This section provides the following procedures to change the role of a site cluster:
A cluster that is part of a site can have one of two roles, controller or member:
A cluster that has the controller role for a site is authorized to perform operations on the other site members and the multigroups they manage. The controller authorization is based on mutual agreement, any cluster can propose itself as a controller, but it can only control those clusters which have then agreed to accept its authority.
A cluster that is a simple site member has agreed to accept commands from the site controllers, but cannot issue commands with site-wide effect.
When no existing site controller is accessible, a site member can be forcibly changed to a site controller. The site must have at least one other accessible member.
The site member submits itself or another site member as a candidate for site controller. Each site member cluster must individually accept the candidate cluster as a new controller. No controller operations that are issued by the candidate cluster are obeyed by a site member cluster that has not yet accepted the candidate cluster as a controller.
If a site controller cluster was unavailable at the time a site member cluster submits itself to be a controller, the controller automatically accepts and synchronizes the site configuration change when it again becomes available.
If the site member is the only cluster in the site, the controller role is immediately assigned to the cluster. If later another cluster is added to the site, the new cluster must then accept the existing cluster's state as a site controller.