I have recently been exploring options for enhancing the functionality of an existing website by integrating some streaming data feeds.
In the interests of making this functionality available on a wide range of devices (read iPads and iPhones as well as PCs) I would like this to be achieved without Flash or any other proprietary plug-in technology.
Almost every article and blog post that I have read on the subject emphasises that client side polling is not appropriate, and that instead a continuous connection must be kept open between the web browser and the http server.
Historically the way that most http servers have served their content involved dedicating a thread or process to serve each incoming request from start to finish. This does not scale well when incoming requests need to hold a connection over a prolonged period of time, so alternative approaches such as Comet have been implemented.
The Tomcat implementation of Comet is not supported when Tomcat is hosted behind apache httpd over AJP.
I was considering keeping the data serving system physically separate from the serving of HTML content anyway, so this restriction is just giving a friendly push to try using a separate sub-domain.