection
const UserM2 = conn.on('admin').model('User', userSchema);
// USING CUSTOM MODEL
// default connection
const UserC1 = new Model('User', {
schema: userSchema
});
// admin connection
const UserC2 = new Model('User', {
schema: userSchema,
connection: 'admin'
});