Changing the machine that is the coordinator

During cluster operations, you might need to change the machine that is the coordinator of the cluster; for example, to:

• Remove the machine currently acting as the coordinator
• Shut down the existing coordinator for maintenance
• Troubleshoot problems with the coordinator

You can change the machine that is the coordinator by using the Cluster Management page. You can make a member the coordinator by selecting Make coordinator from the Actions menu corresponding to that machine in the Current Members list. You can also make another cluster member the coordinator by selecting Make coordinator from the Actions menu corresponding to the other machine.

You can also perform other cluster management tasks from this page.

Changing the machine that is the coordinator

1. From the main menu, click the Administration Settings icon, and then click Cluster Management in the Appliance section.
2. On the Cluster Management page, select Make coordinator from the Actions list next to the cluster member you want to make the coordinator.
   

3. Confirm that you want to make the selected machine a coordinator

   Note

   As a part of this operation, all services on all machines in the cluster are restarted.

   An offline page is displayed, showing progress messages about the coordinator-change process. If you attempt to log in to any machine that is a member of the cluster, the same offline page is shown.

Changing the coordinator when the coordinator has failed

1. Access the UI of the machine you want to make the coordinator.
2. From the main menu, click the Administration Settings icon, and then click Cluster Management in the Appliance section.
3. On the Cluster Management page, from the actions list for the machine you want to become the coordinator, select Make Coordinator.
   

4. Confirm that you want to make the selected machine the coordinator.

   The operation takes place immediately after you click OK.

   Warning

   This operation forcibly removes all failed machines, including the current coordinator, and restarts discovery services on all remaining machines in the cluster.

   An offline page is displayed, showing progress messages about the coordinator-change process. If you attempt to log in to any machine that is a member of the cluster, the same offline page is shown.

When the operation is complete, the Cluster Management page is refreshed and shows the previous coordinator in the Previous Members section.

Restoring a failed and forcibly removed coordinator

If a coordinator fails and is forcibly removed from the cluster, it must be reverted to a standalone state before it can be used again. To do this:

1. Log in to the appliance command line as the tideway user.

2. Use tw_cluster_control to revert the machine to a standalone state. Enter:

   [tideway@wilkoapp1 ~]$ tw_cluster_control --revert-to-standalone
   Removing this machine from the current cluster
   
   WARNING: This will delete all data on this cluster member!
   
     Do you wish to proceed? (yes/no) yes
   Stopping Cluster Manager service:
   ...
   

   The machine can be added back into the cluster.

Making an existing cluster member the coordinator

Where you have changed a failed coordinator and the cluster has not restarted, you must make another machine become the coordinator. To do this:

1. Log in to the appliance command line for the machine you want to make the coordinator. Log in as the tideway user.

2. Use tw_cluster_control to to make that machine become the coordinator. Enter:

   [tideway@wilkoapp1 ~]$ tw_cluster_control --become-coordinator
   
   Password for BMC Discovery UI user system:
   Making this machine the cluster coordinator
   Becoming coordinator... (see UI for progress)
   [tideway@wilkoapp1 ~]$
   

   The machine then becomes the coordinator.