Network fetching policy hits rate limits

[chrislloyd]

The extension looks like it's extremely efficient at fetching the user information cache on startup. However, because it fetches so quickly, it can block other phabricator operations from happening from the same machine. This is what happens when I try and arc diff as the extension is fetching new users:

[cdanis]

We at the Wikimedia Foundation have a relatively sizable Phabricator installation with over 22,000 users.

Unfortunately we've had a few issues created for all users by just a couple users of this extension, and for now we don't have a great choice aside from ratelimiting its user-agent string at our CDN edge.

From the extension's POV it might make sense to warn the user and 'give up' on fetching 100% of users after you've fetched N users already (a few hundred?), and then disable autocompletion for users.