There were being logged at VLOG(2):
In the same spirit as
MESOS-9340, we'd like to log all networking related errors as warnings and include any relevant information (IP address, etc).
- relates to
MESOS-9340 Log all socket errors in libprocess.
MESOS-9787 Log slow SSL (TLS) peer reverse DNS lookup.
MESOS-9773 Log the peer address during SSL handshake failure.