Sounds like you're interested in stale-while-revalidate [1].  It does not appear to be supported in ATS, but is implemented in Squid [2] and works quite well.

[1] http://www.mnot.net/blog/2007/12/12/stale
[2] http://www.squid-cache.org/Doc/config/refresh_pattern/

On Sep 24, 2011, at 11:55 AM, Mav Peri wrote:

Hi Guys,
 
Is it possible to get ATS on stale hit to serve from cache and refresh the cache in the background?

The use case is when we are experiencing issues with the origin server I would like to serve stale content (compared to nothing) and then get ats to refresh it in the background instead of holding traffic up.
 
Thanks

Mav