memcache and nginx

[Igor Sysoev]

On Thu, May 15, 2008 at 01:40:34PM -0400, Sean Allen wrote:

> 
> On May 14, 2008, at 3:26 PM, Igor Sysoev wrote:
> 
> >On Wed, May 14, 2008 at 09:41:20AM -0400, Sean Allen wrote:
> >
> >>>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 ).
> >
> >The log will be in error_log and it will be large. VERY LARGE.
> >So it should be set per some addresses only or if the load is low (as
> >in your case) for short time.
> >
> >You need to build nginx using
> >
> >./configure --with-debug ...
> >
> >Then you should enable debug log level in nginx.conf:
> >
> >error_log  /path/to/log  debug;
> >
> >Otherwise you may set debug per some addresses only:
> >
> >events {
> >    debug_connection  192.168.1.0/24;
> >    debug_connection  192.168.10.32;
> >    ...
> >}
> >
> >Disabled debug has very low CPU overhead.
> 
> damn. the advertiser running the banners that caused the problem  
> finally fixed an outstanding issue on their end
> and it fixed the problem on our end. how the two were related is a  
> little beyond me but apparently they were
> so this is going to end up lurking as i cant create the situation  
> anymore.

The "memcached sent invalid trailer" message means that after reading
specified number of bytes, nginx espects to see memcached trailer
"\r\nEND\r\n". For some reason, nginx did not see the trailer, it may be 
nginx bug, or software that put the item to memcached (I do not know
if it's possible to put in memcached item with wrong length).


-- 
Igor Sysoev
http://sysoev.ru/en/