Upgrading a Liberty collective

You can upgrade a collective by replacing existing collective members or replica sets or by adding new members or replicas.

About this task

A Liberty collective can contain members, controllers, and replica sets. See Collective architecture. Over time, you might need to upgrade replica sets or members in the collective or otherwise change the collective configuration.

Procedure

Upgrade a replica set.
1. Choose one replica in the replica set to upgrade. You upgrade replicas one at a time. If the replica is running, stop it.
2. Back up the replica.
  
  You can back up the entire replica server directory, $WLP_USER_DIR/servers/server_name directory and its subdirectories. Or, at minimum, back up the frappe database (fdb) directory that holds the replica data, $WLP_USER_DIR/servers/collective_controller_name/resources/collective/repository/fdb. See Backing up and restoring a Liberty collective.
  
  You can use the first replica backup for the remaining replicas.
3. Upgrade the Java archive (JAR) files for the replica. See Installing Liberty using downloaded archives and Installing Liberty Repository assets
  
  Note: WebSphere® Application Server Network Deployment Liberty or WebSphere Application Server for z/OS® Liberty provides collective-wide SSH support. When upgrading a replica set to this version or higher, collective-wide SSH support will not be enabled unless explicitly configured following the steps in Updating collective-wide remote authentication keys.
4. Start the upgraded replica.
5. After the replica is running, look for the CWWKX6011I message in the replica messages to see if the replica synchronized correctly.
  The message resembles:
```
CWWKX6011I: The collective controller is ready, and can accept requests. The leader is replicaHost:replicaPort. Current active replica set is [replicaHost:replicaPort, replicaHost:replicaPort, replicaHost:replicaPort]. The configured replica set is [replicaHost:replicaPort, replicaHost:replicaPort, replicaHost:replicaPort].
```
6. After verifying that the replica synchronized, complete steps 1 through 5 for another replica. You can skip step 2 if you use the first replica backup.
  
  Repeat this step 6 until all replicas in the replica set have been upgraded and started one at a time and messages show that the replicas synchronized correctly.
  After all replicas are upgraded, the messages.log file for each replica contains message CWWKX6047I, which resembles:
```
CWWKX6047I: The active collective controller replica set was upgraded successfully. The current active replica version is version_number.
```
Add a new member to an existing collective.

Use the collective join command to add a Liberty server as a member to a collective. See step 2 in Configuring a Liberty collective.
Add a new replica to an existing collective.

Use the collective addReplica command to add a replica to a collective. See Configuring Liberty collective replica sets.