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What should I do with pods after adding a node to the Kubernetes cluster?
I mean, ideally I want some of them to be stopped and started on the newly added node. Do I have to manually pick some for stopping and hope that they'll be scheduled for restarting on the newly added node?
I don't care about affinity, just semi-even distribution.
Maybe there's a way to always have the number of pods be equal to the number of nodes?
For the sake of having an example:
I'm using juju to provision small Kubernetes cluster on AWS. One master and two workers. This is just a playground.
My application is apache serving PHP and static files. So I have a deployment, a service of type NodePort and an ingress using nginx-ingress-controller.
I've turned off one of the worker instances and my application pods were recreated on the one that remained working.
I then started the instance back, master picked it up and started nginx ingress controller there. But when I tried deleting my application pods, they were recreated on the instance that kept running, and not on the one that was restarted.
Not sure if it's important, but I don't have any DNS setup. Just added IP of one of the instances to /etc/hosts with host value from my ingress.
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Kubernetes automatically spreads the Pods for workload resources (such as Deployment or StatefulSet) across different nodes in a cluster. This spreading helps reduce the impact of failures.
First of all you cannot “move” a pod from one node to another. You can only delete it from one node and have it re-created on another. To delete use the kubectl delete command. To ensure a pod lands on a specific node using node affinity/taints and tolerations.
In order to distribute pods evenly across all cluster worker nodes in an absolute even manner, we can use the well-known node label called kubernetes.io/hostname as a topology domain, which ensures each worker node is in its own topology domain.
Pods are only scheduled once in their lifetime. Once a Pod is scheduled (assigned) to a Node, the Pod runs on that Node until it stops or is terminated. So the answer to your question is “no”, as others had already mentioned: the pod will not be re-scheduled to any other node.
descheduler, a kuberenets incubator project could be helpful. Following is the introduction
As Kubernetes clusters are very dynamic and their state change over time, there may be desired to move already running pods to some other nodes for various reasons:
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