The eksctl by default will create your default nodegroup for you with cloudformation.
You can update this cloudformation stack with current stack and update Parameters to initiate the nodegroup update.
Or alternatively, update this cloudformation stack with template URL provided from pahud/eks-template.
Paste the following URL into the "Specify an Amazon S3 template URL" input box
https://s3-us-west-2.amazonaws.com/pahud-cfn-us-west-2/eks-templates/cloudformation/nodegroup.yaml
click Next and you will need to update some Parameters as below
NodeImageId - clear and empty this field to use the latest EKS-optimized AMI as default
NodeAutoScalingGroupMaxSize - make sure the value is higher than NodeAutoScalingGroupDesiredSize. You can set it to 3, 5 or any higher value.
Now you can define both an AutoScaling Group(above) and a SpotFleet(below) in this template. Both ASG and SpotFleet will hybrid your default Amazon EKS nodegroup with different node labels respectively.
click Next and update your existing cloudformation stack
Now you have a customized ASG and a customized SpotFleet registering to the same K8s nodegroup.
You can list nodes from ASG and nodes from SpotFleet like this:
(this cluster consists of 2 on-demand nodes fron ASG and 2 spot nodes from spotfleet)
You may configure the scheduled scaling policy of your Spot Fleet in response to the predictable traffic spikes or just set max/min to 0 for your testing/development environment for the weeekend for cost optimization. Check this tweet.
The official Amazon EKS nodegroup cloudformation template can be found here - https://github.com/awslabs/amazon-eks-ami/blob/master/amazon-eks-nodegroup.yaml - you can always customize your own nodegroup template based on the official one.