Extensions need more exemplar support

[MikeSpreitzer]

I am working on some histogram extensions in kubernetes/kubernetes#109277 , and have run into a couple of blockages regarding examplars.

(1) constHistogram (

client_golang/prometheus/histogram.go

Line 570 in 29e8191

type constHistogram struct {

) does not support exemplars.

(2) once it does, I may need to call the private function newExemplar (like histogram::updateExemplar does).

[bwplotka]

Thanks for this report, but I think it's already implemented. Merged recently with #986

See how to use it here: https://github.com/prometheus/client_golang/blob/main/prometheus/examples_test.go#L601

I will close it for now, but feel free to comment if you think it's should be reopened (something is missing?). Cheers!

[MikeSpreitzer]

Thanks.
Now I need this to appear in a release.