Possible dead loop

[damnever]

The regexp exec stack has been continuing for several hours, and I've had to restart the instance to resolve it. I'm unable to reproduce this issue at the moment, yet I'm posting here to see if anyone might have some insight.

The version of this library is main@6b5c0a4cb7fddca7a0857c0643e3f2a62527934b.

github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52350?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0x8f43?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec523f8?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xc28320f590?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec524a0?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0x8f41?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52548?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0x8f40?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec525f0?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xc5d69d9818?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52698?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xc28320f590?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52740?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0x8f3d?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec527e8?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0x8f3c?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52890?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xc28320f590?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52938?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xc5d69dad08?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec529e0?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0x8f39?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52a88?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xc5d69db848?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52b30?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0x8f37?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0x41e60?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xc45c25d120?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52c80?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xc28320f590?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52d28?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xb990?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52dd0?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xc5d69dd850?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52e78?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0x8f32?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52f20?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xc28320f590?)
/go/src/github.com/cortexproject/cortex/vendor/github.com/grafana/regexp/exec.go:340 +0x2b1
github.com/grafana/regexp.(*machine).add(0xc28320f590, 0xc28320f5d0, 0xbec52fc8?, 0x1, {0xc45c491ce0?, 0x0, 0x4}, 0xc4bf232938, 0xb994?)
...additional frames elided...

[damnever]

The issue could be that the regex pattern is exceptionally large (several MBs) and thereby slow..