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sassoftware / viya4-iac-aws

This project contains Terraform configuration files to provision infrastructure components required to deploy SAS Viya platform products products on Amazon AWS.
Apache License 2.0
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Why is the eks-default VM running on the private subnet and not on the control-plane subnet? #260

Closed miaeyg closed 8 months ago

miaeyg commented 8 months ago

Using the current version of this project I see that the VM named "sas-eks-default" ("sas" is the cluster name) is running in subnet "sas-private-" which is a surprise as I thought the eks-default machines should run on the "control-plane" subnets and not on the "private" subnets. Is this a bug or my understanding is incorrect about placement of VMs on subnets?

dhoucgitter commented 8 months ago

@miaeyg, none of the worker nodes are expected to be placed in either of the two control-plane subnets. The single private subnet, which is located in a single AZ, is the subnet that all worker node IPs should be allocated from. Your "sas-eks-default" VM is running in the private subnet as expected.

miaeyg commented 8 months ago

Hi @dhoucgitter, I have 4 "sas-eks-generic" instances + 1 "sas-eks-cas" instance + 1 "sas-eks-default" instance All of them are running on the single "private" subnet.

I do not understand what is supposed to run on the "control-plane" subnets...

dhoucgitter commented 8 months ago

Hi @miaeyg, all of the Viya pods, any existing worker nodes and any new worker nodes that get created through auto scaling are intended to use the pool of IPs from the larger private subnet pool. The placement of your VMs in the private subnet is intentional and expected. The intentionally smaller sized control plane subnets only host the cluster API server and elastic network interfaces (ENIs) that connect the control plane components (like the etcd cluster for managing cluster state and the controller manager for managing cluster resources) to your VPC.