DJ Carnage went OFF on Deadmau5 Friday night after he allegedly got pushed by him ... and claims about 20 security guards were sicced on him afterward.

Carnage posted an angry rant after the altercation at the Cemetery of Sound concert in Calgary, Canada. He says he'd just finished up his set when Deadmau5 was walking up to the stage to start his ... and got shoved out of the way by Deadmau5.

Carnage claims he heard Deadmau5's tour manager was talking trash and admits he confronted him about it ... and that's when the shove happened.

Deadmau5 responded with his own account -- he claims Carnage hung around way too long after his set and was looking for trouble, but when he ignored him ... Carnage got pissed and shoved HIS security guard. Deadmau5 says that's when the horde of event security jumped in and escorted Carnage away.

Either way, this beef isn't going away anytime soon -- Carnage says he's going to be performing with Deadmau5 at many festivals to come ... and Deadmau5 is getting his own shots in.