DDG and Blueface turned up at a packed house party -- there was even a real-live goat at the spot -- before the night went from lit to straight-up baa-d with cops swarming the scene last night, TMZ has learned.

Law enforcement sources tell TMZ ... LAPD was called to a Mecca Ave address in Tarzana, Los Angeles around 10:40 PM for a massive gathering of about 200 people on site, including rapper Blueface.

We’re told things got messy ... reports of fights breaking out, along with possible gang activity.

There were five armed security guards trying to keep control, but more people outside were in front of the location trying to force their way in.

It ended with multiple LAPD units showing up, and the whole crowd -- including the guy with the goat -- scattered.