cp4029 was reported throwing errors by @bd808 on IRC, upon a quick look it was clear that the host was not performing well so @CDanis depooled it.
From grafana and syslog it seems that the host started to log errors at around 20:39 UTC.
Investigation afterwards shows that the uid=vcache varnishd process is consuming approximately 499.8k file descriptors (all but a hundred or so are sockets). However, said sockets do not show up in any of the usual socket-reporting tools like ss or netstat.
Currently the host is depooled pending further investigation.