Error "foris_controller_backends.collectd" since a few days

Hi folks,
since a few days, every two seconds the following error message is logged in /var/log/messages:

Jun 28 19:09:40 turris foris-controller[17530]: WARNING:foris_controller_backends.collectd:Socket error occured '[Errno 2] No such file or directory'

I couldn’t determine which file foris_controller_backends.collectd is looking for.

Any idea?

Thank you
Lorenz