On an internal cluster with security enabled, it was reported that queries couldn't be cancelled via the shell. When the user tried to cancel the query via ctrl-C, the shell printed the warning:
The shell did not return with a new prompt and the query was still active on the server until the query was manually cancelled via the web UI. At that point, the query was cancelled successfully, and the shell finally returned with the message:
This was using kerberos/ssl. It seemed to be reproducing regularly.