amazon-eks-ami VS amazon-vpc-cni-k8s

Careful assuming system reserved will be present. Last I checked, AWS EKS does not have system reserved resources for the kubelet by default and as a result, pods can starve those for resources (e.g., https://github.com/awslabs/amazon-eks-ami/issues/79). This is of course more important for memory, but could impact CPU as well.

For example, this is available for AL2: https://github.com/awslabs/amazon-eks-ami

I found this document that lists the pod limits per node size. I suspect you will want to consider larger worker nodes or you will very quickly be unable to schedule additional workloads.

source

Issue 1 is a known issue due to memory reservation being to low, see e.g. https://github.com/awslabs/amazon-eks-ami/issues/1145

No, the new node is added if there are not enough resiurces to start a new pod. So if you have many pods with small resource usage you can hit the pod per node limit, on eks you have a max number of pods depending on the instance type - https://github.com/awslabs/amazon-eks-ami/blob/master/files/eni-max-pods.txt You can incerase that limit : https://docs.aws.amazon.com/eks/latest/userguide/cni-increase-ip-addresses.html

# of pods are essentially capped by the worker node choice.

below excerpt from: https://github.com/awslabs/amazon-eks-ami/blob/master/files/...

  # Mapping is calculated from AWS EC2 API using the following formula:

See also: EKS nodes lose readiness when containers exhaust memory

So it manifests itself in this way: your pod is scheduled but remains pending forever. You check the logs and you see that it's complaining that the an IP address. Ultimately, if you check here, you see the maximum number of pods that can be scheduled on any underlying ec2 instance, even if you have remaining IPs in your subnet. I found this to be one of the most poorly understood phenomena in EKS. Even those who claimed to "crack" it and wrote fancy blog posts about it fundamentally got it wrong. AFAIK this document reflects the official AWS guide on how to mitigate this.

The same approach hasn't worked very well or very consistently with RHEL. I'm using containerd as the runtime. Because iptables-legacy is hardcoded out of RHEL 8, I'm using iptables-nft (installed on OS). I use Terraform to deploy the cluster and provide configuration values to tell vpc-cni to enable nftables (noted at the bottom here: https://github.com/aws/amazon-vpc-cni-k8s/blob/master/docs/troubleshooting.md), as well as to install and enable ipvs on kube-proxy.

Virtual Private Cloud (VPC) Container Network Interface (CNI) plugin. You must upgrade your VPC CNI plugin version to 1.12 or higher. Earlier versions of the VPC CNI will cause the CNI to crash, because it relied on the CRI v1alpha2API, which has been removed from Kubernetes v1.26. For step-by-step instructions to upgrade the VPC CNI in your cluster, refer to Working with the Amazon VPC CNI plugin for Kubernetes Amazon EKS add-on.

I believe you're correct, although pedantically that would only apply if one is using their vpc-cni <https://github.com/aws/amazon-vpc-cni-k8s#readme> and not with a competing CNI. Kubelet offers a configurable for the number of Pods per Node <https://github.com/kubernetes/kubelet/blob/v0.26.2/config/v1...> which defaults to 110 for what I would presume is CIDR or pid cgroups reasons and thus is unlikely to differ by instance size as the ENI limit you mention does (IIRC)

Upgraded to v1.12 on EKS and CNI 1.5.0. This issue was closed stating CNI 1.5.0 solved the issue. It did not for us. In another thread leaking ENIs was blamed but was also closed due to CNI upgrade.

Take a look a the github repo for the EKS CNI I think the parameter AWS_VPC_K8S_CNI_RANDOMIZESNAT will address the port issue. We had a similar problem and this worked around it. (we did end up solving it another way)

EKS, the managed Kubernetes offering by AWS, by default uses the Amazon VPC CNI plugin for Kubernetes. Different to most networking implementations, this assigns each pod a dedicated IP address in the VPC, the network the nodes reside in.

You might be able to get better help or research closed issues on the github issues page. https://github.com/aws/amazon-vpc-cni-k8s/issues . Are you able to scale up your old node group with the smaller instance size and see if it works. The few times I hit issues around the network not being ready on a worker node in EKS, it ended up being permission related issue. Wondering if there are some missing permissions on the new node group role or on the aws-node iam role. Make sure the aws-node role has AmazonEKS_CNI_Policy policy attached to it.

By default, the number of IP addresses available to assign to pods is based on the number of IP addresses assigned to Elastic network interfaces and the number of network interfaces attached to your Amazon EC2 node. The Amazon VPC CNI add-on (v1.9.0 or later) can be configured to assign /28 (16 IP addresses) IP address prefixes, instead of assigning individual IP addresses to network interfaces.