memcache and nginx

[Sean Allen]

>>
>
> It seems you have small number of request/s. Could you enable debug  
> logging
> for several minutes until the bug will appear ?

have a small number of requests related to this problem, have a large  
number overall.

i'm not familiar with debug logging, how do i enable that?
can i enable only on the error log ( as its small but the access logs  
are about 250 megs
a day ).