Ah! I just realized how to do this for ourselves. It turns out the source: srv- tags actually correspond to the render service id and don’t change on deploys. I can use that in my filter.
More context on what was happening: we have a LogDNA alert set on warnings from our applications. We do this in LogDNA by creating a view that sends us an email whenever it sees logs with the level warn. I needed to filter metabase warnings out of that view, but I wasn’t able to find a good identifier to do so. I’d deployed Metabase using instructions from Deploy Metabase | Render · Cloud Hosting for Developers. After a little sleuthing I found the srv- ids associated with log lines by render and noticed they were the same as url identifier for our services.