I've had an instance of Graphana running for 2 years on an Ubuntu box using Prometheus as a data source.

After updating ubuntu via apt I noticed my all my dashboards went down.
Going to the Prometheus DataSource settings I see the error
`Error reading Prometheus: Metric request error`

Looking in my apt upgrade log it looks like things broke with the update batch

```
Upgrade: libglapi-mesa:amd64 (21.0.3-0ubuntu0.3~20.04.4, 21.0.3-0ubuntu0.3~20.04.5),
libgl1-mesa-dri:amd64 (21.0.3-0ubuntu0.3~20.04.4, 21.0.3-0ubuntu0.3~20.04.5), 
grafana:amd64 (8.2.5, 8.3.0), 
mesa-vulkan-drivers:amd64 (21.0.3-0ubuntu0.3~20.04.4, 21.0.3-0ubuntu0.3~20.04.5), 
libglx-mesa0:amd64 (21.0.3-0ubuntu0.3~20.04.4, 21.0.3-0ubuntu0.3~20.04.5)

```

If I use curl to access Prometheus from the same machine I get results for endpoints like `/metrics` or `api/v1/query`. So it appears that Prometheus is working fine.

Also, googling the error message `Error reading Prometheus: Metric request error` returns zero results. So, not sure what to do here ... roll back the grafana version?

I've also posted a question in the grafana community.
<https://community.grafana.com/t/prometheus-ds-metric-request-error-new-error-on-upgrading-ubuntu/57443>