Add maintenance.html page

deploy/files/sites-available/impress.conf

@@ -8,6 +8,8 @@ server {
 }
 
 server {
+  set $maintenance 0; # To enable maintenance mode, set this to 1.
+
   server_name {{ impress_hostname }};
   listen 443 ssl;
   listen [::]:443 ssl;
@@ -31,10 +33,19 @@ server {
     add_header  ETag "";
   }
 
+  # On status 503, return the maintenance page.
+  error_page 503 maintenance.html;
+
   # Try serving static files first. If not found, fall back to the app.
   try_files $uri/index.html $uri @app;
 
   location @app {
+    # If we're hardcoded as being in maintenance mode, return status 503, which
+    # will show the maintenance page as specified above.
+    if ($maintenance = 1) {
+      return 503;
+    }
+
     proxy_pass http://127.0.0.1:3000;
     proxy_set_header X-Real-IP $remote_addr;
     proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;