Scaling

In the context of Magnum and Kubernetes, there are two types of scaling:

1. Scaling nodes

2. Scaling containers

Scaling nodes

For redundancy and to increase the number of resources available to your cluster, you can scale up the number of nodes (instances). You can also scale them down.

• When you scale up, Magnum creates a new Nova instance and adds it to the cluster

• When you scale down, Magnum deletes a node in the cluster. Pods might be deleted without draining, so it is a good idea to build your services to automatically recover from the loss of a node

To scale up and down, use the openstack coe cluster resize command. The default nodegroup should be default-worker:

openstack coe nodegroup list mycluster
+--------------------------------------+----------------+-----------+------------------+------------+---------------+--------+
| uuid                                 | name           | flavor_id | image_id         | node_count | status        | role   |
+--------------------------------------+----------------+-----------+------------------+------------+---------------+--------+
| 5884f8c8-1975-4f7a-9fcd-9d765638d442 | default-master | r3.small  | fedora-coreos-32 |          2 | UPDATE_FAILED | master |
| ce7dc214-6dd7-4ddf-b83b-c5f784ae346b | default-worker | r3.small  | fedora-coreos-32 |         14 | UPDATE_FAILED | worker |
+--------------------------------------+----------------+-----------+------------------+------------+---------------+--------+

These can be scaled as so:

openstack coe cluster resize mycluster --nodegroup default-worker 16

Scaling containers

Adjusting the number of running containers is a standard operation in Kubernetes and can be performed using the kubectl command-line tool. For instance, you can scale the number of Pods in a Deployment using kubectl.

kubectl scale deployment <deployment-name> --replicas=<number> -n <namespace>

More information

For more information, refer to:

• Magnum scaling documentation.