During master election each node pings in order to discover other nodes and validate the liveness of existing nodes. Based on this information the node either discovers an existing master or, if enough nodes are found (based on `discovery.zen.minimum_master_nodes>>) a new master will be elected.
Currently, the node that is elected as master will currently update it the cluster state to indicate the result of the election. Other nodes will submit a join request to the newly elected master node. Instead of immediately processing the election result, the elected master
node should wait for the incoming joins from other nodes, thus validating the elections result is properly applied. As soon as enough nodes have sent their joins request (based on the `minimum_master_nodes` settings) the cluster state is modified.
Note that if `minimum_master_nodes` is not set, this change has no effect.
Closes#12161
Boaz Leskes
Clinton Gormley
Andrzej Wisłowski
Alex Chan
Pascal Borreli
Martijn van Groningen