Question

I just got asked to reduce the traffic made by my GWT app. There is one method that checks for status.

This method is an asynchronous call wrapped in a Timer. I know web apps are stateless and all that, but I do wonder if there is some other way to do this, or if everyone has a Timer wrapped around a call when they need this kind of behaviour.

Answer 1

You can check out gwteventservice. It claims to have a way to push server events and notify the client.

I have a feeling they might be implemented as long running (hanging) client to server RPC calls which time out after an interval (say 20sec), and then are re-made. The server returns the callback if an event happens in the meanwhile.

I haven’t used it personally but know of people using it to push events to the client. Have a look at the docs . If my assumption is correct, the idea is to send an RPC call to the server which does not return (hangs). If an event happens on the server, the server responds and that RPC call returns with the event. If there is no event, the call will time out in 20 seconds. Then a new call is made to the server which hangs in the same way until there is an event.

What this achieves is that it reduces the number of calls to the server to either one for each event (if there is one), or a call once every 20 seconds (if there isn’t one). It looks like the 20 sec interval can be configured.

I imagine that if there is no event the amount of data sent back will be minimal – it might be possible to cancel the callback entirely, or have it fail without data transfer, but I don’t really know.

Here is another resource on ServerPush – which is likely what’s implemented by gwteventservice.