Mongoose switching multiple connections

Question

I am using Node.Js 8.6 along with Mongoose 4.11 and have multiple database connections. Db connections are established via mongoose.createConnection. I found out that mongoose object has connections property (array), where I can see established connections. My question is, what is the proper way, to switch between connections when creating db models in separate modules.

index.js

async function db1() {
    await mongoose.createConnection(
        process.env.MONGODB_URI_1,
        { useMongoClient: true }
    );
}

async function db2() {
    await mongoose.createConnection(
        process.env.MONGODB_URI_2,
        { useMongoClient: true }
    );
}

model.js

//connect to db1

const Test1 = mongoose.model('Test1', new mongoose.Schema({ name: String }));

//connect to db2

const Test2 = mongoose.model('Test2', new mongoose.Schema({ name: String }));

Answer 1

You can use the object return by createConnection in order to handle your multiple connections.

const db1Link = await mongoose.createConnection(
    process.env.MONGODB_URI_1,
    { useMongoClient: true }
);

// Connect to db1
db1Link.model('Test1', new mongoose.Schema({ name: String }));

const db2Link = await mongoose.createConnection(
    process.env.MONGODB_URI_2,
    { useMongoClient: true }
);

// Connect to db2
db2Link.model('Test2', new mongoose.Schema({ name: String }));

---

Here is what the documentation says about it

Multiple connections

So far we've seen how to connect to MongoDB using Mongoose's default connection. At times we may need multiple connections open to Mongo, each with different read/write settings, or maybe just to different databases for example. In these cases we can utilize mongoose.createConnection() which accepts all the arguments already discussed and returns a fresh connection for you.

var conn = mongoose.createConnection('mongodb://[username:password@]host1[:port1][,host2[:port2],...[,hostN[:portN]]][/[database][?options]]', options);

This connection object is then used to create and retrieve models. Models are always scoped to a single connection.

Answer 2

//config.json

   {
    "Tenants": {
            "5c061f432c9e9e499325b": {
                "dbConfig": "mongodb://admin:Password@IP/DBname",
                "dbName": "DBname",

            },
            "5c0432ebabb6c9e9e499325b": {
                "dbConfig": "mongodb://admin:Password@IP/DBname",
                "dbName": "DBname",

            },
            "5c061f43bb6c9e9e499325b": {
                "dbConfig": "mongodb://admin:Password@IP/DBname",
                "dbName": "DBname",

            }
        },

    }

//ModelFactory.js

var mongoose = require("mongoose");
var models = [];
var conns = [];
var path = __dirname + "\\models";
var config = require("config");


function factory(tenant) {
    let dbName = config.get("Tenants." + tenant + ".dbName");
    let dbConnection = config.ge`enter code here`t("Tenants." + tenant + ".dbConfig");
    if (conns[dbName]) {
    } else {
        conns[dbName] = mongoose.createConnection(dbConnection);
    }
    if (models[dbName]) {
    } else {
        var instanceModels = [];
        var schemas = ["users","products"];
        schemas.forEach(function (models) {
            instanceModels[models] = conns[dbName].model(models, require([path, models].join("\\")));
        });
        // DB name and tenant ID also pushing in the same object
        //instanceModels["tenantID"] = tenant; 
        //instanceModels["db"] = conns[dbName];
        models[dbName] = instanceModels;        
    }
    return models[dbName];
}
module.exports = factory;

//API End point

exports.users = function (req, res) {

var models = modelFactory(req.headers.tenantid);
models.User.find() //query