Setup
Galera --> maxscale binlog router with second master --> slaves

If a node is down and maxscale switch to second master,
maxscale search for the fake gtid in the old binlog file,
because maxscale work in tree mode.

see example error message:

"server-id 2 reached end of file for binlog file [0/1/mariadb-bin.000005] at 222 which is not the file currently being downloaded " 

To use on every node and wsrep_domain id the same domain id is not a solution, because the binlogs are different, even if the same gtid are included.

Sugggestion:

• setup according
  https://mariadb.com/kb/en/library/using-mariadb-gtids-with-mariadb-galera-cluster/

• Maxscale must handle all transactions in gtid mode with wsrep_gtid_mode differently

• Maxscale must download the binlogs in the treefolder
• search transactions also in the new master folder , forget old poistion (can be different for the same gtid)
  the new master and have to use the gtid in the new binlog with the new path. (tree mode)

• failover with do_domain_id (see MXS-2581=