dns_exporter is a multi-target Prometheus exporter with an exclusive focus on DNS monitoring. It is built on the excellent libraries dnspython and the Prometheus Python client library.
dns_exporter can be used to monitor availability and performance of DNS servers, and to validate the responses they return. It can monitor recursive and authoritative servers regardless of the software they run. You can use it to make sure your (or your providers) DNS servers are sending the replies you expect and configure Prometheus and Alertmanager to notify you if something stops working.
dns_exporter works similar to the Blackbox exporter where Prometheus asks the exporter to scrape the target, rather than the exporter itself being the target. This is called the Multi Target Exporter Pattern. It is typically used in black-box style exporters where 1) the thing you are monitoring is not under your control, or 2) you want to measure the path as well. Often when monitoring DNS both 1) and 2) are relevant.
This means that for each scrape Prometheus speaks HTTP to the dns_exporter which then speaks DNS with the target DNS server and returns the resulting metrics over HTTP to Prometheus. dns_exporter supports doing DNS queries over plain port 53 UDP and TCP, as well as DoT and DoH (and DoQ pending the next release of dnspython).
The documentation is available on ReadTheDocs
Versioning, branching and tagging of dns_exporter is done based on https://semver.org/ and https://nvie.com/posts/a-successful-git-branching-model/