A proof of concept of how CPU and Memory usage are allocated per container when using LimitRange.
Remarks:
- nginx-deployment pod gets assigned a QoS class of Burstable
$ ./deploy.sh
Switched to context "docker-for-desktop".
deployment.extensions "nginx-deployment" deleted
limitrange "cpu-limit-range" deleted
deployment.apps "nginx-deployment" created
limitrange "cpu-limit-range" created
=============================
Limits:
NAME AGE
cpu-limit-range 0s
=============================
=============================
Quality of Service Class:
Burstable
=============================
=============================
Compute Resources:
{
"limits": {
"cpu": "1"
},
"requests": {
"cpu": "1m"
}
}
=============================
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
docker-for-desktop Ready master 35d v1.10.11
$ kubectl describe node docker-for-desktop
.. omitted
Capacity:
cpu: 4
ephemeral-storage: 61255492Ki
hugepages-1Gi: 0
hugepages-2Mi: 0
memory: 10216828Ki
pods: 110
Allocatable:
cpu: 4
ephemeral-storage: 56453061334
hugepages-1Gi: 0
hugepages-2Mi: 0
memory: 10114428Ki
pods: 110
.. omitted
Non-terminated Pods: (9 in total)
Namespace Name CPU Requests CPU Limits Memory Requests Memory Limits
--------- ---- ------------ ---------- --------------- -------------
default nginx-deployment-584cdf8c7f-llgjk 1m (0%) 1 (25%) 0 (0%) 0 (0%)
docker compose-74649b4db6-hwgpf 0 (0%) 0 (0%) 0 (0%) 0 (0%)
docker compose-api-769f8d59b9-cstbl 0 (0%) 0 (0%) 0 (0%) 0 (0%)
kube-system etcd-docker-for-desktop 0 (0%) 0 (0%) 0 (0%) 0 (0%)
kube-system kube-apiserver-docker-for-desktop 250m (6%) 0 (0%) 0 (0%) 0 (0%)
kube-system kube-controller-manager-docker-for-desktop 200m (5%) 0 (0%) 0 (0%) 0 (0%)
kube-system kube-dns-86f4d74b45-45mr8 260m (6%) 0 (0%) 110Mi (1%) 170Mi (1%)
kube-system kube-proxy-j5kg5 0 (0%) 0 (0%) 0 (0%) 0 (0%)
kube-system kube-scheduler-docker-for-desktop 100m (2%) 0 (0%) 0 (0%) 0 (0%)
Allocated resources:
(Total limits may be over 100 percent, i.e., overcommitted.)
CPU Requests CPU Limits Memory Requests Memory Limits
------------ ---------- --------------- -------------
811m (20%) 1 (25%) 110Mi (1%) 170Mi (1%)
- We have an allocatable
4 vCPU - As we can see, the CPU limit has reached
25%of the node's CPU capacity. - This means that with this current setup, once we add more replicas of the
nginx-deploymentpod, we could overcommit the node which could affect it's stability.
- CPU requests are greater than the default resource limits, the pod won’t be created.
$ ./deploy.sh
Switched to context "docker-for-desktop".
deployment.extensions "nginx-deployment" deleted
limitrange "cpu-limit-range" deleted
deployment.apps "nginx-deployment" created
limitrange "cpu-limit-range" created
=============================
Limits:
NAME AGE
cpu-limit-range 0s
=============================
=============================
Quality of Service Class:
Burstable
=============================
=============================
Compute Resources:
{
"limits": {
"cpu": "5"
},
"requests": {
"cpu": "5"
}
}
=============================
=============================
Pods:
NAME READY STATUS RESTARTS AGE
nginx-deployment-6f9d8ff8f-mxbkf 0/1 Pending 0 0s
=============================
=============================
Pod condition:
0/1 nodes are available: 1 Insufficient cpu.
- The pods can't be created because CPU requests is higher than the allocatable resource.