Add startup (maintenance) mode
Write and update a /wp-content/maintenance.php file during the core/plugin/theme/language update and install steps; and run those steps in a background process, while the FastCGI server starts-up ASAP.
-
Ensure writing said file works as intended; returns 503 and content -
Background install steps à la wp-cron -
Set caching headers to disable caching? -
Build a page including a spinner and self-updating mechanism (meta-redirect?)
Edited by Dom Sekotill