Comet scrubs off old technologies to let imagination and potential shine to the face of the world. Comet indeed consists of a new technology that gives “real time” applications a new meaning. Stop! Just start thinking of everything that can come true if you don’t need content piggybacking anymore. Imagine receiving what is desired with no need to request. This is what Comet brings into the sky: a new era that will enlighten the dark ages of the Ajax Knight .

Up to Comet, web designers have had to cleverly invent ways on the browser side to palliate the slowly delivered responses of a web server. Now Comet shifts all the burden from the client side to the server side. Why? Because even if Comet promises real time content updates, the burden of delivering those updates on time falls on the web server.

The currently known “click-request-wait-push-response” real time protocol failed to deliver on time responses to the client so many times that we are looking for a new expression to describe the new simple “push-receive protocol”.

However marvel, just like trouble, never comes alone . Comet also comes with a tail: performance challenges!

An application might claim to use Comet, but performance-wise are server pushes really delivered on time?

Let’s use the “infamous” chat example. With 10,000 connected clients, will the content really be delivered in real time? Of course, if you have a dedicated web server per application, this problem might never arise… but we all know this is not the case. The first 700 users might get a decent responses time, but what about the remaining outliers? They might get the most decent responses, but too late. Delayed response could be tolerable for a chat, but as soon as we envision more demanding applications, like stock quote or online games, Comet may fail to deliver what the web designer is expecting: real time pushes from the server.

Most of the Comet actual literature (Comet Daily included ) focus on the client side of Comet, but new challenges are now on the server side: how can the push operations be efficient enough to deliver what Comet is meant for? Web designers must start thinking right from the beginning about how their applications will execute the push operations without too much contention. Web servers that claim to support Comet must offer the tools and APIs to let web designers efficiently deliver what Comet is all about: real time pushes.

With Comet, challenges remain but their nature changes. So for now start thinking of all the new applications while waiting for my upcoming contributions to Comet Daily that will try to orient you to a new frame of thoughts towards efficient design of Comet applications.