Desired Size for both Self managed and EKS managed not working after the EKS deployment

[sourabhsharma487]

Scenario: I needed to provision a couple of EKS clusters using both EKS managed and Self managed node groups. I tried provisioning it with this code using the 18.8.1 version and I am able to deploy it for both node groups.

Problem statement: This code is not accepting "desired_size" changes in terms of adding/removing the nodes after the EKS cluster deployment is done based on the need.

Versions:
Terraform-aws-eks: 18.8.1
Terraform 1.1.6
OS: Windows 10 Enterprise

EKS: 1.21

`

terraform-aws-eks/main.tf

module "eks" {
source = "terraform-aws-modules/eks/aws"

version = "18.8.1"
vpc_id = var.vpc_id
subnet_ids = var.public_subnets
cluster_endpoint_private_access = var.cluster_endpoint_private_access
cluster_endpoint_public_access = var.cluster_endpoint_public_access
cluster_name = var.cluster_name
cluster_version = local.cluster_version
tags = local.tags

eks_managed_node_group_defaults = {
ami_type = "AL2_x86_64"
disk_size = 20
instance_types = ["m6i.large", "m5.large", "m5n.large", "m5zn.large"]
vpc_security_group_ids = [aws_security_group.all_worker_mgmt.id]
}

eks_managed_node_groups = {
# blue = {}
green = {
min_size = 1
max_size = 5
desired_size = 4
instance_types = ["t3.large"]
capacity_type = "SPOT"
labels = {
Environment = "eks-terraform"
}
taints = {
dedicated = {
key = "dedicated"
value = "gpuGroup"
effect = "NO_SCHEDULE"
}
}
tags = {
Maintainer = "Sourabh Sharma"
}
}
}
}
`

[bryantbiggs]

Desired size is ignored due to the nature of Kubernetes and predominant use of autoscaling (i.e. - cluster autoscaler, Karpenter, etc.). Therefore changing desired_size after provisioning will not influence the number of nodes. If you need to force more nodes into the pool, you can raise the min_size as a work around

[llacoste]

Desired size is ignored due to the nature of Kubernetes and predominant use of autoscaling (i.e. - cluster autoscaler, Karpenter, etc.). Therefore changing desired_size after provisioning will not influence the number of nodes. If you need to force more nodes into the pool, you can raise the min_size as a work around

I'm afraid only increasing the min size only works if it is smaller than or equal to your desired size. If you increase the minimum beyond the desired capacity, then you will get an error: InvalidParameterException: Minimum capacity <Some Number> can't be greater than desired size <Some smaller number>

[gordonmurray]

Desired size is ignored due to the nature of Kubernetes and predominant use of autoscaling (i.e. - cluster autoscaler, Karpenter, etc.).

This makes sense. However the desired size as well as min/max can be changed in the EKS UI in the AWS Console. I would assume if the AWS UI can do it, it could also be possible for the Terraform module to do it also.

[github-actions]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues. If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.

[bryantbiggs]

https://github.com/bryantbiggs/eks-desired-size-hack