Yep, Prometheus is on the same VM and deployed as a docker container. Everything works (I’ve other exporters deployed as well) but for some reason the Discourse Prometheus plugin, even if being clearly up and running, is not accepting requests.
When you say the ENV variable you are talking about the environment in the app.yaml file of Discourse right?
So, something like this:
env:
DISCOURSE_PROMETHEUS_TRUSTED_IP_ALLOWLIST_REGEX: 172.20.0.3
172.20.0.3 being the current internal IP that Prometheus will have on the docker virtual network on which also Discourse is attached.
I tried already using the external IP that all the containers share anyway (the VM static IP) but as they are in the same network, when one try to access the other, it does through the internal IP.
A ./launcher restart app should suffice for the envs to be picked up right?
In that case I get:
Get "http://vmi1187507-app:80/metrics": dial tcp: lookup vmi1187507-app on 127.0.0.11:53: server misbehaving
vmi1187507-app is the container network name in its network. The name is correct, I can ping it from the Prometheus container running.
No idea where that 127.0.0.11:53 is coming from to be honest 
The message is the same if I comment out the env variable.