How to upgrade Cassandra using this Docker image?

[alejom99]

The Readme file says that a user can scale the service to as many containers as needed. My question is is how to upgrade Cassandra when the Rancher service has a scale of more than one? According to the Cassandra documentation (upgrade steps), then user must run nodetool drain on every node (container) before upgrading that node and then perform the upgrade; then repeat the steps on the next node. Since rancher does not allow a user to upgrade a specific container, but the entire service, how would you go about upgrading Cassandra using your image if the Rancher service scale is more than one?

Thanks