[web-devel] Happstack events and timeouts

I've a timeline that is automatically updated when a user I follow post something new. I've already done the client-side code and some of the server-side as well. But I have a couple of issues that I cant figure out how to with happstack: How do I set a timeout for the request? I don't want to have more than one request for a same user. How can I stop all other request when I get a new one for a given user ?