Backing up and restoring a Liberty collective
Before changing a collective controller, member or replica set, it is recommended to store a copy of the collective server files so that you can restore the collective, if needed, in the future. You might restore a backed-up copy to fix corrupted files or to downgrade the collective to a previous configuration. When restoring a replica set, it is important to start restored replicas one at a time to synchronize data.
Procedure
- Back up a collective.
To back up a collective controller, member or replica set, copy the server files that you want to preserve to a safe location. The server files are in the $WLP_USER_DIR/servers/server_name directory and its subdirectories. To avoid locking problems when copying the files, stop the server before backing up its files.
- Restore a collective controller or member.
To restore a backed-up collective controller or member server, you can use files in the backed-up directory to configure a new server or, if the Liberty version is the same, copy the backed-up files into the Liberty installation. You do not need to copy the logs and workarea directories into the target installation. Ensure the server.xml file of a restored server sets the correct host value and has unique port values in the target installation.
Optionally, start the restored server with the --clean parameter to clean cached server information:
server start server_name --clean
You use the --clean option only once; all subsequent server starts do not require it.
- Restore
or downgrade a replica set.
- Stop all replicas in the replica set.
- Restore the frappe database (fdb)
directory on one replica from a backup.
Replace the frappe database of the replica that you want to restore with the frappe database of the backed-up replica. The frappe database is the $WLP_USER_DIR/servers/collective_controller_name/resources/collective/repository/fdb directory of the replica.
- Delete the fdb directory contents of all other replicas in the replica set.
- If you want to downgrade to a previous version, replace the Java archive (JAR) files on all replicas with older versions of the JAR files to roll back the replicas to a previous version.
- Start the replica with the restored fdb directory.
- Look for the CWWKX6012I message in the messages for
the restored replica.
To see the replica messages, open an editor on the $WLP_USER_DIR/servers/collective_controller_name/logs/messages.log file. The message resembles:
CWWKX6012I: The collective controller is temporarily unavailable, probably due to a change in the replica set. It should become available within a few seconds. Current active replica set is [active_replicas]. The configured replica set is [configured_replicas].
- Start only a minimal majority of the replicas.
Include the restored replica in the number of minimal majority replicas. For example, if a replica set has 5 replicas, a minimal majority is 3 replicas. Because the restored replica is already running, you would start 2 replicas in step 7a.
- Start a minimal majority of the replicas.
- After these replicas are running, look for the CWWKX6011I message
in the messages of each replica that you started. The message resembles:
CWWKX6011I: The collective controller is ready, and can accept requests. The leader is replicaHost:replicaPort. Current active replica set is [active_replicas]. The configured replica set is [configured_replicas].
The CWWKX6011I message indicates that the replicas synchronized correctly, with the restored fdb directory fully replicated in the majority replicas.
Verify that the [active_replicas] section in the message lists all the majority replicas that you have started. Also verify that the [configured_replicas] section lists all the replicas in the replica set, including replicas that you have not started yet.
- Start all remaining replicas.
- Start the remaining replicas.
- After the replicas are running, look for the CWWKX6011I message
in the messages of each replica.
Verify that the [active_replicas] and [configured_replicas] sections in the message list all the replicas in the replica set.
The replicas are now running on the restored version.

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