presto-plugin-toolkit/src/main/java/io/prestosql/plugin/base/authentication/KerberosAuthentication.java/KerberosAuthentication/getServerPrincipal
class KerberosAuthentication:    private static String getServerPrincipal(String principal, String hostname)
    {
        String[] components = principal.split("[/@]");
        if (components.length != 3 || !components[1].equals(HOSTNAME_PATTERN)) {
            return principal;
        }
        return format("%s/%s@%s", components[0], hostname.toLowerCase(ENGLISH), components[2]);
    }