Now YarnClient will automatically get a timeline DT when submitting an app in a secure mode. It will try to parse the yarn-site.xml/core-site.xml to get the RM daemon operating system user. However, the RM principal and auth_to_local may not be properly presented to the client, and the client cannot translate the principal to the daemon user properly. On the other hand, AbstractDelegationTokenIdentifier will do this translation when create the token. However, since the client has already translated the full principal into a short user name (which may not be correct), the server can no longer apply the translation any more, where RM principal and auth_to_local are always correct.