Page 18 from nginx for Windows - documentation 1.3;

map $request_uri $loggablevhts {
default 1;
/ngxvtstatus 0; # zero=do not log
/vtsvalues.js 0; # zero=do not log
/vtsvalues-eop.js 0; # zero=do not log
/ngxvtstatus/format/json 0; # zero=do not log
}
map $remote_addr $lcladdrvhts {
default 1;
~^(127.0.0.*)$ 0; # zero=do not log
}

# don't log vhts entries when request is local or from management interface
map $loggablevhts$lcladdrvhts $loggable {
default 0;
~1 1;
}

access_log /path/to/access.log combined if=$loggable;

“A request will not be logged if the (IF) condition evaluates to "0" or an empty string”

Two simple ‘maps’ which are then combined tested in the third ‘map’ which is used in the
IF evaluation of the log directive.

Tweak, change, add your own stuff with $request

See also nginx-simple-WAF.conf in the nginx for Windows release archives.

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nginx for Windows http://nginx-win.ecsds.eu/