nginx.conf

worker_processes     auto;

events {
    multi_accept       on;
    worker_connections 65535;
}

http {
  upstream sinatra_app {
     server app:9292;
  }

  charset                utf-8;
  sendfile               on;
  tcp_nopush             on;
  tcp_nodelay            on;
  server_tokens          off;
  log_not_found          off;
  types_hash_max_size    2048;
  types_hash_bucket_size 64;
  client_max_body_size   16M;

  include                mime.types;
  default_type           application/octet-stream;

  access_log             /var/log/nginx/access.log;
  error_log              /var/log/nginx/error.log warn;

  map $http_upgrade $connection_upgrade {
      default upgrade;
      ""      close;
  }
  
  map $remote_addr $proxy_forwarded_elem {

      # IPv4 addresses can be sent as-is
      ~^[0-9.]+$        "for=$remote_addr";

      # IPv6 addresses need to be bracketed and quoted
      ~^[0-9A-Fa-f:.]+$ "for=\"[$remote_addr]\"";

      # Unix domain socket names cannot be represented in RFC 7239 syntax
      default           "for=unknown";
  }

  map $http_forwarded $proxy_add_forwarded {
      # If the incoming Forwarded header is syntactically valid, append to it
      "~^(,[ \\t]*)*([!#$%&'*+.^_`|~0-9A-Za-z-]+=([!#$%&'*+.^_`|~0-9A-Za-z-]+|\"([\\t \\x21\\x23-\\x5B\\x5D-\\x7E\\x80-\\xFF]|\\\\[\\t \\x21-\\x7E\\x80-\\xFF])*\"))?(;([!#$%&'*+.^_`|~0-9A-Za-z-]+=([!#$%&'*+.^_`|~0-9A-Za-z-]+|\"([\\t \\x21\\x23-\\x5B\\x5D-\\x7E\\x80-\\xFF]|\\\\[\\t \\x21-\\x7E\\x80-\\xFF])*\"))?)*([ \\t]*,([ \\t]*([!#$%&'*+.^_`|~0-9A-Za-z-]+=([!#$%&'*+.^_`|~0-9A-Za-z-]+|\"([\\t \\x21\\x23-\\x5B\\x5D-\\x7E\\x80-\\xFF]|\\\\[\\t \\x21-\\x7E\\x80-\\xFF])*\"))?(;([!#$%&'*+.^_`|~0-9A-Za-z-]+=([!#$%&'*+.^_`|~0-9A-Za-z-]+|\"([\\t \\x21\\x23-\\x5B\\x5D-\\x7E\\x80-\\xFF]|\\\\[\\t \\x21-\\x7E\\x80-\\xFF])*\"))?)*)?)*$" "$http_forwarded, $proxy_forwarded_elem";

      # Otherwise, replace it
      default "$proxy_forwarded_elem";
  }

  server {
    listen  80;
    server_name preview.biohackrxiv.org;
    root /var/www/html;

    proxy_http_version                 1.1;
    proxy_cache_bypass                 $http_upgrade;

    # Proxy headers
    proxy_set_header Upgrade           $http_upgrade;
    proxy_set_header Connection        $connection_upgrade;
    proxy_set_header Host              $host;
    proxy_set_header X-Real-IP         $remote_addr;
    proxy_set_header Forwarded         $proxy_add_forwarded;
    proxy_set_header X-Forwarded-For   $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header X-Forwarded-Host  $host;
    proxy_set_header X-Forwarded-Port  $server_port;

    # Proxy timeouts
    proxy_connect_timeout              60s;
    proxy_send_timeout                 60s;
    proxy_read_timeout                 60s;

    location / {
      proxy_pass http://sinatra_app;
    }
  }
}