Reminder: MTS = Multi-Threaded Slave.
Update 2017-04-17: since the publication of this post, many things happened:
the procedure for fixing a crashed slave has been automated (Bug#77496) Bug#80103 as been closed at the same time as Bug#77496 but I still think there are unfixed things, see Bug#81840
End of update 2017-04-17.
I will be talking about parallel replication at FOSDEM in Brussel on