Mongoose not returning records in .find() when used with multiple connections

Question

I am facing a weird issue when working with multiple connections in mongoose 4.x.

After following the instructions in their documentation, I created two connections for the two databases I need to use (db1.js and db2.js).

When I try to fetch records in both databases, for some reason one of the find() calls returns no data. For instance, considering the database below, User1.find({}) should return 3 records (which is correct), and User2.find({}) should return 2 (which doesn't happen).

Any idea on what would be the issue is much appreciated!

Database dump to reproduce

use db1;

db.createUser({
    user: "admin",
    pwd: "admin",
    roles: [
        { role: "dbAdmin", db: "db1" },
        { role: "dbAdmin", db: "db2" },
    ]
});

db.user1.insert({ "name": "Isa1" });
db.user1.insert({ "name": "Joe1" });
db.user1.insert({ "name": "Doe1" });

use db2;

db.createUser({
    user: "admin",
    pwd: "admin",
    roles: [
        { role: "dbAdmin", db: "db1" },
        { role: "dbAdmin", db: "db2" },
    ]
});

db.user2.insert({ "name": "Isa2" });
db.user2.insert({ "name": "Doe2" });

db1.js

const Mongoose = require("mongoose");
const RSVP = require("rsvp");

Mongoose.Promise = RSVP.Promise;
let options = {
    useMongoClient: true,
    autoReconnect: true,
    keepAlive: 3000000,
    connectTimeoutMS: 300000
};

let schema = new Mongoose.Schema({ name: String });

const conn1 = Mongoose.connect('mongodb://admin:admin@localhost/db1', options);
module.exports = conn1.model('User1', schema);

db2.js

const Mongoose = require("mongoose");
const RSVP = require("rsvp");

Mongoose.Promise = RSVP.Promise;
let options = {
    useMongoClient: true,
    autoReconnect: true,
    keepAlive: 3000000,
    connectTimeoutMS: 300000
};
const conn2 = Mongoose.connect('mongodb://admin:admin@localhost/db2', options);

let schema = new Mongoose.Schema({ name: String });
module.exports = conn2.model('User2', schema);

index.js

const Mongoose = require("mongoose");
const RSVP = require("rsvp");

const User1 = require("./db1");
const User2 = require("./db2");

User1.find({})
    .then(res => {
        console.log(res.length); //print 3
        return User2.find({});
    })
    .then(res => {
        console.log(res.length); //print 0 (should be 2) <----- ERROR
        return User1.find({});
    })
    .then(res => {
        console.log(res.length); //print 3
        return User2.find({});
    })
    .then(res => {
        console.log(res.length); //print 2
    })
    .catch(err => {
        console.log(err);
    });

Answer 1

I believe you'll need to utilize Mongoose.createConnection() when making multiple connections instead of Mongoose.connect() as stated in the docs.