I've put up a simple grafana dashboard for the trending service:
https://grafana-admin.wikimedia.org/dashboard/db/trending-service
and one graph there is a mystery:
https://grafana-admin.wikimedia.org/dashboard/db/trending-service?from=now-3h&to=now&panelId=3&fullscreen
This graph shows the average delay between event creation and event consumption, and the delay steadily grows over time. We need to investigate what's going on, the delay should be stable and it should in an order of seconds.