Control unit election

Election process and rules

Members of the cluster communicate over the cluster control link to elect a control unit as follows:

1. When you deploy the cluster, each unit broadcasts an election request every 3 seconds.

2. Any other units with a higher priority respond to the election request; the priority is set when you deploy the cluster and is not configurable.

3. If after 45 seconds, a unit does not receive a response from another unit with a higher priority, then it becomes the control unit.

4. If a unit later joins the cluster with a higher priority, it does not automatically become the control unit; the existing control unit always remains as the control unit unless it stops responding, at which point a new control unit is elected.

5. In a split brain scenario when there are temporarily multiple control units, then the unit with highest priority retains the role while the other units return to data unit roles.