AJAX maybe improving the experience for users of web based application but that improvement doesn’t come for free. Using AJAX means that users now place a much higher demand for connections on the supporting web server and that translates into a tougher job for those building web servers.

Thus an AJAX application needs a connection to the server almost continuously and it is no longer the case that the number of simultaneous users can greatly exceed the number of simultaneous TCP/IP connections

In his blog Greg Wilkins explains how Jetty is changing to adapt to the stress and strain that an AJAX application can place on it.

So has everybody else. WAS 6.0 was redesigned to use the a similar architecture using NIO as I'm sure WebLogic 8.x/9.x are also.

It's usually a little slower than blocking for small numbers of connections but scales better with larger numbers of connections.

NIO also introduces latency which the AIO stuff should solve.

I'm glad somebody is bringing up this topic - it's too easy to get blinded by (the very good things) Ajax can do for you, add it to new/existing applications assuming everything else stays the same, the get surprised when your live app server doesn't perform the way it used to...

Will become less of a problem as 'Ajax Aware' versions of products get delivered (ones that have learnt to live in the strange new Ajax world).

Paul Browne