How write at access log only part of $request?

[Maxim Dounin]

Hello!

On Mon, Mar 02, 2015 at 05:32:34AM -0500, ertyi wrote:

> Hi All,
> 
> I have next question:
> is it possible at nginx access log file decrease stored $request to smaller
> size?
> 
> We have very big traffic, and $request part is significant for us only at
> some start substring of $request value.
> 
> Is it possible write at log for example some kind of SubString( $request, 0,
> someLengthFromStart ) instead of full $request length ?

For example, you can do something like this using map:

   map $request $request_truncated {
       "~(?<tmp>.{0,100})"  $tmp;
   }

See log_format directive description for details on how to 
configure custom access logging formats.

http://nginx.org/r/map
http://nginx.org/r/log_format

-- 
Maxim Dounin
http://nginx.org/