error_log levels

[Maxim Dounin]

Hello!

On Thu, Apr 08, 2010 at 10:18:03PM -0400, flash wrote:

> I'm getting a lot of entries in my error_log from memcache 
> throwing a 404 and sending the request to the back end.
> 
> 2010/04/08 21:07:50  29914#0: *3207 pcre_exec() failed: -8 on "example.com" using "" while sending to client, client: 66.249.71.23, server: _, request: "GET example.com HTTP/1.1", upstream: "memcached://127.0.0.1:11211", host: "example.com"
> 
> I'm assuming this is correct behavior since it cannot find the 
> requested url in memory;

No, it isn't.  It's unexpected error returned by pcre_exec() 
function, and according to pcreapi manpage it means the following:

         PCRE_ERROR_MATCHLIMIT     (-8)

       The  backtracking  limit,  as  specified  by the match_limit field in a
       pcre_extra structure (or defaulted) was reached.  See  the  description
       above.

You may want to investigate further why it happens.  Default limit 
according to pcre docs is 10 million, so either you have 
completely wrong regex, or something wrong with your pcre library, 
or it's nginx bug.

> however, I have not been able to find 
> any error level descriptions in the docs - could you either fill 
> me in on what level I need to include on my conf file or point 
> me in the direction of where this info can be found?

Logging levels from harmless to most critical are:

debug, info, notice, warn, error, crit, alert, emerg 

It is not recommended to ignore any messages at crit level and above.

First part of this list can be found here:

http://wiki.nginx.org/NginxCoreModule#error_log

Maxim Dounin