/etc/nginx/includes/http-common.conf

upstream docservice {
  server localhost:8000;
}

upstream spellchecker {
  server localhost:8080;
}

upstream example {
  server localhost:3000;
}

map $http_host $this_host {
    "" $host;
    default $http_host;
}

map $http_x_forwarded_proto $the_scheme {
     default $http_x_forwarded_proto;
     "" $scheme;
}

map $http_x_forwarded_host $the_host {
    default $http_x_forwarded_host;
    "" $this_host;
}

map $http_upgrade $proxy_connection {
  default upgrade;
  "" close;
}

proxy_set_header Host $http_host;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection $proxy_connection;
proxy_set_header X-Forwarded-Host $the_host;
proxy_set_header X-Forwarded-Proto $the_scheme;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;