presto-hive/src/main/java/io/prestosql/plugin/hive/authentication/CachingKerberosHadoopAuthentication.java/CachingKerberosHadoopAuthentication/calculateNextRefreshTime
class CachingKerberosHadoopAuthentication:    private static long calculateNextRefreshTime(UserGroupInformation userGroupInformation)
    {
        Subject subject = getSubject(userGroupInformation);
        checkArgument(subject != null, "subject must be present in kerberos based UGI");
        KerberosTicket tgtTicket = getTicketGrantingTicket(subject);
        return getRefreshTime(tgtTicket);
    }