The poll component delivers PollEvents to the server at fixed intervals. This can be used either for steady updates, or to deliver a heartbeat to keep a user logged in, or to warn a user about to be logged out (for some examples).One classic use of Poll component would be to keep User Session active as long as browser window is open. In this case, you will set Poll Interval (interval) and dummy pollListener. Poll Listener can be empty method, it does not have to do anything. Poll Interval should be less than HTTP Session Timeout. HTTP Session Timeout is setup in web.xml.
Such use of Poll component fails to keep User Session active, after upgrading from 18.104.22.168. This is due to new attribute timeout for af:poll, value for which defaults to 10 minutes (This property is added with 22.214.171.124). So if user does not perform any activity on Keyboard or Mouse for 10 minutes, Poll component will stop delivering any Poll Events. If you are using af:poll to keep User Session (by sending regular heartbeat) active, add timeout property to af:poll with very high value to avoid stopping Poll Events.