Wikimedia Bugzilla is closed!

Created attachment 14320 [details]
Screenshot of hanging screen

Opening a page like https://www.wikidata.org/wiki/Q19837 takes around 10 seconds to appear.

The initial HTML and any request in particular seems quick, but something somehow is causing it to hang for roughly 10 seconds during which a spinner is visible on the page, and the html layout is incomplete (causing the white/blue Vector skin content container to be collapsed through the partially loaded content).

After those 10 seconds the page ready event fires and then the remaining resources are all loaded quickly and appear at once without any visible delay or build up.

I've captured a network graph (attached) and can't figure out what is causing it to hang for so long. There are no pending or blocking requests during that time. After the first 100-200ms burst, it just idles for 10 seconds, and then it continues and loads everything at once within another 100-200ms burst, mostly just regular 304s, nothing out of the ordinary. 

Tried both logged-in and logged-out, as well as in Chrome Incognito, caching not disabled, hits are mostly 304s and the hanging is still there, even after a soft refresh.

In the screenshot you can see it showing "Establishing secure connection", however that is not consistent. The message shown during those 10 seconds is sometimes "Waiting for upload.wikimedia.org...", sometimes "Waiting for bits.wikimedia.org...", sometimes "Waiting for meta.wikimedia.org.." and sometimes "Establishing secure connection". None of these seem to be more common during those 10 seconds, but whichever it is, that message is shown for the full 10 seconds.