Data Explorer cluster running idle that will never stop itself
A running Azure Data Explorer cluster with no queries and no ingestion in the window, which auto-stop will never reach because it is switched off or the cluster sits in a virtual network.
Why it happens
A Data Explorer cluster bills its engine nodes for every hour it is Running, whether or not a query is ever run, and stopping it releases that compute without deleting the database. Azure already stops inactive clusters after five days and the setting defaults to on, so an idle cluster is usually about to fix itself and reporting it would recommend something the platform is already doing. This rule therefore fires only where auto-stop cannot help: the customer switched it off, or the cluster is deployed in a virtual network, which Azure excludes from auto-stop however the flag reads. The second case is invisible from the portal, where the setting still shows as enabled. Idleness uses Azure own auto-stop criteria, no queries and no ingestion, read at maximum so a single busy sample disqualifies the window, and it deliberately ignores CPU and keep-alive because both report non-zero on a perfectly idle cluster. The saving covers the virtual machine half of the bill only: Azure charges a separate markup per vCore per hour that cannot be derived from the cluster record, so the figure is a floor and the rate is quoted beside it. Restarting takes about ten minutes before the cluster answers and longer before the hot cache refills, and a leader cluster with followers attached must not be stopped at all, which nothing on the cluster record reveals.
What the agent does about it
A running Azure Data Explorer cluster with no queries and no ingestion in the window, which auto-stop will never reach because it is switched off or the cluster sits in a virtual network.
It will not fix this one
It reports this and takes no action. A check only earns the right to change something once the action behind it can re-read live state before it fires and knows the way back.
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