Ok, this is most likely caused due to the usage of the vlogger script from ubuntu as ispconfig uses a different table name. Please undo the change of the customlog directive in the ispconfig.conf file that we did in this step:
so that the vlogger script from ispconfig is used again, but keep the edited /etc/vlogger-dbi.conf file and check if the problem is solved now.
to sum it up, perl can not connect to mysql on hostname localhost but it can connect to the IP of localhost, now we just have to try to find out what the problem in the mysql or hostname configuration is.
Please post the /etc/hosts file of your server and the output of: