On a shared hosting server (centos8), thousands of websites are hosted. They all use single DNS service running as local recursive resolver (BIND 9).
We observe random overload events with no clear culprit.
One hypothesis is that some website (unix user) is attacking local DNS resolver.
In the context of locally running bind daemon, what is the best way to make it log not only the DNS query, but also the unix user that sent it? Is it even possible?
You might look into running DNStop on your recursive box. It will clearly identify if you have clients abusing your service in a glance. Can be easier than observing logs, especially if you are taking a significant amount of traffic.
You should be able to find DNStop in the EPEL repositories and install with ease.
more information on this nifty tool can be found here: http://dns.measurement-factory.com/tools/dnstop/