Configuration to avoid dog-pile when cache is empty

[Evgeniy Dolzhenko]

I've been having that problem for awhile and haven't yet saw the clean
and simple solution to it. Also I'm really new to Varnish so please excuse
my ignorance if there is any.

The scenario is as follows:

1. There is the page on Application Server which takes forever to load
(/takes_forever_to_load.html) and which is not user-specific and
can be always cached for a known period of time.

2. Varnish cache is empty

3. Multiple users request /takes_forever_to_load.html page.
If my understanding is correct with the default configuration all requests
will hit Application Server.

Now what I would like ideally to achieve with Varnish is that only
first request hits Application Server and every other request is
"joined" to that request, i.e. will be served as soon as
Application Server responds to the first request and with
the content of the response. I.e. Varnish will have to hold
the connections open and then use response cached by first request

Is that possible? Or is it just a too crazy thing to do?

TIA,
Evgeniy