Prometheus datasource (grafana proxy) failures - during server side image rendering

### What happened? When I use the grafana image renderer plugin (or standalone service) with graphs that have a Prometheus datasource, the rest call goes into timeout and does not deliver a rendered png. I post this here because after many hours of debugging I found there seems to be an issue in the Grafana datasource proxy. If I configure the Prometheus datasource "access" parameter to "**direct**". All renders work smoothly. In the grafana debug logs (renderer + dumpio logs) I foundthis: ``` logger=plugin.grafana-image-renderer t=2025-11-05T16:27:05.910382124+01:00 level=error msg="Browser request failed" url="https://localhost:3000/api/ds/query?ds_type=prometheus&requestId=SQR100" method=POST failure=net::ERR_ABORTED logger=rendering renderer=plugin t=2025-11-05T16:27:09.90878518+01:00 level=error msg="Failed to render image" path="d-solo/Apl2X3a7k/dataplane-basic?panelId=57&orgId=1&from=1762334688040&to=1762356288040&var-Port=$__all&var-TS=$__al l&var-channel_id=$__all&var-ProcessFilter=$__all&render=1&kiosk&width=1000&height=500&tz=CET&var-Host=meg-mini-10&var-host=meg-mini-10&var-Instance=meg-mini-10" error="rpc error: code = Canceled desc = context canceled" ``` So it looks like the /api/ds/query call is hanging and not providing any data. This does not always happen. I have a list of graphs to render, and the one that fails changes at random. Usually the render is done after 2.5 seconds. The graph render timeout is set to 60 seconds. Strangely I don't see this issue if I just open up Grafana in a browser and view the dashboards. Prometheus runs locally on the same device as Grafana. => The same graphs with the same data but fetched from **influxdb** always renders **correctly**. I have this behavior on many devices in my company, especially the ones with low performing cpus ### What did you expect to happen? The image renderer to provide a png ### Did this work before? I am transitioning our product from Influxdb to Prometheus. This problem never showed with…