Removing a controller from a Liberty collective replica set

During the life of a replica set, it might become necessary to remove one or more replicas from the replica set. You can use the collective utility removeReplica command to remove a replica from a replica set. A replica is a collective controller. The removeReplica command does not delete the collective controller server.

About this task

Administrators of a collective can enable a Liberty server to act as a collective controller using the replicate and addReplica commands and, after the controller is no longer needed, remove the controller from the collective using the removeReplica command.

After removal of a replica, the remaining replicas in the replica set do not require any updates to their configuration. However, you might want to update them so that their configurations in the server.xml files more accurately reflect the updated replica set.

Note: It is not necessary to change the replicaSet value in the server.xml file of a remaining replica in the set. No change to the configuration of a remaining replica is required. If you do want to update the replicaSet values in the configurations of remaining replicas in the set so that the configuration values are consistent across all replicas in the set, you must set the isInitialReplicaSet value in the configurations of the remaining replicas to false. This is because after you change the replicaSet value, it no longer describes the initial replica set; it now describes a changed replica set.

Procedure

Optional: Back up the replica set.
Ensure the collective controller is running.
For a controller named myController, run the status command:
```
wlp/bin/server status myController
```
If the collective controller is not running, then start it using the start or run command:
```
wlp/bin/server start myController
```
Remove a collective controller or replica from the replica set.
Run a removeReplica command that uses the administrative security domain configuration of the collective controller and specifies the endpoint of the replica that you want to remove in the form replicaHost:replicaPort. Look at the server.xml file of the collective controller to find the values for the --host, --port, --user, and --password parameters. For information about these required parameters and about optional parameters, run collective help removeReplica at a command line.
```
wlp/bin/collective removeReplica replicaHost:replicaPort --host=host_of_running_controller --port=https_port_of_running_controller --user=user_for_running_controller --password=user_password
```
To reduce the number of options needed, use the --controller option instead of --user, --password, --host, and --port.
```
wlp/bin/collective removeReplica replicaHost:replicaPort --controller=user_for_running_controller:user_password@host_of_running_controller:https_port_of_running_controller
```
For example, to remove myController2 from the example replica set in Configuring Liberty collective replica sets, run the following command:
```
wlp/bin/collective removeReplica localhost:10011 --host=host_of_myController --port=https_port_of_myController --user=user_for_myController --password=user_password
```
To reduce the number of options needed, use the --controller option instead of --user, --password, --host, and --port.
```
wlp/bin/collective removeReplica localhost:10011 --controller=user_for_myController:user_password@host_of_myController:https_port_of_myController
```