Testing nginx locally with Rails

config.ru

# frozen_string_literal: true

# This file is used by Rack-based servers to start the application.

require_relative 'config/environment'

map Rails.application.config.relative_url_root || '/' do
  run Rails.application
  Rails.application.load_server
end

nginx.conf

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log debug;
pid        /var/run/nginx.pid;


events {
    worker_connections  1024;
}


http {
    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;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;


    server {
      listen 80;
      server_name localhost;

      location /atlas {
        proxy_set_header Host $host:8082;
        proxy_set_header X-Forwarded-Host localhost:3000;
        proxy_pass http://host.docker.internal:3000/atlas;
      }
    }

    include /etc/nginx/conf.d/*.conf;
}

I was working on a little Rails project called Atlas and we wanted to mount it at https://our.domain.com/atlas via our nginx rev proxy.

Rails had some interesting issues with being mounted at a subdirectory. To test this out, I temporarily added an nginx.conf file to my Rails root and ran:

docker run -p 8082:80 --network=bridge -v $(pwd)/nginx.conf:/etc/nginx/nginx.conf nginx

For local testing, I ran:

RAILS_SERVE_STATIC_FILES=true RAILS_RELATIVE_URL_ROOT=/atlas rails s

In prod, make sure you set RAILS_SERVE_STATIC_FILES=true and RAILS_RELATIVE_URL_ROOT=/atlas in your ENV.