Using variables in Nginx location rules

You can't. Nginx doesn't really support variables in config files, and its developers mock everyone who ask for this feature to be added:

"[Variables] are rather costly compared to plain static configuration. [A] macro expansion and "include" directives should be used [with] e.g. sed + make or any other common template mechanism." http://nginx.org/en/docs/faq/variables_in_config.html

You should either write or download a little tool that will allow you to generate config files from placeholder config files.

Update The code below still works, but I've wrapped it all up into a small PHP program/library called Configurator also on Packagist, which allows easy generation of nginx/php-fpm etc config files, from templates and various forms of config data.

e.g. my nginx source config file looks like this:

location  / {
try_files $uri /routing.php?$args;
fastcgi_pass   unix:%phpfpm.socket%/php-fpm-www.sock;
include       %mysite.root.directory%/conf/fastcgi.conf;
}

And then I have a config file with the variables defined:

phpfpm.socket=/var/run/php-fpm.socket
mysite.root.directory=/home/mysite

And then I generate the actual config file using that. It looks like you're a Python guy, so a PHP based example may not help you, but for anyone else who does use PHP:

<?php


require_once('path.php');


$filesToGenerate = array(
'conf/nginx.conf' => 'autogen/nginx.conf',
'conf/mysite.nginx.conf' => 'autogen/mysite.nginx.conf',
'conf/mysite.php-fpm.conf' => 'autogen/mysite.php-fpm.conf',
'conf/my.cnf' => 'autogen/my.cnf',
);


$environment = 'amazonec2';


if ($argc >= 2){
$environmentRequired = $argv[1];


$allowedVars = array(
'amazonec2',
'macports',
);


if (in_array($environmentRequired, $allowedVars) == true){
$environment = $environmentRequired;
}
}
else{
echo "Defaulting to [".$environment."] environment";
}


$config = getConfigForEnvironment($environment);


foreach($filesToGenerate as $inputFilename => $outputFilename){
generateConfigFile(PATH_TO_ROOT.$inputFilename, PATH_TO_ROOT.$outputFilename, $config);
}




function    getConfigForEnvironment($environment){
$config = parse_ini_file(PATH_TO_ROOT."conf/deployConfig.ini", TRUE);
$configWithMarkers = array();
foreach($config[$environment] as $key => $value){
$configWithMarkers['%'.$key.'%'] = $value;
}


return  $configWithMarkers;
}




function    generateConfigFile($inputFilename, $outputFilename, $config){


$lines = file($inputFilename);


if($lines === FALSE){
echo "Failed to read [".$inputFilename."] for reading.";
exit(-1);
}


$fileHandle = fopen($outputFilename, "w");


if($fileHandle === FALSE){
echo "Failed to read [".$outputFilename."] for writing.";
exit(-1);
}


$search = array_keys($config);
$replace = array_values($config);


foreach($lines as $line){
$line = str_replace($search, $replace, $line);
fwrite($fileHandle, $line);
}


fclose($fileHandle);
}


?>

And then deployConfig.ini looks something like:

[global]


;global variables go here.


[amazonec2]
nginx.log.directory = /var/log/nginx
nginx.root.directory = /usr/share/nginx
nginx.conf.directory = /etc/nginx
nginx.run.directory  = /var/run
nginx.user           = nginx


[macports]
nginx.log.directory = /opt/local/var/log/nginx
nginx.root.directory = /opt/local/share/nginx
nginx.conf.directory = /opt/local/etc/nginx
nginx.run.directory  = /opt/local/var/run
nginx.user           = _www

You could do the opposite of what you proposed.

location (/test)/ {
set $folder $1;
}


location (/test_/something {
set $folder $1;
}

A modified python version of @danack's PHP generate script. It generates all files & folders that live inside of build/ to the parent directory, replacing all \{\{placeholder}} matches. You need to cd into build/ before running the script.

File structure

build/
-- (files/folders you want to generate)
-- build.py


sites-available/...
sites-enabled/...
nginx.conf
...

build.py

import os, re


# Configurations
target = os.path.join('.', '..')
variables = {
'placeholder': 'your replacement here'
}




# Loop files
def loop(cb, subdir=''):
dir = os.path.join('.', subdir);


for name in os.listdir(dir):
file = os.path.join(dir, name)
newsubdir = os.path.join(subdir, name)


if name == 'build.py': continue
if os.path.isdir(file): loop(cb, newsubdir)
else: cb(subdir, name)




# Update file
def replacer(subdir, name):
dir  = os.path.join(target, subdir)
file = os.path.join(dir, name)
oldfile = os.path.join('.', subdir, name)


with open(oldfile, "r") as fin:
data = fin.read()


for key, replacement in variables.iteritems():
data = re.sub(r"\{\{\s*" + key + "\s*}}", replacement, data)


if not os.path.exists(dir):
os.makedirs(dir)


with open(file, "w") as fout:
fout.write(data)




# Start variable replacements.
loop(replacer)

This is many years late but since I found the solution I'll post it here. By using maps it is possible to do what was asked:

map $http_host $variable_name {
hostnames;


default       /ap/;
example.com   /api/;
*.example.org /whatever/;
}


server {
location $variable_name/test {
proxy_pass $auth_proxy;
}
}

If you need to share the same endpoint across multiple servers, you can also reduce the cost by simply defaulting the value:

map "" $variable_name {
default       /test/;
}

Map can be used to initialise a variable based on the content of a string and can be used inside http scope allowing variables to be global and sharable across servers.