If my upstream goes away I get an error

upstream prematurely closed connection while reading response header from upstream

or

recv() failed (104: Connection reset by peer) while reading response header from upstream

unfortunately, this still gives me a 200 code and this return is entered incomplete into my memcache. Is there some way to get the size of the current request from proxy_pass so I can compare it to the Content_Length and discard it if it's mismatched?

Ideally the system wouldn't tag incomplete responses as 200 OK, so they wouldn't end up as short returns in my memcache for their cache duration.