Event-driven publish-subscribe technology changes developer's thinking
The event-driven, publish-subscribe model offers a new way of conceptualizing development, says Doug Moore, president of Accius Systems, a software consultant specializing in data-driven Internet applications.
'You get to a new way of thinking about applications,' Moore says of these projects. 'Dealing with events rather than saying, 'I'm going to build a query, go to the database, get the data and refresh the page.' It's a different approach.'
'They needed the persistence data for up to a month or two, and the KnowNow system has built-in persistence,' Moore says. 'It does event routing, but it also persists the event for as long as you tell it to because it has a built-in database to do that.'
Not having to link to a third-party database was a major time saver in the project. 'Instead of leveraging SQL Server, Oracle or some other database system to persist the trades,' he says, 'we just leveraged event router and set the expiration time on the events to about a month. That sped up development tremendously. We didn't have to develop a schema, an engine, the code to request it and the response and all that.'
The subscribe-and-publish approach also takes pressure off servers and provides faster updates without having to rebuild the entire Web page.
'One advantage to this push technology is there's no page refresh,' Moore says. 'So there's no reload of the page and graphics. You get anywhere between half-a-second and an eighth-of-a-second response time. Only the changes get pushed to the browser. The data is just pushed into the display. There's no user interaction, no polling by the browser client. It really reduces the load on the servers.'
Moore recalls that before he found the KnowNow technology, he built a trading system that relied on polling to update prices.
'With that system, we had to poll for all the prices in the market every five seconds to see if any changes had been made,' he says. 'As you can imagine, that creates quite a bit of load on the server as it scales up.'
KnowNow is announcing the latest version of its product,
KnowNow 3 Enterprise Edition, this week. Further information is available at http://www.knownow.com.
More information on Accius is available at http://www.accius.com.
Rich Seeley is Web Editor for Campus Technology.