The current technique installs a separate rw-core deployment to each Kubernetes node, where each deployment consists of a pair (replicas = 2) of co-located rw-cores. Co-location is enforced by making use of the Kubernetes nodeSelector constraint applied at the pod spec level.
In order for node selection to work, a label must be applied to each node. There is a set of built-in node labels that comes with Kubernetes out of the box, one of which is kubernetes.io/hostname. This label can be used to constrain the deployment of a core pair to a node with a specific hostname. Another approach is to take greater control and create new node labels.
The following discussion assumes installation of the voltha-k8s-playground (https://github.com/ciena/voltha-k8s-playground) which configures three Kubernetes nodes named k8s1, k8s2, and k8s3.
Create a "nodename" label for each Kubernetes node:
kubectl label nodes k8s1 nodename=k8s1 kubectl label nodes k8s2 nodename=k8s2 kubectl label nodes k8s3 nodename=k8s3
Verify that the labels have been applied:
kubectl get nodes --show-labels NAME STATUS ROLES AGE VERSION LABELS k8s1 Ready master,node 4h v1.9.5 ...,kubernetes.io/hostname=k8s1,nodename=k8s1 k8s2 Ready node 4h v1.9.5 ...,kubernetes.io/hostname=k8s2,nodename=k8s2 k8s3 Ready node 4h v1.9.5 ...,kubernetes.io/hostname=k8s3,nodename=k8s3
Ensure that a nodeSelector section appears in the deployment's pod spec (such a section should already exist in each manifest):
...
nodeSelector:
nodename: k8s1
Once the labels have been applied, deploy the 3 core pairs:
kubectl apply -f k8s/rw-core-pair1.yml kubectl apply -f k8s/rw-core-pair2.yml kubectl apply -f k8s/rw-core-pair3.yml