Wikimedia Bugzilla is closed!

Created attachment 10982 [details]
Patch against 1.19.1

If a DBError is thrown – such as when MySQL is returning the "too many connections" error – MediaWiki returns an error page with the HTTP 200 OK status code. This is quite troublesome, since automatic polling by Varnish only checks the status code of the returned page to determine whether the backend is healthy or not. 

I have attached a simple patch to work around this problem. I notice I have to use the PHP header function directly instead of going via $wgOut – I suppose that's because the error page is being output raw instead of through OutputPage.