Opened 3 months ago

#1785 new enhancement

Support access to environment variables in config file

Reported by: spion-h4@… Owned by:
Priority: minor Milestone:
Component: other Version: 1.15.x
Keywords: Cc:
uname -a:
nginx -V: nginx version: nginx/1.10.3 built with OpenSSL 1.1.0f 25 May 2017 (running with OpenSSL 1.1.0j 20 Nov 2018) TLS SNI support enabled configure arguments: --with-cc-opt='-g -O2 -fdebug-prefix-map=/build/nginx-0TiIP5/nginx-1.10.3=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-z,relro -Wl,-z,now' --prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log --lock-path=/var/lock/nginx.lock --pid-path=/run/nginx.pid --modules-path=/usr/lib/nginx/modules --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-debug --with-pcre-jit --with-ipv6 --with-http_ssl_module --with-http_stub_status_module --with-http_realip_module --with-http_auth_request_module --with-http_v2_module --with-http_dav_module --with-http_slice_module --with-threads --with-http_addition_module --with-http_geoip_module=dynamic --with-http_gunzip_module --with-http_gzip_static_module --with-http_image_filter_module=dynamic --with-http_sub_module --with-http_xslt_module=dynamic --with-stream=dynamic --with-stream_ssl_module --with-mail=dynamic --with-mail_ssl_module --add-dynamic-module=/build/nginx-0TiIP5/nginx-1.10.3/debian/modules/nginx-auth-pam --add-dynamic-module=/build/nginx-0TiIP5/nginx-1.10.3/debian/modules/nginx-dav-ext-module --add-dynamic-module=/build/nginx-0TiIP5/nginx-1.10.3/debian/modules/nginx-echo --add-dynamic-module=/build/nginx-0TiIP5/nginx-1.10.3/debian/modules/nginx-upstream-fair --add-dynamic-module=/build/nginx-0TiIP5/nginx-1.10.3/debian/modules/ngx_http_substitutions_filter_module

Description

Currently nginx doesn't directly support access to environment variables in the config file. This makes it difficult to use it in a 12-factor-app style setup, where the docker container / VM / machine image use environment variables for configuring things such as static assets.

One way to work around this is to use envsubst to generate the config file on the fly. However, that means the target config file needs to be writable.

Another one would be to use something like ngx_http_lua_module. The process is two step: first, prevent the variable from being filtered out:

env MY_STATIC_ASSETS_PATH;

Then, set a variable using nginx syntax:

http {
...
  server {
    location /static {
      # set var using Lua
      set_by_lua $static_assets 'return os.getenv("MY_STATIC_ASSETS_PATH")';
      alias "$static_assets"
      ...
    }
  }
}

Since using the lua module seems heavy-handed for something like this, I'd like to propose a set_from_env directive that does exactly that. The result would be:

http {
...
  server {
    location /static {
      # set var using built in directive
      set_from_env $static_assets MY_STATIC_ASSETS_PATH;
      alias "$static_assets"
      ...
    }
  }
}

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