Inform ember-data about server changes

Question

I am currently planning a complex application using ruby on rails and ember.js. What I have seen about ember-data so far is that it caches records automatically; post.comments will first result in a Ajax-call to fetch all comments for the given post, but if the user visits the same route the next time, it will just fetch the records from the store-cache.

The problem is: What if another user added a comment to this post? How to tell ember it has to reload its cache because something changed?

I already thought about a solution using websockets to tell clients which stuff to reload - but I don't think this is best-practice. And in addition, I can't imagine this isn't a common problem, so I am wondering what other developers are doing to solve this issue.

Answer 1

I tried to implement model updating in (experimental) chat application. I have used SSE: ActionController::Live on server side (Ruby on Rails) and EventSource on client side.

Simplified code:

App.MessagesRoute = Ember.Route.extend({
  activate: function() {
    if (! this.eventSource) {
      this.eventSource = new EventSource('/messages/events');

      var self = this;
      this.eventSource.addEventListener('message', function(e) {
        var data = $.parseJSON(e.data);
        if (data.id != self.controllerFor('messages').get('savedId')) {
          self.store.createRecord('message', data);
        }
      });
    }
  }
});

App.MessagesController = Ember.ArrayController.extend({
  actions: {
    create: function() {
      var data = this.getProperties('body');
      var message = this.store.createRecord('message', data);
      var self = this;
      message.save().then(function (response) {
        self.set('savedId', response.id);
      });
    }
  }
});

The logic is simple: I'm getting each new record from EventSource. Then, if record was created by another client, the application detects it and new record being added to store using ember-data's createRecord. Suppose this logic may have some caveats, but at least it serves well as 'proof of concept'. Chat is working.

Full sources available here: https://github.com/denispeplin/ember-chat/

I have something to say about reloading: you probably don't want to perform full reloading, it's resource-consuming operation. Still, your client side needs some way to know about new records. So, getting new records one-by-one via SSE is probably the best option.