KubeCPUOvercommit doesn't take node pools

[Duologic]

kubernetes-mixin/alerts/resource_alerts.libsonnet

Lines 25 to 41 in dc563cb

	{
	alert: 'KubeCPUOvercommit',
	expr: |||
	sum(namespace:kube_pod_container_resource_requests_cpu_cores:sum{%(ignoringOverprovisionedWorkloadSelector)s})
	/
	sum(kube_node_status_allocatable_cpu_cores)
	>
	(count(kube_node_status_allocatable_cpu_cores)-1) / count(kube_node_status_allocatable_cpu_cores)
	||| % $._config,
	labels: {
	severity: 'warning',
	},
	annotations: {
	message: 'Cluster has overcommitted CPU resource requests for Pods and cannot tolerate node failure.',
	},
	'for': '5m',
	},

The KubeCPUOvercommit doesn't take node pools and tolerations into account and it might even be a stretch to cover that. Anyone has thoughts about that?

[brancz]

I definitely love where you're going.

I have a feeling that only an effort like kubernetes/enhancements#1916 could potentially go in this direction. Node pools are not well defined unfortunately, I actually poked around on sig-node yesterday if there might be possibilities to standardize this, but even if that were to lead to something, it's in the very beginning.

I think this would make sense for node-pools where you are aware of the scheduling constraints, I don't think going as far as tolerations is really reasonable or possible, as we would essentially implement the scheduler again I think.

[Duologic]

I think this would make sense for node-pools where you are aware of the scheduling constraints, I don't think going as far as tolerations is really reasonable or possible, as we would essentially implement the scheduler again I think.

Agreed, probably sufficient to link a pod to a node pool through a recording rule.

[nhuray]

Hi guys,

Maybe my question is not directly related but I don't understand the expression of the alerting rule.

I have a very small cluster with just 1 instance and that rule is always firing because (count(kube_node_status_allocatable_cpu_cores)-1) returns 0.

For example:

Let's say my containers reserved a total of 2 cpu on a single 4 cpu instance. The alerting rule give:

sum(namespace:kube_pod_container_resource_requests_cpu_cores:sum{%(ignoringOverprovisionedWorkloadSelector)s}) / 
               sum(kube_node_status_allocatable_cpu_cores)    = 0.5
                 > 
               (count(kube_node_status_allocatable_cpu_cores)-1) / count(kube_node_status_allocatable_cpu_cores)  = 0

but in reality I just commit 50% of the CPU resource of the entire cluster

so for me the expression should be:

sum(namespace:kube_pod_container_resource_requests_cpu_cores:sum{%(ignoringOverprovisionedWorkloadSelector)s}) / 
               sum(kube_node_status_allocatable_cpu_cores)
                 >  1

Am I not understanding something here ?

[Duologic]

The alert message says:

... and cannot tolerate node failure

So this alert is not applicable if you don't intend to run more than one node.

[nhuray]

I get your point but the message should be:

Cluster has overcommitted CPU resource requests for Pods or cannot tolerate node failure.

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This issue has not had any activity in the past 30 days, so the
stale label has been added to it.

• The stale label will be removed if there is new activity
• The issue will be closed in 7 days if there is no new activity
• Add the keepalive label to exempt this issue from the stale check action

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