G-EAZY AND HALSEY CLEAR SIGNS OF TROUBLE AT POST MALONE SHOW

Halsey and G-Eazy's breakup could be seen coming a mile away ... according to sources close to the exes at a concert last week.

We're told the 2 attended Post Malone's show at the Hollywood Bowl last Thursday -- G-Eazy performed a song with Posty -- but weren't their usual inseparable, lovey-dovey selves. In fact, our sources say they were very distant and never hung out together backstage.

Even more telling -- Halsey left the concert and was spotted hitting up the club, Poppy, afterward ... but not with G-Eazy ... with rapper Machine Gun Kelly.

We're told G-Eazy was not at the club. Halsey and MGK were actually linked last summer, but it was never confirmed they were dating. A couple months later ... she was definitely hooking up with G-Eazy.

As we reported ... Halsey announced her split from the rapper Tuesday, saying, "I feel the need to inform my fans. G-Eazy and I are taking some time apart."

Source: tmz