First, place the cluster into MAINTENANCE mode.

shell> cctrl
cctrl> set policy maintenance

Stop the software on the existing cluster node

shell> stopall

Stop MySQL on the existing cluster node (Syntax is an example and may differ in your environment)

shell> systemctl stop mysqld

Update the ini on all nodes (including connectors) changing the reference to the node to be a witness node, example below.

Before:

[defaults]
user=tungsten
home-directory=/opt/continuent
application-user=app_user
application-password=secret
application-port=3306
profile-script=~/.bash_profile
replication-user=tungsten
replication-password=secret
replication-port=13306
rest-api-admin-user=apiuser
rest-api-admin-password=secret
mysql-allow-intensive-checks=true

[nyc]
topology=clustered
master=db1
members=db1,db2,db3
connectors=db1,db2,db3

After:

[defaults]
user=tungsten
home-directory=/opt/continuent
application-user=app_user
application-password=secret
application-port=3306
profile-script=~/.bash_profile
replication-user=tungsten
replication-password=secret
replication-port=13306
rest-api-admin-user=apiuser
rest-api-admin-password=secret
mysql-allow-intensive-checks=true

[nyc]
enable-active-witnesses=true
topology=clustered
master=db1
members=db1,db2,db3
witnesses=db3
connectors=db1,db2,db3

Update the software on the existing cluster nodes and connector nodes (If separate). Include --no-connectors if you want to manually restart them when convenient.

shell> cd /opt/continuent/software/tungsten-clustering-7.1.4-10
shell> tools/tpm update --replace-release

Update on the host you are converting:

shell> cd /opt/continuent/software/tungsten-clustering-7.1.4-10
shell> tools/tpm update --replace-release -f

Once the updates have been complete, you should then run the tungsten_reset_manager command on each node in the entire cluster. This will ensure the metadata is clean and reference to the node is reflected to be a witness, rather than a full cluter node. On each node, simply execute the command and follow the on screen prompts:

shell> tungsten_reset_manager

Restart the managers on the nodes you have not converted:

shell> manager start

Start the software on the node that you converted:

shell> startall

If you issued --no-connectors during the update, restart the connectors when convenient

shell> connector restart

Check within cctrl from one of the existing database nodes to check that the status returns the exptected output, and then return the cluster to AUTOMATIC and the process is complete.