Feature request to "access_log" directive

Fabiano Furtado Pessoa Coelho fusca14 at gmail.com
Mon Apr 11 13:02:40 UTC 2022

Hi, Francis.

Thanks for the reply.

I'm gonna try to implement this feature, but I think it will be hard for me.
For now, I'll change the NGINX configuration files to use access_log
according to my needs.

I've one more question about an access_log weird behavior, when it's
configured with a $1 regex return variable.

For instance:

location ~ ^/(system1|system2) {
  access_log /var/log/nginx/$1_access.log;
  proxy_pass ...;

The only way NGINX can write to system1_access.log and
system2_access.log files is when they exist in the specified
directory. Otherwise, the log isn't computed.
I think creating them at the moment of system start is impossible
because the $1 variable isn't initialized yet, but why can't NGINX
automatically create them at the moment they are used?

Thanks again.

On Sat, Apr 9, 2022 at 3:55 AM Francis Daly wrote:
> On Mon, Apr 04, 2022 at 04:28:54PM -0300, Fabiano Furtado Pessoa Coelho wrote:
> Hi there,
> > Sorry to bother you with this feature request. I believe you software
> > engineers already thought about it and there are a million reasons to
> > not implement it.
> I suspect that what you are asking for probably breaks the current nginx
> processing and logging model, and would probably require significant
> code changes.
> You are welcome to submit a patch for it -- after either having written
> one, or incentivised someone to write one for you -- and it will
> presumably be considered for inclusion in the stock nginx code.
> (And if it isn't included in stock, you can always use it in your
> version.)
> But you may find there is a simpler way to achieve your desired end
> result.
> > Well, I'm exactly in this situation described here
> > https://serverfault.com/questions/498799/how-to-log-nginx-requests-made-to-a-specific-location-in-a-different-file
> > I want to use "try_files" and log the access within the location with
> > "try_files" directive...
> As you probably know, that will do what you say you want if the file
> $document_root$uri is present, and not otherwise.
> >     location /my_system {
> >       access_log /var/log/nginx/my_system_access.log;
> >       try_files $uri @named_loc;
> >     }
> >     location @named_loc {
> >         access_log off;
> >         proxy_pass http://...;
> >     }
> >
> > ... and I can't! "Requests are logged in the context of a location
> > where processing ends. It may be different from the original location,
> > if an internal redirect happens during request processing."
> > I can make it work using the "#include" directive and removing the
> > named location, but using "try_files" is more clean and sophisticated.
> As you say, you can change the config to match what nginx does to what
> you want.
> Alternatively, you could possibly post-process the log files to end up
> with what you want -- either read the old log files and split the contents
> according to what you want; or maybe have nginx write to a stream, and
> have your own processor reading that stream and writing each log entry
> to your desired place for it.
> > Is there a way to include the "now" directive to "access_log"?
> > Something like: "access_log /var/log/nginx/my_system_access.log now;"
> I suspect: only if you provide the code to do so.
> Cheers,
>         f
> --
> Francis Daly        francis at daoine.org
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