Currently YARN's REST API supports killing an application without setting a diagnostic message. It would be good to provide that support.
Usually this helps in workflow management in a multi-tenant environment when the workflow scheduler (or the hadoop admin) wants to kill a job - and let the user know the reason why the job was killed. Killing the job by setting a diagnostic message is a very good solution for that. Ideally, we can set the diagnostic message on all such interface:
yarn kill -applicationId ... -diagnosticMessage "some message added by admin/workflow"