I guess I don't know well what `SERVER_NAME` will be when we are running behind gunicorn/nginx. `SERVER_NAME` is a value in the the request header or in some cases the environment, which means it may be overwritten by the user. Behind gunicorn/nginx we can almost guarantee that is correct because otherwise it would not have made it passed the virtualhost/proxypass resolver. I don't think we can make that assumption for all cases.

One concern I have is that under certain configurations `SERVER_NAME` could be the same regardless of the machine, in which case it would not help figuring out which server originated the event, which I think can be handy for associating events with the last event registration.

You are correct that `fqdn` makes a reverse DNS lookup, hence my comment about how expensive it is. I am not really sure that we should use it, just starting the discussion. I'll investigate on the side. Since we have been using `SERVER_NAME` in the current logs, we should continue using it for `host`. The idea above was to add one more field called `fqdn`.