nginx-1.2.6

[Maxim Dounin]

Hello!

On Tue, Dec 11, 2012 at 04:44:52PM +0000, Jonathan Matthews wrote:

> On 11 December 2012 15:01, Maxim Dounin <mdounin at mdounin.ru> wrote:
> > Changes with nginx 1.2.6                                         11 Dec 2012
> >
> >     *) Feature: the $request_time and $msec variables can now be used not
> >        only in the "log_format" directive.
> 
> This is great! Could you give some examples of other variables that
> these can now be considered similar to, with respect to when and where
> they're available for use?

There are some (semi-)variables which were only available in the 
log_format directive, see here for a full list:

http://nginx.org/r/log_format

These variables wasn't available as generic ones as they weren't 
expected to be usable during request processing.  For now this 
aproach is reconsidered, and the plan is to eventually make all such 
variables generic, even if they don't make much sense till request 
processing is complete.  This will allow, in particular, to use 
such variables in other modules similar to ngx_http_log_module, or 
to log some derivative variables using map{}.

Semantic of such variables didn't change when they are made 
available as generic variables as long as they are used in the 
"log_format" directive, i.e. evaluated during request logging.  If 
you'll try to use them at other phases of a request processing, in 
some cases previous definitions no longer apply or slightly 
changes.

E.g. $msec, previously defined as (quote from 
http://nginx.org/r/log_format):

    time in seconds with a milliseconds resolution at the time of 
    log write

now defined as (quote from 
http://nginx.org/en/docs/http/ngx_http_core_module.html#var_msec):

    current time in seconds with a milliseconds resolution

Where "current" means a time of the variable evaluation.  E.g. if 
you'll use it in proxy_set_header directive, it will be the time 
when request to an upstream was created.

The $request_time was defined as (quote from 
http://nginx.org/r/log_format):

    request processing time in seconds with a milliseconds 
    resolution; time elapsed between the first bytes were read from 
    the client and the log write after the last bytes were sent to the 
    client

It remains the same when used in log format, but more generic 
definition is now available (quote from 
http://nginx.org/en/docs/http/ngx_http_core_module.html#var_request_time):

    request processing time in seconds with a milliseconds 
    resolution (1.3.9, 1.2.6); time elapsed since the first bytes were 
    read from the client

Much like $msec, if you'll use it in proxy_set_header, it will be 
the time from a request start till nginx created a request to an 
upstream.  And if used in add_header, it will be the time from a 
request start till sending response headers to a client.

Hope this helps.

-- 
Maxim Dounin
http://nginx.com/support.html