With the blackout set up by itwiki in the last days, we learned that it could be handy to have a tool which would allow sysops to enable a serverside blackout, instead of a clientside one. For this purposal, we currently have Extension:Blackout. However, an extension like that isn't handy: it requires a patch to be planned for a SWAT window, and in an emergency situation this could take way too much time. Discussing about it, we came to the conclusion that it could be useful to have a dedicated page in MediaWiki namespace (e.g. Mediawiki:Blackout) containing a JSON configuration for enabling a serverside blackout without devs' help. A very basic configuration could be this one:
"enabled": false, "displayedContent": "Mediawiki:page_with_the_text_to_display (like a transclusion)", "whitelistedPages": [ "page 1", "Help: page 2", "MediaWiki: page 3" ], "whitelistedGroups": [ "sysop" ]
I'd be glad to work on it, but I'm not sure if that needs some kind of approval, both from a technical and ethical POV (although sysops can already effectively break the site). Please note that this could also be implemented in Extension:Blackout, which at the current state needs a new skin for every blackout.