connect-mongo: why can't I write to the 'sessions' collection?

Question

I am using connect-mongo with express-session, and the session data is being written to Mongo as expected.

However, I would like to reuse the sessions collection that connect-mongo uses to write my own fields in that collection on top.

I have defined my own sessions models in sessions.js such as:

const mongoose = require('mongoose');

const SessionSchema = new mongoose.Schema({
    _id: {},
    session: {},
    expires: {},
    myNewVariable: {}
});

const Sessions = mongoose.model('sessions', SessionSchema);

module.exports = {Sessions};

Then, in my server file I have:

const session = require('express-session');
const {mongoose} = require('./db/mongoose.js');
const {Sessions} = require('./models/sessions.js');
const MongoStore = require('connect-mongo')(session);

app.use(session({
  secret: SECRET,
  resave: true,
  saveUninitialized: true,
  store: new MongoStore({ mongooseConnection: mongoose.connection })
}));

app.post('/myRoute', function(req, res, next) {
      Sessions.findOneAndUpdate(
        {_id: req.session.id},
        {$set:{myNewVariable: myNewValue}},
        {new: true}).then((session) => {

            console.log('session: ' + JSON.stringify(session)); // prints OK!

            // Do something with the session
      }).catch((e) => console.log('Something went wrong: %s', e));
});

What really surprises me is that the print statement above actually logs the updated session object. However, when I inspect the database later the documents are not updated.

I have also tried creating a completely different SessionsAlternative collection. In that case, the collection is updated correctly. That would be a solution, but it wouldn't be optimal as conceptually what I'm trying to write should belong in a single sessions collection.

Is this possible at all, and if so, what am I doing wrong?

Answer 1

Why not directly save to session?

req.session.myNewVariable = "abc";