FYI, a Compute Canada staff member has created GitHub - guilbaults/cvmfs-exporter to gather CVMFS client stats for Prometheus. As I understand it was forked from cloud / cvmfs-prometheus-exporter · GitLab , with some recent updates and improvements.
Hopefully it could be useful for others to use too. In case of questions/issues about the CVMFS prometheus exporter please go to the github issues to contact Simon, as I am not involved in it.