You may found that you created a cluster many days ago, and you didn't delete it, but it is disapear. Why did this happen? Who deleted the cluster?

Actually, 30 days after a compute is terminated, it is permanently deleted automaticlly.

If your workspace has Unity Catalog enabled, you can use this sql to check who deleted the cluster. If the sql returns null, the cluster was removed automatically due to it being inactive for 30 days.

SELECT max(event_time) AS EventTime, request_params["cluster_id"] AS ClusterID, user_identity.email as User, source_ip_address AS IPAddress  
FROM system.access.audit
WHERE action_name = "permanentDelete" AND service_name = "clusters" AND workspace_id = "xxxxxxxxxx"AND request_params["cluster_id"] = ""
GROUP BY request_params["cluster_id"], user_identity.email, source_ip_address

If you want to keep the all-purpose cluster after 30 days of termination, you can pin it. Up to 100 compute resources can be pinned.