ruby on rails multiple custom domains over Https using Openresty and lua (https://www.babar.im/blog/sysadmin/serve-your-saas-customer-domains-over-https-for-free.html)

1. nginx.conf

## /etc/openresty/nginx.conf


user www-data;
events {
  worker_connections 1024;
}

http {
  lua_shared_dict auto_ssl 1m;
  lua_shared_dict auto_ssl_settings 64k;
  resolver 8.8.8.8 ipv6=off;

  init_by_lua_block {
    auto_ssl = (require "resty.auto-ssl").new()
    auto_ssl:set("allow_domain", function(domain)
      return true
    end)
    auto_ssl:init()
  }

  init_worker_by_lua_block {
    auto_ssl:init_worker()
  }

  access_log /var/log/openresty/access.log; 
  error_log /var/log/openresty/error.log;
  server {
    listen 127.0.0.1:8999;
    client_body_buffer_size 128k;
    client_max_body_size 128k;

    location / {
      content_by_lua_block {
        auto_ssl:hook_server()
      }
    }
  }
  include /etc/nginx/sites-enabled/*;
}

2. default

#### /etc/nginx/sites-available/default (ln -s /etc/nginx/sites-enabled/default)


upstream app_server {
    server unix:///home/rails/html/shared/tmp/sockets/puma.sock fail_timeout=0;
}

server {
  listen 80 default_server;
  listen [::]:80 default_server;
  server_name _;

  # Required to verify domain with LetsEncrypt
  location /.well-known/acme-challenge/ {
    content_by_lua_block {
      auto_ssl:challenge_server()
    }
  }
  location / { return 301 https://$host$request_uri; }
}


server {
    listen 443 ssl http2 default_server;
    server_name _;

    ssl_certificate_by_lua_block {
      auto_ssl:ssl_certificate()
    }
    ssl_certificate /root/.acme.sh/fullchain.cer;
    ssl_certificate_key /root/.acme.sh/app.key;
    # ssl_protocols       TLSv1 TLSv1.1 TLSv1.2;
    # ssl_ciphers         HIGH:!aNULL:!MD5;

    root /home/rails/html/current/public;
    index index.html index.htm;

    location / {
	# First attempt to serve request as file, then
	# as directory, then fall back to displaying a 404.
	try_files $uri/index.html $uri.html $uri @app;
    }

    location ~* ^.+\.(jpg|jpeg|gif|png|ico|zip|tgz|gz|rar|bz2|doc|xls|exe|pdf|ppt|txt|tar|mid|midi|wav|bmp|rtf|mp3|flv|mpeg|avi)$ {
	try_files $uri @app;
    }


    location @app {
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header Host $http_host;
        proxy_redirect off;
        proxy_pass http://app_server;
    }

  }