I run a PiHole dns server, I keep seeing mass dns requests for the domain mariadb from my Ubuntu Server. About 50,000 a day, 3 A and 3 AAAA every 10 seconds. I can't seem to find a way to identify the program that is sending them. I've tried setting the entry manually to a non existant ip in /etc/hosts and that stopped the requests for a while but then they came back and there was still no way to identify what program was sending them. Looking for a way to identify the program doing this. I've checked configs and temporarily stopped almost every program I can think of and the requests have continued.
UPDATE: These dns requests are showing up in my dns query log on my pihole and occasionally overloading it. This is why I thought pihole relevant, pihole is running on a different machine, and this machine is not running anything to do with dns except the "systemd-resolved stub resolver". Mariadb is running on the server in a docker container for bookstack (Also dockerized), mysql is running on the server (not in docker) for several wordpress sites but there is no configuration in any of these services that should be causing them to lookup the "mariadb" domain. PHP7.4.9 is installed as required for the wordpress sites.