Does MySQL 5.6 support fan-in replication?
At present, MySQL does not support a native Multiple Master, Single Slave topology.

The phrase "Arbitrary Topology" is exact what it says. It is a topology of your making.

If you really want to create a Multiple Master, Single Slave topology, you came to the right place.

You will have to construct the topology based on the book



Pages 373-375 has two diagrams of three DB Servers (M1, M2, S1)

DIAGRAM #1


M1 has the following characteristics


Slave of M2
Database db1 has real data 
Database db2 all tables use BLACKHOLE Storage Engine

M2 has the following characteristics


Slave of M1
Database db1 all tables use BLACKHOLE Storage Engine
Database db2 has real data 

S1 has the following characteristics


Slave of M2
Database db1 has real data 
Database db2 has real data 



DIAGRAM #2


M1 has the Database db1
M2 has the following characteristics


Slave of M1
Database db1 all tables use BLACKHOLE Storage Engine
Database db2 has real data 

S1 has the following characteristics


Slave of M2
Database db1 has real data 
Database db2 has real data 



WARNING : As long as you do not run ALTER TABLE statements against a database that is made up of all BLACKHOLE tables, this approach is the closest you can get to Single Slave/Multiple Master Replication. You will have to live with possible latency issues.

Give it a Try !!!

I have written about such topologies before


Apr 18, 2013 : Single slave - multiple master MySQL replication
Feb 03, 2012 : One slave, multiple masters MySql
May 16, 2011 : Is Multi Master Single Slave possible in mySQL DB?
Mar 11, 2011 : MySQL in star topology