Basic Pod CPU and Memory Management

We will create four pods:

  • A request deployment with Request cpu = 0.5 and memory = 1G
  • A limit-cpu deployment with Limit cpu = 0.5 and memory = 1G
  • A limit-memory deployment with Limit cpu = 1 and memory = 1G
  • A restricted deployment with Request of cpu = 1/memory = 1G and Limit cpu = 1.8/memory=2G

Deploy Metrics Server

We will deploy metrics-server using Helm to help with monitoring resource utilization. Helm can be installed following the steps in the earlier [module] (/beginner/060_helm/helm_intro/install/)

# Create the metrics-service namespace
kubectl create namespace metrics

# Install metrics-server into namespace
helm install metrics-server \
    stable/metrics-server \
    --version 2.9.0 \
    --namespace metrics

 # After 2 minutes verify current system metrics are shown
 kubectl top node
 kubectl top pod  --all-namespaces

CPU units are expressed as 1 CPU or 1000m, which equals to 1vCPU/Core. Additional details can be found here

Deploy Pods

In order to generate cpu and memory load we will use stress-ng with the following flags.

  • vm-keep: maintain consistent memory usage
  • vm-bytes: bytes given to each worker
  • vm: number of workers to spawn ex. vm=1 uses 1000m CPU vm=2 uses 2000m CPU
  • oomable: will not respawn after being killed by OOM killer
  • verbose: show all information output
  • timeout: length of test
# Deploy Limits pod with hard limit on cpu at 500m but wants 1000m
kubectl run --limits=memory=1G,cpu=0.5 --image  hande007/stress-ng basic-limit-cpu-pod --restart=Never --  --vm-keep --vm-bytes 512m --timeout 600s --vm 1 --oomable --verbose 

# Deploy Request pod with soft limit on memory 
kubectl run --requests=memory=1G,cpu=0.5 --image  hande007/stress-ng basic-request-pod --restart=Never --  --vm-keep   --vm-bytes 2g --timeout 600s --vm 1 --oomable --verbose 

# Deploy restricted pod with limits and requests wants cpu 2 and memory at 1G
kubectl run --requests=cpu=1,memory=1G --limits=cpu=1.8,memory=2G --image  hande007/stress-ng basic-restricted-pod  --restart=Never --  --vm-keep  --vm-bytes 1g --timeout 600s --vm 2 --oomable --verbose 

# Deploy Limits pod with hard limit on memory at 1G but wants 2G
kubectl run --limits=memory=1G,cpu=1 --image  hande007/stress-ng basic-limit-memory-pod --restart=Never --  --vm-keep  --vm-bytes 2g --timeout 600s --vm 1 --oomable --verbose

Verify Current Resource Usage

Check if pods are running properly. It is expected that basic-limit-memory-pod is not not running due to it asking for 2G of memory when it is assigned a Limit of 1G.

kubectl get pod

Output: 


NAME                     READY   STATUS      RESTARTS   AGE
basic-limit-cpu-pod      1/1     Running     0          69s
basic-limit-memory-pod   0/1     OOMKilled   0          68s
basic-request-pod        1/1     Running     0          68s
basic-restricted-pod     1/1     Running     0          67s

Next we check the current utilization

# After at least 60 seconds of generating metrics
kubectl top pod

Output: 


NAME                   CPU(cores)   MEMORY(bytes)   
basic-limit-cpu-pod    501m         516Mi           
basic-request-pod      1000m        2055Mi          
basic-restricted-pod   1795m        1029Mi

Running multiple stress-ng on the same node will consume less CPU per pod. For example if the expected CPU is 1000 but only running 505 there may be other pods on the nodes consuming CPU.

Kubernetes Requests and Limits can be applied to higher level abstractions like Deployment.

Expand here to see the example

Cleanup

Clean up the pods before moving on to free up resources

kubectl delete pod basic-request-pod
kubectl delete pod basic-limit-memory-pod
kubectl delete pod basic-limit-cpu-pod
kubectl delete pod basic-restricted-pod