We are redesigning our Microservice example and want our frontend service to be deployed on Spot Instances when they are available. We will use Node Affinity in our manifest file to configure this.
Open the deployment manifest in your Cloud9 editor - ~/environment/ecsdemo-frontend/kubernetes/deployment.yaml
Edit the spec to configure NodeAffinity to prefer Spot Instances, but not require them. This will allow the pods to be scheduled on On-Demand nodes if no spot instances were available or correctly labelled.
We also want to configure a toleration which will allow the pods to “tolerate” the taint that we configured on our EC2 Spot Instances.
For examples of Node Affinity, check this link
For examples of Taints and Tolerations, check this link
Configure Affinity and Toleration
Add this to your deployment file under spec.template.spec
affinity:
nodeAffinity:
preferredDuringSchedulingIgnoredDuringExecution:
- weight: 1
preference:
matchExpressions:
- key: lifecycle
operator: In
values:
- Ec2Spot
tolerations:
- key: "spotInstance"
operator: "Equal"
value: "true"
effect: "PreferNoSchedule"
We have provided a solution file below that you can use to compare.
First let’s take a look at all pods deployed on Spot instances
for n in $(kubectl get nodes -l lifecycle=Ec2Spot --no-headers | cut -d " " -f1); do echo "Pods on instance ${n}:";kubectl get pods --all-namespaces --no-headers --field-selector spec.nodeName=${n} ; echo ; done
Now we will redeploy our microservices with our edited Frontend Manifest
cd ~/environment/ecsdemo-frontend
kubectl apply -f kubernetes/service.yaml
kubectl apply -f kubernetes/deployment.yaml
cd ~/environment/ecsdemo-crystal
kubectl apply -f kubernetes/service.yaml
kubectl apply -f kubernetes/deployment.yaml
cd ~/environment/ecsdemo-nodejs
kubectl apply -f kubernetes/service.yaml
kubectl apply -f kubernetes/deployment.yaml
We can again check all pods deployed on Spot Instances and should now see the frontend pods running on Spot instances
for n in $(kubectl get nodes -l lifecycle=Ec2Spot --no-headers | cut -d " " -f1); do echo "Pods on instance ${n}:";kubectl get pods --all-namespaces --no-headers --field-selector spec.nodeName=${n} ; echo ; done