sticky-node-scheduler is a custom Kubernetes
scheduler that schedules all variants of a given pod on the same node.
If a pod variant isn't running on any nodes, we pick a node to schedule on to based on which node is running the least amount of our sticky-scheduled pods. If any varients of a pod are running, then we place all copies of the pod on the same node.
If you're using e.g. EBS volumes, which can only be attached to a single node at a time, and need seamless updates of your stateful Deployments, this might be useful to you.
This scheduler only works with Kubernetes >= 1.6, which support custom schedulers as a beta feature.
NOTE: This is not ready for production usage.
How to use
First, deploy the scheduler into your cluster:
$ kubectl apply -f deployment.yml
Then, for each Deployment or ReplicationController you want to schedule using this scheduler, add:
to the pod spec. For instance:
apiVersion: extensions/v1beta1 kind: Deployment metadata: name: my-stateful-service spec: replicas: 2 template: metadata: labels: app: my-stateful-service spec: schedulerName: stickToExistingNodeScheduler containers: - name: my-stateful-service image: stateful-service-image
The scheduler identifies 'variants' of your pods based on the
metadata.labels entry in your pod template.
NODE_FILTER_QUERY environment variable controls which nodes are
selected for scheduling. By default, it is set to
labelSelector=kubernetes.io/role=node, which will filter only nodes (e.g.
we won't schedule on to your master nodes).
POLL_FREQUENCY environment variable controls how often we poll the
Kubernetes API for changes, per second. The default is
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