I want to make an AJAX call to my Java webapp. The Java webapp will in turn make an asynchronous return call elsewhere. The result of that call will then be returned as the result of AJAX request.
The crux of my question is what would I do with the HttpRequest whilst I'm waiting for the second call to return?
Do I just block and wait for the call within the AJAX handler method or do I store the request somewhere and wait for a callback? How would I handle errors / timeouts?
For those who care further information as to how I arrived at this situation follows:
This is part of an XMPP based instant messaging system. There is one global support user which is displayed as an icon on every page in our webapp. I also want to display the presence of this user, so, I could just use the IM system to request this users presence on every single page load for every user and eventually DDOS myself. Instead I want to have a single user query the presence from the webapp periodically and cache the result.
The AJAX call is therefore to the server which will then either return the cached presence or query the XMPP server asynchronously.