Will it work smoothly on EKS with Karpenter

[Tomer9000]

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Will it kube-startup-cpu-boost work smoothly on EKS with Karpenter?

[adiospeds]

Yeah I feel like it will compete with the consolidation process of karpenter. We need more discussion around this.

[dgdelahera]

What I've observed is that it enters in a loop when consolidation when the WhenEmptyOrUnderutilized consolidation policy is enabled:

• Pod running on Node A with normal CPU requests (e.g., 200m)
• Node B has 1 core available
• Karpenter reads the pod spec (200m CPU) and decides to kill the node Node A
• Mutating webhook (startup CPU boost) changes CPU requests to 3 cores
• Pod needs 3 cores, but Node B only has 1 core
• Karpenter creates Node C with enough capacity for 3 cores
• Loop repeats

The problem is not really in the kube-startup-cpu-boost. It is on Karpenter not being aware of the boost, so it only takes the CPU request as reference to calculate if a pod fits in a node.