Question

I need to create a web page (using asp.net MVC2 and possibly WCF) showing exceptions that occur when csv type files are being reconciled with another data source. Any records (exceptions) that do not match the data source will be sent to a table in Oracle. To manually update the exceptions there will be x number of users using the web page to choose the correct value for each record via an expandable grid of some sort. So when records are added to the Oracle table the new records need to get displayed at the top of the web page somehow. Is there some kind of ‘push’ scenario/algorithm/design pattern to do this?
I’ve looked at the Observer pattern in which observers register with a subject and the subject informs the observers whenever there’s an update. I’m not sure how this would work in my scenario – would the web page somehow register each user that views the page? If so how would the subject (Oracle table or some middle tier object) send the new records to the web page?
How do real time stock trading systems typically work? In this scenario I would imagine that trading screens are updated instantly when a trade/sale etc goes through, also I’m sure these systems get updated or notified as stock prices change. I’d be curious to know some of the technologies behind these systems.

Answer 1

ODP.NET provider supports push notifications. You could implement it on the server side but the problem will be push notification to the client because of the nature of the HTTP protocol. There you might need constant AJAX polling, or if you really need push, you might take a look at Comet and WebSocket in HTML 5.