A recent example is this job that failed due to DNS resolution errors [1] "Could not resolve host: trunk.rdoproject.org; Name or service not known".
Was this via the default nameservers setup in /etc/resolv.conf on the machine ?
AFAIK jobs do not change resolv.conf. The job log is gone now, but I've seen in the log it wasn't just trunk.rdoproject.org even mirror.centos.org was not resolving.
Cheers, Alan