Question

I would like a webpage that constantly updates a graph with new data as it arrives. Regularly, all the data you have is passed to the page at the beginning of the request. However, I need the page to be able to update itself with fresh information every few seconds to redraw the graph.

Background

The webpage will be similar to this http://www.panic.com/blog/2010/03/the-panic-status-board/. The data coming in will temperature values to be graphed measured by an Arduino and saved to the Django database (this part is already complete).

Update

It sounds as though the solution is to use the jQuery.ajax() function ( http://api.jquery.com/jQuery.ajax/) with a function as the .complete callback that will schedule another request several seconds later to a URL that will return the data in JSON format.

How can that method be scheduled? With the .delay() function?

Answer 1

So the page must perform periodic jQuery.ajax calls with a url parameter set to a server’s URL where the latest up-to-data information (possibly just as an incremental delta from the last instant for which the client has info — the client can send that instant as a query parameter in the Ajax call) is served, ideally in JSON form. The callback at the completion of the async request can schedule the next ajax calls for a few seconds in the future, and then repaint the graph.

The fact that, server-side, you’re using Django, doesn’t seem all that crucial — the server just needs to format a bunch of data as JSON and send it back, after all.