I mean when we have a multi-master cluster with 3 master nodes then after we added a new master node (fourth node) we have to be somehow notified when it will be up to date or may be ask it every 5 seconds to find out if it up to date.
Is it possible to realize?
This feature currently is not present, and looking at the roadmap, i don't think there will be. Consider the fact that if you get to have a situation with 5 nodes (therefore the quorum is 3), so the sync takes place only between two nodes, while the other 3 have a quorum to write data. So you can always keep doing insert or other and you do not need a mechanism to tell you that for example the node 5 is ready or not. This of course if you can get a situational so.