Scheduling pods with resource requests and limits #

This image shows you what you should expect when testing this scenario. You can follow the step-by-step guide after seeing this.

Prerequisites #

• KWOK must be installed on the machine. See installation.
• Install kubectl

Create cluster #

kwokctl create cluster

View clusters #

• This ensures that the cluster was created successfully.

kwokctl get clusters

Deploy nodes #

Below are the node resource specifications:

• Nodes: 2 worker nodes in the cluster
  • Node 1: 4 CPUs
  • Node 2: 2 CPUs

kwokctl scale node node-1 --replicas 1 --param '.allocatable.cpu="4000m"'
kwokctl scale node node-2 --replicas 1 --param '.allocatable.cpu="2000m"'

Pod resource usage specifications #

• Pod 1: Requests 2.7 CPU. Limits 3 CPU.
• Pod 2: Requests 1.2 CPU. Limits 1.5 CPU.

Scheduling process #

Step 1: Deploy Pod 1 and 2 #

apiVersion: v1
kind: Pod
metadata:
  name: pod-1
  namespace: default
spec:
  containers:
  - name: fake-container
    image: fake-image
    ports:
    - containerPort: 80
    resources:
      requests:
        cpu: 2700m
      limits:
        cpu: 3000m
  tolerations:
  - key: "kwok.x-k8s.io/node"
    operator: "Exists"
    effect: "NoSchedule"

apiVersion: v1
kind: Pod
metadata:
  name: pod-2
  namespace: default
spec:
  containers:
  - name: fake-container
    image: fake-image
    ports:
    - containerPort: 80
    resources:
      requests:
        cpu: 1200m
      limits:
        cpu: 1500m
  tolerations:
  - key: "kwok.x-k8s.io/node"
    operator: "Exists"
    effect: "NoSchedule"

kubectl apply -f pod-1.yaml
kubectl apply -f pod-2.yaml

Step 2: View the node the pod is scheduled to #

kubectl get pod -o wide

NAME    READY   STATUS    RESTARTS   AGE   IP         NODE            NOMINATED NODE   READINESS GATES
pod-1   1/1     Running   0          10s   10.0.0.1   node-1-000000   <none>           <none>
pod-2   1/1     Running   0          6s    10.0.0.2   node-2-000000   <none>           <none>

• Pod 1 is scheduled to Node 1.
• Pod 2 is scheduled to Node 2.

Step 3: View node resource usage #

kubectl describe node node-1-000000 | awk '/Allocated resources:/,/ephemeral-storage/'
kubectl describe node node-2-000000 | awk '/Allocated resources:/,/ephemeral-storage/'

This will provide detailed information about the node’s resource capacity and usage.

Delete the cluster #

kwokctl delete cluster

Conclusion #

This example demonstrates how to use KWOK to simulate a scheduling scenario based on resource requests and limits policy.