So, I had a deeper look into it. The offending part is the discovered host label:
'cmk/vsphere_object':
{
'value': 'vm',
'plugin_name': 'esx_vsphere_vm.running_on'
}
The plugin_name
contains a non valid character, thats where the ValueError comes from.
I don’t know when this label got added, but it is in a lot of our hosts. I guess it’s a 1.6 legacy thing? I used sed to remove the .running_on
in var/check_mk/discovered_host_labels
and checkmk is now happy again!