How can I use OS environment variables in Nginx config? - linux

Question

How do I use environment variables set in the OS inside nginx configs?
For example environment variables set are ENVIRON=dev, APP_NAME=test
Here's my Dockerfile:
FROM openresty/openresty:alpine
RUN set -ex && \
rm /etc/nginx/conf.d/default.conf
ADD nginx.conf /etc/nginx/
ADD custom.conf /etc/nginx/conf.d/
Here's my main nginx.conf
user nginx;
worker_processes auto;
pcre_jit on;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;
events {
worker_connections 1024;
}
env ENVIRON;
env APP_NAME;
set_by_lua $environ 'return os.getenv("ENVIRON")';
set_by_lua $appname 'return os.getenv("APP_NAME")';
http {
server_tokens off;
include /etc/nginx/mime.types;
default_type application/octet-stream;
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log /var/log/nginx/access.log main;
sendfile on;
keepalive_timeout 65;
include /etc/nginx/conf.d/*.conf;
}
Here's my custom.conf from /etc/nging/conf.d/
upstream app.$environ-$appname {
server $environ-$appname:80;
}
server {
listen 80;
server_name $hostname;
error_log /dev/stdout info;
access_log /dev/stdout;
location / {
proxy_redirect off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
add_header X-Info proxied;
proxy_pass http://app.$environ-$appname;
}
}
Thanks!

Answer 1

That thing you are trying to do, I dont think you can do that.
From the documentation on the server directive of the upstream module:
Defines the address and other parameters of a server. The address can
be specified as a domain name or IP address, with an optional port, or
as a UNIX-domain socket path specified after the “unix:” prefix
You can't create upstream servers on the fly using variables.
If you want to route requests like this either use the map directive if the different locations are known at runtime, or set up an auth_request directive which points at an application on your server which can return the correct variables for each request in real time. Then have Nginx store that response in a variable using the auth_request_set directive.