Allow only one pod of a type on a node in Kubernetes

Question

How to allow only one pod of a type on a node in Kubernetes. Daemon-sets doesn't fit into this use-case.

For e.g. - Restricting scheduling of only one Elasticsearch pod on a node, to prevent data loss in case the node goes down.

It can be achieved by carefully planning CPU/memory resource of pod and machine type of cluster.

Is there any other way to do so?

Answer 1

Kubernetes 1.4 introduced Inter-pod affinity and anti-affinity. From the documentation: Inter-pod affinity and anti-affinity allow you to constrain which nodes your pod is eligible to schedule on based on labels on pods that are already running on the node.

That won't prevent a pod to be scheduled on a node, but at least the pod will be scheduled on the node if and only if the scheduler has no choice.