# CoreDNS monitoring with stunnel


This article can be seen as a follow up
to [Monitor with SSH and
Prometheus](/2016/february/24/monitoring-with-ssh-and-prometheus/), but in
a different, hopefully, more simple way.[^1]

Now I want to monitor [CoreDNS](https://coredns.io) running as a
[DNS to HTTPS proxy](https://blog.coredns.io/2016/11/26/dns-over-https/) in my home network.

In one word: *stunnel*. (I had to upgrade Raspbian to Debian Testing to get an up to date stunnel
though.)

I've setup a simple TLS tunnel with a pre-shared-key between my prometheus server and the NATted
Raspberry Pi running in my homenetwork.

The *client* config on the server; `% more /etc/stunnel/coredns-monitor.conf`:
~~~ txt
pid = /var/run/stunnel4/coredns-monitor.pid

[PSK coredns]
client = yes
accept = 1149
connect = <my IP addr>:1149
ciphers = PSK
PSKsecrets = /etc/stunnel/psk.txt
~~~

And on the client, the *server* config:
~~~ txt
pid = /var/run/stunnel4/coredns-monitor.pid

[PSK coredns]
accept = 1149
connect = 9153
PSKsecrets = /etc/stunnel/psk.txt
~~~

CoreDNS has been started with exporting the montioring, which by default happens on port 9153.
On my server a `curl localhost:1149/metrics` now returns the metrics.

On the Prometheus side, this look like any other scraped job:
~~~ yaml
- job_name: coredns
  static_configs:
    - targets: ['localhost:1149']
  relabel_configs:
    - source_labels: ['__address__']
      target_label: 'instance'
      regex: '.+(:1149)'
      replacement: 'pi'
~~~

Marvel it this colorful dashboard, but *again*, I'm struggling to get to one qps:

{{<figure src="/images/2016/grafana-coredns-proxy.png" caption="Grafana screenshot." link="/images/2016/grafana-coredns-proxy.png">}}

[^1]: I never go those ssh-tunnels to start reliably on boot.