Q:

Is long polling possible in Google App Engine?

I need to make application that needs to poll server often, but GAE has limitations on requests, so making a lot of requests could be very costly. Is it possible to use long polling and make requests wait for the maxium 30 seconds for changes?

A:

Google AppEngine has a new feature Channel API, with that you have 
a possibility to build a good realtime application.
Another solution is to use a third part comet server like mochiweb 
or twisted with a iframe pattern.
Client1, waiting a event:
client1 --Iframe Pattern--> Erlang/Mochiweb(HttpLongPolling):

Client2, sending a message:
client2 --XhrIo--> AppEngine --UrlFetch--> Erlang/Mochiweb

To use mochiweb with comet pattern, Richard Jones has written a good 
topic (on google: Richard Jones A Million-user Comet Application).

