I am trying to make an area chart which shows the average size of the parsing queue over time. I would like to add a horizontal bar as a threshold. I noticed that some logs have different values for the max_size_kb, so I thought I could use max to get the value and set my threshold to that, but for some reason, my search is returning zero results. I don't know why it's not working. If I hardcode a number for zzz, it'll work, but doesn't seem to work the way it is written now. The value changes between my hosts, so I don't want to hard code it.
index=_internal host=$hostToken$ group=queue name=parsingqueue
| stats max(max_size_kb) AS zzz
| timechart avg(current_size_kb) by ingest_pipe
| eval threshold = zzz