Stalled cache updating and upstream timeouts?

[TECK]

Hi,

I get 2 errors into nginx logs, constantly:
* stalled cache updating, error:0 while closing request AND
* upstream timed out (110: Connection timed out) while reading response
header from upstream

I use fastcgi as upstream, with next_upstream set to error only and
send_timeout at 60s.
Could you be kind and help me understand when these 2 errors occur?

Thank you.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,202697,202697#msg-202697