At this time when I set-up a mysql datasource on locahost for users and when I use this datasource on front-office (on a second server). Then The FO try to connect to mysql locahost and failed. A pop-up is displayed in the back-office when I set-up this population on FO. This is nice!.
The next step would be to help the admin to solve quickly the problem. For example to alert him that he set mysql datasource on localhost...

Thank you.