NGINX Maintenance Mode: easy to set and render a template

gistfile1.txt

## THIS IS A WORKAROUND TO SET A GLOBAL VARIABLE
## THIS IS WHAT YOU SHOULD CHANGE TO TURN ON MAINTENANCE MODE
map $host $maintenance {
  default false;
}


## THEN ON THE SERVER BLOCK
## IF MAINTENANCE MODE IS TURNED ON
## WE RETURN A ERROR CODE
## AND RENDER THE APPROPRIATE TEMPLATE

if ($maintenance = true){
  return 502;
}

error_page 503 502 @maintenance;

## THE REWRITES ARE NEEDED SO THE ASSETS OF THE MAINTENANCE MODE TEMPLATE
## ACTUALLY GET SERVED AND NOT RETURNED WITH A 502 ERROR
## THIS WAY THEY GET RENDERED, DESPITE THE FACT THAT THEY STILL RETURN 502
## THIS DOESNT WORK WITH .js NOR .css FILES ¯\_(ツ)_/¯

location @maintenance {
  root     /var/www/maintenance;
  rewrite  (\/assets\/image\.png)$ /$1 break;
  rewrite  (\/assets\/image_2\.jpg)$ /$1 break;
  rewrite  ^(.*)$ /index.html break;
}