Only one node in the cluster can be appointed the role of cluster leader but it is possible to promote another node in the cluster to become the new cluster leader.
To promote a node in a cluster to cluster leader you need to be logged onto the node. From the Web Management Interface System Configuration > Cluster tab, you will find the
Set cluster leader button. Clicking on this button will trigger an API call to the cluster service to promote the follower node to take on the role of leader.
During the promotion the cluster service will perform the following:
Demote the leader node: write permission is dropped to read-only and status changed to follower node.
Promote the follower node: write permission is restored, the database is updated to match the demoted leaders database and status changed to leader node.
All other nodes: will be updated to ensure they know who the new leader is.
If the current cluster leader is not contactable the node will still be promoted.
If the original cluster leader is turned on after another node is promoted as leader the cluster service will continue to demote the original cluster leader to a follower.