nginx with proxy_cache_use_stale not returning from cache when connection refused

[new299]

After adding the following:

proxy_cache_valid 200 302 301 10m;

It appears to be working. It's unclear to me why:

proxy_cache_valid any 10m;

Wasn't working, for me.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,255408,255441#msg-255441