Linux - Centos 7 64bit

I don't think it is MaxScale's task to do this - perhaps a better place is in your monitoring solution?

I think my description is not very clear.

I have an environment with 2 Multi Master Nodes, however, I wish the application to send writes commands (inserts, updates, deletes) to Node A only, but send read commands to both Node A and B (selects).
However, I want B to be able to take over write capabilities in case A fails and also receive writes from other components (AppB for instance).
This is why I cannot set global read only to B.
Without these constraints, the global read only approach would work fine in today's implementation.

It has nothing to do with monitoring I believe.

Ah, I see. The concept of 'mmmon' is that the node who does not have read_only enabled is the master. That monitor is not suitable for your need.

You could do this with weighting, however I found a bug with that: MXS-842 - I am not sure if that's a mmmon bug or a readconnroute bug. If you setup a router with db1 weight 1000 and db2 weight 0 you would have that same effect.

Also you could not run a monitor in MaxScale it would not change or touch the 'slave' and 'master' states. Using the 'maxadmin' command you could set and clear these statuses yourself:
maxadmin -pmariadb set server db1 slave
maxadmin -pmariadb set server db1 slave

By the way, forcing a master to be a slave thus no longer receiving write traffic is not how MaxScale works. A node receives writes because it has the master state (instead of receiving writes because it does not have the slave state). You can set the master set as well using maxadmin.

Good luck!

Mmmon is not really being worked on anymore.