minikube // rebalance pods across the cluster farm

three nodesthree nodes

#minikube delete --all
minikube start --driver=docker --nodes 3
minikube addons enable metrics-server

fix the role labels for the workers

kubectl get nodes
kubectl label nodes minikube-m02 kubernetes.io/role=worker
kubectl label nodes minikube-m03 kubernetes.io/role=worker

three replicasthree replicas

#kubectl delete deploy web
vi example-web.yml

apiVersion: apps/v1
kind: Deployment
metadata:
    name: web
    labels:
    app: web
spec:
    replicas: 3
    selector:
    matchLabels:
        app: web
    template:
    metadata:
        labels:
        app: web
    spec:
        containers:
        - name: web
          image: gcr.io/google-samples/hello-app:1.0
          ports:
          - containerPort: 8080
        affinity:
          nodeAffinity:
        requiredDuringSchedulingIgnoredDuringExecution:
        #preferredDuringSchedulingIgnoredDuringExecution:
          nodeSelectorTerms:
          - matchExpressions:
            - key: kubernetes.io/hostname
              operator: In
              values:
              - minikube
              - minikube-m02
              - minikube-m03

kubectl apply -f example-web.yml
kubectl get deploy -o wide
kubectl get pods -o wide

see what happens when shutting down a node

minikube node list
minikube node delete minikube-m03
kubectl get pods -o wide

==> the third replica goes to minikube-m02

restore the node and rebalance

minikube node add
minikube node list

git clone https://github.com/kubernetes-sigs/descheduler.git
cd descheduler/
kubectl create -f kubernetes/base/rbac.yaml
kubectl create -f kubernetes/base/configmap.yaml

#kubectl delete deploy descheduler -n kube-system
kubectl create -f kubernetes/deployment/deployment.yaml

kubectl get pods -o wide

==> back to normal

troubleshootingtroubleshooting

Warning  FailedScheduling  4m4s (x2 over 9m30s)  default-scheduler  0/3 nodes are available: 3 node(s) didn't match Pod's node affinity/selector. preemption: 0/3 nodes are available: 3 Preemption is not helpful for scheduling..

==> that was with default nodeSelector: role: worker

resourcesresources

minikube // rebalance pods across the cluster farm

three nodesthree nodes

three replicasthree replicas

troubleshootingtroubleshooting

resourcesresources

multi-node

affinity

rebalance

moar / nodeSelector