During some of the discussions between @jcrespo and myself, we have been talking about the future of multi source in our infrastructure and if it is worth trying to go for it or if it is better to go towards multi instance (several MySQL processes running on different ports).
There are several pro and cons for each design, and at the moment we have both solutions in place.
dbstore servers + labsdbservers + db1095 (new sanitarium) -> multisource
db1069 (old sanitarium) -> multi instance
We have found a bug in MariaDB (https://jira.mariadb.org/browse/MDEV-12012) that doesn't allow us to turn on GTID on multi source just yet, which prevent us to have "crash safe" replication.
Meaning that if a multisource slave crashes, it might corrupt data and we might need to rebuild it. The nature of a multisource slaves is a server with lots of data to import, so that work can take weeks to complete.
Those issues have triggered the discussion of what should we head to: multisource vs multi instance.
This is just the epic ticket so we can discuss and try to decide what we want to go for in the near future.
Feel free to change the description if needed.