Loki datasource is not reachable from Grafana when using a domain name in Traefik

[Abuelodelanada]

Bug Description

Grafana can't connect to Loki because the fqdn is provided to Grafana instead of the k8s svc DNS.

This issue was initialy reported by @kian99 in this chat

To Reproduce

1. Deploy cos-lite : juju deploy cos-lite --channel=edge --trust
2. Config external hostname: juju config traefik external_hostname=foobar.com
3. Add this line to you /etc/hosts: 192.168.1.250 foobar.com (check what is Traefik external IP)
4. Check in Grafana thar you cannot connect to Loki datasource.

Environment

• juju 3.4.2
• edge charms

Model  Controller  Cloud/Region        Version  SLA          Timestamp
cos    microk8s    microk8s/localhost  3.4.2    unsupported  15:31:49-03:00

App           Version  Status  Scale  Charm             Channel      Rev  Address         Exposed  Message
alertmanager  0.27.0   active      1  alertmanager-k8s  latest/edge  109  10.152.183.45   no       
catalogue              active      1  catalogue-k8s     latest/edge   39  10.152.183.232  no       
grafana       9.5.3    active      1  grafana-k8s       latest/edge  111  10.152.183.218  no       
loki          2.9.5    active      1  loki-k8s          latest/edge  137  10.152.183.67   no       
prometheus    2.50.1   active      1  prometheus-k8s    latest/edge  176  10.152.183.28   no       
traefik       v2.11.0  active      1  traefik-k8s       latest/edge  182  192.168.1.250   no       

Unit             Workload  Agent  Address      Ports  Message
alertmanager/0*  active    idle   10.1.165.8          
catalogue/0*     active    idle   10.1.165.1          
grafana/0*       active    idle   10.1.165.30         
loki/0*          active    idle   10.1.165.62         
prometheus/0*    active    idle   10.1.165.23         
traefik/0*       active    idle   10.1.165.24  

Relevant log output

.

Additional context

No response

[Abuelodelanada]

Closing, since there was an error in step 3.
If you add that line to grafana container /etc/hosts it is working: