Mongodb notify on document updated

Question

Imagine if i had a mongodb with some documents and a nodejs server which emits json data from the mongodb to the client using socket.io, and some process has updated that mongodb document that is currently in the client view, i was wondering if there is a way so that the mongodb notifies the nodejs server when the object gets updated by anyone other than the client himself so that i could emit the updated document json through the open socket, is such thing possible?

i have tried to find some resources on google with no luck.

Answer 1

Say this is a document schema

'use strict';

import mongoose from 'mongoose';

var MessageSchema = new mongoose.Schema({
  toid: String,
  fromid: String,
  toname: String,
  fromname: String,
  content: String,
  date: { type: Date, default: Date.now }
});

export default mongoose.model('Message', MessageSchema);

And here is the backend code where where you change the contents of document

import {Router} from 'express';
var router = new Router();
router.post('/create/:id', function(req, res){
return Message.create(req.body)
    .then(respondWithResultAndEmitAnEvent(res, 201))
    .catch(handleError(res));
}); 

So this respondWithResultAndEmitAnEvent function look something like this, as the name suggest where even a user POST a data to server (say on the url xyz.com/api/create/:id ) the server will emit an event that can be captured by other clients.

function respondWithResultAndEmitAnEvent(res, statusCode) {
  statusCode = statusCode || 200;
  return function(entity) {
    if (entity) {
      socket.emit('message_added', entity);
      res.status(statusCode).json(entity);
    }
  };
}

On the client side you can listen to this event "message_added" and update it.

    socket.on('message_added', function ( data ) {
      console.log(data);
      //update the client with new data;
    });