Is this a nginx error?

found it in my error log, not sure what exactly it means

2013/04/11 11:15:11 [alert] 906204#0: *7071 stalled cache updating, error:0 while closing request, client:, server:  

It looks related to Nginx's fastcgi_cahce.

Which Nginx version you are using? Has this error appeared again and again?

Also check:,206445,206445#msg-206445

I've got about 10 of these errors spread over 3 days...

latest nginx available from Debian Squeeze, I think its 1.2.8.

Is there any other error above or below that line? Specially about timeout. I guess PHP-FPM backend is running out of time before fastcgi_cache can get a reply from it.

You can try increasing PHP timeout:

Also you can try enabling mysql slowlog to check if its some bad MySQL query which is taking more time than it should:

Thanks, will try your suggestions but there was nothing close to this error in the logs.