Can we create an alert on a singlestat? I don't see an "alert tab" to create an alert. Can you please suggest me a way to compare two singlestat from 2 data sources.
At the moment, you cannot define alert on Singlestat. Future request is still open: https://github.com/grafana/grafana/issues/6983
As of Grafana version 2.5 you can create Panels which can query multiple datasource at once. You just need to switch the Data Source into --Mixed--
mode.
You can try it here: https://play.grafana.org/d/000000014/elasticsearch-metrics?panelId=4&fullscreen&edit