add warnings when apply container memory resources are less than 6Mi

[chengjoey]

What would you like to be added?

When I create the following pod, and the resources requested by the container are less than 6Mi:

apiVersion: v1
kind: Pod
metadata:
  name: app
spec:
  containers:
  - name: nginx
    image: nginx
    resources:
      limits:
        cpu: "0.1"
        memory: "5Mi"
      requests:
        cpu: "0.1"
        memory: "5Mi"

i got CreateContainerError status

kubectl get pod app -o json | jq '.status.containerStatuses[0].state':

{
  "waiting": {
    "message": "Error response from daemon: Minimum memory limit allowed is 6MB",
    "reason": "CreateContainerError"
  }
}

kubelet log:

May 13 08:07:13 minikube kubelet[28281]: E0513 08:07:13.446599   28281 pod_workers.go:1298] "Error syncing pod, skipping" err="failed to \"StartContainer\" for \"nginx\" with CreateContainerError: \"Error response from daemon: Minimum memory limit allowed is 6MB\"" pod="default/app" podUID="bebb6b1b-a2d8-4916-be19-7314e1ba70f8"
May 13 08:07:29 minikube kubelet[28281]: E0513 08:07:29.539556   28281 remote_runtime.go:319] "CreateContainer in sandbox from runtime service failed" err="rpc error: code = Unknown desc = Error response from daemon: Minimum memory limit allowed is 6MB" podSandboxID="5a7642634307f697bfedee131056d1b24e191754bdb0ef3ff46d65fdc83e84d9"
May 13 08:07:29 minikube kubelet[28281]: I0513 08:07:29.539689   28281 kuberuntime_manager.go:1258] Container start failed in pod app_default(bebb6b1b-a2d8-4916-be19-7314e1ba70f8): CreateContainerError: Error response from daemon: Minimum memory limit allowed is 6MB
May 13 08:07:29 minikube kubelet[28281]: E0513 08:07:29.539762   28281 kuberuntime_manager.go:1259] container &Container{Name:nginx,Image:nginx,Command:[],Args:[],WorkingDir:,Ports:[]ContainerPort{},Env:[]EnvVar{},Resources:ResourceRequirements{Limits:ResourceList{cpu: {{100 -3} {<nil>} 100m DecimalSI},memory: {{5242880 0} {<nil>} 5Mi BinarySI},},Requests:ResourceList{cpu: {{100 -3} {<nil>} 100m DecimalSI},memory: {{5242880 0} {<nil>} 5Mi BinarySI},},Claims:[]ResourceClaim{},},VolumeMounts:[]VolumeMount{VolumeMount{Name:kube-api-access-mkv5j,ReadOnly:true,MountPath:/var/run/secrets/kubernetes.io/serviceaccount,SubPath:,MountPropagation:nil,SubPathExpr:,RecursiveReadOnly:nil,},},LivenessProbe:nil,ReadinessProbe:nil,Lifecycle:nil,TerminationMessagePath:/dev/termination-log,ImagePullPolicy:Always,SecurityContext:nil,Stdin:false,StdinOnce:false,TTY:false,EnvFrom:[]EnvFromSource{},TerminationMessagePolicy:File,VolumeDevices:[]VolumeDevice{},StartupProbe:nil,ResizePolicy:[]ContainerResizePolicy{ContainerResizePolicy{ResourceName:cpu,RestartPolicy:NotRequired,},ContainerResizePolicy{ResourceName:memory,RestartPolicy:NotRequired,},},RestartPolicy:nil,} start failed in pod app_default(bebb6b1b-a2d8-4916-be19-7314e1ba70f8): CreateContainerError: Error response from daemon: Minimum memory limit allowed is 6MB

I hope to display a warning reminder when the requested memory resources are less than 6Mi

Why is this needed?

6Mi is the minimum memory value defined in moby

	// It's not kernel limit, we want this 6M limit to account for overhead during startup, and to supply a reasonable functional container
	linuxMinMemory = 6291456

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[saschagrunert]

/sig node

The minimum amount of memory is a runtime requirement which can vary across implementations. I don't think that Kubernetes needs to apply any limit on top of that.

[chengjoey]

The minimum amount of memory is a runtime requirement which can vary across implementations. I don't think that Kubernetes needs to apply any limit on top of that.

It is not a restriction, but a warning.

[ffromani]

Just wondering, how warnings should be displayed?
Still wondering, isn't this use case something that can be solved with a (cluster-specific) validating webhook?